Losses in AC Motors

Losses in AC Motors

 The electrical input power to a motor is always greater than the mechanical output power. There are five different kinds of power losses:

•  Copper losses - Since the windings in a motor are made of copper, there will be i2R losses due to the resistance of the copper.
•  Eddy current losses - The changing magnetic fields in an AC system cause currents to flow in the iron of the rotor and stator. These currents flow in small circles, like the eddies in a river. Most rotors and stators are made of laminated iron to reduce the loss due to eddy currents.
•  Hysteresis loss - In a 60 Hz system, the current, and thus the magnetic field, reverses 120 times per second. Some power loss occurs with each reversal.
•  Friction loss - Friction exists in all mechanical systems.
•  Windage loss - This is loss due to the generation of air movement.

 All of these losses manifest as heat generated in the motor.