I know AC is more expensive and DC does quite have the performance... but I'd like a secondary input. Cost is of no matter, however performance, torque, maintenance, and efficiency are all concerns.
If you look at motors like the Tesla motors motor or the UQM powerphase 150, it's obvious that AC has more potential power to weight. But you can't buy either one of those motors, no matter how much you're willing to pay. They're only available e to manufacturers. Of the motors you can actually get, DC is just as good. Power and peak efficiency are about the same, AC being slightly more efficient. AC can rev a little higher in general and DC has more torque. So you gear down the AC a little farther to get the same acceleration. Gearing it down also gets the motor in it's peak efficiency range sooner, but if you use a transmission (which I don't like doing, you shouldn't have to with the right motor) that's not a factor. The power band is generally a little wider on an AC motor but that's only a benefit at higher speeds. For cost do benefit you might as well just get a DC motor.
