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Author Topic: Winding a strong electromagnet  (Read 204277 times)

capthook

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Re: Winding a strong electromagnet
« Reply #105 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)

capthook

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Re: Winding a strong electromagnet
« Reply #106 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........

Xaverius

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Re: Winding a strong electromagnet
« Reply #107 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


Xaverius

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Re: Winding a strong electromagnet
« Reply #108 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?

capthook

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Re: Winding a strong electromagnet
« Reply #109 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.

capthook

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Re: Winding a strong electromagnet
« Reply #110 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
« Last Edit: December 03, 2008, 10:36:10 AM by capthook »

Xaverius

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Re: Winding a strong electromagnet
« Reply #111 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




Xaverius

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Re: Winding a strong electromagnet
« Reply #112 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.

capthook

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Re: Winding a strong electromagnet
« Reply #113 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.
« Last Edit: December 04, 2008, 07:50:21 PM by capthook »

Xaverius

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Re: Winding a strong electromagnet
« Reply #114 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?

capthook

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Re: Winding a strong electromagnet
« Reply #115 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?

capthook

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Re: Winding a strong electromagnet
« Reply #116 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.

Xaverius

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Re: Winding a strong electromagnet
« Reply #117 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.

Xaverius

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Re: Winding a strong electromagnet
« Reply #118 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?

capthook

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Re: Winding a strong electromagnet
« Reply #119 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.