class c chopper problem

[xaolong]

hi Tahmid ,

thanx for advice i added 1k resistor each igbt and they work

but still there is something wrong,
when i apply pwm signal to igbts the main bus voltage (200V) is changing, whatever i tried i couldnt make it fixed, do you have and advice for this problem too? should i change the capasitors with ones greater capasity

here is the modificated circuit

Taken from:https://www.edaboard.com/threads/197011/

I am currently working on building a dc class c chopper. It is rather similar to the one as depicted in the quoted picture. Instead of three chopper, I am only using one.I encountered the same problem. The 2 power mosfet blew up when powering a shunt dc motor coupled to a synchronos generator with a rating of 230v 3 to 10a. It managed to turn on the shunt motor for a while at 60v 2.5a not reaching its max speed,but there seemed to be a short which blew the power mosfet instantly.On the other hand, it works fine with a 12v 3a dc brushess fan.I not sure whether is it due to the back emf(whereby I didn't attached a resistor to burn off the emf) or the parasite capacitance at the gate to source, my dead time is aproximately 1us which I think should be enough to prevent both mosfet from switching on. If the problem lies with the resistor between the gate and source may I know what power rating resistor would do (eg. 1k ohm ?watt)
Thank you!

 

[Prototyp_V1.0]

Maybe one of the mosfet's where bad. Bad mosfets tend to short when voltage rises to a certain level, but below the ratings.

Maybe the mosfet is too slow to change state, compared to the chip. Maybe a coil between drain's would help, so it reduces peak currents due to slow mosfets.