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Mechanical free energy devices => mechanic => Topic started by: capthook on October 28, 2008, 06:27:47 PM

Title: Winding a strong electromagnet
Post by: capthook on October 28, 2008, 06:27:47 PM
Winding a strong electromagnet:

The strength of an electromagnet at its simplest boils down to amp-turns: N*I (# turns x amps).

Most discussion and information deals with a "traction" (attraction and in contact) style electromagnet. 
What about an electromagnet over an air-gap, and even more specifically, in repulsion against a permanent magnet? (polarised)
The information available on this type of electromagnet is severely lacking, and is of a primary interest of this post.

If attempting to obtain OU in a device using electromagnets - maximum effect for minimum input is a critical design goal.

Parameters:

1) CORE         
 a) material                    
 b) length            
 c) width         
 d) pole surface area   
 e) permeability   

2) WINDINGS
 a) length (depth)
 b) width
 c) wire size
 d) wire length
 e) resistance (OHMS)

3) power
 a) amps
 b) voltage
 c) watts

So lets take a specific, practical example:

core: 1/2" x 3" hex bolt
windings: #26 AWG wound to 1.5" length x 1.5" width (1" windings + 1/2" core)
air-gap: 1/4"
Magnet being affected: 1.5"x.75"x.25" N42
power: 1 "D" battery

This is a relatively strong electromagnet- given the small size and power input - but what can/should be done to improve it?

Discussion:
what parameters will create the strongest repulsion electromagnet over an air-gap?
How might repulsion vs. attraction designs differ?

1) CORE
 a) Material: a soft iron core, or electrical steel or laminated core are good options.
 Is a hex bolt going to be acceptable - considering the permeability is sufficient given the small power?
 It's easy and cheap to source.
 Or - sparing no expense - would one of the other materials offer more strength as the domains will line up more readily?
 And what would be THE BEST material of all?

 b) Length: How long is too long?
 
 c) Width: Will an over-all larger core mass create a stronger EM for the same power?

 d) surface: in traction electromagents - surface area is of huge importance.  The more the better.  And round is better.
 The same should apply for activation over an airgap.

2) WINDINGS
 a) Length/depth: how long is too long? 
At what point does the length begin contributing just more resistance without additional  appreciable force as the windings are too far away?
What is the effect of unwound space at the end (for mounting etc)? So if windings are 1.5" deep - the core length should be as close to that as possible?

 b) width: at some point - the windings are too far away from the core to be of significant value.
 What would a rule of thumb be?  Some stated are:
   aa) no further than 1/2" from core
   bb) 1.5 times as wide as long  (so these two conflict)
   cc) twice the diameter of the item you are trying to affect?

 c) wire size: the smaller the wire, the more turns, the stronger the EM. But the more resistance, requiring more voltage push the same amps through it.

Please post any comments, discussion, details, thoughts and links.

Title: Re: Winding a strong electromagnet
Post by: capthook on October 28, 2008, 06:45:35 PM
Something else you have to consider is the pulse rate of your electromagnet, the faster it is switched off and on the higher the Reactance which is a form of electrical resistance.  So the higher the Reactance then the more Voltage needed to produce the necessary Coil power.  One way around this is to wind multiple coils around the core and wire them in parallel.  For example if you are using 100 feet of wire for your coil, you can divide it up in to 10 foot lengths. Wind each ten foot section individually one on top of the other and attach the ends of the wires together at each end.  This will reduce the Reactance and keep the required voltage from rising.

Interesting idea... thoughts?
Title: Re: Winding a strong electromagnet
Post by: capthook on October 28, 2008, 06:52:28 PM
"there is known "trick"  or idea to defeat the attraction between the core and the permanent magnet so that you can even get a benefit of not using extra input power to defeat it.
About 2 years ago I mentioned this idea here, see:  http://www.overunity.com/index.php/topic,1621.msg16347.html#msg16347  and the link to that old patent is here, the old link mentioned there now needs log-in, this one is not: http://www.pat2pdf.org/patents/pat3670189.pdf
(explanation in Page 12, Column 2,  from line 31 and onwards)

With some tinkering of the size of the air gap between the bottom part of the electromagnet's core and a permanent magnet placed under the core and maybe using a slightly stronger permanent magnet there than the permanent magnet to be lifted above the electromagnet, you could reduce or totally eliminate the natural attraction between the core and the upper magnet and increase the 'tossing hight'  further upwards, with the same current into the coil.
The patent is rather long and needs patience to go through but may be worth studying from other aspests too, with respect to your gravity motor.

I agree, the energy in the flyback pulse (I prefer calling it flyback pulse instead of back emf) can also be regained when the electromagnet is switched off  (ala Bedini or by others) so this is another possibility to reduce input power.

rgds,  Gyula"

- -

Placing a small magnet at the far end of the electromagnet in repulsion to the armature magnet will negate the attraction of the armature to the core (providing a sufficient airgap) requiring less power to repulse.
Also, the electromagnet core now already has some of the domains aligned.  When the power is introduced, it provides a greater effect.
ie:
end magnet: 5,000 Gauss
power em: 5,000 Gauss
when used together: 20,000 Gauss - a doubling of the Gauss
(not exact figures - just presenting the idea)
Title: Re: Winding a strong electromagnet
Post by: mondrasek on October 28, 2008, 08:53:08 PM
capthook,

I hope you get good responses to those questions.  I am also very interested in them.  My own projects lead me to using air core EMs (solenoids) and I was lucky to already have the simulator here:  http://www.coilgun.info/mark2/inductorsim.htm  I would love to see something similar for cored EMs that allowed one to play with all the variables you have listed.  Unfortunately I have not found one on the web.  Maybe someone can point us to such a tool if one already exists.

M.
Title: Re: Winding a strong electromagnet
Post by: Spider on October 28, 2008, 08:57:56 PM
Google: Brooks Coil :)


Spider
Title: Re: Winding a strong electromagnet
Post by: Xaverius on October 29, 2008, 07:39:45 AM
Interesting idea... thoughts?
Actually if you use Ferrite or laminated electrical steel you will eliminate almost all of the Reactance but you still have DC resistance.  This can be reduced by using the parallel winding method.  Eighty feet of 27 guage wire has approximately 4 ohms of resistance.  If you used a bifilar winding, that is divide the 80 feet by 2 (40 feet) and wound each section in parallel the total resistance would drop to 1 ohm, meaning you could obtain 4 times the amount of amperage for the same amount of voltage.  Conversely, you can obviously increase the number of turns without increasing the resistance, by using this method.  Of course, if you increase the amperage or the number of turns or both you increase the magnetic field strength.  I'm presently pursuing an electromagnet using Ferrite, which has a permeabilty of around 2000.  I'm trying to optimize the design deciding how much wire to use, my voltage source is a bicycle generator, 8 watts @ 1amp, 8 volts.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on October 29, 2008, 07:51:16 AM
Winding a strong electromagnet:

The strength of an electromagnet at its simplest boils down to amp-turns: N*I (# turns x amps).

Most discussion and information deals with a "traction" (attraction and in contact) style electromagnet. 
What about an electromagnet over an air-gap, and even more specifically, in repulsion against a permanent magnet? (polarised)
The information available on this type of electromagnet is severely lacking, and is of a primary interest of this post.

If attempting to obtain OU in a device using electromagnets - maximum effect for minimum input is a critical design goal.

Parameters:

1) CORE         
 a) material                    
 b) length            
 c) width         
 d) pole surface area   
 e) permeability   

2) WINDINGS
 a) length (depth)
 b) width
 c) wire size
 d) wire length
 e) resistance (OHMS)

3) power
 a) amps
 b) voltage
 c) watts

So lets take a specific, practical example:

core: 1/2" x 3" hex bolt
windings: #26 AWG wound to 1.5" length x 1.5" width (1" windings + 1/2" core)
air-gap: 1/4"
Magnet being affected: 1.5"x.75"x.25" N42
power: 1 "D" battery

This is a relatively strong electromagnet- given the small size and power input - but what can/should be done to improve it?

Discussion:
what parameters will create the strongest repulsion electromagnet over an air-gap?
How might repulsion vs. attraction designs differ?

1) CORE
 a) Material: a soft iron core, or electrical steel or laminated core are good options.
 Is a hex bolt going to be acceptable - considering the permeability is sufficient given the small power?
 It's easy and cheap to source.
 Or - sparing no expense - would one of the other materials offer more strength as the domains will line up more readily?
 And what would be THE BEST material of all?

 b) Length: How long is too long?
 
 c) Width: Will an over-all larger core mass create a stronger EM for the same power?

 d) surface: in traction electromagents - surface area is of huge importance.  The more the better.  And round is better.
 The same should apply for activation over an airgap.

2) WINDINGS
 a) Length/depth: how long is too long? 
At what point does the length begin contributing just more resistance without additional  appreciable force as the windings are too far away?
What is the effect of unwound space at the end (for mounting etc)? So if windings are 1.5" deep - the core length should be as close to that as possible?

 b) width: at some point - the windings are too far away from the core to be of significant value.
 What would a rule of thumb be?  Some stated are:
   aa) no further than 1/2" from core
   bb) 1.5 times as wide as long  (so these two conflict)
   cc) twice the diameter of the item you are trying to affect?

 c) wire size: the smaller the wire, the more turns, the stronger the EM. But the more resistance, requiring more voltage push the same amps through it.

Please post any comments, discussion, details, thoughts and links.



Please see replies 6319 and 6320 in the "Roll on the 20th" topic.
Title: Re: Winding a strong electromagnet
Post by: capthook on October 29, 2008, 09:01:34 AM
I was lucky to already have the simulator here:  http://www.coilgun.info/mark2/inductorsim.htm  I would love to see something similar for cored EMs that allowed one to play with all the variables you have listed.  M.

Hi mondrasek!  Yes - that online coil simulator is awesome.  I've used it often to determine wire length and resistance of coils of certain dimensions - works fine for cored-coils in that sence.
Have you done anything more on your gravity/latch wheel?

- - -
Spider - thanks for the suggestion - not too many hits.  Thoughts on a Brooks coil design in relation to an EM?  Would the recommended relative coil dimensions translate into a stronger/more effecient EM?

 - - -
Actually if you use Ferrite or laminated electrical steel you will eliminate almost all of the Reactance but you still have DC resistance.  This can be reduced by using the parallel winding method.
...I'm presently pursuing an electromagnet using Ferrite, which has a permeabilty of around 2000. 

Thanks for the reply Xaverius!  I will wind my next EM using the multi-strand method (this weekend) and post results.  So if I'm winding 300' - break it out into 4 in-hand?

And on your ferrite rods - you have sourced 1"x7" size?  Any U.S. supplier links?
And is this just 'non-magnetized' ferrite/ceramic material, like is used to make ceramic magnets?
Results?  Remanence of the material?
And the math stuff is good - I have a minor grasp of it - but hands-on is really the only way I fully comprehend it!

"The permeabilty of ordinary iron/steel is ur=50"
See this link: http://hyperphysics.phy-astr.gsu.edu/Hbase/tables/magprop.html#c2

Iron, 99.95% pure:
Initial Relative Permeability: 10,000
Maximum Relative Permeability: 200,000
Iron, 99.8% pure: 150 : 5,000
Steel, 0.9% C: 50 : 100
(amazing to see the huge disparity in the permability in relation to the purity of iron.  .15% equals a 40x increase!)

So a Grade 2 hex bolt is low carbon steel w/ perm. of 50-100.  So a pure iron core would boost the power of an EM by like 2,000 times?  Or would a small, low-power (1.5 watts) EM not see much difference?  Does the permeablility deal more with saturation point? Or does it also indicate "how easily the domains will align" thus offer a larger effect for the same power?


Any comments on core and winding dimensions?

2 interesting ideas you have presented - thanks!

Any progress on your pulse motor/generator?
Title: Re: Winding a strong electromagnet
Post by: Xaverius on October 29, 2008, 10:54:06 PM
Hi mondrasek!  Yes - that online coil simulator is awesome.  I've used it often to determine wire length and resistance of coils of certain dimensions - works fine for cored-coils in that sence.
Have you done anything more on your gravity/latch wheel?

- - -
Spider - thanks for the suggestion - not too many hits.  Thoughts on a Brooks coil design in relation to an EM?  Would the recommended relative coil dimensions translate into a stronger/more effecient EM?

 - - -
Thanks for the reply Xaverius!  I will wind my next EM using the multi-strand method (this weekend) and post results.  So if I'm winding 300' - break it out into 4 in-hand?

And on your ferrite rods - you have sourced 1"x7" size?  Any U.S. supplier links?
And is this just 'non-magnetized' ferrite/ceramic material, like is used to make ceramic magnets?
Results?  Remanence of the material?
And the math stuff is good - I have a minor grasp of it - but hands-on is really the only way I fully comprehend it!

"The permeabilty of ordinary iron/steel is ur=50"
See this link: http://hyperphysics.phy-astr.gsu.edu/Hbase/tables/magprop.html#c2

Iron, 99.95% pure:
Initial Relative Permeability: 10,000
Maximum Relative Permeability: 200,000
Iron, 99.8% pure: 150 : 5,000
Steel, 0.9% C: 50 : 100
(amazing to see the huge disparity in the permability in relation to the purity of iron.  .15% equals a 40x increase!)

So a Grade 2 hex bolt is low carbon steel w/ perm. of 50-100.  So a pure iron core would boost the power of an EM by like 2,000 times?  Or would a small, low-power (1.5 watts) EM not see much difference?  Does the permeablility deal more with saturation point? Or does it also indicate "how easily the domains will align" thus offer a larger effect for the same power?


Any comments on core and winding dimensions?

2 interesting ideas you have presented - thanks!

Any progress on your pulse motor/generator?


Hi Capthook, actually you can divide the 300 feet into as many smaller wires as you like. The more smaller wires the lower the resistance.  The formula is the number 1 divided by 1/r+1/r+1/r........r = resistance of each indivdual wire, ex: r=2 and you have 5 small wires, then total resistance is 1 divided by 1/2 + 1/2 +1/2 +1/2 +1/2 = .4 ohms.

Yes, the ferrite rod I have is 1" diameter and 6" long.  This is experimental, I don't know how effective it will work as an electromagnet although I've read the results of other experimenters has been favorable.  I'll post once it is wound and energized, a lot of work at the regular job, lately, LOL.  It is similar to ceramic magnetic material, specifically it is used in the Radio-Frequency field, usually for antennas, tuners, attenuators,etc.  I sourced it at Stormwise.com, it is Material "T" and you must look for the 2000 u(permeability).  They order it about once a month and then cut the lengths to order,  one week to one month wait time.   I agree hands on is the way to go, the math gives me a clue beforehand if the concept will work or not.....If the math does not make sense, then the pursuit is useless.  Actually, the Remanence is unimportant as this is used for an electromagnet, but I think the Remanence is low.

You're right, impure iron has low permeabilty, but very pure iron has high permeabilty.  Pure iron would boost the power 2000X, low power EM(1.5 watts) would see a tremendous boost in MAGNETIC power.  Permeabiltiy deals with "how easilty the domains align" offering a larger effect for the same power.  It does not normally effect saturation point as most magnetic materials saturate anywhere from .5 tesla to 1.5 tesla, however usually as a general rule the higher the permeability, the lower the saturation point.

I don't think that core and winding dimensions are a factor per se, however, the larger the cross-sectional area of the core, the stronger the magnetic field and also the more wire that is needed.  Hope this answers everything and sorry if I explained things you already know.  I'll try to get to my EM this weekend.
Title: Re: Winding a strong electromagnet
Post by: capthook on October 30, 2008, 11:09:28 AM
Well I've spent the last 4 hours searching on core materials.....

Sourcing pure iron is VERY expensive: $250 for a small rod ....(from www.goodfellows.com) or
$100 from http://www.surepure.com/products.php?ID=7&meas1_ID=41&subCat=23

1018 cold rolled steel is (relatively) easily sourced and reasonably priced.... is this a decent option?

BUT - the ferrite rods idea has peaked my interest the most.....

Found this supplier: https://www.amidoncorp.com/categories/6

The 77 is 2000u but limited sizes... the 33 is 800u with more selection... and cheap....
guess I'll order some to test........

How to mount an unthreaded rod securely? (can't thread brittle ferrite)
- - -

Winding a 'kiddie' electromagnet on a bolt from Lowe's is not the solution..........

Shout out!!! ->  What is THE material for EM core construction and where to source it?!?

Anyone else used ferrite rods as cores?
Title: Re: Winding a strong electromagnet
Post by: mondrasek on October 30, 2008, 04:54:03 PM
Hi mondrasek!  Yes - that online coil simulator is awesome.  I've used it often to determine wire length and resistance of coils of certain dimensions - works fine for cored-coils in that sence.
Have you done anything more on your gravity/latch wheel?

Capthook, no, I have not done anything more with the gravity/latch wheel that uses PM stators.  Once I found the flaw in my logic I realized that I had nothing new and was therefore bound by the laws that show a pure gravity powered machine is impossible (barring the invention/introduction/generation of anti-gravity).  Until finding that mistake I had to assume that something unknown or untried with the magnet arrangement was supplying something more.  I was/am fairly ignorant about magnetics.  But that lead me to thinking more about them and the possabilities for using electromagnetic stators.  I've researched that a bit as you have seen, but only so far.  Since what I've seen so far supports that magnetic fields are, like gravity, a conservative field of force, I've little hope for that route either. 

But I am still intrigued with the relationship of magnetism and electricity, as this has been harnessed successfully to do work in many forms, including the electric motor.  I have no ideas how to design anything that can produce work without consuming or wasting more input electricity than it outputs (so far), but I've built and played with a couple Imohtep/Bedini fans and a Tesla switch while learning more about some of the different electromagnetic phenomenon that I hoped had potential.  The Tesla switch had me looking at electrical resonance as well.  Nothing has shown me OU potential.

The one thing that I still have in the back of my mind is the testing where I learned that a PM being accelerated away from an EM/solenoid induces a current in the EM/solenoid that appears to assist the acceleration and not oppose it.  This is still very interesting to me.

I had hoped Clanzer might find the desire to finish the "Mondrasek wheel" he started, just to see how close to unity he could come.  Maybe I will try that myself some day if I ever have the extra resources.

Nice to see Xaverius adding more EM info on this thread.  Spider's reference to Brooks coils also sent me back to the coilgun.info sim to do some testing.  I'd like to build a high self inductance, low resistance EM that does not have a core that is attracted by a PM, but I don't think that is possible.

M.
Title: Re: Winding a strong electromagnet
Post by: TinselKoala on October 30, 2008, 05:55:35 PM
I've had good results using soft iron wire (available cheaply at local hardware stores) for EM cores. The wire can be straightened by clamping an end in a vise and pulling the other end; individual pieces can be insulated with heatshrink, and a bunch of straight, insulated pieces bundled together or stuffed into a tube makes a very nice core.
Ferrites or other smooth cores can be held securely in compression fixtures that can be easily fabricated from plastic stock.
Title: Re: Winding a strong electromagnet
Post by: capthook on October 31, 2008, 05:46:54 AM
I've had good results using soft iron wire (available cheaply at local hardware stores) for EM cores. The wire can be straightened by clamping an end in a vise and pulling the other end; individual pieces can be insulated with heatshrink, and a bunch of straight, insulated pieces bundled together or stuffed into a tube makes a very nice core.
Ferrites or other smooth cores can be held securely in compression fixtures that can be easily fabricated from plastic stock.

Iron wire is similar to the Bendini design using welding rods.  The problem is the airgap between the individual pieces, resulting in less total material and thus a less effective core.
For mounting - I have considered something along the lines of adjustable hose clamps.

- - -
A few other design notes:

For traction magnets - a slightly rounded, convex  core end will actually have stronger holding power than a flat face.

And as to adding a permanent magnet to the far end of the EM to give the core an initial starting polarity as mentioned earlier - consider this:
"If we have a certain number of magnetic lines, N, the pull is proportional to N(squared).
So the more powerful the pull to begin with, the greater is the change of pull when you produce a small change in the number of magnetic lines."

I'd like to build a high self inductance, low resistance EM that does not have a core that is attracted by a PM, but I don't think that is possible.
M.

