Please help ! IGBT exploded ...

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Original poster: "Rajesh Seenivasan" <rajeshkvs-at-hotmail-dot-com> 

Dear forum members,

Yesterday I was experimenting with an old IGBT - BSM100GB60DLC, which I got 
from my friend,
for my SSTC. I used the same gate driver I designed for IRFP460 MOSFET H 
bridge.
I connected the terminals to 220V line and neutral and switched ON my gate 
drive circuit.
The IGBT exploded immediately ! I did not give any load to IGBT. The H 
Bridge's
output terminals were not connected to anything !
The gate drive was at 70kHz approx.
I observed that the gate drive waveform was not clean like a square wave.
Any advise for me ?