I am running 32- 3amp DC motors on a 12v system with and alternator and using N Type MOSFETS to drive the motors. I am having problems with the MOSFETS failing...going into a closed state. I have a kickback diode between the drain and 12v. Its a 3S2D. My frequency to the MOSFETS is 400 hz. The MOSFETS fail randomly. It will run from 2 minutes to 5 hours with no problems, then randomly a MOSFET will fail. I was able to get a scope on the drains today. With the ES2D's installed I still see a 70 volt spike when the MOSFET is turned off. I ordered a FFPF20UP20DN rectifier with a much higher voltage and amperage rating.
I know the MOSFETS aren't failing due to amperage overload. I even tried using two MOSFETS in parallel and they still failed. There is no heat on the MOSFET either.
I have been reading up on using a resistor along with a rectifier to help with kickback. How do I get the right resistor?
This thing has been a <snip> to sort out with its randomness of failure. Any input is greatly appreciated.
I know the MOSFETS aren't failing due to amperage overload. I even tried using two MOSFETS in parallel and they still failed. There is no heat on the MOSFET either.
I have been reading up on using a resistor along with a rectifier to help with kickback. How do I get the right resistor?
This thing has been a <snip> to sort out with its randomness of failure. Any input is greatly appreciated.
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