Quote:
Originally Posted by lutach
A question for the engineers out there  . Would it make sense to have a lot of MOSFET (Lets say a FET driver already was chosen and powerful enough to drive close to 300 FETs) on a controller to make each MOSFET work less to provide the power some of us need? Lets say I have a design for a controller with 240 MOSFET total, 80 per board, would it actually run cooler because there will be less load for each MOSFET? The reason for this is I see a few controllers with less FET that actually run a bit hot, but a controller with the same spec (AMP rating wise) with more FETs will actually run cooler. One example is one of my 30A old Kontronik controller runs cooler then some of the latest 35A controllers. |
Very nice post,
Five-oh-joe 
More fet's bigger foot print more surface area to dissipate heat, more overall losses...
Fet's driver need to be very nice or need to be on each FET's board, but try to sync them...possible.
Let's do quick theoretical calc, if you can drive fet's as fast as fet can switch (non-real) then 300 fet's you meant total, so 50 fet's per leg/100 fet's per phase. Dynamic losses would be ~10W on fet and ~10W on diode, check attached image. With 3 phases your loss would be ~60W just for switching at 15kHz PWM, that would cook ESC pretty fast without proper heatsinking, by the way can be a nice heater :)
It would be nice to keep dynamic losses matched to pcb heat dissipation capacity.
I am pretty sure, Patrick can add/correct my post if required.