I am trying to build an inductive oven control (for temperatures up to 1500 C), that controls the temperature by turning on the the inductive oven on and off like a commercial inductive hotplate.
The problem I am facing is, that the IGBTs (K75EEH5 rated for 75Amps and 650V) I am using for switching got killed twice with my schematic. The collector and emitter is permanently shorted, even after shorting gate and emitter.
Here is a short clip that I filmed for myself as proof that it is working with a 24V light bulb (not an inductive load!); sorry that its in german but it should give you a rough idea how it looks The IGBT is isolated from the cooling body.
The first time It didn't work at all (no flyback-diode at the load). The second time it worked when running a test with 24V power (this time with flyback diode) but after shutting down and then starting with 36V it shorted like it did the first time.
My Arduino microcontroller controls the signal by applying 5V to the D0 pin when turning on and 0V when turning off.
Not shown in the schematic is, that the Arduino is connected to a computer which sends commands, that the microcontroller executes.
It says in the datasheet, that the driver module (1EDI60I12AF) and the voltage converter SIM-0512D is galvanically isolated.
What I will change next time is:
- Swap places of load and IGBT (shouldn't matter though)
- Add a 1k to 10k Ohm resistor between gate and emitter to slowly discharge when not in operation. (doesn't matter either)
- Measure voltage across collector to emitter and gate to emitter to identify spikes. (Gate emitter voltage musn't be more than +-20V)
What I need now is some external input on what might be causing the death of my IGBTs. I will provide you with any further information that I can give you.