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Author Topic: Winding a strong electromagnet  (Read 204294 times)

capthook

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Re: Winding a strong electromagnet
« Reply #45 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.

capthook

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Re: Winding a strong electromagnet
« Reply #46 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?


Kator01

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Re: Winding a strong electromagnet
« Reply #47 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


hoptoad

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Re: Winding a strong electromagnet
« Reply #48 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.

Xaverius

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Re: Winding a strong electromagnet
« Reply #49 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.

Xaverius

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Re: Winding a strong electromagnet
« Reply #50 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.

capthook

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Re: Winding a strong electromagnet
« Reply #51 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.

« Last Edit: November 09, 2008, 11:31:12 AM by capthook »

capthook

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Re: Winding a strong electromagnet
« Reply #52 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."

i_ron

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Re: Winding a strong electromagnet
« Reply #53 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

Kator01

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Re: Winding a strong electromagnet
« Reply #54 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

Xaverius

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Re: Winding a strong electromagnet
« Reply #55 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.

Kator01

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Re: Winding a strong electromagnet
« Reply #56 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

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


capthook

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Re: Winding a strong electromagnet
« Reply #57 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?)
« Last Edit: November 09, 2008, 09:56:05 PM by capthook »

Xaverius

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Re: Winding a strong electromagnet
« Reply #58 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!

capthook

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Re: Winding a strong electromagnet
« Reply #59 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.....
« Last Edit: November 10, 2008, 12:53:26 PM by capthook »