Winding a strong electromagnet

[capthook]

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]

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!!

[Xaverius]

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!!    (+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]

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]

Hi Xaverius,

just a short note on your calculation because this also confused me at the beginning of this discussion:

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