I am using two MOSFETs (IXFB210N30P3) at about 100kHz (with different duty cycles) to split current from a 100-200V rectifier into three separate coils. This is a very rough schematic of (one branch of) the circuit (apologies for the diagram, I'm in no way an electrical engineer), where the box is actually a PWM controller putting 15V across the gate at 100kHz.
If the diagram isn't clear, here is a hand-drawn version with the details of the FET driver. The capacitor across the FET is supposed to be a snubber circuit, but I'm not sure if I need a smaller capacitor or a resistor in series to actually work. Either way, with even just a few volts across the coil (the 1 ohm, 6 mH component), I start seeing huge voltage spikes at the MOSFET gate
which I haven't been able to remove. I imagine this has something to do with the enormous inductance of the coil, but I've tried a number of filters and diodes with little success. I'm wondering if someone could explain this to me, and potentially recommend a solution. I have ferrite beads on just about every component, and a few low pass RC filters now, but the voltage spikes are still there. What value resistors and capacitors should I have on the snubber circuit across the FET? The diode and FET are quite large, so potentially they're just too slow for the high-frequency switching.