Original poster: Steve Conner <steve@xxxxxxxxxxxx>
Anyway, commercial product (not 833C compliant) is allowed to fail and will someday. Electron tunneling will put small holes in silicon no mater what you do (run at spec), and someday a path to metal will happen.
If you ever run your DRSSTC long enough for this to happen, I'll eat my hat, and any other items of clothing I might have on at the time. Assuming I haven't died of old age that is. I'm no reliability expert, but as far as I understand, if the device is run within its ratings, systematic failures like this should not happen for >100,000 hours.
There isn't much work done on reliability of IGBTs that are pushed outside their ratings (well not in the public domain anyway- maybe you know some "trade secrets" that I don't) but I'm willing to bet that that 100,000 hour figure drops like a stone as soon as you go outside the datasheet peak current. I don't know why it would, but I just have that feeling. After all, if the devices were capable of taking higher peak currents with good reliability, then the manufacturer would print that bigger number on his spec sheet to make the device look better.
So I reckon it all comes down to the same tradeoff as Terry Fritz explored with MMCs. He discovered that you can run the capacitors outside of their AC voltage rating. It shortens their life drastically, often to less than 100 hours. But that is still plenty enough for hobby Tesla coil use. We discovered that you can run IGBTs outside their peak current ratings, but the life implications are nothing more than a "Bad feeling" just now. That is in opposition to the case with MMC caps, where there is even an equation to tell you how long they will last at a given overvoltage. If someone could figure out a similar equation for overcurrented IGBTs, it would be worth a NoPig Prize ;-)
Steve Conner http://www.scopeboy.com/