Here is a quick run-down on a more detailed toriod inductor analysis.
It turns out I was quite a bit off on the first stab - the LI^2 calculation was off.
Fortunately, that big core I mentioned will work at 25kHz, with a max design current of 200A.
I reduced the current density to 500A/cm^2, and this requires 3 parallel windings.
Specs:
L = 110uH
Design current: 200A Absolute max current 300A
copper loss: approximately 400W
core loss: 13W
Inductor OD: 228mm (this includes the windings)
Inductor thickness: 203mm
Core weight: 2800g
Winding weight: 10.9kg total weight: 13.7kg >> 30lbs.
3 windings of 6AWG wire; 127 turns >> very high fill factor of 66%
So, it will work for the booster switching at 25kHz. Unfortunately it's much bigger than I had wanted, but losses are low. I guess it's ok at 30lbs, but that's pretty chunky IMHO.
Most of the weight is windings. A quick way to reduce weight would be to increase the current density to 800A/cm^2. This would make a 2 parallel winding coil. It may not be so bad, as the DC current is 175A. The 202A is the combination of the DC+AC, so with a duty cycle of .3375, the two windings would probably be ok.
I need to sleep.
- E*clipse