Question

The power factor of an induction motor operating at no load is around:
1. 0.9 lag
2. 0.2 lag
3. 0.9 lead
4. 0.2 lead

Answer 1

Correct Answer - Option 2 : 0.2 lag

Power factor in Induction motor:

• The induction motor may be regarded as a transformer with a primary coil and a secondary coil loaded with a load that changes its impedance.
• When the rotor of an induction motor is stationary the current in the shorted conductive loops of the rotor is very high as the resistance and the inductance is low.
• Because of the air gap, the reluctance of the magnetic circuit of the three-phase induction motor is very high.
• Consequently, the current drawn by the motor on no load is largely magnetizing current, the no-load current is lagging the applied voltage by a large angle.
• For this reason, the power factor of a lightly loaded (or no load) three-phase induction motor is very low about 0.2 to 0.3 lagging