Power Losses in an Induction Motor

 Power Losses in an Induction Motor

The input electric power fed to the stator of the motor is converted into mechanical power at the shaft of the motor. 

The various losses during the energy conversion are

1. Fixed losses

✓ Stator iron loss

✓ Friction and windage loss

The rotor iron loss is negligible because the frequency of rotor currents under normal running condition is small.

2. Variable losses

✓ Stator copper loss

✓ Rotor copper loss

The following points may be noted from the above diagram:

(1) Stator input, Pi-Stutor output + Stator losses

Stator output + Stator Iron loss + Stator Cu loss

(i) Rotor input, Pr - Stator output

It is because stator output is entirely transferred to the rotor through air-gap by electromagnetic induction.

(i) Mechanical power available. Pm Pr-Rotor Co loss

This mechanical power available is the gross rotor output and will produce a gross torque Ty. (iv) Mechanical power at shaft, Pout Pin Friction and windage loss Mechanical power available at the shaft produces a shaft torque Ta

Clearly, Pm - Fout Friction and windage loss.