EDIT: SOLVEDHi,
as some of You might know I'm remaking my sit/stand table control PCB and i'm keep getting trouble making it work – mosfet keeps dying.
I ordered 100V 57A 23mOhm IRF3710
http://www.irf.com/product-info/datasheets/data/irf3710.pdfI didn't do a lot of testing with it due to being a noob and picked too high resistance fets for this purpose, but it seems they work, getting very hot in a few sec when only one actuator is powered (need to power two), so unless I want to burn my house down (heatsinks inbound) I needed to get less resistance fets, and I did.
Today I received 100V 195A 2mOhms (more than 11 times less resistance)
https://www.infineon.com/dgdl/irfp4468pbf.pdf?fileId=5546d462533600a40153562c73472019Aaaaaaand I killed 2 of them already....
I got back to old PCB and compared old and new circuits and found out that I missed 1 extra diode near mosfet and 2 small SMD (ceramic?) capacitors, picture below – marked them in yellow.
Mosfet purpose is to PWM 50V to ~24V.
In Picture on the left is old PCB, on the right is new one (I removed 2 extra mosfets because all they do is on/off power to relays, no PWM)
All mosfest I burned were without those 3 components, is this it? Is this the reason why fets dies? Before killing 3rd mosfet I thought I give it a try on this forum
I know that mosfets dies probably from voltage spike from DC motors, but should diodes next to relays take care of it?
I'm assuming that those small caps "eats" spike and protects fets, please enlighten me, I'm getting a bit frustrating here
BTW, I killed original mosfets same way as well (I know, I know, I'm a genus...)
Original mosfet markings:
ON5247
PEm 0519 D6
5291
OLD PCB (don't mind other parts, its for logic):