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Paul,
Don't you want to the forensic examination on your controller. After all, nobody knows it better than you, no offense to Ben.
A couple thoughts:
One of the advantages to Mosfets over IGBTs is that they have a positive temperature coefficient. This means the hotter they get the larger their voltage drop, so it helps balance the current. The ones with a higher temperature get less of the current. IGBTs are prone to thermal runaway due to their negative temperature coefficient. That makes them hard to parallel, verses Mosfets. So, slight variations in the pressure against the heat sink may not be the problem. No guarantee, but I wouldn't jump to conclusions.
Regarding safety. You may recall that I suggested that the controller take care of engaging the precharge resistor, time delay and then the closing the main contactor. If the controller is in charge of closing the main contactor, it can also open it back up the instant it senses a fault. Failing in full throttle mode with no controller interlock (besides a manual disconnect) is not safe. We all are glad Ben is OK, but we have to redesign for safety first.
Its great that Fran is helping you redesign the control board. Remember my offer to pay for the first batch of control boards for you. Sounds like we may be getting closer.
I hope your not feeling to bad about this failure. We learn more from failure than we do from success.
Roger
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