And adding this magnet - in  repulsion to the PM, at the far end of the EM will negate the PM attraction to the core IF the airgap is sufficiently large and the end magnet is of sufficient strength (the airgap/end magnet strength/PM are relative)
- - -
A good (long) read is the following book, courtesy of Google scanned books project.  Though written in 1892, it is still valid in (most of) it's principles.

http://books.google.com/books/pdf/The_Electromagnet__and_Electromagnetic_M.pdf?id=CLmFTg_j0pwC&output=pdf&sig=ACfU3U3SDSRbaHhRwpQzx6pb7kwk3pCBuA

- - -
And I ordered some ferrite rods today for testing as cores (https://www.amidoncorp.com/categories/6) ... .5" x 3" 800u....should be here early next week...

As to breaking the windings down into smaller segments to reduce resistance:
This seems a huge idea - why isn't it the norm and why is X's mention of it (apparently) the first I can find mention of it anywhere?  Multiply the available amps, and thus amp-turns, seems HUGE!

However - for my particular application - I am pulsing the EM with a small capacitor.  As such, to increase the capacitor discharge time constant, I actually need some resistance in the circuit.

And the EM I'm using is a polarized (permanent magnet on armature/rotor) electromagnet in repulsion over an air-gap.  Once again - information/data on this style of EM is in short supply.

Any and all comments, thoughts and links would be of great assistance!
Title: Re: Winding a strong electromagnet
Post by: Xaverius on October 31, 2008, 06:41:18 AM
@ CaptHook, how is it going.  I can totally relate to your frustration on finding high permeabilty materials.  You're right pure iron is very expensive.  You might try ScientificAlloys.net.  They have a variety of materials and their sales personnel can provide information.  Have you tried Stormwise.com?  That's where I got my ferrite.

I'm not sure about cold rolled steel?  Could you provide more information about it?  The permeabilty is most important.  Another route you might try is to solicit a supplier for a sample. Usually it's free, you'll have to pay shipping and consult with a salesman.

I tried using GIron before.  It is similar to MuMetal, it has a permeabilty of 100,000 and is used in magnetic shielding.  Cost me $40.00 for a piece of foil one foot square.  I cut the foil into strips, stacked them together, wound tape around it and then wound it with wire.  A total dud!!!  No magnetic strength whatsoever.

I think the best material is silicon electrical steel which is very common but manufacturers will only sell to buyers with LARGE orders.  If you can salvage the cores from used transformers or inductors you could obtain the material, but I'm not sure how to do this.

@ TinselKoala, what is soft iron wire, is it picture hanging wire?  What is it normally used for and what should I ask the salesman for?  I've heard that welding rods bunched together make good magnetic material, but I haven't verified it.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on October 31, 2008, 07:04:14 AM
As to breaking the windings down into smaller segments to reduce resistance:
This seems a huge idea - why isn't it the norm and why is X's mention of it (apparently) the first I can find mention of it anywhere?  Multiply the available amps, and thus amp-turns, seems HUGE!

Why isn't it the norm?  Why indeed!  In the century and a half that motor/generators have been in existence this concept has been known, yet ignored.  Manufacturers/engineers are only concerned with practical applications of electrical equipment. Since the prime mover provides power to a generator the input energy is considered no object.  Since the generator provides power to the motor the energy used by the motor is no object.  Where innovation enters the picture is where for reasons of size reduction and energy conservation higher permeabity(electrical steel) materials are used.

It was not the aim of the original industrialists to produce overunity, their aim was(and is) providing products(motors) and services(electrical generation).  Modern capitalism is based on this premise, energy operates the world.  Without it, the modern world as we know it would not exist.  The only thing that will crush the power of the bankers/corporations is the implementation of free energy.
Title: Re: Winding a strong electromagnet
Post by: TinselKoala on October 31, 2008, 02:04:58 PM
@X: Picture hanging wire is generally steel (higher tensile strength) and is smaller in gauge or multi-stranded, here in North America. The soft iron wire is a general-purpose stuff usually sold in fairly large rolls (several pounds?) and is used for fencing, baling hay, concrete rebar tieing, anything you need a stout but formable wire for. I see that it is also called black iron wire (http://www.galvanizedwire-mesh.com/en_wiremesh_html/black_iron_wire.html).
When using it for cores it can be left bare, insulated with varnish, heat shrink, or any combo. You can also experiment with using the core itself as part of the circuitry, in whole or in part. Pack it tight, or even embed it in epoxy, to keep things from vibrating under AC stimulation.

EDIT to add there's a trade-off between number of turns and the added inductance. It isn't just resistance of the windings that is of concern. So there is an optimum number of turns, wire gauge, etc. for a particular core geometry and purpose (motor, transformer, choke, etc.) Electric motors and generators are remarkably efficient already and more efficiency would be a very strong sales incentive. IF motors could really be improved by reducing wire size and adding turns, beyond what has already been done, even just a little bit, it would be big news. Joe Newman's motors are remarkably inefficient flywheel energy storage systems; the main benefit from all that wire is the rotating mass it provides for the flywheel.
Title: Re: Winding a strong electromagnet
Post by: capthook on October 31, 2008, 05:34:28 PM
@ CaptHook, how is it going.  I can totally relate to your frustration on finding high permeabilty materials.  I'm not sure about cold rolled steel?  Could you provide more information about it?  The permeabilty is most important....
I think the best material is silicon electrical steel which is very common but manufacturers will only sell to buyers with LARGE orders.  If you can salvage the cores from used transformers or inductors you could obtain the material, but I'm not sure how to do this.

 think the best material is silicon electrical steel which is very common but manufacturers will only sell to buyers with LARGE orders.  If you can salvage the cores from used transformers or inductors you could obtain the material, but I'm not sure how to do this.


Cold rolled steel:
http://www.ussteel.com/corp/sheet/cr/mls.htm
http://www.coilgun.info/theorymath/home.htm
Maximum permeability: 2,000u

Silicon electrical steel:  I second your motion and also wonder where to source a small, inexpensive, rod shaped piece !?!?
Title: Re: Winding a strong electromagnet
Post by: Xaverius on October 31, 2008, 06:58:05 PM
@X: Picture hanging wire is generally steel (higher tensile strength) and is smaller in gauge or multi-stranded, here in North America. The soft iron wire is a general-purpose stuff usually sold in fairly large rolls (several pounds?) and is used for fencing, baling hay, concrete rebar tieing, anything you need a stout but formable wire for. I see that it is also called black iron wire (http://www.galvanizedwire-mesh.com/en_wiremesh_html/black_iron_wire.html).
When using it for cores it can be left bare, insulated with varnish, heat shrink, or any combo. You can also experiment with using the core itself as part of the circuitry, in whole or in part. Pack it tight, or even embed it in epoxy, to keep things from vibrating under AC stimulation.

EDIT to add there's a trade-off between number of turns and the added inductance. It isn't just resistance of the windings that is of concern. So there is an optimum number of turns, wire gauge, etc. for a particular core geometry and purpose (motor, transformer, choke, etc.) Electric motors and generators are remarkably efficient already and more efficiency would be a very strong sales incentive. IF motors could really be improved by reducing wire size and adding turns, beyond what has already been done, even just a little bit, it would be big news. Joe Newman's motors are remarkably inefficient flywheel energy storage systems; the main benefit from all that wire is the rotating mass it provides for the flywheel.

Hi, I have a lot of picture hanging wire here in my gallery.  I am familiar with baling wire, rebar wire, etc. so now I know what to look for.  I hope it is more permeable than ordinary hardware(nails, screws, bolts).  Enamel spray paint would be my insulator of choice with wire bundles to reduce eddy currents and Reactance.

You're right, motors are now extremely efficient, approaching 100% in most cases.  This has to do primarily with rising electricity prices  and using motors in small places such as electric razors, cd drives etc.  In my experience there are already some small motors(primarily DC) that are overunity.  For a given amount of electrical input, the mechanical output is greater.  What is very frustrating is that most small motors don't give their rated output, but if you search Data Sheets for small motors you can sometimes find the information.  The larger motors, used for compressors, pumps, etc. usually have a horsepower rating but I've never found any that are overunity.  It seems the larger the motor,  the less efficient but the greater output in absolute terms.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on October 31, 2008, 07:11:24 PM
Cold rolled steel:
http://www.ussteel.com/corp/sheet/cr/mls.htm
http://www.coilgun.info/theorymath/home.htm
Maximum permeability: 2,000u

Silicon electrical steel:  I second your motion and also wonder where to source a small, inexpensive, rod shaped piece !?!?
I see cold rolled is the same as silicon electrical.  Like I say you can salvage core material from used motors and transformers, but obtaining the right size might be difficult because these cores are machined to a particular shape.  Also have you tried ScientificAlloy.net?  You'll have to telephone them before 5:00 P.M central time and talk to a salesman.  They quoted me $250.00 for pure iron, ask them about EM core material.
Title: Re: Winding a strong electromagnet
Post by: mondrasek on November 01, 2008, 08:34:10 PM
I know this might step off topic, but I've got to ask...

Say you are to make an electromagnet where you use a great number of single turn conductors wired in parallel.  Does this create an EM with nearly zero resistance, reactance, and impedance?  What kind of capacitance would such a device have compared to one of an equal number of turns wound from only one continuous conductor?

M.
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 01, 2008, 09:23:25 PM
Hey capthook,

this google-book link returns a message that this link does not exist.

Regards

Kator
Title: Re: Winding a strong electromagnet
Post by: capthook on November 02, 2008, 02:49:19 AM
It appears the ultimate core material could be metglass?

http://www.metglas.com/products/page5_1_2_4.htm

Maximum DC Permeability (µ):
As Cast: 45,000
Annealed (High Freq.): 600,000

Saturation Induction (Tesla)   
As Cast: 1.56

Supposedly very expensive.....

"The material with the highest magnetic permeability is Metglas Magnetic Alloy 2714A (Cobalt-based) [7] with a high frequency annealed permeability of 1,000,000 (Maximum DC Permeability (µ)). "

I guess you would have to laminate numerous thin sheets together to make a larger core (or find a company that does that?!?)

This seems beyond my scope at this point.....

Sourcing ANY of the 'fancy' materials is expensive and difficult.  Also - getting them in an easily-usable form seems non-existant (as in solid rod form).
I'm of the notion that an EM core does NOT need to be laminated - and that a solid core would actually produce the best results.

Grain orientated silicon steel (electrical steel) seems a more practical option/the next-best option.

Looking forward to recieving ferrite rods next week for testing.....

Any other ideas/sourcing for other high permeability, practical core material?
Something like a .5" x 3" grain oriented silicon steel rod?

Also - going to the University next week for some research/reading materials.....
- - -
I think the best material is silicon electrical steel which is very common but manufacturers will only sell to buyers with LARGE orders.  If you can salvage the cores from used transformers or inductors you could obtain the material, but I'm not sure how to do this.

Me either!  But I would like to find out!

You might try ScientificAlloys.net.  They have a variety of materials and their sales personnel can provide information. 

I will call them Monday.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 02, 2008, 08:54:53 AM
I know this might step off topic, but I've got to ask...

Say you are to make an electromagnet where you use a great number of single turn conductors wired in parallel.  Does this create an EM with nearly zero resistance, reactance, and impedance?  What kind of capacitance would such a device have compared to one of an equal number of turns wound from only one continuous conductor?

M.

The more single turn conductors wired in parallel, the closer to zero the resistance, reactance, impedance.  The capacitance would be the same with an equal number of turns from the same conductor.  You can use the Medhurst formula.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 02, 2008, 09:03:31 AM
It appears the ultimate core material could be metglass?

http://www.metglas.com/products/page5_1_2_4.htm

Maximum DC Permeability (µ):
As Cast: 45,000
Annealed (High Freq.): 600,000

Saturation Induction (Tesla)   
As Cast: 1.56

Supposedly very expensive.....

"The material with the highest magnetic permeability is Metglas Magnetic Alloy 2714A (Cobalt-based) [7] with a high frequency annealed permeability of 1,000,000 (Maximum DC Permeability (µ)). "

I guess you would have to laminate numerous thin sheets together to make a larger core (or find a company that does that?!?)

This seems beyond my scope at this point.....

Sourcing ANY of the 'fancy' materials is expensive and difficult.  Also - getting them in an easily-usable form seems non-existant (as in solid rod form).
I'm of the notion that an EM core does NOT need to be laminated - and that a solid core would actually produce the best results.

Grain orientated silicon steel (electrical steel) seems a more practical option/the next-best option.

Looking forward to recieving ferrite rods next week for testing.....

Any other ideas/sourcing for other high permeability, practical core material?
Something like a .5" x 3" grain oriented silicon steel rod?

Also - going to the University next week for some research/reading materials.....
- - -
Me either!  But I would like to find out!

I will call them Monday.

Some of the more exotic materials such as Metglas, SuperMalloy, etc have extremely high permeablities but relatively low saturation points(.25-.5 Tesla). Metglas can be purchased as a spool of ribbon but I priced it on Ebay for $125.00 for 50 feet.  It is also very sharp so it's difficult to handle.  I tried thin strips of GIron which is similar material and it didn't perform at all, I think these materials are only magnetized along the plane of the material(normally used for magnetic shielding) so I don't have a lot of confidence in using them. 

If you have access to a Sabre Saw with a metal cutting blade you might be able to obtain electrical steel laminations from salvaged objects.  You'll need it to cut the core material into the desired lengths/shapes.  I've heard old washing machine motors have cores that are easily used.  Might be worth trying.

If you don't use laminated steel or ferrite, the Reactance will be much greater.  If this is not a factor in your design then no problem, but if amperage optimization is important then you must consider using them.
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 03, 2008, 01:02:26 AM
Hello All,

here a good website from australia :

http://www.magneticsolutions.com.au/ (http://www.magneticsolutions.com.au/)

@capthook: Some Killerrobot is obviously observing certain activities. I was accessing the patent-link

http://www.pat2pdf.org/patents/pat3670189.pdf (http://www.pat2pdf.org/patents/pat3670189.pdf)

and downloaded the Pdf-File. A minute later accessing the same link again ( I had closed the window after download ) an error-message popped up saying that the file has been removed.

Regards

Kator
Title: Re: Winding a strong electromagnet
Post by: gyulasun on November 03, 2008, 01:25:09 AM
Hi capthook,

Thanks for your P.Message. I think most of the aspects of making a good electromagnet have been included in this and in some other threads, I cannot add much new ideas unfortunately. Thanks also for quoting one of my earlier text on this subject earlier in this thread.
Some additional thoughts: I agree with Honk by saying that solid pure iron should be used with caution because of the eddy currents (unless you do not pulse-operate your EM),  see his thoughts: http://www.overunity.com/index.php?topic=2222.msg135629#msg135629 and here:
http://www.overunity.com/index.php?topic=5279.msg118679#msg118679
Also an important thing on response timewhen you do pulse the EM: http://www.overunity.com/index.php?topic=4948.msg105636#msg105636

You maybe noticed member DMMPOWER electromagnet offer? see here http://www.overunity.com/index.php?topic=4624.msg96814#msg96814
This reminds me to Jack Hildenbrand magnet valve but unfortunately DMMPOWER does not give any hint on the construction...   By the way, there is (I think) a valid argument against combining an EM with a permanent magnet to increase the flux by saying you can make the same increased flux by choosing a core with bigger permeability...
Well, this can be true up to a limit in the budget or fast switching speed or simply using already the highest exotic permeability core above which there is no higher and still you can increase the flux by including the flux from a perm. magnet too...

Thanks,  Gyula

Title: Re: Winding a strong electromagnet
Post by: capthook on November 03, 2008, 07:16:45 AM
Gyula-

Thanks so much for the reply!  As always - your input is HIGHLY valued and most excellent!

By the way, there is (I think) a valid argument against combining an EM with a permanent magnet to increase the flux by saying you can make the same increased flux by choosing a core with bigger permeability...
Well, this can be true up to a limit in the budget or fast switching speed or simply using already the highest exotic permeability core above which there is no higher and still you can increase the flux by including the flux from a perm. magnet too...

Thanks,  Gyula

Agree.  From several text-books, as well as recent hands-on tests, adding a permanent magnet(PM) is helpful in that the PM can greatly multiply the relative force of the EM.
I can't provide exact figures, but...

Example in non-exact terms:
Supply an EM with 5 watts you get 1000 gauss.
Now take a permanent magnet with 1000 gauss and attach to the far end of the EM.
Apply the same 5 watts to EM.
You now end up with (1000+1000)x4= 8,000 gauss.
So you have greatly increased the efficiency of that 5 watts of power.

"If we have a certain number of magnetic lines, N, the pull is proportional to N(squared).
So the more powerful the pull to begin with, the greater is the change of pull when you produce a small change in the number of magnetic lines."

I see it as: it takes A watts to produce the needed flux from the EM.
Attaching a PM provides B watts of equivalent flux.
A-(Bx2)= C, the watts now needed to produce the needed flux.
The PM has 'pre-charged' the EM for free by 'pre-aligning' some of the magnetic domains.

Once again - I don't know the exact relative effect - is it 4x or 8x or x2?  Wish I knew - but it is large.  One reference book states it as x2.

Also - as in my project - if you are (only) repulsing a PM with the EM, it is an additional benefit by nullifying/reducing the attraction of the PM to the EM core.

Honks points are good ones on eddy currents and hysteresis losses (which points again to laminated electric steel as the core of choice), and I still need to learn more about these as well as reactance.

As to powdered cores, what I've found thus far is that most have them have low permability (20-150u) and saturation points and would be inferior in most designs over laminated electrical steel.

I'm still reading through the full threads of the links you gave....
Still reading the interesting Hilden motor thread: http://www.overunity.com/index.php?topic=2222.0
and this: http://www.overunity.com/index.php?topic=3456.0

- -
As to metglas, permalloy etc... it seems the super high permeabilities translates into excellent shielding - but not as EM or generator cores.  As Xaverius mentions, I think it has to do with low saturation points, as well as their 'orientations'.

It seems the practical/efficient core solution is electrical steel - grain-oriented even being the best.
Ferrite cores might also be a good choice, depending on the application.  I'll know more first hand info next week...

- -
Ways to source scrap laminated electrical steel:

Old microwave: http://www.overunity.com/index.php?topic=4047.msg101636#msg101636 \

"You can also get good laminations from junked alternators." wattsup


So much to learn - so little time!  One little step after the other  :)

Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 04, 2008, 04:54:54 PM
Hi capthook,

I would be very interested in reading this electromagent-book. Can you please review your link ?
It is no valid. No such book exists in this library.

http://books.google.com/books/pdf/The_Electromagnet__and_Electromagnetic_M.pdf?id=CLmFTg_j0pwC&output=pdf&sig=ACfU3U3SDSRbaHhRwpQzx6pb7kwk3pCBuA (http://books.google.com/books/pdf/The_Electromagnet__and_Electromagnetic_M.pdf?id=CLmFTg_j0pwC&output=pdf&sig=ACfU3U3SDSRbaHhRwpQzx6pb7kwk3pCBuA)

Do you have a copy saved ?


Regards

Kator01
Title: Re: Winding a strong electromagnet
Post by: mondrasek on November 04, 2008, 05:40:16 PM
Kator01,

Link works for me.  Book is ~11.8Mb which is over my outgoing e-mail limit here at work or I'd offer to send it to you.

M.
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 04, 2008, 09:23:12 PM
Hi mondrasek,

thank you anyway... but this is strange. Must be somthing wrong with the german-google-books-database.

Regards

Kator01
Title: Re: Winding a strong electromagnet
Post by: capthook on November 05, 2008, 06:49:00 AM
Any recommendations on coil/core geometry/dimensions?  Something like how a Brooks coil dimensions is proposed for an air core design?
Maximum width/depth of windings/ distance from core?
Core width/length? etc...

- - -

Kator - I've tried to upload the Ebook to the uploads section of this site - but stated file size limit is 5meg and the Ebook is 12meg.  However - the link given before IS active and links to the .pdf download of the Ebook....

- - -

Silicon Steel  (Electrical Steel)
 
"When low carbon steel is alloyed with small quantities of silicon, the added  volume resistivity helps to reduce eddy current losses in the core.  Silicon
steels are probably of the most use to designers of motion control products
where the additional cost is justified by the increased performance.  These
steels are available in an array of grades and thicknesses so that the material may be tailored for various applications.  The added silicon has a marked impact on the life of stamping tooling, and the surface insulation selected also affects die life.  Silicon steels are generally specified and selected on the basis of allowable core loss in watts/lb.

