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Re: IGBT's



Original poster: Jimmy Hynes <jphynes@xxxxxxxxx>


The main source of overvoltage is from hard-switching some current causing voltage transients across the IGBTs. The best way to cure this is to 1) install TVS (transient voltage supressors) rated for say 880V across the C-E of each IGBT, and 2) install low inductance capacitors across the power rails of the bridge. I cannot stress how crucial a low inductance setup is (the voltage spikes will be proportional to the inductance... V=-L*di/dt).


While those are important steps, I think the most important thing is to keep it from hard switching in the first place. Hard turnoffs are really bad, and can be avoided by using primary feedback, and some way of assuring a soft turn off at the end of the burst.


You still need to do what Steve was talking about to deal with the diodes reverse recovery spike due to hard turn ons though