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Old 06-17-2017, 06:43 PM   #3134 (permalink)
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Originally Posted by MPaulHolmes View Post
I know they have low power 6 pack chips that can be very affordable, with a maximum current of maybe 10 amps or something. But they are not isolated. I"ve never messed around with those, but I would like to eventually. Those are rated for 600v though, so the sevcon probably uses some low voltage mosfets and boot-strapping (however the heck that works). The 6 isolated supply way of doing it is the sledge hammer approach.

I love the idea of the LED morse code!!
If the controller is very close to the motor, and it pretty much HAS to be on a vehicle ... then the reflected wave stuff is minimized (since the impedance of the cable is quite different from the impedance of the motor, any waves or pulses will 'reflect' from the motor and you can see a bit over 2X buss voltage at the motor terminals and the controller terminals). A 48V (57V) buss with full reflection is only 96V (115V). Add some safety factor ... 200V (230V) or so? That's still well within the MOSFET range. But driving MOSFETs to switch both the high side and low side takes a bit more circuitry and effort .. so I read. The EVTV episode where they take apart a blown-up TESLA controller showed a *BUNCH* of what looked like TO22 MOSFETs clamped to water-cooled tubes ... not sure if they mixed P channel for switching the positive side with N channel for the negative side?

Mouser lists 300V 400A IGBTs at $35 each, you'd need 6, plus the low esr caps .. anything else that would change based on the lower voltage? I know that you have 6 isolated supplies - would that change with the lower voltage? Somehow I doubt it.

400A does not match the 650A SEVCON I have but SEVCON have a 450A model available for the Ranger EV as well. I'm not actually sure what they would do continuous either. If you are pulling 650A for more than a few seconds, you would melt the cables, the motor, or the batteries even if the controller COULD put out that sort of power.

It's interesting to think about, anyway
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