Quote:
Originally Posted by adamj12b
More isn't always better. having multip MOSFET drivers increases the chance of them being out of sync from each other turning switches on off microseconds before or after each other. Paul used one MOSFET driver because that was all that was needed to drive all of the MOSFETs. The total gate charge of all ten MOSFETs is still less than limit on one driver.
the controller turns turn on off extremely quickly when current limiting. The motor actually makes like a groaning noise and switching on and off only a few hundred times a second. What you feel is probably individual MOSFET blowing up.
Adam
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Hi Adam.
Thanks for the reply.
Yes I was worried about multiple drivers switching at different times but thought maybe at the fairly slow switching speed it would not have too much of an effect. Someone had told me that each mosfet could require up to about 3.5amps to charge fully and with the 30ohm resistors they might not make it.
I will revert to the one, I had thought of connecting all the outputs of say three drivers together to combine the power capability... but maybe not.
I have decided to fit 75A 600V IGBT's instead of pure MOSFET's the info on the net seems to indicate that these are a better proposition.
On the current limiting front what do you think of the idea of instead of chopping the motor power zero and back up I over ride the throttle pot and drop it to say one third power with a slight delay on releasing. I feel it might be a little kinder on everything, it would still operate fast but a little smoother and I would still have some drive power.
I have already got a fail safe in that if the cct goes into over current for 1.6secs continuous (everything goes short and over current has no effect) then the main contactor is dropped out.
Regards John