I'm building an electronic load and I need to protect the transistors from overvoltage. This is the over-simplified version of it:
I can't use a relay, because what if voltage changes after the relay is connected? Aside from that, I couldn't find a relay with contact voltage rating higher than 30 VDC.
I can't use any transistors because it's a 200W load with maximum current of 10A, any transistor there would be fried without a proper heatsink that I don't have. (I only have a big heatsink with fan for the main transistors.)
Can varistors help or are they too slow? How do I protect the transistors from over voltage?
Electronic load spec: 50 V / 10 A / 200W