IGBT failing on load

[vinu gopalakrishnan]

For my 3 phase inverter based speed control of IM, whenever i test it IGBT burns out.
if i take the DC bus from a voltage regulator there is no problem, motor doesnt move but a humming sound can be heard. If i take the DC from a rectifier, two of the IGBTs allways fail.Why does this happen?
please note that:
IGBT 1200v,35A (15n120)
RC snubbers used.
dead time of 3.6us given
IM- 3hp, 1500rpm....
pls help......

 

[jpsganesh]

During testing give more dead time. So that u can ensure no shoot through.

After rectifier did u put filter capacitor? That is mandatory.

Check the pulse pattern.

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post ur ckt. so that we can suggest u better.