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I've got a way to get rid of the isolation pads now. It started with an idea from someone that got a power board from me (Michael Black is his name), who figured a way to remove the isolation pad. I modified the idea to reduce the loop inductance.
Each mosfet will be bolted to a 1/2" x 1.5" copper bus bar which will also act as the heat spreader. That heat spreader will be bolted directly to a finned heatsink. A fan will suck air across the heatsink fins. The fins will be inside the controller, since they will be connected to M-.
The diodes will be connected to a 1/2" x 1.5" copper bus bar which also acts as a heat spreader. IT will be connected to its own finned heat sink, and will have a fan sucking air across its fins. The fins will be exposed to the outside air, but the electronics inside won't be, so no dirt on the electronics will be possible. The modified power board is almost done. The plan is to use 12 gigamos mosfets, 230amp 200v, and 12 schottky diodes that are rated for 240amp each.
the thermal resistance should be very very tiny. And the equivalent of a 1" x 1.5" x 10" copper block, but smaller loop than anything I've done so far. The mosfets will be able to be mounted so that only the thick part of the legs are right up against the pcb. I think 140amp per device will be possible.
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