Chapter 43, Problem 1RQ

What are the disadvantages of low-speed, directly coupled induction motors?

To determine

The disadvantages of low-speed, directly coupled induction motor.

Explanation of Solution

The directly coupled induction motors are rarely used in the applications where the required speed is below 500rpm. The induction motor take very less current from the supply main.

The vector sum of load current and magnetizing current lags voltage by around 75-80 degrees and hence, the power factor is low. Due to high magnetizing current, the copper losses of the motor increase. This in turn leads to decrease in the efficiency of the motor.

Thus Disadvantage of low-speed, directly coupled induction motors are low power factor and low efficiency.