user TURBO?s replication of Steven Mark?s TPU ?

[Groundloop]

[EDIT] Deleted.

[MeggerMan]

Hi Alex,
Yes, I would go for the easy option first, at least you can drop a link across the resistor legs quite easy.

Hi Grumpy,
It is not a zener diode, its a schottky diode, very low dropout, just my poor sketching, the curly bits are a bit unclear, zener has slants:
http://www.onsemi.com/pub/Collateral/1N5820-D.PDF

The other is an ultra fast diode:
http://www.vishay.com/docs/88685/mur420.pdf

Mosfet:
http://www.irf.com/product-info/datasheets/data/irf3707.pdf

Circuit is from page 8 of this document:
http://focus.ti.com/lit/ds/symlink/uc28025.pdf

Regards
Rob

[Groundloop]

[EDIT] Deleted.

[MeggerMan]

Hi Alex,
I am building the MEG replication, not the TPU (at the moment).
The input coils on the MEG consist  of 2 coils, each with 150 turns of 0.4mm enameled copper wire and are unlikely to carry much current. I have not wound them yet so I cannot say what the resistance will be.

Like I said before, I would say that your input voltage needs to be very low, say only a couple of volts.
If you reduce the duty, then the average current will also fall.

So if you can for now, try a much lower voltage, you have very heavy gauge wire for your input coils.  What is the resistance of the coils?
I am guessing the resistance will be less than 0.1 ohms so you will need a good meter to give an accurate reading.
Average current with 50% duty = 18A
Current peak = 36A
Total resistance = V/I = 12/36 = 0.3333 Ohms
IRF540 on resistance = 0.044 Ohms.
Coil resistance = 0.3333 - 0.044 = 0.289 Ohms (this is my guess)

I think you will need to play with the frequencies to find resonance and at that point the output should go up.

Starcruiser is probably the best person ask about testing your setup, I can only advise on pulse driving.  Your ideal frequencies will need to match your coil setup, and most likely be a little higher than others because the number of turns your input coils look less than others I have seen on this forum.
Keep us posted on your progress.

Regards

Rob

[Thaelin]

@groundloop
   Did the math on your coils.
      P=12X18 for your 216 watts

Take that and solve for the R

That gives you .66666 ohms for the coils. Basicly a dead short for the  Fets and thats why the overheat. I have found that a coil needs to be around 6 ohms to run fairly cool. I too have had the same problems with the heating up of the fets. This brings me to take a new look at how big these would need to be vs the purpose involved.