The grades are called out, in increasing order of core loss by M numbers,
such as M19, M27, M36 or M43, with each grade specifying a maximum  core loss.  (Note that this means that material can be substituted up , as M19 for M36, but not vice versa.) The higher M numbers (and thus higher core losses) are progressively lower cost, although only a few percent is saved with each step down in performance.  M19 is probably the most common grade for motion control products, as it offers nearly the lowest core loss in this class of material, with only a small cost impact, particularly in low to medium production quantities.
In addition to grade, there are a number of other decisions to make regarding silicon steels.  These are:

1. Semi vs. Fully processed material,
2. Annealing after stamping,
3. Material Thickness,
4. Surface insulation. 

  Fully processed material is simply material which has been annealed
to optimum properties at the steel mill.  Semi processed material always
requires annealing after stamping in order to remove excess carbon as well as to stress relieve.  The better grades of silicon steel are always supplied fully processed while semi processed is available only in grades M43 and worse.  The designer considering semi processed M43 should evaluate Low Carbon Steel which may provide equivalent performance at lower cost.

Even though annealed at the mill, fully processed material may require further stress relief anneal after stamping.  The stresses introduced during punching degrade the material properties around the edges of the lamination, and must be removed to obtain maximum performance.  This is
particularly true for parts with narrow sections, or where very high flux
density is required.  In one instance, a tachometer manufacturer was able to
reduce the stack height in his product by 10% by annealing after stamping.  The annealing cycle requires a temperature of 1350-1450 F in a non oxidizing, non carburizing atmosphere. Endothermic, nitrogen, and vacuum atmospheres all work well. The selection of lamination thickness is a fairly
straightforward trade off of core loss versus cost.  Thinner laminations exhibit lower losses (particularly as frequency increases), but thinner material is more expensive initially, and more laminations are required for a given stack height.  The most common thicknesses are .014 in., .0185 in., and .025 in. (29 Gauge, 26 Gauge, and 24 Gauge, respectively.)  These thicknesses are supplemented by thin electrical steels, available in .002, .004, and .007 in. thick.  Thin electrical steels are available in one grade (Equivalent to M19) and are made by re-rolling standard silicon steel.  Due to substantially higher material cost, thin electrical steel is used primarily for high performance and high frequency applications.  In order to gain full advantage from a laminated core, the laminations must be insulated from one another.  The simplest way to do this is to specify a surface insulation on the raw material.  Silicon steels are available with several types of insulation: 
--C-0:
Also called bare, or oxide coated.  This is a thin, tightly adherent oxide
coating put on the material at the steel mill, or during the annealing process
after stamping. This is the lowest cost insulation, but offers little
resistance.
--C-3:
Enamel or varnish coating which offers excellent insulation, but parts so
coated cannot be annealed after stamping.
--C-4:An inorganic coating providing higher resistance than C-0, but which will withstand annealing temperatures.
--C-5:
An improved inorganic coating similar to  C-4 but with significantly higher
resistance. It withstands annealing well in most cases.  This is probably the
best choice for most performance sensitive applications.  The main drawback to C-5 is  an increase in tool wear due to abrasiveness."
- - -

Anyone have a source for ordering small quantities of electrical steel?
Title: Re: Winding a strong electromagnet
Post by: scotty1 on November 05, 2008, 10:19:17 AM
Hi all, I have loads of thin iron.  ;D
I have to keep it on my trolley jack it is so heavy..maybe 400lbs or more  :o
I took it from an old electric induction furnace...the strips are about 3 feet long x 3 inches wide, very thin.
BTW, if you want to make a strong EM for lifting, then you need to put an iron tube around the coil and core....You can do better still...connect one end of the iron core to one end of the iron or steel tube with a plate of iron or steel....then at the same end of the coil,  if the core was a N pole, the tube will be a S pole.
http://outdoors.webshots.com/photo/1309921210053353196vJTSMY (http://outdoors.webshots.com/photo/1309921210053353196vJTSMY)
My wife gives me "THE LOOK" when i bring things like 400lbs of iron strips home  >:(
"BUT I MIGHT BE ABLE TO USE IT ONE DAY"   I say  ;D
Everybody here surley understands that. ;)
Scotty.
 

Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 05, 2008, 10:34:14 AM
 Hi capthook,

thank you. I simply can not believe it how scattered information in the web is. But anyway look here,  even searched with google´s book-search-engine and could not find it.

Regards

Kator01



Title: Re: Winding a strong electromagnet
Post by: gyulasun on November 05, 2008, 10:43:43 AM
Hi Kator01,

I receive the same page you show above, I think it is country-specific what we can download...  Probably it is ok for download in the USA but not allowed in Europe...

Maybe it could be uploaded to a free file sharing site?

rgds, Gyula
Title: Re: Winding a strong electromagnet
Post by: capthook on November 05, 2008, 11:23:12 AM
Huh - must be a US thing.
Google caused a bit of an uproar when they started the book scan project.  Royalties issues etc.
Just a week ago or so they settled a law suit for over $20 million relating to it.
Maybe it will clear some of the hurtles in the near future.

I upload the file to a free file service:

http://www.filepanda.com/file/vjdxk5ztmx4m/

It will take a min. or two (or more on dial-up - 12 MB) to download and then opens a .pdf window.
You can then click on "save a copy" in the top-left menu to save to your hard drive.

 :)
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 05, 2008, 12:09:43 PM
Hi capthook,

thank you very much. Now I have saved a copy. Great find.

Regards

Kator01
Title: Re: Winding a strong electromagnet
Post by: capthook on November 05, 2008, 12:47:00 PM
A 2nd Ebook of interest is:

Solenoids, Electromagnets & electromagnetic windings
423 pages, 7MB

A good complement to the first and written 25 later.
The author, Underhill, writes this in reference to the author of the 1st ebook link:

"The labors of Professor Silvanus P. Thompson in this field deserve recognition from the electrical profession, to which the author desires to add his personal acknowledgments."

The file is here:

http://www.filepanda.com/file/2rpkksms11kj/
Title: Re: Winding a strong electromagnet
Post by: capthook on November 07, 2008, 05:17:34 AM
1st attach picture:

A graph showing the results of different core materials using a small test coil as a generator coil.


2nd pic: MIG welding wire

Ran across this interesting core idea:

"Get yourself a roll of .030 MIG welding wire.

Make your coil form so that there is very little airspace at the center of the winding.

Wind the steel wire in tandem with the copper wire on the same form.

What you have there is an integrated, ultra-low eddy-current ferrous core.

You can also do this with regular mechanics wire. But, it's usually kinda dirty and oily right on the roll. MIG wire is nice and shiny."

What you lose in winding space for the copper wire because of the steel wire might be similiar to what you gain in being able to wind the coil to a smaller inner dimension?
Either way - an interesting idea I've never heard of!
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 07, 2008, 08:46:10 AM
1st attach picture:

A graph showing the results of different core materials using a small test coil as a generator coil.


2nd pic: MIG welding wire

Ran across this interesting core idea:

"Get yourself a roll of .030 MIG welding wire.

Make your coil form so that there is very little airspace at the center of the winding.

Wind the steel wire in tandem with the copper wire on the same form.

What you have there is an integrated, ultra-low eddy-current ferrous core.

You can also do this with regular mechanics wire. But, it's usually kinda dirty and oily right on the roll. MIG wire is nice and shiny."

What you lose in winding space for the copper wire because of the steel wire might be similiar to what you gain in being able to wind the coil to a smaller inner dimension?
Either way - an interesting idea I've never heard of!


Nice suggestion, any idea of the permeabilty of welding wire?  Btw, how is your electrical steel/ferrite projects progressing?  I received a 6" long/1" diameter ferrite rod from Stormwise.com.  It was encased in 1/8th thick plastic tubing for weatherproofing.  I chiseled off the plastic today and found two 3" segments pushed together end to end.  I wound one segment with 80' of 26 gauge wire.  When I went to test it, I found that my 9 volt battery was dead!  #%!&^$...very frustrating.  I'll have to get a battery and test it Saturday, will post the results then.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 07, 2008, 10:49:31 AM
The welding wire idea was just a new/odd idea I thought I'd share - thinking it's probably not a real solution.

Glad you got your ferrite - looking forward to your results! Odd it is 2 pieces - hopefully they are even a better size now to work with.

I ordered mine from where I did because I didn't want that plastic tubing, wanted different sizes, was cheaper, and quicker delivery.  It should be here tommorrow  8)

What are your winding dimensions?
How are you going to test?  1 or 2 "D" batteries (1.5v or 3v) may be easier for testing than 9v?

The "strength" tests I've done are holding strength - as in a traction style EM.  It should be relative to an airgap EM.  They have been geared towards wire size, winding depth and length, and power consumption. 
Using a 5/16" hex bolt as weight and adding nuts and washers to add/subtract to that weight to determine the holding power.  Then weighing it to determine ounces/lbs of pull.
It could also be expressed as: 5/16" x 4" hex bolt with 5 nuts and 3 washers.

Is this a testing method you will pursue?  What other options/methods have you considered?
Anyone else with comments?

The earlier tests were add hock - and I didn't take adequte notes.

Once I get the ferrite - I will perform the above method with various cores and windings and post results.

Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 07, 2008, 01:39:28 PM
Hey capthook,

Ah, great idea. I like your random way of thinking. A side-effect with this idea is that you reduce the capacity between the windings as well. Some time ago member pese was speaking of a transformer-design
build in germany in the 50 ´s or 60 ´s. They used only iron-wire-windings and by this there was no need of a core because the permeability was built in - so to say.  Of course this design had heat-losses. But it would be intersting to rebouild such a transformer.

Another thing I found some time ago - and I was not sucessfull to find it in my files - but I rememer this :

They said - and this was backed by calculation and tests - that once a load ( weight ) drawn to the coil-core-surface and has come to rest and is in close contact - you can reduce the current to a certain percentage to hold it in place.
So you can try this with your test-rig you already have.

There is another effect where you could combine magnetic-attraction with electrostatic-attraction-forces to hold a load-weight in place if this is needed.By  this combination you can switch off your electromagnet and only have a few miliamps at 200 Volt DC left to to hold the load in place.
It is called Johnson-Rahbeck-Effect ( dicovered in 1920 ) I only have a german description and will provide this here but it will take some time as I have to scan this from an  old german physics-book ( 1940)  and translate it for you.

In the meanwile you can try to find it via different search-engines. One of my favorites is this one here :

http://clusty.com/search?input-form=clusty-simple&v%3Asources=webplus&query= (http://clusty.com/search?input-form=clusty-simple&v%3Asources=webplus&query=)

Best Regards

Kator01

Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 08, 2008, 07:23:11 AM
The welding wire idea was just a new/odd idea I thought I'd share - thinking it's probably not a real solution.

Glad you got your ferrite - looking forward to your results! Odd it is 2 pieces - hopefully they are even a better size now to work with.

I ordered mine from where I did because I didn't want that plastic tubing, wanted different sizes, was cheaper, and quicker delivery.  It should be here tommorrow  8)

What are your winding dimensions?
How are you going to test?  1 or 2 "D" batteries (1.5v or 3v) may be easier for testing than 9v?

The "strength" tests I've done are holding strength - as in a traction style EM.  It should be relative to an airgap EM.  They have been geared towards wire size, winding depth and length, and power consumption. 
Using a 5/16" hex bolt as weight and adding nuts and washers to add/subtract to that weight to determine the holding power.  Then weighing it to determine ounces/lbs of pull.
It could also be expressed as: 5/16" x 4" hex bolt with 5 nuts and 3 washers.

Is this a testing method you will pursue?  What other options/methods have you considered?
Anyone else with comments?

The earlier tests were add hock - and I didn't take adequte notes.

Once I get the ferrite - I will perform the above method with various cores and windings and post results.



You're wise to avoid the plastic coated ferrite, a real pain in the neck to remove the plastic, LOL!

Winding dimensions are 80 feet of 26 guage wire which is approximately 300 turns at 4 ohms resistance, 2 layers.  I'm testing with a 9V battery, I can use alligator clip jumper wires, connect one clip to the wire, the other clip to the battery terminal.

My test method consists of an eye bolt approximately 1/2 inch diameter with a nut threaded flush on the end giving an approximate surface diameter of 1 inch.  The eye on the other end is a ring of metal, I place an S hook on it and attach a bucket to the S hook.  While the EM is energized I pour water into the bucket until it breaks loose and falls.  Then I weigh the bucket with water and the hardware(eye bolt and S hook) for pounds of force.  I then multiply that number by 4.4 to obtain the force in Newtons.

BTW, Stormwise advertises their rods as easy to wind wire on the plastic, while keeping the ferrite weather proof.  However, no magnetic field is set up if you try it that way.  Sounds like deceptive advertising to me.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 08, 2008, 08:39:07 PM
@ CapnHook

No luck with the Ferrite.  A 3 inch core wound with 300 turns of wire and 1.5 amperes yielded 1/10th of a pound of force.  Essentially useless.  I'm going to query some manufacturers for some electric steel samples.  Hope I have better luck, next time.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 08, 2008, 09:27:14 PM
Your weight/pull testing idea is a good one.  It's much easier and more accurate to pour water than my method with the nuts and washers.  It's time consuming to add some nuts, then remove a nut, add some washers, etc..
Thanks!!

No luck with the Ferrite. 

What?!!?  Really?  DAMN!  It SEEMS it would make a great core.  I have a little piece laying around, and when I attach a magnet (large or small), the flux pours right through it like it was the magnet itself.

............................... :'(

once a load ( weight ) drawn to the coil-core-surface and has come to rest and is in close contact - you can reduce the current to a certain percentage to hold it in place.
Good point. The effect of an air-gap is almost exponential.  So the smaller the airgap, the flux is x2.  A close approximation is: half the pull for every 1/8" increase of airgap.
However - I wouldn't know how to design a circuit/process for automatically/accurately  adjusting the power draw to take advantage of this effect.  And in real time - it happens very quickly!
Or how to apply it to a (short) pulse/repulsion style EM.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 08, 2008, 09:44:11 PM
Your weight/pull testing idea is a good one.  It's much easier and more accurate to pour water than my method with the nuts and washers.  It's time consuming to add some nuts, then remove a nut, add some washers, etc..
Thanks!!

What?!!?  Really?  DAMN!  It SEEMS it would make a great core.  I have a little piece laying around, and when I attach a magnet (large or small), the flux pours right through it like it was the magnet itself.

............................... :'(
Good point. The effect of an air-gap is almost exponential.  So the smaller the airgap, the flux is x2.  A close approximation is: half the pull for every 1/8" increase of airgap.  Of course it depends on the strength of the flux to begin with and the material being affected.

However - I wouldn't know how to design an circuit/process for automatically/accurately  adjusting the power draw to take advantage of this effect.  And in real time - it happens very quickly!
Or how to apply it to a pulse/repulsion style EM.

That small piece of ferrite you have, is it soft or hard?  The one that I ordered is soft.  Is the one you have already magnetized?  Could be I have a defective core.  Perhaps you'll have better luck with the Amidon material.    If you do I might try some.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 08, 2008, 09:46:43 PM
It is "soft" - non-magnetized. As is the ferrite I ordered (guess it will be here Monday).
And when you remove the magnet - it loses it's magnetisim right away - no remenance.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 08, 2008, 11:00:04 PM
Amp turns per watt:

Some time ago I ran some numbers to try to find the "efficiency" of an EM winding.  How to get the most AT (ampturns) per watt.

I used the awesome coil calculator to determine wire length, # turns and ohms at:
http://www.coilgun.info/mark2/inductorsim.htm

The attached picture is of an excel spreadsheet showing these.
I'll run some more in the near future - and post the thing as a .pdf (I hate downloading an unknown .xls)

This is a winding comparison using the same winding length - 1.5" (not wire length) and core.  The actual gauss/tesla would depend on the permeability/width of the core?

Note the appreciable difference between the 1st and 2nd winds.  #2 is MUCH more efficient!

Comments?  Additional math to apply? etc?

Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 09, 2008, 01:36:34 AM
Hy capthook,

tedious work, really. I now would take double the length 740 ft ( not double the AT) of this #2 calculation and make two seperate coils a 370 ft and put these two coils in parrallel. Now you have the same input-wattage and much more Tesla.

I have to think about optimization based on your excel-data.

good work

Rgards

Kator

Title: Re: Winding a strong electromagnet
Post by: hoptoad on November 09, 2008, 05:09:39 AM
This is a little off topic (sorry), but, if you are not an electromagnet purest, and you don't mind the idea of utilizing permanent magnets to aid the electromagnets in their specific task, then you may try to incorporate one of NASA's early space exploration ideas:

visit this link: http://www.cheniere.org/misc/astroboots.htm

Cheers from Hoptoad.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 09, 2008, 08:42:21 AM
It is "soft" - non-magnetized. As is the ferrite I ordered (guess it will be here Monday).
And when you remove the magnet - it loses it's magnetisim right away - no remenance.

Yeah, the ferrite I have reacts to a permanent magnet positively, that is it is attracted to it, and no remanence.  Very little EM abiltiy however.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 09, 2008, 09:38:51 AM
Amp turns per watt:

Some time ago I ran some numbers to try to find the "efficiency" of an EM winding.  How to get the most AT (ampturns) per watt.

I used the awesome coil calculator to determine wire length, # turns and ohms at:
http://www.coilgun.info/mark2/inductorsim.htm

The attached picture is of an excel spreadsheet showing these.
I'll run some more in the near future - and post the thing as a .pdf (I hate downloading an unknown .xls)

This is a winding comparison using the same winding length - 1.5" (not wire length) and core.  The actual gauss/tesla would depend on the permeability/width of the core?

Note the appreciable difference between the 1st and 2nd winds.  #2 is MUCH more efficient!

Comments?  Additional math to apply? etc?



Sorry, I can't seem to make the coilgun calculator work.   I don't know what the problem is.  A few observations on the excel spreadsheet, for a 1/2 inch diameter bolt the number of turns for 125 feet should be approximately 960.  Also, 10000 gauss = 1 Tesla, therefore .1T should be 1000 gauss. 

Gauss/Tesla is a function of H (magnetic field strength, Ampere-turns/meter) multiplied by permeability.  The width of the core determines the cross-sectional area which determines the amount of flux, a wider core produces more flux.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 09, 2008, 10:33:32 AM
I now would take double the length 740 ft ( not double the AT) of this #2 calculation and make two separate coils a 370 ft and put these two coils in parallel. Now you have the same input-wattage and much more Tesla.

Kator

Interesting idea.  I'm not sure how to figure what the possible boost might be.  Is it something like:
The amps is half - but you are now influencing two cores - so the relative boost of each core is 50%, but you now have two cores influenced so you might see a total increase of 25% because you now have 2 magnets and are at the low end of permeability curve for each?  Not sure how to state what I'm thinking.  Could you explain your thinking a little more?

- -
Hoptoad!  Thanks for the link!  I've seen some stuff here and Utube that shows something similar to the effect in that link.  Can't remember the threads or links or titles etc.  Interesting idea to ponder.....

- -
Xaverius: yea - guess I spaced on the Gauss=Tesla conversion - used 1,000 instead of 10,000  :-[

Gauss/Tesla is a function of H (magnetic field strength, Ampere-turns/meter) multiplied by permeability.  The width of the core determines the cross-sectional area which determines the amount of flux, a wider core produces more flux.

