NEIEP Mechanics Practice Exam

What will a squirrel cage motor do when connected in ABC sequence if it runs clockwise in ACB sequence?

1. It will stop

2. It will run in the same direction

3. It will run counterclockwise

4. It will reverse direction intermittently

The correct answer is: It will run counterclockwise

When a squirrel cage motor is connected in a different phase sequence than it was originally designed for, it will change the direction of its rotation. In this case, if the motor runs clockwise in an ACB sequence, changing to an ABC sequence will reverse the phase order and thus reverse the direction of the magnetic field interacting with the rotor. This change in the magnetic field causes the rotor to turn in the opposite direction, which in this scenario would be counterclockwise. Understanding the concept of phase sequences is crucial; an ACB sequence produces a different phase relationship for the current flowing through the motor compared to the ABC sequence. This dictates the motor's rotational direction. Therefore, the correct response reflects that the motor's rotation direction is reversed when the phase sequence is altered from ACB to ABC, resulting in counterclockwise movement.