Quote:
Originally Posted by MightyMirage
this is pretty much true across the board?
|
Yes. Eddy current losses increase with the square of speed (although field strength decreases, so it's a linear increase in losses), and cooling fan losses increase with the cube of speed. Lower speed is nearly always better.
If you look at a similar amperage and kV permanent magnet motor to an alternator you'll notice that they need 1kW just to spin at full speed. Since the field current of an alternator is reduced at high speed it's more like a few hundred watts, but that's still a lot.