The actual gauss/tesla would depend on the permeability/width of the core

Yes - the Gauss listed is just a reference point - and for an absolute - would in fact be dependant on core permeability/width.  I guess a grade 2 hex bolt is somewhere in the range of 50-100u. I could convert the AT to AT/meter (show me please) and I could (throw a dart at the wall and) pick a number between 50-100 for a multiplier.  ;)  100 it is! (of course the goal is what - 2,000u electrical steel?)(and how does the permeability curve affect the calculations? Isn't 1/2 watt going to be way different than 10 watts?)(and which permeablity figure would you use? A materials specs is listed as intial, max, or the other one (can't remember it))
Now you see why it's listed as relative - you are the math guy  :)
The calculation I gave in the chart was a simplied one presented by a reed switch manufacturer as a way to give an approximation for AT/gauss conversion needed to activate the switch.
So in line 1 of the chart - please show me the calculation for converting 298 AT to the projected gauss. (tx)

I re-checked the # of turns for 125' ( I'm assuming you are ref. line 1 - the 22AWG).
Same result (actually 616 instead of 620)

1" = 25.4 mm
1' = .3048 m

1. Choose wire size: 22
2. input inner dimension (1/2" core): .5" x 25.4mm = 13mm
3. input coil length: 1.5" x 25.4 = 38mm
4. convert 125' to meters = 125 x .3048 = 38m
5. adjust the outer dimension slider until the wire length line shows about 38m wire length
6. observe: # turns, # of layers, resistance, and coil outer dimensions etc.

Title: Re: Winding a strong electromagnet
Post by: capthook on November 09, 2008, 11:41:12 AM
X - I maybe misunderstood you comment of can't get coil calculator to work?  It doesn't load?

It is a java applet - you may need to update your java.  The website says this:

"This program requires Java Runtime Environment (JRE) 1.4 or above. Please visit www.java.com/en/download/index.jsp to download and install the JRE."
Title: Re: Winding a strong electromagnet
Post by: i_ron on November 09, 2008, 05:23:26 PM
X - I maybe misunderstood you comment of can't get coil calculator to work?  It doesn't load?

It is a java applet - you may need to update your java.  The website says this:

"This program requires Java Runtime Environment (JRE) 1.4 or above. Please visit www.java.com/en/download/index.jsp to download and install the JRE."

The applet is very handy, well worth the trouble.... but... installing java also installs the Yahoo tool bar!
in Firefox go to "tools", "add-ons" and delete this screen waster, if you so desire... lol

Ron
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 09, 2008, 07:32:01 PM
Capthook,

no, no two cores. Your calculation was triggering my mind of just combining what was said earlier - by xaverius reply # 22 - you wind one coil on one core,  but you first wind 370 ft on the core than take another sperate 370 ft and wind this above the first coil. Now you connect both the beginnings and endings of each coil. Now you have these two cores in parallel . But this would not double the AT, so forget this idea. It is just a means of reducing the resistance and inductance.You are right , it only will make sense if it is put on two seperate cores.  I was mistaken - sorry - too long computer-sessions until early in the morning.

Regards

Kator01
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 09, 2008, 07:40:56 PM
Interesting idea.  I'm not sure how to figure what the possible boost might be.  Is it something like:
The amps is half - but you are now influencing two cores - so the relative boost of each core is 50%, but you now have two cores influenced so you might see a total increase of 25% because you now have 2 magnets and are at the low end of permeability curve for each?  Not sure how to state what I'm thinking.  Could you explain your thinking a little more?

- -
Hoptoad!  Thanks for the link!  I've seen some stuff here and Utube that shows something similar to the effect in that link.  Can't remember the threads or links or titles etc.  Interesting idea to ponder.....

- -
Xaverius: yea - guess I spaced on the Gauss=Tesla conversion - used 1,000 instead of 10,000  :-[

Yes - the Gauss listed is just a reference point - and for an absolute - would in fact be dependant on core permeability/width.  I guess a grade 2 hex bolt is somewhere in the range of 50-100u. I could convert the AT to AT/meter (show me please) and I could (throw a dart at the wall and) pick a number between 50-100 for a multiplier.  ;)  100 it is! (of course the goal is what - 2,000u electrical steel?)(and how does the permeability curve affect the calculations? Isn't 1/2 watt going to be way different than 10 watts?)(and which permeablity figure would you use? A materials specs is listed as intial, max, or the other one (can't remember it))
Now you see why it's listed as relative - you are the math guy  :)
The calculation I gave in the chart was a simplied one presented by a reed switch manufacturer as a way to give an approximation for AT/gauss conversion needed to activate the switch.
So in line 1 of the chart - please show me the calculation for converting 298 AT to the projected gauss. (tx)

I re-checked the # of turns for 125' ( I'm assuming you are ref. line 1 - the 22AWG).
Same result (actually 616 instead of 620)

1" = 25.4 mm
1' = .3048 m

1. Choose wire size: 22
2. input inner dimension (1/2" core): .5" x 25.4mm = 13mm
3. input coil length: 1.5" x 25.4 = 38mm
4. convert 125' to meters = 125 x .3048 = 38m
5. adjust the outer dimension slider until the wire length line shows about 38m wire length
6. observe: # turns, # of layers, resistance, and coil outer dimensions etc.



If you use two cores and wire them in parallel (360 turns each?) you will effectively use the SAME voltage but DOUBLE the amperage which will increase your consumed wattage X 2.  However you will DOUBLE the flux which will QUADRUPLE  the amount of magnetic FORCE.

AT/m: Your winding is 1.5 inches.  1.5/39(inches per meter)=.0384 meters.  If you have 360AT/1.5inches(.0384m) then H(magnetic field strength)=9375 AT/m.

Generally, the higher the wattage, the higher amperage at a steady voltage and therefore higher magnetic field strength until saturation.  The permability curve does not affect the wattage calculations, it's the other way around.  Also, I personally would use the initial permeabilty because you know that is what the minimum is, in other words the permeability will not fall below that number.  If a device will work with the initial permeability then it must work with the maximum.

Line 1 of the chart: converting 298AT to gauss:  given the length of the windings, 1.5 inches(.0384m) then H=298/.0384=7760 AT/m.  u @ 50=.00006282 for a hardware bolt, u @ 2000=.0025 for electrical steel, 7760 X .00006282=.487 Tesla/4875 gauss for  hardware bolt, 7760 X .0025=19.4 Tesla/194,000 gauss for electrical steel.  Of course electrical steel saturates at 1-1.5 Tesla so you would never reach that amount.

If you have 125 feet of wire and your bolt is .5 inches diameter then for one turn of wire, .5 x pi(3.1416)=1.57 inches/turn, which is 7.64 turns/foot.  7.64 x 125=955 turns.  Hope this helps, please let me know if I've made any errors.
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 09, 2008, 07:49:48 PM
capthook,

another possibility here are special multi-layer-wires for fast impuls-switching :

Pay attention to the rectangular forms. This would be the optimum for the space used around the core :

http://www.pack-feindraehte.de/en/products/litzwire/litz_wires.html (http://www.pack-feindraehte.de/en/products/litzwire/litz_wires.html)

I was not able up until now to find an american company with my search-enginge. This is a german manufacturer.But it will give you the idea.

Not cheap - for sure

Regards

Kator01

Title: Re: Winding a strong electromagnet
Post by: capthook on November 09, 2008, 09:35:29 PM
Line 1 of the chart: converting 298AT to gauss:  given the length of the windings, 1.5 inches(.0384m) then H=298/.0384=7760 AT/m.  u @ 50=.00006282 for a hardware bolt, u @ 2000=.0025 for electrical steel, 7760 X .00006282=.487 Tesla/4875 gauss for  hardware bolt, 7760 X .0025=19.4 Tesla/194,000 gauss for electrical steel.  Of course electrical steel saturates at 1-1.5 Tesla so you would never reach that amount.

If you have 125 feet of wire and your bolt is .5 inches diameter then for one turn of wire, .5 x pi(3.1416)=1.57 inches/turn, which is 7.64 turns/foot.  7.64 x 125=955 turns.  Hope this helps, please let me know if I've made any errors.

Xaverius - thanks for the calculations!!! Learning the math behind the function is of great value.

How did you figure this?  "u @ 50=.00006282"
And will 620 turns (298AT - consuming .5 watts power) on electrical steel produce (theoretically) 19.4T?  This seem excessively massive?  So one could greatly reduce the power below the already tiny .5 watt to achieve 1.9T?  And where is the width of the core/cross section taken into account?  Something doesn't seem to compute.

In the # turns calculation - you haven't accounted for wire size.  The larger the wire, the more feet of winding will be consumed per turn as the layers (and thus diameter) increase. (11 layers in the case of line 1)

Did you get the coil calculator working?
(and the yahoo toolbar install isn't from the java site, it just updates/installs your java
 i_ron you might have downloaded elsewhere?)
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 09, 2008, 10:19:59 PM
Xaverius - thanks for the calculations!!! Learning the math behind the function is of great value.

How did you figure this?  "u @ 50=.00006282"
And will 620 turns (298AT - consuming .5 watts power) on electrical steel produce (theoretically) 19.4T?  This seem excessively massive?  So one could greatly reduce the power below the already tiny .5 watt to achieve 1.9T?  And where is the width of the core/cross section taken into account?  Something doesn't seem to compute.

In the # turns calculation - you haven't accounted for wire size.  The larger the wire, the more feet of winding will be consumed per turn as the layers (and thus diameter) increase. (11 layers in the case of line 1)

Did you get the coil calculator working?
(and the yahoo toolbar install isn't from the java site, it just updates/installs your java
 i_ron you might have downloaded elsewhere?)


Hi CapNHook, glad to help out.  I tried to get Java to update last night but it wouldn't save to my browser, I'll have to toy with it later.

u=4 x pi(3.1416) x 10 x ^-7=.000001257 permeablity of air/vacuum

ur=relative permeability of other materials

ur of hardware iron= 50 x(4 x pi(3.1416) x 10 x ^-7)=.00006282

ur of electrical steel=2000 x(4 x pi(3.1416) x 10 x ^-7)=.0025

620 turns at 298AT consumes, I believe you mean .5 amperes(not watts).  Yes, theoretically it would reach approximately 19 Tesla but this is impossible because electrical steel saturates around 1.5 Tesla.  In a word, your AT is overkill, yes you could use less amperage.

The width of the core/cross section has to do with the amount of magnetic flux(webers).  The wider, the more flux.  I'm not sure of your exact application but I am working on a motor/generator and I need to produce as much flux as possible, to produce as much magnetic FORCE as possible to drive the rotor into overunity.  That is why I am using a 1 inch diameter EM, larger surface area(cross section) produces more flux, thus more force.

The number of feet of turn is the same per wire size, but you're right, the larger the gauge the more number of layers you would require.

Hope this helps, keep those cards and letters coming!
Title: Re: Winding a strong electromagnet
Post by: capthook on November 10, 2008, 12:28:14 PM
X - u da man!

When it comes to math - often I'll skim through it to get to the conclusions/summary at the end.

Having it translated into English is most excellent.
(I sucked at Spanish - and that's really what math is - another language.  A useable translation means an increase in the ability to 'speak' and understand it)

 :)

And yes - (line 1) .5 watt: 1.12V x .48A = .54 watts.  That's the thing - seems crazy strong for so little juice. Still seems something is out of wack?
Holding test resulted in: 3/4 lb. calculated Gauss: 4875
3/4" x 1/4" N42: 18 lb (stated spec - not tested) Gauss: 13,200
So the offered calculation would seem to imply a stronger holding force than the observed 3/4 lb?
(edit: then again, there is a difference is surface area 1/2" EM core vs. the neos 3/4"... and?)

As to application - I'm pulsing the EM in repulsion against a PM over a small airgap.
However - texts state attraction forces are stronger than repulsion.  The flux gets 'squeezed out the sides' in repulsion.  Just some side-thinking on the maybes.....
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 11, 2008, 06:04:12 AM
X - u da man!

When it comes to math - often I'll skim through it to get to the conclusions/summary at the end.

Having it translated into English is most excellent.
(I sucked at Spanish - and that's really what math is - another language.  A useable translation means an increase in the ability to 'speak' and understand it)

 :)

And yes - (line 1) .5 watt: 1.12V x .48A = .54 watts.  That's the thing - seems crazy strong for so little juice. Still seems something is out of wack?
Holding test resulted in: 3/4 lb. calculated Gauss: 4875
3/4" x 1/4" N42: 18 lb (stated spec - not tested) Gauss: 13,200
So the offered calculation would seem to imply a stronger holding force than the observed 3/4 lb?
(edit: then again, there is a difference is surface area 1/2" EM core vs. the neos 3/4"... and?)

As to application - I'm pulsing the EM in repulsion against a PM over a small airgap.
However - texts state attraction forces are stronger than repulsion.  The flux gets 'squeezed out the sides' in repulsion.  Just some side-thinking on the maybes.....

Hi, yes, attraction is more efficient and it keeps the permanent magnet from degaussing, which is a hazard of repulsion.

Yes, it is a strong attraction for a small amount of electricity but the key is the number of turns and the permeability.

For the N42 with a surface area of 3/4"  I calculated 58 pounds, and for 1/4" it was 6 pounds.  From my understanding the permanent magnets don't always have the apparent pulling power because of geometric constraints, such as shapes and sizes of attractants.

For the EM I calculated 3.5 pounds.  Are you using ferrite?  Something is wrong with the parameters, did you obtain the 4800 gauss figure from the chart?  Needs more investigation.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 13, 2008, 12:24:26 AM
Got my ferrite rods - will do some testing next few days....

- - -
Magnetic Design Formula (math stuff someone might find useful - it's all Latin to me  ;) )

--------------------------------------------------------------------------------
Voltage-Flux Density-Frequency (Faraday's Law).
Flux density must be determined to assure proper operating level. The level of flux density changes the value of Rac, the core loss resistance, and has an effect on the permeability as shown below. Flux density can be calculated from:
Bmax=[(Erms * 108)/(4.44*A*N*f) ]
   (4.44 for sine wave, 4.0 for square wave) where:
Bmax=Maximum flux (gauss) density
Erms=equivalent rms voltage across coil
N=number of turns
A=core cross section (cm2)
f=frequency (hertz)
 

--------------------------------------------------------------------------------
Ampere's Law
Ampere's Law relates magnetizing force to peak current, number of turns and mean magnetic path length. H=(0.4*pi* N*I)/l  where:
H=magnetizing force (oersteds)
N=number of turns
I=peak current (amperes)
l=mean magnetic path (cm) 
The magnetizing force determines the estimate of flux density using the normal magnetization (B/H) curves. The relative permeability at that magnetizing force can then be determined by:
µ=B/H  where:
µ=relative permeability
B=flux density (gauss)
H=magnetizing force (oersteds) 

--------------------------------------------------------------------------------
Inductance Considerations
The inductance of a wound core can be calculated from the core geometry using the following formula: L=(0.4*pi*µ*N2*A*10-8)/l where:
L=inductance (henries)
µ=core permeability
N=number of turns
A=core across section (cm2)
l=magnetic path length(cm) 

AL is the Inductance Factor of a core, and is expressed as nH/turn2 (or mH/1000 turns).
L(nH) = N2 * AL
where:
L = inductance in nH for N turns
AL = core inductance factor
--------------------------------------------------------------------------------
Magnetic Formula Conversions
The following table lists conversion factors for magnetic units.
oersteds * 0.795 = amp-turns/cm
gauss * 0.0001 = tesla
mH/1000 turns * 10 = uH/100 turns
in2 * 6.425 = cm2
circ mils * 5.07 x 10-6 = cm2
watts/lb * 17.62 = mW/cm3
Title: Re: Winding a strong electromagnet
Post by: capthook on November 13, 2008, 02:35:11 AM
Well - ferrite sucks as an EM core........ >:(

Wound a quick coil - has like 1/4 the holding power of the hex bolt.

Guess that's why that make filters out of the stuff - it's high permeability sucks up flux great - and doesn't transmit it well?

Oh well - only cost me $20.........

Maybe I'll see if I can get some electrical steel from a junkyard - an old car alternator or microwave or something this weekend.  (actually - I have a junk riding mower - maybe it's got something)

- - -

As to the discrepancy of the holding power of line 1 in the chart - turns out I was testing the hold on a much smaller coil - 40' of #22 - not 125'...... DOH  ::)
Title: Re: Winding a strong electromagnet
Post by: capthook on November 13, 2008, 03:55:50 AM
May have finally found a US supplier for premium EM core material:
"CMI specializes in ultra low carbon electromagnetic iron, not merely low carbon steel."

http://www.cmispecialty.com/products.cfm

"CMI-C Magnetic Core Iron Cold Drawn Rod and Bar per ASTM A-848-01
Diameters:  .2500, .3125, .3750, .4375, .5000, .5620, .6875, .7500, .8750, 1.000, 1.250, 1.500, 1.750, 2.000, 2.250, 2.500, 2.750, 3.000, 3.250, 4.125, 4.500,  6.000"

"PRODUCT DESCRIPTION
CMI-C Electromagnetic Iron Rod is specially processed with a critical strain for optimum uniformity. Maximum magnetic properties are achieved following suggested final anneal applied to fabricated parts.

• BENEFITS
Hi-permeability, low coercivity. Low loss provides highest force/watt input."

Will call tommorrow for prices etc......sounds expensive and like it comes in 6' sections min.
Title: Re: Winding a strong electromagnet
Post by: Freezer on November 13, 2008, 04:46:53 AM
Perhaps someone could try a pyramid type electromagnet coil design.  See the video for an explanation.

http://www.youtube.com/watch?v=tR_8f0DYK5s&feature=related
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 13, 2008, 07:50:29 PM
Well - ferrite sucks as an EM core........ >:(

Wound a quick coil - has like 1/4 the holding power of the hex bolt.

Guess that's why that make filters out of the stuff - it's high permeability sucks up flux great - and doesn't transmit it well?

Oh well - only cost me $20.........

Maybe I'll see if I can get some electrical steel from a junkyard - an old car alternator or microwave or something this weekend.  (actually - I have a junk riding mower - maybe it's got something)

- - -

As to the discrepancy of the holding power of line 1 in the chart - turns out I was testing the hold on a much smaller coil - 40' of #22 - not 125'...... DOH  ::)


Sorry about your results CapNhook, I lament the same effect, however I feel you have vindicated my effort, it isn't just me that thinks ferrite is a loser.  I think you're on to something, ferrite as well as GIron(which I've tried before, ur=100,000) absorbs lots of flux but does not transmit it.  Good observation

Please let me know how your salvage operation goes on used alternators, microwaves, etc.  That may be my next avenue.  Contacted ScientificAlloy.net the other day.  The technician told me at $100.00 minimum order I could obtain a two feet long/one inch diameter electrical steel rod.  The catch is, once I receive the material I will have to send it off to a foundry for heat treating/annealing which is what give it it's magnetic properties.  The material they have there is raw, untreated.  The heat process can easily cost another $100.00++

Oh well, I'm out $20.00 too, live and learn.  Keep on truckin', Rome wasn't built in a day!
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 13, 2008, 07:59:05 PM
May have finally found a US supplier for premium EM core material:
"CMI specializes in ultra low carbon electromagnetic iron, not merely low carbon steel."

http://www.cmispecialty.com/products.cfm

"CMI-C Magnetic Core Iron Cold Drawn Rod and Bar per ASTM A-848-01
Diameters:  .2500, .3125, .3750, .4375, .5000, .5620, .6875, .7500, .8750, 1.000, 1.250, 1.500, 1.750, 2.000, 2.250, 2.500, 2.750, 3.000, 3.250, 4.125, 4.500,  6.000"

"PRODUCT DESCRIPTION
CMI-C Electromagnetic Iron Rod is specially processed with a critical strain for optimum uniformity. Maximum magnetic properties are achieved following suggested final anneal applied to fabricated parts.

• BENEFITS
Hi-permeability, low coercivity. Low loss provides highest force/watt input."

Will call tommorrow for prices etc......sounds expensive and like it comes in 6' sections min.


Nice catch,  will investigate further.................
Title: Re: Winding a strong electromagnet
Post by: capthook on November 21, 2008, 10:03:18 AM
Update:

Sourcing EM core material is a PAIN in the A$$!!

Haven't had time for the junk yard or the visit to the University (going Sunday).......

Carpenter Steel offers some great (expensive) stuff and good info. 
This is a great read on core materials:
http://www.cartech.com/techarticles.aspx?id=1624
Sound like their Vacumet Core Iron or the Silicon Core Iron C would be EXCELLENT cores.
(if one could get a small quantity AND it was fully annealed  :-\ )
They only offer large orders directly and all the materials need further final annealing.
edfagan.com and frysteel.com were offered as small suppliers when I spoke to them, but they don't offer the premimum em core materials and still not annealed.
Frysteel: $30 per ft. plus $40 packing cost plus $9 per cut (1' to 6' rods) plus shipping
(maybe I'll call Carpenter Steel again........)

