The following is a schematic for a solenoid that failed after ~200k cycles. I found that the MOSFET drain to source failed short. I am getting~ 26 ohms resistance.
The way this circuit works is as follow: SW1 is a microswitch that gets cycled mechanically (one cycle is when the switch moves from NC to NO then to NC) when that happens, the solenoid turns off after ~45 ms delay it then turns on again.
I have removed the dead MOSFET and simulated a ground removal (MOSFET turning off). The scope screen shot is captured below. You could see a very fast pulse of almost 84 V with a 54 ns rise time.
The MOSFET drain-source max rating is 100 V.
What could have caused the MOSFET failure specially after so many cycles and how I could make this circuit more robust?
Mosfet datasheet link:
Looking forward to your feedback. Thank you in advance.
TVS2 Datasheet link:
Updating the MOSFET Turn off time scope shot