What size KW motor?
When you start the motor are you starting it at low speed?
Was the FET dead the second time?
Could be the start up current is killing the FET.
Also note you are mixing EARTH and Signal ground - Possibly should all be
tied to signal ground only apart from the bypass capacitors at the incoming
supply.

:-) Roy

 where I have no GROUND connection.

        The problem it presented was that it worked fine for a few days,
one day, I live my place for about an hour and a half and leave the
board powered, but with out any input signal (no PWM). When I came back,
I turn on the control board, wich only sends some PWM to the power board
and then I couldn t stop the motor anymore, even if I disconnect the PWM
source from the power board.

        Okay, I changed the FET (by the way it s a IRF 730) and though,
ok, perhaps it has to happened, let's see if it happens again. It worked
fine the rest of the day. When my day finished, I just unplug everything
from the mains and leave it there.

        This morning when I turn on the boards, it didn't work again,
but this time the motor doesn't receive any power at all, I know that
there is pWM, the 300V bus is powered,....



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