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Author Topic: Winding a strong electromagnet  (Read 204283 times)

capthook

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Re: Winding a strong electromagnet
« Reply #75 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?
« Last Edit: November 25, 2008, 07:39:49 AM by capthook »

Kator01

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Re: Winding a strong electromagnet
« Reply #76 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

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

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


Xaverius

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Re: Winding a strong electromagnet
« Reply #77 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..................

capthook

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Re: Winding a strong electromagnet
« Reply #78 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.
« Last Edit: November 26, 2008, 11:54:48 AM by capthook »

Kator01

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Re: Winding a strong electromagnet
« Reply #79 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

capthook

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Re: Winding a strong electromagnet
« Reply #80 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........)

capthook

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Re: Winding a strong electromagnet
« Reply #81 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!!
« Last Edit: December 07, 2008, 03:18:29 AM by capthook »

Xaverius

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Re: Winding a strong electromagnet
« Reply #82 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.

Xaverius

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Re: Winding a strong electromagnet
« Reply #83 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.

Kator01

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Re: Winding a strong electromagnet
« Reply #84 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

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


Regards

Kator01

Regards

Kator01

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Re: Winding a strong electromagnet
« Reply #85 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

Xaverius

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Re: Winding a strong electromagnet
« Reply #86 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.

TinselKoala

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Re: Winding a strong electromagnet
« Reply #87 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.


capthook

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Re: Winding a strong electromagnet
« Reply #88 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)
« Last Edit: November 27, 2008, 11:29:07 PM by capthook »

TinselKoala

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Re: Winding a strong electromagnet
« Reply #89 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.