Quote:
Originally Posted by isaac_alaska
as stated before, the reason for going with igbt's and higher voltage would be for efficiency purposes. right now, from what i've read, it looks like the mosfets in most motor controllers are dumping around 50 watts of heat each. .
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A MOSFET controller has the potential for greater efficiency.
A IGBT will always drop a volt or two. Yes, voltage drop is reduced a bit under load, but not by much.
A MOSFET can be modeled as a resistor, and you can parallel many more of them. If the device has an on resistance of 6.5 milliohm, and you are putting a steady state 20 amps through each, that's only a 0.13V drop, about 1/10 the power loss of the IGBT design. Neglecting the switching losses (which will still be lower than for an IGBT), that's only 2.6 watts per device.
Yes, that's a unfair comparison. It omits many other efficiency effects. And the situation can reverse at peak loads. But in general a MOSFET design will be more efficient. It's just easier to throw in a few more device than buy a bigger heatsink.