I have a 3-phase bridge rectifier (shown below). I am using an IGBT (STGE200NB60S) to limit the inrush current from the capacitors at start up. I also added the NTC thermisters to help with the inrush current. That end is all fine in that the main breaker is not tripping and and the current is fairly smooth looking.

The problem is that the IGBT is failing a lot, the collector-emitter is completely shorted. Its probably caused by a voltage spike at turn off. I cannot capture it exactly as fails randomly.

The IGBT in question does not have a built in diode. Should I add one and should I add a snubber circuit or would a flyback diode on the load be more suitable or all of the above.

What is the best way to protect the device?

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Thanks.

edit 1:

Gate driver

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Waveforms: diff probe scale 1/50

Vge

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Vce

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  • 1
    When and how are you gating the IGBT? – Marla Sep 14 at 18:40
  • @Marla - The gate driver circuit has been added to the edit. I am gradually turning on the gate from the MCU so slowly charge the caps. – MXG123 yesterday
  • 1
    Are you using an IGBT in the linear region? – Jeroen3 yesterday
  • @Jeroen3 - Yes on start up to charge the caps I am using the IGBT in the linear region then will switch to the active region when charged. – MXG123 yesterday
  • I don't think you can do that. Can't you use phase-angle dimming? – Jeroen3 yesterday

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