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Author Topic: Winding a strong electromagnet  (Read 178609 times)

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #60 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.

Free Energy | searching for free energy and discussing free energy

Re: Winding a strong electromagnet
« Reply #60 on: November 11, 2008, 06:04:12 AM »

Offline capthook

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Re: Winding a strong electromagnet
« Reply #61 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

Offline capthook

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Re: Winding a strong electromagnet
« Reply #62 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  ::)

Free Energy | searching for free energy and discussing free energy

Re: Winding a strong electromagnet
« Reply #62 on: November 13, 2008, 02:35:11 AM »
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Offline capthook

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Re: Winding a strong electromagnet
« Reply #63 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.

Offline Freezer

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Re: Winding a strong electromagnet
« Reply #64 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

Free Energy | searching for free energy and discussing free energy

Re: Winding a strong electromagnet
« Reply #64 on: November 13, 2008, 04:46:53 AM »
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Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #65 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!

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #66 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.................

Free Energy | searching for free energy and discussing free energy

Re: Winding a strong electromagnet
« Reply #66 on: November 13, 2008, 07:59:05 PM »
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Offline capthook

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Re: Winding a strong electromagnet
« Reply #67 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......
« Last Edit: November 21, 2008, 10:36:15 AM by capthook »

Offline capthook

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Re: Winding a strong electromagnet
« Reply #68 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?

?


Free Energy | searching for free energy and discussing free energy

Re: Winding a strong electromagnet
« Reply #68 on: November 22, 2008, 02:51:52 AM »
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Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #69 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.

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #70 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.........

Free Energy | searching for free energy and discussing free energy

Re: Winding a strong electromagnet
« Reply #70 on: November 23, 2008, 08:49:26 AM »
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Offline capthook

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Re: Winding a strong electromagnet
« Reply #71 on: November 24, 2008, 07:12:23 AM »
Attached are useful (and hard to find) material B/H curve comparisons and some annealing data.........

Offline capthook

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Re: Winding a strong electromagnet
« Reply #72 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?
« Last Edit: November 24, 2008, 11:16:17 PM by capthook »

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #73 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

Offline Xaverius

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Re: Winding a strong electromagnet
« Reply #74 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.

 

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