Surepure offers .5" x 1' rods of 99.9% iron at $96
http://www.surepure.com/products.php?ID=7&meas1_ID=41&subCat=23

CMI (from my last post: http://www.cmispecialty.com/index.cfm )
Their min. order is $250 (50 lbs) plus shipping (alot for 50 lbs.) and all their stuff then needs to be further annealed to realize it's full magnetic properties....... (yeeessh  >:( )
And getting them on the phone or their material spec. sheets is like pulling teeth!

I guess the visit to junkyard for some microwave laminations to hack apart is on the list for next week......
Title: Re: Winding a strong electromagnet
Post by: capthook on November 22, 2008, 02:51:52 AM
An EM core of the highest iron content (lowest carbon) available that is easily sourced and inexpensive should suffice (I'm thinking at this point)

1006 Steel:
Iron, Fe 99.43 - 99.75 %  
Carbon, C <= 0.0800
Manganese, Mn <= 0.450 %
Phosphorous, P <= 0.0400 %
Sulfur, S <= 0.0500 %

1018 Steel:  99% iron
1215 steel: 98.5% Iron

Even a small change in the % of iron content can make a large difference in permeability.

A great Material Properties Database:
http://www.matweb.com/index.aspx

And a great source for just about anything - but the only easy source I've found for 1006 steel:

http://www.mcmaster.com

1/2" x 36" 1006 steel rod: $10.07
(also in strips/sheet form to make laminations if desired)

Should be an improvement over a hex bolt anyway?

As to annealing - X, you mentioned annealing price of over $100 - where to find a resource?

What about blasting the material with a propane torch until it turns (as close as you can get to) red hot and then stick it in the oven for awhile?
Would this help 'anneal' it and improve it's magnetic/permeability properties?

?

Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 23, 2008, 08:42:10 AM
An EM core of the highest iron content (lowest carbon) available that is easily sourced and inexpensive should suffice (I'm thinking at this point)

1006 Steel:
Iron, Fe 99.43 - 99.75 %  
Carbon, C <= 0.0800
Manganese, Mn <= 0.450 %
Phosphorous, P <= 0.0400 %
Sulfur, S <= 0.0500 %

1018 Steel:  99% iron
1215 steel: 98.5% Iron

Even a small change in the % of iron content can make a large difference in permeability.

A great Material Properties Database:
http://www.matweb.com/index.aspx

And a great source for just about anything - but the only easy source I've found for 1006 steel:

http://www.mcmaster.com

1/2" x 36" 1006 steel rod: $10.07
(also in strips/sheet form to make laminations if desired)

Should be an improvement over a hex bolt anyway?

As to annealing - X, you mentioned annealing price of over $100 - where to find a resource?

What about blasting the material with a propane torch until it turns (as close as you can get to) red hot and then stick it in the oven for awhile?
Would this help 'anneal' it and improve it's magnetic/permeability properties?

?



Pain in the A$$?!?  You're right, I've been there too.  Seems your steel source ideas have some merit.  I'll be checking into some of these materials.

I've never really inquired as to who/where to get annealing done, although I'm sure a search would suffice.   As I am a physicist and not a metallurgist, I cannot tell you if a propane torch would provide the needed annealing.  Some annealing techniques require a hydrogen atmosphere to be effective, also.  You would have to know what temperature propane burns at and also the amount of time for heat exposure, and if the material should be cooled slowly or quenched.(cooled rapidly).  This is an area that needs further research.  If I find out anything I will pass it along.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 23, 2008, 08:49:26 AM
@ CapNhook,

      please let me know how your salvage operation goes, that is where you find junk and how you dissect the metal.

Another avenue is motor/generator components.  I contacted a local motor rebuilder.  He had no parts in stock.  He said to contact the manufacturer directly, that's what he does.  It is possible to obtain pole pieces, they are used for salient rotors and stators.  I did a search from several manufacturers including GE.  Their site is so damn big it's like looking for a needle in a haystack.  Any parts you find should list a data sheet with dimensions, core material, heat resistance, etc.  So far I haven't found anything, but I'll keep looking, it seems the manufacturers don't list their product components.........
Title: Re: Winding a strong electromagnet
Post by: capthook on November 24, 2008, 07:12:23 AM
Attached are useful (and hard to find) material B/H curve comparisons and some annealing data.........
Title: Re: Winding a strong electromagnet
Post by: capthook on November 24, 2008, 10:35:30 PM
Xaverius-
I have ordered some 1006 steel and am proceeding that route for now.
I'm thinking that is going to improve performance significantly over a hex bolt and is the best material when considering ease of sourcing and cost.
(An upgrade to 99.99% iron fully annealed to 1700 deg. F in hydrogen atmosphere would be my next choice: $$$ )

Ways to source scrap laminated electrical steel:

Old microwave: http://www.overunity.com/index.php?topic=4047.msg101636#msg101636
(step by step pictorial)

"You can also get good laminations from junked alternators." wattsup

- - - -

And I've been doing some thinking on your "2-in-hand" winding of an EM to reduce resistance and thereby increase amps and AT.  But......

(if) The goal is the most AT/watt.

Ex:

3/8" x 3" core
#24 AWG
Windings 1"OD x 1 7/8" L
10mm ID x 26mm OD x 48mm L

# turns: 1232   
Ohms: 5.87   
volts: 1.5
amps: 0.256   
watts: 0.383   
AT: 315

Now wind that 2-in-hand.  Each coil then equals:
# turns: 616
Ohms: 2.28
volts: 1.5
amps: 0.658
watts: .987
AT: 405

Add the 2 coils together you get:
ohms: 4.56
watts: 1.97
AT: 810

SO - results:

AT increased by 257%
Watts increased by 514%

A large increase in power for a relatively smaller increase in AT

If AT/watt is not the criteria, but instead is maximum AT for a given coil size/dimensions, the 2-in-hand would be the way to go.

However, if AT/watt IS the criteria, then 2-in-hand is less efficient.

Yes?
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 25, 2008, 05:23:08 AM
CapnHook, good luck with your 1006.  That seems to be a viable way to go.  I would order some from McMasterCarr, myself, but the largest diameter is .5 inch and I need 1 inch.  I'm looking at 1018 now from MSC, lower ur but 1 inch diameter.

I'll check the microwave scrap link.  I guess I would have to look for some used alternators and microwaves.

Actually two coils wired in parallel would have lower total resistance that  would be less than the lesser resistance of the two.  In your example, wind another coil with the 1232 turns, fasten them in parallel, the total resistance is now 5.87x5.87/5.87+5.87=2.9 ohms.

1.5/2.9=.51 Amperes......   .51x1.5=.76 Watts   1232x2=2464   2464x.51=1256AT

1256AT/.76Watts=1653AT/Watt

When you REDUCE
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 25, 2008, 05:34:28 AM
.......(continued).......the TOTAL RESISTANCE, then the AMPERAGE will INCREASE which will INCREASE the TOTAL AMPERE-TURNS.  If the VOLTAGE remains the SAME, then the TOTAL WATTAGE will INCREASE.

I believe in your first application: 315AT/.383 watts=822AT/watt

1653/822=200% gain


Please let me know if this makes sense with your application.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 25, 2008, 07:00:26 AM
X -
The 1215 steel (.09%C) is going to have a lower carbon content than the 1018 (.18%C) and thus a higher permeability.  McMaster-Carr has it in diameters up to 4".  The 1215 is comparable to 1010.

"Actually two coils wired in parallel would have lower total resistance that  would be less than the lesser resistance of the two.  In your example, wind another coil with the 1232 turns, fasten them in parallel, the total resistance is now 5.87x5.87/5.87+5.87=2.9 ohms."

(?)  How do you conclude 2.9ohms?
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 26, 2008, 12:53:07 AM
Hi capthook
As I recall your quote here :

Quote
As to application - I'm pulsing the EM in repulsion against a PM over a small airgap.

Are you working on a Adams-Motor-design ?

If so have you ever had a closer look at what Thane Heins is doing ?
http://www.overunity.com/index.php?topic=4047.3600 (http://www.overunity.com/index.php?topic=4047.3600)

There is an important paper of an engineer by name of Dixon on eddy-current in different coil-design.

http://focus.ti.com/lit/ml/slup197/slup197.pdf (http://focus.ti.com/lit/ml/slup197/slup197.pdf)

The subject of Peripiteia a a delayed Lenz-action on a prime-mover so the p-m is accellerated unter load.
A must-read.

Regards

Kator01

Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 26, 2008, 06:45:55 AM
X -
The 1215 steel (.09%C) is going to have a lower carbon content than the 1018 (.18%C) and thus a higher permeability.  McMaster-Carr has it in diameters up to 4".  The 1215 is comparable to 1010.

"Actually two coils wired in parallel would have lower total resistance that  would be less than the lesser resistance of the two.  In your example, wind another coil with the 1232 turns, fasten them in parallel, the total resistance is now 5.87x5.87/5.87+5.87=2.9 ohms."

(?)  How do you conclude 2.9ohms?

Thanx for the data on 1215, I'll look into it further.

The formula for parallel circuit resistance is 1 divided by 1/r1+1/r2.  The resistance that you gave is 5.87ohms therefore 1 divided by 1/5.87+1/5.87=2.93 ohms..................
Title: Re: Winding a strong electromagnet
Post by: capthook on November 26, 2008, 11:30:09 AM
AT/m: Your winding is 1.5 inches.  1.5/39(inches per meter)=.0384 meters.  If you have 360AT/1.5inches(.0384m) then H(magnetic field strength)=9375 AT/m.

Line 1 of the chart: converting 298AT to gauss:  given the length of the windings, 1.5 inches(.0384m) then H=298/.0384=7760 AT/m.  u @ 50=.00006282 for a hardware bolt, u @ 2000=.0025 for electrical steel, 7760 X .00006282=.487 Tesla/4875 gauss for  hardware bolt, 7760 X .0025=19.4 Tesla/194,000 gauss for electrical steel.  Of course electrical steel saturates at 1-1.5 Tesla so you would never reach that amount.

Ok - think I know where things are screwed up?

Look at the B/H curves - the H is listed as Oersted or A/m (amperes/meter).  A/m is easier on my brain.
(1 oersted = 79.577 ampere/meter btw)
HOWEVER - the calculations you gave earlier are using AT/m (ampturns/meter).
So one would need to use the AMPS in the circuit rather than the AT.
So NOT the 298 AT but the .48 amps in the circuit?

(1.12V x .48A  = .54W)

So the above SHOULD be:
H= .48/.0384 = 12.5 A/m
12.5 x .0025 = 0.03125 Tesla or 312.5 Gauss (for 2000u electrical steel)

This looks more like it as the tiny input shouldn't be able to generate the large Tesla of the earlier calculations.

(can anyone validate the above calculations please!)

- - -
Thanks for the clarification on the resistance - sorry to make you state it again as you had given that equation before (but this time used 5.87x5.87/5.87+5.87=2.9 ohms ?algebra?). 
It's just hard for me to make "real-world sense" of it.  It's like saying split 1 gallon of gas that weights 2lbs into 2 separate gas tanks and now the gas weighs .25 lbs!

You have renewed my interest in pursing this approach!!  ;D  (+200% !!)
- - -

Kator - yes, working on an Adams motor type project.  Thanks for the links.
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 26, 2008, 12:36:56 PM
Hey Capthook,

it is of  importance to understand this Dixon-Paper. Here it is explained how eddy-currents build up in High-Voltage-Coil ( these hV-Coils are used in Thanes coil-setup in combination with high-current-coils the ones you have in mind ) because Thane is demontrating in many videos that it is possible by combining the two coil-types to cause a delay in the Kick-Back-Force ( drag ) while the high-current-coil is under load.
This leads to a phase-shift of the magnetic kick-back-force right at the moment the driver-magnet is retreating from the coil-setup thus giving it an additional kick ( in the ass so to say ). Just watch the videos an ask him. He is very helpful but also excentic in his answers at times.

If you ever decide to change your concept and adapt your coil-design to Peripiteia-Standard I am almost sure you will end up with an new self-accellerating Adams-Motor.


Regards

Kator01
Title: Re: Winding a strong electromagnet
Post by: capthook on November 27, 2008, 02:44:54 AM
So - the more I learn and the more equations I try to implement - the more confused I seem to get.
It seems the only REAL way (absent actually winding a bunch of them of course) to fully determine how an EM will perform is it model the interactions in FEMM.  As a newbie to FEMM - anyone have a pre-modeled EM FEMM file they want to share?

Or the best equation to use for a close approximation of EM performance?

- - -
As to the 2-in-hand winding of EM to reduce resistance and thus increase AT:

In a parrallel circuit - the amps are split.  In a series circuit, the volts are split.
So 2 windings in parrallel will reduce resistance by 50%.  But it will ALSO reduce the AMPS to each wire by 50%. 
So it seems like its all the same relative?
1/2 the resistance but 1/2 the amps = the same total AT and thus EM strength in both methods??
 ???

Edit:
(hmmm - then again - since you have less TOTAL resistance, you have more TOTAL amps, so even if the amps are split in 2 wires, you still have more AT total because you still have more overall amps total - but not 200%?  And watts increases?  How does this then effect the AT/watt?
I think I need to turn off my cluttered brain for awhile........)
Title: Re: Winding a strong electromagnet
Post by: capthook on November 27, 2008, 05:15:27 AM
Attached in an excel spreadsheet you can download that I created with numerous equations to compare various EM variables. (*deleted*)

The idea is to 'simulate' various coil windings to determine things like AT, AT/w and 'm'.

Please offer any suggestions, corrections or comments!!
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 27, 2008, 09:03:39 AM
Ok - think I know where things are screwed up?

Look at the B/H curves - the H is listed as Oersted or A/m (amperes/meter).  A/m is easier on my brain.
(1 oersted = 79.577 ampere/meter btw)
HOWEVER - the calculations you gave earlier are using AT/m (ampturns/meter).
So one would need to use the AMPS in the circuit rather than the AT.
So NOT the 298 AT but the .48 amps in the circuit?

(1.12V x .48A  = .54W)

So the above SHOULD be:
H= .48/.0384 = 12.5 A/m
12.5 x .0025 = 0.03125 Tesla or 312.5 Gauss (for 2000u electrical steel)

This looks more like it as the tiny input shouldn't be able to generate the large Tesla of the earlier calculations.

(can anyone validate the above calculations please!)

- - -
Thanks for the clarification on the resistance - sorry to make you state it again as you had given that equation before (but this time used 5.87x5.87/5.87+5.87=2.9 ohms ?algebra?). 
It's just hard for me to make "real-world sense" of it.  It's like saying split 1 gallon of gas that weights 2lbs into 2 separate gas tanks and now the gas weighs .25 lbs!

You have renewed my interest in pursing this approach!!  ;D  (+200% !!)
- - -

Kator - yes, working on an Adams motor type project.  Thanks for the links.

Sorry for the confusion about parallel resistance.  Actually, if you have two parallel circuits then this formula applies:  R1xR2/R1+R2, if you have more than two parallel circuits, then you MUST use this formula: 1 divided by 1/R1+1/R2+1/R3........, of course you can use this formula for two parallel circuits as well.

H=AT/m, you MUST use amperes AND turns to calculate total Magnetomotive Force.  The wattage is based ONLY on the amperage(regardless of number of turns) AND the voltage.  That is why simply increasing the number of turns produces a much greater magnetic field strength for the same wattage.  Of course more wire windings increases the resistance, which would reduce the amperage, but we've already found a way around that with the parallel coil windings.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 27, 2008, 09:14:26 AM

Edit:
(hmmm - then again - since you have less TOTAL resistance, you have more TOTAL amps, so even if the amps are split in 2 wires, you still have more AT total because you still have more overall amps total - but not 200%?  And watts increases?  How does this then effect the AT/watt?
I think I need to turn off my cluttered brain for awhile........)

LOL!  I think I need to turn mine off too!  You're right, less total resistance increases amperage.  Remember, you also increased the windings because you added another coil  Now you have doubled the amperage and doubled the number of turns, so you have QUADRUPLED the number of AT.  Also, since you have doubled the amperage you have DOUBLED the wattage because the voltage has stayed the same.  V x A=W, V x 2A=2W.  4XAT/2W=2AT/W.  You have effectively doubled the AT/W, 200% efficient.
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 27, 2008, 01:07:28 PM
Hi Xaverius,

just a short note on your calculation because this also confused me at the beginning of this discussion:

Quote
Actually two coils wired in parallel would have lower total resistance that  would be less than the lesser resistance of the two.  In your example, wind another coil with the 1232 turns, fasten them in parallel, the total resistance is now 5.87x5.87/5.87+5.87=2.9 ohms.

1.5/2.9=.51 Amperes......   .51x1.5=.76 Watts   1232x2=2464   2464x.51=1256AT

... unless you do not use two cores for the two coils in parallell - the ampere-turns are 1232 x.51 = 628.32 Amp. but at lower resistance as you already stated Two parallel coils on one core act as one coil with reduced resistance, No doubling of the AT.

Is this ( two cores ) what you mean in your calculation ?

Now this brought me some other idea of using many small flate core-stripes from laminated core - wind one or two layers of planar-coil on it - and put them all in parallell.
I have to do a calculation on this idea. In addition to this one can then finish this design with a convex iron-lense
at the front-surface in order to focus the field.

The pic attached is from the german producer :

http://www.pack-feindraehte.de (http://www.pack-feindraehte.de)

I already posted here. I have to check the prices and minimum order.


Regards

Kator01

Regards
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 27, 2008, 01:13:50 PM
Hi ,

i forgot to attach the physical dimension-table of abailable flat-coils.
This is just an example. As the smallest one is 6 mmm in width I will ask them for smaller width

Regards

kator01
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 27, 2008, 06:44:09 PM
Hi Xaverius,

just a short note on your calculation because this also confused me at the beginning of this discussion:

... unless you do not use two cores for the two coils in parallell - the ampere-turns are 1232 x.51 = 628.32 Amp. but at lower resistance as you already stated Two parallel coils on one core act as one coil with reduced resistance, No doubling of the AT.

Is this ( two cores ) what you mean in your calculation ?


Two coils, one core.  Think of the coils as one long wire at a high resistance, it is severed in two, the ends are wired in parallel reducing the resistance.  Now you have the same large number of turns AND an increase in amperage due to the lesser resistance, thereby DOUBLING amperes AND turns.
Title: Re: Winding a strong electromagnet
Post by: TinselKoala on November 27, 2008, 08:15:04 PM
Two coils, one core.  Think of the coils as one long wire at a high resistance, it is severed in two, the ends are wired in parallel reducing the resistance.  Now you have the same large number of turns AND an increase in amperage due to the lesser resistance, thereby DOUBLING amperes AND turns.

So I have one long wire. I sever it in two lengthwise. Now I have 2 long wires, each with half the cross-sectional area of the original wire. Now I join the ends back together. And I have, magically, created a wire with less resistance than the original wire.

Sorry, there must be something I'm missing.

Title: Re: Winding a strong electromagnet
Post by: capthook on November 27, 2008, 10:55:43 PM
12' of #30 AWG = 1.4 ohms
cut in half, twist the 2 ends together at each end:
6' x 2 in parallel of #30 AWG = .7 ohms

How does this affect ampturns?  Xaverius has proposed it increases efficiency....

Attach those wires to a power source: 1 'D' battery  1.5v
Measure voltage with DMM
I=V/R

12':  .67V / 1.4ohms = .479A    .67V x .479A = 0.32093 W
6' x 2 parallel: .23V / .7ohms = .329A    .23V x .329A = 0.07567 W

So with the same power source, in the parallel circuit, the RESISTANCE goes DOWN, the VOLTS go DOWN, the AMPS go DOWN and the POWER draw goes DOWN.

Which winding makes for a better EM?  Which will give you the most ampturns per watt?

Let's say 40 turns.
12': 40T x .479A = 19.16 AT  @ .32093W  = 60 AT/w
6'x2: 40T x .329A = 13.16 AT @ .07567W = 174 AT/w

290% increase in AT/w for parallel in this example.

Gonna wind some test coils tommorrow.....

(edit: corrected numbers)
Title: Re: Winding a strong electromagnet
Post by: TinselKoala on November 28, 2008, 12:25:04 AM
OK, I thought what was meant was to split the wires lengthwise and use the same length (because that's how you double the turns).

