I'm working on a coilgun and I need to discharge a capacitor bank through a coil to create a strong magnetic field. My coil has a resistance of 266 milliohms and when fully charged, the capacitors are at 200V with a capacitance of 4700uF total. This will result in a peak current of 750A (ignoring wire resistance and ESR of the capacitors). Up until now I have just touched the wires together to close the circuit but I need to time the switching in a controlled way. My problem is that I have no clue what component to use to switch ~700A 200V. Of course the 700A peak is only for a very short amount of time and the whole pulse should last around a millisecond.
I have tried using 5x irfp260n MOSFETS in parallel, each MOSFET should be able to handle 200A peak so it would total 1000A when connected in parallel. Unfortunately one of the MOSFETS always dies after a couple shots (I did take care of the reverse voltage generated by the coil). I also am aware that connecting MOSFETS in parallel is generally not a good practice.
I have looked into thyristors but the inability to switch them off through the gate makes them useless for me. "Gate turn-off thyristors" looked interesting but I could only find really expensive ones (in order of hunderds of euros). IGBTs are known for being able to handle more current but I failed to find any that were rated for this kind of current.
Does anyone know a solution to switch 700A 200VDC for 1 millisecond?