InPhase Posted May 15, 2022 Share Posted May 15, 2022 (edited) This is a different beast than the other FET blowing problem so I started a new thread. This time, it's personal 😂 I've been tinkering around for about a year building a DIY inverter. Ben in WV sent me a transformer and I've gathered the other stuff from Mouser and Digikey. The gist of it is an H-bridge with two FETs per quadrant and each FET has its own TLP351 driver. Isolated supplies power the two high side quadrants and the low side shares a 12 volt supply. Each gate has a 10 ohm resistor and reverse biased Schottky as well as a 15 V zener. The SPWM comes from an Arduino Nano through a pair of IRF21844 half bridge drivers and then to the TLP351s. Lots of perfboard prototyping proved the theory in my mind and I had some PCBs made as modular FET boards. I've finally just assembled everything using IRFB7545 MOSFETs and was able to get around 1 kW out of it before I reached the limit of my power supply. Incandescent lamps, space heaters, and brushed motors as test loads. But as soon as I tried to run my 1/3 HP bench grinder, the FETs instantaneously exploded. This was with four FETs. So I tried again with eight FETs thinking I just need to overcome the locked rotor current of the stationary motor. Nope, instant explosion. Both with and without RC snubbers across the drain-source. Finally, I replaced the FETs with some IRF3205s I got from work and managed to blow the low side FETs just by turning a 250 watt lamp off and back on. The drive signals are very clean. There is no ringing that I can see at the gates. What are your thoughts on this Sid? I imagine you've blown up a few FETs and might have some insight. Edited May 15, 2022 by InPhase Typo Quote Link to comment Share on other sites More sharing options...
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