Awl --
How do they determine motor or generator efficiency, in industry? Seems to me the only fundamental way to do this would be to have the motor lift a weight, calculate mgh, and compare to ExI x power factor x time.
Then, for a generator, have the motor drive a generator, measure ExI through a resistor, compare.
How would a diy-er determine motor/generator efficiency?
A related Q: Why don't dynomometers measure generated current through a resistance, rather than calc'ing torque x rpm? Seems to me you would have better control of the load with I^2xR, and varying R.