Anyway, with an input of about 1.3A at 400V DC it was producing 36" strikes to a grounded target. The break rate was about 80 bps. The sparks had a very nice look to them, they formed and moved slowly because of the low rep rate.
All of a sudden there was a blinding flash and a huge BANG!!!! The H-bridge exploded and little pieces of IGBTs flew all over the room! I was gutted- we never even had time to take any pictures of it operating. (But Alan and Richie witnessed it so that's ok.) The explosion also took out the OLTC II power supply, ruining our day's coiling.
*Note I later found out this was due to a design flaw in the power supply. There was a very high impedance node in the protection circuit that picked up noise and made it go into oscillation when short-circuited. The high frequency oscillation (combined with the high current) caused extreme switching losses in the protection circuit's IGBT, destroying it. I have fixed this and the power supply seems to be robust now.
Next- Further work
Return to Tesla page