IGBT death

[AstRii]

Hello,
I recently blew up my IGBTs FGA60N65SMD TO-247.
I use these IGBTs in my DRSSTC and i always ran the tesla coil at about 120VAC input.
This time i wanted to go higher, i slowly rose the voltage and at 190VAC it popped
I was sensing the current on the primary and there were 280A peaks. I ran it with ontime 100us at BPS of 340.
I checked out these IGBTS on http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/. They should
withstand 300A primary current and i used pretty low ontime. What do you think could cause the death of my IGBTs?
I'm using this inverter schematics https://prnt.sc/pot281 (snubber and bus caps not on schematics)
All other components survived it, so i think it wasn't from any over-voltage transients, they would destroy the bipolar diodes across the IGBTs first.

[Hydron]

280A is still pushing them pretty hard! Were you scoping the IGBTs to see how big the transients actually were? What is the resonant frequency?

If you're gonna stick with TO-247 there is a slightly higher current version of the one you popped, namely the FGY75N60SMD - a little higher current rating, a little lower voltage (though I'm not sure whether the 600 vs 650V rating is really due to different silicon or more the package rating - e.g. the FGA60N65SMD appears to use the same die as the FGH60N60SMD).

[AstRii]

I was not scoping the transients, since i don't have differential probe. The resonant frequency is about 210kHz. So i should stick with lower currents?
Therefore lower ontimes?

[Hydron]

You don't always need lower on-time to reduce peak current - if the tuning isn't optimal then fixing that may reduce the current a bit (due to better energy transfer into the secondary and then streamer). Setting a safe over-current trip point would help reduce the risk while tuning.

Other than that you might try a couple of IGBTs in parallel on each leg - they won't share current perfectly (especially during switching, though this isn't so critical on a zero-current-switching DRSSTC) but may help enough to be worth it.

Finally if it is definitely the peak current doing the damage (rather than duty cycle), then a freewheeling type controller (e.g. UD+, UD3) may also help - this would allow long on-times while preventing the peak current rising above a setpoint.

Edit: Oh, and if you don't have a differential probe but do have a 100X probe (10X probe is unlikely to have a big enough peak voltage spec), then you could just scope between mains earth (i.e. same as the scope's earth) and the bridge output. If you're using a full wave (non-doubling) rectifier then the mains voltage will be super-imposed on the signal, but you'll still be able to see the 210kHz switching as well.