Question

A 3-phase induction motor is operated with rotor blocked, its power factor is:

• A. 0.9 lag
• B. 0.2 lag
• C. 0.9 lead
• D. 0.2 lead

Hint:

When the rotor of an induction motor is blocked, the motor operates like a transformer, and the power factor tends to be low and lagging.

Answer 1

The Correct Option is A

When a 3-phase induction motor operates with the rotor blocked, it is essentially acting as a transformer with a very high slip (close to 1). At this point, the current drawn by the motor is highly inductive, and the power factor is primarily determined by the magnetizing reactance of the motor.
In this case, the power factor is typically around 0.9 lag, indicating that the motor draws lagging current due to the inductive nature of the motor under blocked rotor conditions.
Thus, the correct answer is a power factor of 0.9 lag.