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Author Topic: Winding a strong electromagnet  (Read 178614 times)

Offline capthook

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Winding a strong electromagnet
« 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.


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Winding a strong electromagnet
« on: October 28, 2008, 06:27:47 PM »

Offline capthook

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Re: Winding a strong electromagnet
« Reply #1 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?

Offline capthook

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Re: Winding a strong electromagnet
« Reply #2 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)

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Re: Winding a strong electromagnet
« Reply #2 on: October 28, 2008, 06:52:28 PM »
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Offline mondrasek

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Re: Winding a strong electromagnet
« Reply #3 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.

Offline Spider

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Re: Winding a strong electromagnet
« Reply #4 on: October 28, 2008, 08:57:56 PM »
Google: Brooks Coil :)


Spider

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Re: Winding a strong electromagnet
« Reply #4 on: October 28, 2008, 08:57:56 PM »
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Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #5 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.

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #6 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.

Free Energy | searching for free energy and discussing free energy

Re: Winding a strong electromagnet
« Reply #6 on: October 29, 2008, 07:51:16 AM »
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Offline capthook

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Re: Winding a strong electromagnet
« Reply #7 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?
« Last Edit: October 29, 2008, 09:24:07 AM by capthook »

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #8 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.

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Re: Winding a strong electromagnet
« Reply #8 on: October 29, 2008, 10:54:06 PM »
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Offline capthook

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Re: Winding a strong electromagnet
« Reply #9 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?

Offline mondrasek

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Re: Winding a strong electromagnet
« Reply #10 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.

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Re: Winding a strong electromagnet
« Reply #10 on: October 30, 2008, 04:54:03 PM »
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Offline TinselKoala

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Re: Winding a strong electromagnet
« Reply #11 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.

Offline capthook

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Re: Winding a strong electromagnet
« Reply #12 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!
« Last Edit: October 31, 2008, 06:16:10 AM by capthook »

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #13 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.

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #14 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.

 

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