What occurs when a motor loses one phase out of three?

When a three-phase motor loses one phase, the condition is known as "single phasing." In this situation, the motor does not have balanced power supply across all three phases, which leads to significant issues.

As the motor operates under single phasing, it experiences a reduction in the available torque because it is relying on only two of the three phases for operation. This imbalance can lead to the motor overheating, which in turn affects the motor's windings. To protect the motor from damage due to this overheating, the overload heaters will trip, stopping the motor and preventing further damage.

Understanding single phasing is crucial because it emphasizes the importance of having all phases functioning properly for the effective operation of the motor. The other effects of losing a phase—like the motor running faster or drawing less current—are not accurate because the loss of a phase does not allow for normal operational efficiency and can actually cause higher current draw on the remaining phases as the motor struggles to maintain its function.