But this isn't correct:
"So with the same power source, in the parallel circuit, the RESISTANCE goes DOWN, the VOLTS go DOWN, the AMPS go DOWN and the POWER draw goes DOWN."
Because you really aren't using the same power source. The battery's voltage depends on the load resistance, as you know. So to get correct figures you need to measure the current using a voltage-regulated power supply that won't sag the way a small battery does.

I have often pondered this same question. Taken to the limit, one would expect all electric motors to be wound with extremely fine wire and lots of it. But they aren't, usually. When I was a kid, we used to rewind the armatures of the little Mitsubishi can motors on our slot cars. But we would use fewer turns of thicker wire than original, and it would indeed make the motors more powerful. Of course we didn't care about power consumption, and the motors would generally fail from overheating after a few hours, or "throw a wrap" when a winding came loose from the epoxy at extreme RPM.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 28, 2008, 01:15:07 AM
Redid the earlier test - results seemed inconsistent.  Battery used was an older one with lower charge (1.2V) and a DMM is not highly accurate measuring resistance of small OHMS.  So in this test I also did amp measurement in circuit and R=V/I for resistance with a fresh battery.

12' : .88v / .74a / 1.19 ohms : 0.6512w
6' x 2 : .46v / 1.44a / .319 ohms : 0.6624w

12' : 40T x .74a = 29.6AT  :  29.6AT / .6512w = 45.45 AT/w
6' x 2 : 40T x 1.44a = 57.6AT  :  57.6AT / .6624w = 86.95 AT/w
Edit: or is it 6' x 2 :((20T x .72a) x 2) = 28.8AT ?? This is the question??

191% increase in AT/w with parallel winding.

Additional testing/results/observations/comments requested !!!

- - -
TK -

"measure the current using a voltage-regulated power supply that won't sag the way a small battery does."

As resistance decreases, amps increases, and voltage decreases.

If you are powering your EM with a small battery, then this is a 'real-world' test of the operating conditions.

What is your take on the parallel winding? (2 wires that are 1/2 the length each of the original wire wound '2-in-hand')

Would you conclude that it will increase the efficiency of the EM by increasing the ampturns per watt?

What WOULD you conclude?

tx
Title: Re: Winding a strong electromagnet
Post by: gyulasun on November 28, 2008, 01:55:35 AM
12' of #30 AWG = 1.4 ohms
cut in half, twist the 2 ends together at each end:
6' x 2 in parallel of #30 AWG = .7 ohms

Hi,

If you cut the 1.4 Ohm 12 feet long wire in half, then you should get two 0.7 Ohm wire pieces, right?  (0.7+0.7=1.4)  And if you connect these 6 feet long wire pieces in parallel, then the resistance will be 0.35 Ohm, is that right?

Quote
How does this affect ampturns?  Xaverius has proposed it increases efficiency.... 

If I am correct with the parallel connected wires resultant resistance value, then assuming the same voltage source (like in the non parallel case), the AmperTurns should be about 2 times as many as it was in the 12 feet long wire case (because the number of turns for the two 6 feet long wires roughly halves, compared to that of the 12 feet wire turns and the current will be roughly 4 times as much than it was for the 12 feet wire, the resultant AT is 1/2*4= 2 times as many)   Assuming the voltage source inner resistance is much lower than 0.35 Ohm and little voltage drop develops across it so that the source is hefty enough to drive 4 times as many current through the quartered resistance.

rgds,  Gyula
Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 28, 2008, 04:59:55 PM
Tineskota,

of course it is done, the so called multilayer-wires. They are used for fast-power-puls-applications. See my last post.

Another user posted an american supplier of square-wire :

http://www.mwswire.com/square.htm (http://www.mwswire.com/square.htm)

@xaverius : Can we agree on this : two coils on one core - where each coil has 10 windings - switched in parallell will enter the formula with  10 Turnes and no more. It resembles the mulitlayer-wires I posted above.
If you use a multilayer-wire ( 100 thin wires in parallel)  of the above spec you will not increase the Turns by 10 times 100 but only the Amperes by reducing the resistance depending of the 100 parallell inner resistance - let say by 50 % - therefore the result of the formula : Ampere x Turns = 10 Turns  x double Amperage because of 50 % less inner resistance.

LOL but I like this discussion. Yes we have to test it, , no way.

Regards

Kator01



Title: Re: Winding a strong electromagnet
Post by: Kator01 on November 28, 2008, 05:04:28 PM
Folks,

I assumes you would use a power-sypply with stabelized Voltage , dont you ?

Kator01
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 29, 2008, 04:54:54 AM
So I have one long wire. I sever it in two lengthwise. Now I have 2 long wires, each with half the cross-sectional area of the original wire. Now I join the ends back together. And I have, magically, created a wire with less resistance than the original wire.

Sorry, there must be something I'm missing.



Not severed lengthwise, crosswise.  ex:  100 feet of wire would become 50 feet.
Title: Re: Winding a strong electromagnet
Post by: TinselKoala on November 29, 2008, 05:30:44 AM
Yes, I got that now, thanks, in fact I got it a page or two ago.
So there are the same number of turns, half with one strand and half with the other, just more current because of the lessened resistance.
So why not do it again, split that wire into 4, or even 8 short lengths, heck, just use a single turn of 16 tiny short wires in parallel!! Heck, just wind the armature with multi-stranded wire...

I wonder why they don't.
I think there's a tradeoff there somewhere...
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 29, 2008, 05:59:57 AM
Yes, I got that now, thanks, in fact I got it a page or two ago.
So there are the same number of turns, half with one strand and half with the other, just more current because of the lessened resistance.
So why not do it again, split that wire into 4, or even 8 short lengths, heck, just use a single turn of 16 tiny short wires in parallel!! Heck, just wind the armature with multi-stranded wire...

I wonder why they don't.
I think there's a tradeoff there somewhere...

That's right, why stop there, you can use as many wires in parallel as you desire.  Not only will you reduce resistance but you will also reduce reactance which is much greater than resistance in an AC application, that is if you are using and AC power source, or pulsating DC.  Of course if you are using ferrite or laminated steel the reactance in not an issue.

@ TinselKoala, Kator, gyasulun and CapnHook, I owe an apology.  I believe my examples are becoming confusing.

In the wiring scheme, consider this.  10 V,  1 lenghth of wire 80 feet @ 4 ohms.  Number of turns = 100.  Amperes = 10/4=2.5A.  10 x 2.5=25W

Ampere-turns=250

If another 80 feet lenght of wire is coiled on top of the first wire and connected to the first wire in parallel, the total resistance now becomes 1 divided by 1/4 + 1/4=2.  10V/2=5A and number of turns is NOW 200.  10 x 5=50W

Ampere-turns=1000

250AT/25W=10AT/W    1000AT/50W=20AT/W

You could look at it like you have one 160 feet wire to start with, divide it in two and wind two coils on top of each other, wire them in parallel but that is a harder way to understand it.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 29, 2008, 01:24:29 PM
So in your example, you propose AT/W is 2x.

In the wiring scheme, consider this.  10 V,  1 length of wire 80 feet @ 4 ohms.  Number of turns = 100.  Amperes = 10/4=2.5A.  10 x 2.5=25W
Ampere-turns=250

If another 80 feet Lent of wire is coiled on top of the first wire and connected to the first wire in parallel, the total resistance now becomes 1 divided by 1/4 + 1/4=2.  10V/2=5A and number of turns is NOW 200.  10 x 5=50W
Ampere-turns=1000

250AT/25W=10AT/W    1000AT/50W=20AT/W

But is it really?  If total amp draw is 5A and you have to wires in parallel, that means the 5A will be split between the two wires meaning 2.5A on each?
AT = (100x2.5)x2 = 500 AT
500AT/50W= 10AT/W  - the SAME AT/W as the 1 coil
??

So again, muti-wire coils/multiple coils will increase AT for a given coil dimension.
But it will NOT increase AT/W........
(double the AT but double the watts)

??
- - - -
If not: (if my above point is shown incorrect)

How might the winding of the 2 lengths of wire differ?  Which would be preferred?

#1: Should it be wound 1 full coil, then the 2nd coil over top of that?
#2: Wound as 1 coil with 2 wires in hand at the same time.
#3: 1 full coil 1/2 the length of core then 2nd coil the 2nd half length of core.

#1. the 2nd coil is futher from the core thus the ampturns are less effective, reducing the actual ampturns of the 2nd coil by x%, meaning the total AT/w boost is not 200% but only x%?

#2. the width of separation of between turns of each individual wire turn is now 2x, so the density of amps per turn of each wire is less meaning AT is reduced by x%?  Might the field of each wire interact with each other?

#3. Coil 2 is going to be way less effective as it is so far away from the 'active' end of the EM?

Or none of the above apply, it's all relative.  But the preferred winding style would be: #1 or #2? (I vote #2)

Might some of these possible 'issues' mean there is a practical limit to the number of wires/coils used?  What might be the limiting factor of the number of wires used?  Why?
Title: Re: Winding a strong electromagnet
Post by: Xaverius on November 30, 2008, 09:15:17 AM
So in your example, you propose AT/W is 2x.

But is it really?  If total amp draw is 5A and you have to wires in parallel, that means the 5A will be split between the two wires meaning 2.5A on each?
AT = (100x2.5)x2 = 500 AT
500AT/50W= 10AT/W  - the SAME AT/W as the 1 coil
??

So again, muti-wire coils/multiple coils will increase AT for a given coil dimension.
But it will NOT increase AT/W........
(double the AT but double the watts)

??
- - - -
If not: (if my above point is shown incorrect)

How might the winding of the 2 lengths of wire differ?  Which would be preferred?

#1: Should it be wound 1 full coil, then the 2nd coil over top of that?
#2: Wound as 1 coil with 2 wires in hand at the same time.
#3: 1 full coil 1/2 the length of core then 2nd coil the 2nd half length of core.

#1. the 2nd coil is futher from the core thus the ampturns are less effective, reducing the actual ampturns of the 2nd coil by x%, meaning the total AT/w boost is not 200% but only x%?

#2. the width of separation of between turns of each individual wire turn is now 2x, so the density of amps per turn of each wire is less meaning AT is reduced by x%?  Might the field of each wire interact with each other?

#3. Coil 2 is going to be way less effective as it is so far away from the 'active' end of the EM?

Or none of the above apply, it's all relative.  But the preferred winding style would be: #1 or #2? (I vote #2)

Might some of these possible 'issues' mean there is a practical limit to the number of wires/coils used?  What might be the limiting factor of the number of wires used?  Why?


You have very valid points.  I guess I am getting ahead of myself.  Your reference to "AT/W" I distorted somewhat.  Actually the example of 1000AT/50W or 500AT/50W is related to the Magnetic Field Strength which grows the magnetic force geometrically according to wattage.  As the wattage increases, H (magnetic field strength) produces more magnetic force with the square of the increase.

250AT/25W has 1 unit of magnetic force.  500AT/50W has 4 units of force, yet the amount of input has doubled. (25W to 50W)  And yes, the AT/W ratio is the same @ 10.

You're right the two parallel wires reduce to 250AT each for a total of 500AT, 1000AT simply relates to the total input, NOT the effective input.

I think method #2 would probably be most effective as the two wires would have equal spacing from the core.  The distance away from the core reduces the amount of flux influence.

Method #3 would be like two small EMs back to back so would only have half the magnetic flux.

I'd say there is a practical limit as to the number of wires used, mainly the distance of the windings from the core.  Too many wires, too much distance so you would have to carefully balance the number of wires, number of windings, wire thickness and so on.

AT/W may stay the same and total power used may increase but total magnetic force would increase even more.  This would be advantageous with a solenoid or a motor pole where a large amount of force is needed to overcome the resistance of a generator in order to produce the needed wattage.
Title: Re: Winding a strong electromagnet
Post by: TinselKoala on November 30, 2008, 03:35:20 PM
Um-hmm, now you are getting it.
So you can see why it made sense for us kids to rewind our motors with fewer turns of thicker wire, because that was the most effective way to reduce the resistance and thus increase the current, thereby increasing the effective A/T. And it worked, too. The rewound motors would be significantly stronger (more torque, faster acceleration) than the stock ones with more turns of finer wire.
Title: Re: Winding a strong electromagnet
Post by: capthook on November 30, 2008, 10:14:11 PM
the AT/W ratio is the same @ 10.

Xaverius - thanks so much for the clarification!  I had been scratching my head the last few days over that.

As TK points out - fewer turns of thicker wire reduces resistance and increases amps that increases EM strength at the cost of more power consumed.
Winding 2-in-hand further reduces resistance and increases amps that increases strength at the cost of more power consumed.
Two excellent methods for increasing AT per meter.

However, if the goal is OU, the more power you consume the more power you must produce.  Catch-22.
This has been the reason for my focus on the AT/watt.
You may have noticed on my excel spreadsheet the power input of .5 watts.

The last wind I did was:
#22 AWG : 140' : 3/8" x 3" core : 1" OD  x 1 7/8" L coil : 781 turns : 2.3 ohms
1.06V x .461A = .488W : 360 AT : 1/2 lb. of holding power.

So with under 1/2 watt of input, I'm getting what appears to be a sufficient EM strength for my application.
However, thanks to the discussion here, winding it 2-in-hand will increase the EM strength relative to the power draw.  (ie. 50% more power but 75% more strength -)  The same AT/W but a relative larger flux - a larger % of domains aligned.
As such, designing for larger device output to accommodate the larger EM power draw should result in a net system gain.

Another thing I noticed this last week:
A larger core diameter will perform poorly over a smaller diameter at low  input power.
The 3/8" core works better at .5W than the 1/2" core.
My thinking is that the low input can only align a small % of domains.
With a smaller core, that % of alignment is greater than the % of the larger core meaning greater EM strength.
Title: Re: Winding a strong electromagnet
Post by: capthook on December 01, 2008, 03:24:27 AM
What about 'flux focusing'?  Focusing the flux into a small area transmitted over an airgap.

What methods might be used?  How effective might it be?

Something like the attached picture....
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 01, 2008, 07:41:47 PM
Hi CapNHook,

               Sorry for making you scratch your head so much, my technical writing skills are not the best in the world but I'm getting better day by day, LOL!
Also, the math as you can see will sometimes throw you off.  I've been working with electronics and physics for many years and I can easilty get confused when the numbers start flowing, which they most certainly will with these two topics, LOL!

                 That being said, you made a good observation with regard to low power input and a narrow cross-sectional core.  I think you're right, at low power less domains are capable of alignment, also I might note that the same thing happens with shorter cores.  I've had the experience that at low power inputs, shorter cores yield less magnetic force, probably because the domains are squeezed together longitudinally and can't align efficiently.  In other words, a longer core allows the domains to "stretch" lengthwise and align properly.

                  One thing you may know by now, when you DOUBLE the magnetic field strength(H), you QUADRUPLE the magnetic force.  So in your examples, when you DOUBLE the AMPERAGE, you also DOUBLE the WATTAGE, however the AT/W remains the SAME, but the MAGNETIC FORCE QUADRUPLES.

                   In your application you are using repulsion, in mine I am using attraction.  If BOTH modes are used with a pulsating DC power source you are effectively DOUBLING your output.  Attraction and repulsion are used in AC motors, but to no overunity effect because when the cycle changes directions the attraction or repulsion is negated gradually.  With pulsating DC that problem is eliminated.  Also if you use BOTH POLES of the EM you double your output again.  Double the amperage, double the modes(attraction/repulsion), double the poles(N/S), you will increase your output by 16X.

                    BTW, have you achieved any result with 1006?  Good luck.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 02, 2008, 09:15:49 PM
What about 'flux focusing'?  Focusing the flux into a small area transmitted over an airgap.

What methods might be used?  How effective might it be?

Something like the attached picture....

Flux focusing would indeed prevent most leakage and increase efficiency.  I'm not sure how it would be done other than alternate stator poles with opposite polar(N/S) EMs in close proximity.  You might look into Joe Flynn's technology or the Hildenbrand valve on Peswiki, if you haven't already.  They might give you a clue toward flux "steering".
Title: Re: Winding a strong electromagnet
Post by: capthook on December 02, 2008, 09:36:26 PM
Thought I would add this here as equations can get lost in the shuffle and might not be easily 'translated':

Question: I want to duplicate the 2000 Gauss strength in an electromagnet with a 3/4 inch diameter, 2 inch length solid metal core.

Answer:
A rough approximation:

(1) H in Oersted= (.4 x 3.14 x N x I)/coil length in cm

(2) B in Gauss = (H x (core permeability x 0.00000125664)) x 10000

So if 2,000 Gauss needed with core permeability of 800u:

H= 2000/10.05312 = 199
(rearrangement of  (2))

H = (.4 x 3.14 x N x I) / 5.08 = 199

N x I = (199 x 5.08) / 1.256 = 805 ampturns

So you could use:

N x I = 805 turns x 1 amp = 805 ampturns

805 turns of #22 AWG = 8.3 ohms
I=V/R : 9volts / 8.3 ohms ~ 1

So 805 turns of #22 AWG at 9 volts on a 800u permeability core (1010 steel) will achieve a rough approximation of around 2000 Gauss.
Title: Re: Winding a strong electromagnet
Post by: capthook on December 02, 2008, 09:45:51 PM
BTW, have you achieved any result with 1006?

The 1006 showed little noticable difference compared with the 1018 with my small coil, small input and limited testing accuracy.
I think to achieve a noticable difference would require laminated silicon steel, pure iron or an exotic and expensive nickel alloy like fully annealed Carpenter High Permeability "49"® Alloy or the HIPERCO 50.

(http://www.eaglealloys.com/c-8-nickel-iron-alloys.aspx is a possible source of alloys I haven't contacted)
Title: Re: Winding a strong electromagnet
Post by: capthook on December 02, 2008, 11:04:25 PM
Best contact I've found yet (after about 20 calls and 40 hrs of research)

http://www.hightempmetals.com/index.php

Very helpful and many types of products of many different sizes in stock.

PERMENDUR 2V
(HIPERCO ALLOY 50A)
(cobalt alloy - high permeability, highest flux density)

1/2" x 3' : $7.06 per inch
$20 cut charge
$25 packing charge

$298.00

HY MU 80 ROUND BAR
1/4" - 2 1/2" diameter rods
(nickel alloy:  highest permeability, high flux density)
Initial : 50,000u
Max: 200,000u
(currently on order)

All products should then be fully annealed.

If you wanted the best of the best - the HY MU 80 offers super-high permeability and would be an excellent choice........
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 03, 2008, 09:26:00 AM
Thought I would add this here as equations can get lost in the shuffle and might not be easily 'translated':

Question: I want to duplicate the 2000 Gauss strength in an electromagnet with a 3/4 inch diameter, 2 inch length solid metal core.

Answer:
A rough approximation:

(1) H in Oersted= (.4 x 3.14 x N x I)/coil length in cm

(2) B in Gauss = (H x (core permeability x 0.00000125664)) x 10000

So if 2,000 Gauss needed with core permeability of 800u:

H= 2000/10.05312 = 199
(rearrangement of  (2))

H = (.4 x 3.14 x N x I) / 5.08 = 199

N x I = (199 x 5.08) / 1.256 = 805 ampturns

So you could use:

N x I = 805 turns x 1 amp = 805 ampturns

805 turns of #22 AWG = 8.3 ohms
I=V/R : 9volts / 8.3 ohms ~ 1

So 805 turns of #22 AWG at 9 volts on a 800u permeability core (1010 steel) will achieve a rough approximation of around 2000 Gauss.

I think you mean 3/16" diameter core which is .4m.

(1) H in AT/m=NxI/length

(2) B in Tesla=H x (.000001256 x 800)

2000 Gauss=.2Tesla  ur=.0010048
.2/.0010048=199 AT/m

H=N x I/5.08    199 x 5.08=1011 AT

So you could use:
N x I=1011 x 1 amp=1011T

1011 turns of 22 gauge wire @ .4 x pi=106 feet  which yields 1.7 ohms

I=V/R    I=1  R=1.7  V=1.7  W=1.7

1011 turns of 22 gauge wire at 1.7V will yield 2000 gauss at 800 ur

Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 03, 2008, 09:28:39 AM
The 1006 showed little noticable difference compared with the 1018 with my small coil, small input and limited testing accuracy.
I think to achieve a noticable difference would require laminated silicon steel, pure iron or an exotic and expensive nickel alloy like fully annealed Carpenter High Permeability "49"® Alloy or the HIPERCO 50.

