If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, what will be the result?

Correct Answer: Option C — the motor continue to run, but will vibrate and have reduced torque

Single-phasing a lightly loaded three-phase induction motor creates unbalanced air gap magnetic fields, resulting in heavy harmonic vibration, elevated operating temperatures, and reduced torque capacity. IEEE 45 and 46 CFR Subchapter J require phase-loss protection to mitigate such damaging asymmetrical operating conditions.