protection circuitry for IGBTs in inverter

[mc]

I have an three phase inverters (for induction motor) which use IGBTs(without protection circuitry). The problem is every other day, these IGBTs are getting blown out. So, I am thinking of designing protection circuitry for IGBTs. The inverter is driven by 300VDC and the IGBTs are driven by PWM signals from IR21362 driver IC. But I am really stuck on how to design a proper protection scheme. I guess there out to be standard protection methods out there. Your expert advices on this will really be appreciated.

[AN920]

You need to provide more information

1) Which IGBT's are you using?
2) What size motor are you driving?
3) What type of load. Pump, fan etc.

Under which conditions do they fail?