(http://www.eaglealloys.com/c-8-nickel-iron-alloys.aspx is a possible source of alloys I haven't contacted)

Have you tried 1018 already?
Title: Re: Winding a strong electromagnet
Post by: capthook on December 03, 2008, 09:59:07 AM
Yes.
1006, 1018, Grade 2 hex bolt, Grade 5 hex bolt

All seemed similiar with my limited tests.
I have recently read several places that without a proper annealing, you might see a 3% increase between the 1006 and the 1018.....
I put out 3 RFQ's for annealing, haven't heard back...... hard to find a resource (like everything else  >:( ) that deals in small quantities.
Title: Re: Winding a strong electromagnet
Post by: capthook on December 03, 2008, 10:11:59 AM
I think you mean 3/16" diameter core which is .4m.

(1) H in AT/m=NxI/length

(2) B in Tesla=H x (.000001256 x 800)

2000 Gauss=.2Tesla  ur=.0010048
.2/.0010048=199 AT/m

H=N x I/5.08    199 x 5.08=1011 AT

So you could use:
N x I=1011 x 1 amp=1011T

1011 turns of 22 gauge wire @ .4 x pi=106 feet  which yields 1.7 ohms

I=V/R    I=1  R=1.7  V=1.7  W=1.7

1011 turns of 22 gauge wire at 1.7V will yield 2000 gauss at 800 ur

Nicely done!  Thanks for the correction. Plus you used SI - easier on the brain.
And one of the reasons I have half a grasp on the math is due to your considerable math skills and patience!  :D

(P.S. The original question was for 3/4"diameter core so it should be adjusted to 310'  5ohms)

And I've wondered..... how do you the include the core diameter into the flux density calculations (AT)?  It seems you can do this, and that, but not this AND that! lol
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 03, 2008, 08:54:34 PM
Nicely done!  Thanks for the correction. Plus you used SI - easier on the brain.
And one of the reasons I have half a grasp on the math is due to your considerable math skills and patience!  :D

(P.S. The original question was for 3/4"diameter core so it should be adjusted to 310'  5ohms)

And I've wondered..... how do you the include the core diameter into the flux density calculations (AT)?  It seems you can do this, and that, but not this AND that! lol

Actually it is 3/8", not 3/16", my typo.  The adjustment for 3/4"  for the same number of turns would be R=1.7 x 2=3.4ohms, 106 feet x 2=212 feet.  3/4 divided by 2=3/8.

The core diameter does NOT affect FLUX DENSITY.  Flux Density is created by AMPERES, NUMBER OF TURNS, PERMEABILTY, CORE LENGTH only.  The diameter affects the LENGTH of the TURNS, therefore the total length of the coil wire, which affects the wire RESISTANCE, longer wire, more resistance.  The diameter also affects the CROSS SECTIONAL AREA, greater diameter yields greater area.  The larger the area for a given flux density then the greater the amount of MAGNETIC FLUX.  The more magnetic flux then the greater the MAGNETIC FORCE.  DOUBLE the AREA, you will DOUBLE the MAGNETIC FORCE.

F=B^2 x A/2u0   u0=4 x pi x 10^-7

2u0=.000002513


EX:   B=.5    A=.01

.5^2  x  .01=.0025  .0025/.000002513=1000N/226 pounds

        B=1      A=.01

1^2  x  .01=.01       .01/.000002513=3980N/905 pounds



EX:   B=1   A=.02


1^2  x .02=.02   .02/.000002513=7960N/1808 pounds

   
         B=1   A=.04

1^2  x  .04=.04   .04/.000002513=15917N/3617 pounds



Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 03, 2008, 08:57:28 PM
Yes.
1006, 1018, Grade 2 hex bolt, Grade 5 hex bolt

All seemed similiar with my limited tests.
I have recently read several places that without a proper annealing, you might see a 3% increase between the 1006 and the 1018.....
I put out 3 RFQ's for annealing, haven't heard back...... hard to find a resource (like everything else  >:( ) that deals in small quantities.

Have you considered 1010?  I noticed on your reply #71 of this thread, your chart shows 1010 that is NOT ANNEALED has a ur of 1000.  I'm considering trying this.
Title: Re: Winding a strong electromagnet
Post by: capthook on December 04, 2008, 07:25:58 PM
The 1010 in that chart was hot formed .25" plate.  Hot formed bar may be close.  Any further processing of the material will significantly reduce its permeability.  Cold roll it - reduced.  Cut it to length - reduced.
(look at it sideways - reduced.  lol j/k)
In theory the 1006 is .06 carbon and the 1010 is .10 carbon, so the 1006 should outperform the 1010.
But as I (now) see it, whatever material used will require a proper annealing to achieve the benifit of material chemisty.  Otherwise, the chemisty of the steel is basically insignificant.
And after all, most steel is produced for its structural/workability qualities, not its magnetic properties, unless you get something like the  Carpenter or CMI materials.
However, I would suppose that that the difference might be more apparant between non-annealed materials of different classes.  ie: steel vs. nickel alloy or cobolt alloy.
But even then, annealing is the difference between it being a Yugo or a Porche.

Buch la Fonte(?) made a comment somewhere on this website along the lines of:
Many good ideas that may well have worked have failed due to the use of inferior core materials.  To acheive results requires proper funding and the use of premimum materials properly prepared.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 05, 2008, 05:56:19 AM
The 1010 in that chart was hot formed .25" plate.  Hot formed bar may be close.  Any further processing of the material will significantly reduce its permeability.  Cold roll it - reduced.  Cut it to length - reduced.
(look at it sideways - reduced.  lol j/k)
In theory the 1006 is .06 carbon and the 1010 is .10 carbon, so the 1006 should outperform the 1010.
But as I (now) see it, whatever material used will require a proper annealing to achieve the benifit of material chemisty.  Otherwise, the chemisty of the steel is basically insignificant.
And after all, most steel is produced for its structural/workability qualities, not its magnetic properties, unless you get something like the  Carpenter or CMI materials.
However, I would suppose that that the difference might be more apparant between non-annealed materials of different classes.  ie: steel vs. nickel alloy or cobolt alloy.
But even then, annealing is the difference between it being a Yugo or a Porche.

Buch la Fonte(?) made a comment somewhere on this website along the lines of:
Many good ideas that may well have worked have failed due to the use of inferior core materials.  To acheive results requires proper funding and the use of premimum materials properly prepared.


So you think the 1010 non annealed is not worth it?
Title: Re: Winding a strong electromagnet
Post by: capthook on December 05, 2008, 07:13:20 AM
The larger the area for a given flux density then the greater the amount of MAGNETIC FLUX.  The more magnetic flux then the greater the MAGNETIC FORCE.  DOUBLE the AREA, you will DOUBLE the MAGNETIC FORCE.

Magnetic force is what I was referring to rather than density - I should have used the proper term to convey my meaning.

So in the calculations you gave: ??

B= flux density in Tesla: (from the H and B calculations in the earlier post)  ?
A= cross sectional area of core (in meters: pi x r2) ?

N= Newtons ?
1N = 1kg x m ⁄ s2 : (how did you translate into lbs/kgs - what value for m(meters) and s(seconds) ?

So you calculate B (as in earlier post) and then do this futher calculation for F ?
- - -

Also have the following equation that hasn't been listed/mentioned:

Force between electromagnets
For electromagnets (or permanent magnets) with well defined 'poles' where the field lines emerge from the core, the force between two electromagnets can be found using the 'Gilbert model' which assumes the magnetic field is produced by fictitious 'magnetic charges' on the surface of the poles, with pole strength m. Magnetic pole strength of electromagnets can be found from:

m= (N x I x A)/L

The force between two poles is:

F= (u0 x m1 xm2)/ (4 x 3.1459) x (r x r)  (is the F here also Newtons?)

A= meters squared (cross section area of core)
L= length in meters
u0= .000001257
- - -

The 1010 - if my tests on the 1006 vs. the 1018 (both cold rolled rounds of 1/2"D x 3"L)are any indication: the 1010 would be (slightly) better than a bolt from Lowes but would basically the same as 1006 and 1018?
Have you tried something other than the ferrite?
Title: Re: Winding a strong electromagnet
Post by: capthook on December 05, 2008, 07:55:19 AM
And 3 points that haven't been addressed from the original post:

1. Core length vs. diameter:  the preferred core length is at least 5x the diameter

2. Winding length:  a winding length of at least 2x the  winding diameter is preferred.

3. Winding diameter: the windings beyond 1/2" from the core will increasingly contribute more to resistance than to the flux.  See the attached picture posted by Honk in another thread.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 06, 2008, 06:40:10 AM
Magnetic force is what I was referring to rather than density - I should have used the proper term to convey my meaning.

So in the calculations you gave: ??

B= flux density in Tesla: (from the H and B calculations in the earlier post)  ?
A= cross sectional area of core (in meters: pi x r2) ?

N= Newtons ?
1N = 1kg x m ⁄ s2 : (how did you translate into lbs/kgs - what value for m(meters) and s(seconds) ?

So you calculate B (as in earlier post) and then do this futher calculation for F ?
- - -

Also have the following equation that hasn't been listed/mentioned:

Force between electromagnets
For electromagnets (or permanent magnets) with well defined 'poles' where the field lines emerge from the core, the force between two electromagnets can be found using the 'Gilbert model' which assumes the magnetic field is produced by fictitious 'magnetic charges' on the surface of the poles, with pole strength m. Magnetic pole strength of electromagnets can be found from:

m= (N x I x A)/L

The force between two poles is:

F= (u0 x m1 xm2)/ (4 x 3.1459) x (r x r)  (is the F here also Newtons?)

A= meters squared (cross section area of core)
L= length in meters
u0= .000001257
- - -

The 1010 - if my tests on the 1006 vs. the 1018 (both cold rolled rounds of 1/2"D x 3"L)are any indication: the 1010 would be (slightly) better than a bolt from Lowes but would basically the same as 1006 and 1018?
Have you tried something other than the ferrite?

??  B=Tesla,  A=pi x r^2 in meters   N=Newtons  1 pound=4.4N

Yes, after you calculate H(AT/m), you then multiply by ur and obtain B in Tesla and further calculate F in Newtons.

Then it seems like 1010 is a loser as well as 1006 and 1018 unless we can find a foundry that can provide annealing at a reasonable price.

Other than ferrite the only thing I've tried is GIron which is similar to MuMetal but cheaper in cost, with a ur of around 100,000.  I obtained it as a type of foil which I cut into strips with tin snips and laminated them together into a bar.  No magnetic force whatsoever.  I think it is like ferrite, it only reacts to high frequency magnetic fields as in radio circuits.

I am somewhat familiar with the EM force formula but don't use it too much.  The force calculation in this formula is also in Newtons.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 06, 2008, 06:50:19 AM
And 3 points that haven't been addressed from the original post:

1. Core length vs. diameter:  the preferred core length is at least 5x the diameter

2. Winding length:  a winding length of at least 2x the  winding diameter is preferred.

3. Winding diameter: the windings beyond 1/2" from the core will increasingly contribute more to resistance than to the flux.  See the attached picture posted by Honk in another thread.

Could you tell me how you arrived at these conclusions?  @ #2 a winding length would be pi x diameter which is 3.1416 x diameter, not 2x?
Title: Re: Winding a strong electromagnet
Post by: capthook on December 06, 2008, 07:33:57 AM
All 3 are 'rule of thumb' conclusions offered in a number of text books ( I spent 8 hours at the University library reading recent and detailed texts), a number of Ebooks, and websites read over the last few months.

1. Some B/H curves state the B applies IF a given core is length 5x diameter.

2. Winding length:  a winding length of at least 2x the  winding diameter is preferred.
The physical dimensions of the coil.  ie. 1/2" OD mean at least 1" length (depth) of coil.
(not feet of wire)
Guess I should have said it more clearly as 'winding length' sounds more like 'wire length' rather than the physical dimensions of the coil.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 11, 2008, 09:20:12 AM
@ CapnHook,
             
                any luck with electrical steel?  My next step is to try Magnetic Metals, magmet.com...............
Title: Re: Winding a strong electromagnet
Post by: Honk on December 22, 2008, 09:16:16 AM
Hi all.

Just a small question.

I believe your'e going to pulse this electromagnets of yours.
Have you considered the influence of inductance while designing it?
This is of utmost importance if you want a fast response time, aka fast RPM:s.
You might want to keep the inductance below 50mH or less, if possible.
There is a trade of: Higher efficiency = Higher inductance = Slow current build-up = Slow electromagnet.

If you measure the inductance and resistance you can use this calculator to see
how long it will take to reach a certain current level (the desired amp-turns).
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2
It has helped me out tremendously.
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 22, 2008, 09:39:26 AM
Hi all.

Just a small question.

I believe your'e going to pulse this electromagnets of yours.
Have you considered the influence of inductance while designing it?
This is of utmost importance if you want a fast response time, aka fast RPM:s.
You might want to keep the inductance below 50mH or less, if possible.
There is a trade of: Higher efficiency = Higher inductance = Slow current build-up = Slow electromagnet.

If you measure the inductance and resistance you can use this calculator to see
how long it will take to reach a certain current level (the desired amp-turns).
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2
It has helped me out tremendously.

Yes, the higher the Inductance, the higher the reactance, and the lower the current and reduced Ampere-turns. Laminated steel and/or parallel-wired multiple coils should eliminate this problem.
Title: Re: Winding a strong electromagnet
Post by: Honk on December 22, 2008, 09:16:04 PM
My own findings does not show any way to eliminate the sluggishness of high inductance at high RPM:s.
A high inductance will force you to increase pulse voltage just to apply the charge time you desire.
The increased voltage x current = a lot more power. This is not comparable to static mode.
It's possible it'll work for you depending on the wanted RPM. I wish you the best of luck in your research.
Title: Re: Winding a strong electromagnet
Post by: capthook on December 23, 2008, 04:41:25 AM
An application specific question on electromagnet core:

An Adams motor design:
1. The rotor magnet is attracted to the EM core
2. Just before dead center, the EM is powered on just enough to NEGATE the attraction
3. The rotor/magnet travels past the EM due to inertia

How will the permeability of the core effect operation?  Or will it be the same no matter?

(a) the higher the permeability, the greater/sooner the attraction so the better the propulsion
(b) the higher the permeability, the greater the % of domains aligned by the rotor magnet, thus the greater power required by the EM to NEGATE the attraction.

So:
(c) No matter the core, (a) is relative to (b), so any core will be the same net result?
or
(d) a higher permeability core means NEGATING the attraction is easier/lower power?

http://www.surepure.com/view_product.php?prodnum=2192
$100 for 12" x .5"  99.6% pure iron rod
(non-annealed, cold-rolled, so don't even know how much better it might be without heat treating)
(and like 4x as much for 99.9%)

??
Title: Re: Winding a strong electromagnet
Post by: SkyWatcher123 on December 23, 2008, 11:58:22 AM
Hi folks, Does anyone know if a coil, an aircore coil for example when pulsed does the voltage rise instantly within a coil to max or close to the inputted voltage while it takes more time for current to build based on inductance?
Title: Re: Winding a strong electromagnet
Post by: Xaverius on December 23, 2008, 10:53:40 PM
@ Honk:  more voltage would be needed to overcome high Inductance due to eddy currents.  These can be eliminated with steel laminations that are insulated from one another.

@ CapNHook:  both (c) and (d) are correct, although naturally you would desire higher permeabilty in order to use lower input power.

@ SkyHook: the voltage is maximum initiallly, then the current rises relatively slowly to the maximum value.
Title: Re: Winding a strong electromagnet
Post by: Kator01 on December 24, 2008, 12:53:53 AM
Hi capthook,

it turns out a bit more complicated than just permeability and we have to study a bit more about some physical fact( this is also true for me ) I just received this info from an engineer in New Zealand who has constructed an Aspden/Adam-Motor which runs with some excess-energy but is not OU at this stage of development. He was refering to this website here for Aspen/Adam-patent on this motor:

http://www.angelfire.com/ak5/energy21/adamsmotor.htm (http://www.angelfire.com/ak5/energy21/adamsmotor.htm)

Move down to ELECTRICAL MOTOR-GENERATOR ( common patent by Mr. Aspden/Adams ).

Notice : this website is not related to the person I got the message from. He was refering to this website because  he wanted to show me the basis of his design ( Figure 6 and 7 )

But before you read this you should read in Aspeden´s website where the extra-power we all are looking for
is located and how to tap it. It is in the air-gap. And if you have higher permeabilty you will have stronger attraction-forces and need more EM-cancelling-power but you will have more power returned from the air-gap.
Permability can be controlled as it is no a constant along increasing values of  Ampere/windings ( see in the download-section here a document I place named "Permeability of pure iron" ). Have a look at the diagramm only.
Now Aspden talks in the Power from Magnetism of the operating-point below the knee of the B-H-Curve, which can be achieved by magentic-bias of the core-lamination.
May be you already know this topic. It is of utmost importance to fully understand this. Read it three times. I just
read it the second time and still have some problems especially if it comes to his calculations.

http://www.aspden.org/reports/Es1/esr1.htm (http://www.aspden.org/reports/Es1/esr1.htm)

Regards

Kator01



Title: Re: Winding a strong electromagnet
Post by: Honk on December 24, 2008, 11:57:27 AM
@ Honk:  more voltage would be needed to overcome high Inductance due to eddy currents.
These can be eliminated with steel laminations that are insulated from one another.

Yes, higher voltage will accelerate any coil regardless of the inductance, just like higher
voltage will accelerate the charge of a capacitor, if there is no current limiting factor.
And the higher the inductance the higher the voltage, but eddy currents have very little
to do with this. The slugginess is always present in a high inductance coil/electromagnet
regardless of the core material. A core will only amplify flux and increase inductance.
Just use the link I provided. It will give you all the answers you need about coil pulsing.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2
You just need to enter the Inductance, Resistance, Applied voltage and Pulse time.
This will calculate the achieved Current level at the specified Pulse time, aka Amp-Turns.
It can't be any simpler than that.
Title: Re: Winding a strong electromagnet
Post by: Honk on December 25, 2008, 05:43:19 PM
Hi folks, Does anyone know if a coil, an aircore coil for example when pulsed does the voltage rise instantly within a coil to max or close to the inputted voltage while it takes more time for current to build based on inductance?

When pulsing a coil the voltage will rise instantly (just as fast as you can apply it) but the current build-up is slow.
The higher the inductance the slower the build-up time. This is regardless of core material.
A ferromagnetic core amplifies the flux from the windings. And this process also increases inductance.
Ferromagnetic core amplification is named by Permeability. The higher the Permeability the greater the flux amplification.
The trade-off is higher inductance that slows down response time. Slow response = slow current build-up.
There is a middle way where the number of turns, aka amp-turns vs response time is the best combination.
This is totaly dependent on your needs in your own specific project. You'll just have to calculate, wind and measure
the outcome a lot of times. And then use this calculator to see if the amp-turns vs response time will do it for you.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2

 
Title: Re: Winding a strong electromagnet
Post by: capthook on January 08, 2009, 06:55:10 AM
Hi folks, Does anyone know if a coil, an aircore coil for example when pulsed does the voltage rise instantly within a coil to max or close to the inputted voltage while it takes more time for current to build based on inductance?

You can also use this site: http://www.coilgun.info/mark2/inductorsim.htm

Enter the coil dimensions and wire size for many useful calculations including inductance, resistance, # turns and wire length.

Title: Re: Winding a strong electromagnet
Post by: capthook on January 08, 2009, 07:11:16 AM
I STILL can't get me brain around this - thinking I'm brain damaged!  ???

I have a magnet attached to the end of an electromagnet (EM) with a steel core and pulse the EM with just enough juice to get the magnet to drop off.

Which will require less energy input to get it to drop off?

1) a high permeability core
or
2) a low permeability core

(1-A) the magnet is very strongly attached to the high permeability core and almost all the domains of the core are aligned.  This will require a large input of energy to negate the attraction.  BUT, will the high permeability core more readily 'accept' the flux from the EM pulse meaning it will actually require LESS?

