Update #2 on my TIG inverter project

Received 4 Toshiba 200 amp IGBTs today. They are very massive, each is about 1 lb, all four mounted on a large heatsink. I was able to test drive one of them. I simply connected its gate/emitter to my wavetek, working in pulse mode, one pulse per second, positive and negative.

The collector and emitter were connected to about 2-5 VDC (I varied that) from my trusty dual HP power supply. I was able to track wavetek's output on my oscilloscope and also saw amp meter of the HP power supply jump when the IGBT was conducting, and return to zero when it was not conducting.

One disappointment was that turning off gate/emitter voltage on the IGBT did not turn the collector/emitter current off. I had to actually supply negative voltage to turn it off. Perhaps having a 10k resistor between gate and emitter would help (maybe the gate/emitter acts as a capacitor), otherwise this thing is a potential short in case of a failure of the gate driver power supply, it could be left in an all conducting state.

Another interesting finding was that there was voltage drop between collector and emitter. Thusly, if I set my voltage on the power supply too low, it would not conduct at all. I had to set it high enough to overcome that opposing voltage.

If anyone is interested, I can set up a project webpage under

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with details of my progress.

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