danielrlee said:Not quite. Assuming both motors have the same copper fill....
You're forgetting the fact that if you also proportionally reduce the voltage supplied to the higher kV motor at the same time as increasing the current, you get the same heat generated while producing the same torque from the same wattage at the same speed, both running at the same efficiency.
The problem that hurts efficiency more than that is when you use a high kV motor and then run in a lower fraction of its RPM range. Motor efficiency increases with speed, up to a peak of about 80 percent of the motor's free speed. With a slow wind motor, you can often cruise at that speed. With a fast motor, you top out at something less than the motor's most efficient speed. Especially when your typical operating speed can be attained by the slower wind motor.
So it really doesn't matter what the fast wind motor's peak efficiency is, because you never reach it.