(2-A)  the magnet is attached, but not quite as much as a much smaller % of the domains of the core are aligned, thus less energy input to the EM to get it to drop.  BUT, will the core also be less 'accepting' to the EM pulse so it will require more input?

Or a small size core with a relatively large/strong magnet is going to fully saturate the core, so the high permeability core will require less.
But if the core is large with a relatively small/weak magnet this changes things?

Or what and why?

Tx
Title: Re: Winding a strong electromagnet
Post by: Kator01 on January 08, 2009, 11:37:42 AM
Hi capthook,

that is exactly the question I have pondered on and I share your experience of mentally going in a loop on this for the last months´s.  One thing to consider is the spontaneous magnetisation which demands less energy, see here the topic "long range ordering" :

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html (http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)

Now as for a permanent magnet to trigger this allignement in an effective way, meaning not to over-energize
the core-material, there will be just on way to controll it : the air-gap-width. The air-gap if properly spaced will carry most of the energy and complete full saturation of the core.

I will carry this question to this guy from New-Zealand because he has build a special Adam-Aspden-motor.

Also of interest might be the Potter-Debate at Aspden´s Webpage here :

http://www.aspden.org/reports/Es4/esr4.htm (http://www.aspden.org/reports/Es4/esr4.htm)

Hope it heps you.

Regards

Kator







Title: Re: Winding a strong electromagnet
Post by: capthook on January 08, 2009, 06:48:25 PM
Kator01-

Thanks for the link to the Potter-Debate paper.  I've downloaded it and will read soon.  Still haven't fully read the ENERGY SCIENCE REPORT NO. 1: POWER FROM MAGNETISM by HAROLD ASPDEN.

Also did a search of the hyperphysics site (seach term on google):
"long range ordering" site:hyperphysics.phy-astr.gsu.edu

gave me this page:
http://hyperphysics.phy-astr.gsu.edu/Hbase/Solids/ferro.html

Just basic information on ferromagnetism...

And the magnet is actually over a small airgap - was just easier to 'visualize' it as attached.

I would test numerous materials - but the high permeability materials are VERY expensive and VERY VERY hard to source (especially annealled).

As such, I'm still hoping that someone might give me a definitive answer.

tx
Title: Re: Winding a strong electromagnet
Post by: Kator01 on January 08, 2009, 07:57:37 PM
Hi capthook,

in that hyperphysics-Link you have to read this "long range order" thingy.

http://hyperphysics.phy-astr.gsu.edu/Hbase/Solids/ferro.html#c2 (http://hyperphysics.phy-astr.gsu.edu/Hbase/Solids/ferro.html#c2)

Although I can not do the math I can tell you for sure that you can control the saturation-level in your em-core by variation of the air-gap. The bigger the distance ( air-gap) the less power you need for cancelling the allignement to the degree of setting the magnet free.
I am sure even this electronic engineer from New Zealand had just solved this by practical testing.
( variation of air-gap-width )
He was off for some holidays and I wiil contact him today and ask him about this problem. He may have some
working formulas.

Since most of the E-Mag is concentrated in the air-gap ( I have read a tutorial on switched-power-supplies ) you only need to expend that amount of energy to cancel the smaller energy-portion (saturation) in the core. Because you will not be able to cancel the emag in the air-gap in a direct way.

I will do a research on this but it might take some time, as I am a german and need to find relevant english literature.

Some days ago I put a file into the download-section : "E_mag-Fe-Air by Kator01", because there was the same topic which I had to draw the attention to in the Peripiteia-Thread.

http://www.overunity.com/index.php?action=tpmod;dl=0 (http://www.overunity.com/index.php?action=tpmod;dl=0)

I put together some  formulas and explanations from my old german physics-textbook dated 1940. Here in this book is a paragraph about the spark-inductor used at the end of the 19th century. Here it was clearly explained that E-mag in the air (and therefore the  fieldstrength H ) is thousands times bigger than in pure iron. Look at the formulas and you will see the relative permeability is in the denominator of the Energy-formula.
A similar situation occurs ( although not fully equivalent) when the magnet passes by the core at a distance.

Then as a repeater have a look at the file in the same section named "Permeability of pure iron".
Permeability is not a constant. It is depending on the fieldstrength. So you can engineer the point along this graph
where you have most efficiency as the permeability in decreasing at a certain fieldstrengh. It even can be brought down to 1.

Regards

Kator01








Title: Re: Winding a strong electromagnet
Post by: Xaverius on January 15, 2009, 09:04:47 AM
I STILL can't get me brain around this - thinking I'm brain damaged!  ???

I have a magnet attached to the end of an electromagnet (EM) with a steel core and pulse the EM with just enough juice to get the magnet to drop off.

Which will require less energy input to get it to drop off?

1) a high permeability core
or
2) a low permeability core

(1-A) the magnet is very strongly attached to the high permeability core and almost all the domains of the core are aligned.  This will require a large input of energy to negate the attraction.  BUT, will the high permeability core more readily 'accept' the flux from the EM pulse meaning it will actually require LESS?

(2-A)  the magnet is attached, but not quite as much as a much smaller % of the domains of the core are aligned, thus less energy input to the EM to get it to drop.  BUT, will the core also be less 'accepting' to the EM pulse so it will require more input?

Or a small size core with a relatively large/strong magnet is going to fully saturate the core, so the high permeability core will require less.
But if the core is large with a relatively small/weak magnet this changes things?

Or what and why?

Tx

For drop off, a high permeability core should require less power input.  The high u core causes a greater ATTRACTION force between it and the PM.  However, the high u core uses a unit of power to produce a greater REPULSION force.

The REPULSION force must be equal to the ATTRACTION force in order to repel the PM.  If the REPULSION is too weak(such as with a low u core) for a unit of power, then the PM will still be ATTRACTED to the core.  Ex.  PM has 2 units of force, core has 1 unit of force, total attraction 3 units.  If PM has 2 units of attraction and core 1 unit of repulsion you still have 1 unit of attraction, 2+-1=1.  Therefore you would need 2 units of power to produce more force(negative) for the low u core to repel the PM.

BTW, the PM will not just drop off, magnets work on an all or nothing basis, the PM and core will repel with rapid speed and distance between them.

Hope this makes sense, the high u core would use less power.
Title: Re: Winding a strong electromagnet
Post by: tropes on January 18, 2009, 06:24:01 PM
For drop off, a high permeability core should require less power input.  The high u core causes a greater ATTRACTION force between it and the PM.  However, the high u core uses a unit of power to produce a greater REPULSION force.

The REPULSION force must be equal to the ATTRACTION force in order to repel the PM.  If the REPULSION is too weak(such as with a low u core) for a unit of power, then the PM will still be ATTRACTED to the core.  Ex.  PM has 2 units of force, core has 1 unit of force, total attraction 3 units.  If PM has 2 units of attraction and core 1 unit of repulsion you still have 1 unit of attraction, 2+-1=1.  Therefore you would need 2 units of power to produce more force(negative) for the low u core to repel the PM.

BTW, the PM will not just drop off, magnets work on an all or nothing basis, the PM and core will repel with rapid speed and distance between them.

Hope this makes sense, the high u core would use less power.
Before building my 4th Sotropa Motor (3/4' neo. magnet pistons), I used this simple apparatus to test the coil, core and voltage requirements:  http://www.youtube.com/watch?v=pNWAlj_lBUk
In my last motor I used an iron pipe as a core. The core diameter is half the magnet diameter and the coil diameter is equal to the magnet diameter. I used 22 gauge wire and added voltage until the coil heated. Removing the BEMF allowed the coil to run cooler. I found that a solid core with no clearance between the core and magnet was impossible to to separate regardless of how much voltage was applied.
Hope this is of some value to those builders.
Tropes
Title: Re: Winding a strong electromagnet
Post by: capthook on February 02, 2009, 04:43:29 AM
Found this core material study online.

As proper annealing is expensive and difficult to source, especially in small quantitites, the conclusion was that unannealed 'Magnet Iron' was of relative quality compared to expensive annealed Hiperco 50A.

"Magnet iron is recommended for unannealed use"

Title: Re: Winding a strong electromagnet
Post by: Ergo on March 07, 2009, 10:18:51 PM
All of your calculations and drawings is not valid in your pursuit of
making the strongest electromagnet possible.
The permeability only correlates to a closed magnetc circuit.
You will not see any dfference in magnetic strength when using
advanced core material in an open frame electromagnet.
The tiniest airgap present will deteriorate the properties of the
high efficiency core material. So no gain of strength in this case.

But there is still another advantage that not many people know about.
The only really useful advantage of using high tech core material.
Simply the Hysteresis effect.
Hysteresis is the loss on each charge/discharge of the electromagnet.
It takes a certain amount of energy to energise the coil.
But you never get the same amount back as EMF when shut down.
This loss can be minimised by using Hi Tech core material.
When minimising the hysteresis you get rid of the core heating and
you can then run the electromagnet harder without overheating.
But this only matters in a repetitive pulsed state. In static mode
or unfrequently pulsing you can just as well use a regular iron core.
Title: Re: Winding a strong electromagnet
Post by: capthook on March 11, 2009, 04:27:37 PM
The permeability only correlates to a closed magnetc circuit.
You will not see any dfference in magnetic strength when using
advanced core material in an open frame electromagnet.
The tiniest airgap present will deteriorate the properties of the
high efficiency core material. So no gain of strength in this case.

Do you have any supporting evidence/links?
It would seem contrary to any information I've seen.
Either the domains align more easily due to the molecular structure of the material (high permeability) or they don't (low permeability).  How would the airgap be revelant to this?

- - -
Xaverius-
I did some testing on the 2-strand winding idea to reduce the resistance of the coil and thus increase efficiency/flux.
While this idea may be of benefit when additional power is available, I find it not to be so with a fixed power input.

Testing two identical coils with the only difference being a 1 wire winding vs. a 2 wire winding and a power supply of a 4700 uF capacitor charged to 12V:
The 1 wire was on average 17% more efficient(provided more flux) over varying test conditions/airgaps. 
- - -
Some further updates on materials/annealing:

I've found min. charges of around $250 for hydrogen annealing at 1600F for 2 hours with a 4 hour 100F cooling cycle to be about the norm.  1 provider offered to 'piggyback' on a another order providing time was not an issue (maybe 2 weeks) for $150.

Pure iron (99.95%) @ $90 per inch (OUCH!! $$$)
Iron rod (99.6%) @ $95 per ft.

CMI-C magnet iron 4' for $100 to $250 depending on the providers min. order.
Title: Re: Winding a strong electromagnet
Post by: Ergo on March 12, 2009, 08:34:06 AM
Do you have any supporting evidence/links?
It would seem contrary to any information I've seen.
Either the domains align more easily due to the molecular structure of the material (high permeability) or they don't (low permeability).  How would the airgap be revelant to this?

Believe it or not but I have studied magnetics for some time now and I can
tell you that I have tested all kind of alloys in a small electromagnet when
trying to optimise its strength.
I have a gauss meter and no matter what I tried I always got the same end
face flux at the same input current.
The fine alloys, (mu metall, MPP, Sendust, Hi Perm oriented Steel) didn't
give any increase in end face flux. I phoned one of the companies and talked
to an engineer on the matter and he told me that any air gap will detoriate
the performance. He also told me about the importance of hysteresis and
why high tech alloys are so good at this compared to solid structures.
He gave me a hint, if I wanted to have an electromagnet that consumed less
current I had to make sure it was bent into a C and the open gap should be
placed tightly against a solid iron return path thick enough to carry all the flux.
In this scenario I would see a drop in current in reaching high flux levels.
But using a Solenoid shape was not an option. The air gap is simply huge.

I have searched internet for a long time but there is no information on this subject.
Either it's burried deep in some heavy science thesis but I believe myself the lack
of infomation is due to lack of interest in this matter. Any involved engineer find
this obvious and there is no literature written on how to optimise a hopeless case.

Edit: I found a new link today. It might provide you with answers but it costs money.
http://www.coursework.info/AS_and_A_Level/Physics/Fields___Forces/_What_effects_the_strength_of_an_electro_L68298.html
Title: Re: Winding a strong electromagnet
Post by: capthook on April 15, 2009, 08:32:06 AM
Some interesting information on series vs. parallel windings of an electromagnet.

Conclusion: series (or 1 wire) produces greater or equal magnetism vs. parallel (or multiple wires) windings.

"With a power supply configured as a current source, by setting the current and leaving the voltage free to take any value, the nail's magnetism was lower under parallel connection of the coils."
With a variable current supply, the nail's magnetism was equivalent under both series and parallel.

An interesting .pdf is attached.  The author investigates the early work done on parallel vs. series windings electromagnets.

Title: Re: Winding a strong electromagnet
Post by: tropes on April 15, 2009, 05:45:56 PM
Static testing does not give a complete picture. Two things I have found that reduce the amount of current needed to produce an electomagnet. Both involve movement.
1.) As the magnetic piston moves toward the face of the coil, an electric current is induced in the wire. The current induced in the coil wire by the magnet will be of a polarity that repels the magnet. The magnets use the current induced to make the coil core repel the magnetic pistons.

2.) Utilizing CEMF is a method of lowering the overall power consumption required as it collects stored energy from the coils between pulses, and dumps it into a capacitor.

Tropes
Title: Re: Winding a strong electromagnet
Post by: Ergo on May 19, 2009, 10:32:56 AM
This is why the core material doesn't matter in a solenoid shaped electromagnet regarding flux levels.
It's simply due to the extremely large airgap between the poles and this translates into strong reluctance
in getting magnetised by the applied magnetizing force from the coil.
The reluctance is so strong that it doesn't matter how "easy" the core material is.
The force needed to overcome the large airgap is many times greater than the "magnetizing properties".
The reluctance can only be minimised by decreasing the airgap. And the easiest way is to bend the solenoid
shape into a C where the gap is kept as narrow as possible. And the best performance is obtained when
the C-shape is closed into a toroid shape. This is very easy to magnetise but useless as an electromagnet.

Sorry guys. There is no shortcuts in making a strong electromagnet by using exotic core materials.
But in a pulsed state, preferably at 50Hz or higher, the BEMF at turn off can be recycled at much higher
efficiency than using a regular solid iron core. This is the true benefit of using exotic core materials.
Title: Re: Winding a strong electromagnet
Post by: solinear on June 25, 2009, 12:25:01 AM
Ergo is completely correct - once you get a decent core (more than 200-500 permeability rating), the impact of getting higher permeability material is somewhat futile.

The reason why parallel coils are useless is because you end up with identical amp turns/amperage.  If you have a power supply that can handle high amperage, it would be nice for keeping voltage low, but would have zero impact upon wattage used to produce the gauss.  Actually, it would probably be more expensive, in wattage terms, because there will be a small amount of additional resistance created by the leads for each of the separate coils (relatively inconsequential though).

For creating a stronger electromagnet, wrapping your core partially around your magnet will have a much higher impact (think of a putting your electromagnet in a steel can with one side removed - the outside of the steel can would turn into your opposite pole).  Your typical industrial magnets have the can completely around so that both poles are on the same side, creating a magnet that is 3-4 times as strong (if not stronger) with the same number of amp turns.  The closer you can get the two poles together, the stronger the magnetic field will be (in gauss).  For the purposes of attracting or repelling permanent magnets, wrapping your magnet only partially around the coil would likely work best.

A good example would be to look at some industrial magnets, like http://www.magnetechcorp.com/Round.htm .  For that magnet, the outer material is likely some form of iron or steel.  When looking at their opposite pole magnets (they have one listed on their site), they have the same outer shield, but it's made of a non-ferrous material (likely aluminum).  Mattering on your application, you can use a 'U' shape (with one leg of the U having the coil wrapped around it) or an 'E' shape (with the center leg having the coil wrapped around it and the outer legs being the opposite pole as the center).
Title: Re: Winding a strong electromagnet
Post by: capthook on August 29, 2009, 10:54:01 PM
Testing coil strength for repulsion of a permanent magnet:

Another method for testing coil strength when repulsing a permanent magnet.
A length of wire is stretched taught.  A small permanent magnet is attached to a plastic washer and hung from the wire.  Washer/magnet is then pushed against the coil that is then energized for repulsion and the travel distance is measured.

One of the tests was to determine the difference in winding a coil with 1 wire vs. 2-in-hand (parallel / half the resistance).
It has been proposed that 2-in-hand will outperform as there is half the resistance, thus 2x the amps.

Results: Avg. of 10 tests on each with 9V battery.

Coil 1: 20.4"
1/2"diameter core / #22 wire / 2 1/4"L x 1 1/4" OD diameter coil / 2.85 ohms

Coil 2: 18.7" : 20.5" equalized to coil 1 (1.3ohms x 2= 2.6 ohms : 2.85/2.6 = 9.6% : 18.7" x 1.096 = 20.5")
same as coil 1 but with 2-in-hand / 1.3 ohms

Coil 3: 15.5" : 17.7" equalized to coil 1 (2.85/2.5 = 14% : 15.5" x 1.14 = 17.67")
3/8" diameter core / same as coil 1 / 2.5 ohms


Conclusions:
When results are equalized for small variations in winding accuracy, coil 1 and coil 2 provide identical results.  This is a 3rd set of test data (2 methods/results reported previously) that shows no additional benefit of coil strength by winding with multiple wires.

Coil 1, with the larger diameter core, shows a 15% increase over coil 3.

Further tests with larger diameter cores to come.
Title: Re: Winding a strong electromagnet
Post by: capthook on September 02, 2009, 01:27:58 AM
How to wind a coil with a larger diameter core?

Attached pictures show a 1-1/4" diameter 1018 core ready for winding.

Winding with an electric drill is much faster, easier and winds a neater coil than trying to do by hand.  But a large diameter core won't fit into the drill chuck.

The extra prep work is worth it - especially having to wind 4 coils.

How do YOU wind your large diameter coils?
Title: Re: Winding a strong electromagnet
Post by: ltseung888 on August 22, 2015, 03:59:06 AM
I would like to get the highest repulsion between two iron-core coils to demonstrate possible overunity.  The technique is to compare the jumping height of a coil (Output potential energy) with the Input Electrical Energy (via a DSO).

The Coils can have a hole in the middle and the jumping restricted by a non-magnetic rod.

Any useful advice?  Thank you.

More information in:
http://overunity.com/15077/ufo-propu-engine-closed-loop/new/#new

Lawrence Tseung
Title: Re: Winding a strong electromagnet
Post by: ltseung888 on August 22, 2015, 09:38:29 PM
If the magnetic strength is dependent on NI where N is the number of turns and I is the current, the chance of getting Output Potential Energy greater than Input Electrical Energy is high.  COP > 1.

The number of turns N is the key factor.

Ferromagnetic core can produce 2,000 times the magnetic strength of air-core. 

The Input Electric Energy to the air-core and the iron-core can be approximately the same but the magnetic strength can be 2,000 times different.

It is obvious that the Input Electrical Energy is not the only source of energy to repel the magnet.  Magnetic energy is lead-out via alignment of the "tiny magnets" inside the ferromagnetic core.
Title: Re: Winding a strong electromagnet
Post by: ltseung888 on August 23, 2015, 12:23:50 AM
If the magnetic strength is dependent on NI where N is the number of turns and I is the current, the chance of getting Output Potential Energy greater than Input Electrical Energy is high.  COP > 1.

The number of turns N is the key factor.

Ferromagnetic core can produce 2,000 times the magnetic strength of air-core. 

The Input Electric Energy to the air-core and the iron-core can be approximately the same but the magnetic strength can be 2,000 times different.

It is obvious that the Input Electrical Energy is not the only source of energy to repel the magnet.  Magnetic energy is lead-out via alignment of the "tiny magnets" inside the ferromagnetic core.

The Output Potential Energy/Input Electrical Energy (COP) is greater than 1.  This is theoretically predicted.  It will be confirmed by Hong Kong University or other top academic institutions.

If COP is greater than 1 in the straight line case, it will also be greater than 1 in the circular motion case.

Thus the 225HP Pulse Motor, the Laing Car, the QMOGENs, the Witts Generators are all theoretically possible.

The Chinese and USA Military Establishments have lead-out energy flying saucers.  Will they disclose such top secret?  What can we do to get them disclose such secrets to benefit the World?