Re: AC Electric Bicycle Motor
No, wrong on several counts.
The internal resistance of the armature and field windings (assuming series wound here) will determine how much current a motor will draw at a lower voltage. (calculations based on simple resistance, a motor, being a dynamic device with internal inductance would return different but similar actual, measured values.)
120 v / 18 a = 6.66 ohms.
24 v / 6.66 ohms = 3.6 amps.
24 v * 3.6 a = 86.4 watts.
If you were able to load the motor (running at low voltage, and therefore a lower RPM) with sufficient drag to cause it to draw 75 amps, it would probably burn out, as the armature and filed windings are constructed with small, high resistance wire. The excessive current would cause a lot of heat to be generated, resulting in destruction of the motor.
If you intend on running a motor at a voltage far outside of it's design parameters, expect low performance and failures to be the rule.