NATE Electrical Practice Exam 2025 – Comprehensive All-in-One Guide to Success

A voltage imbalance is especially problematic for three-phase motors because these motors rely on a balanced supply of voltage to function efficiently and effectively. In a three-phase motor, the three phases should ideally have equal voltage magnitudes and be phase-shifted by 120 degrees. When there is a voltage imbalance, meaning one or more of the phases have a significantly different voltage, it can lead to several issues such as overheating, excessive vibrations, and reduced torque production.

Overheating occurs as the motor may draw more current to compensate for the loss in torque efficiency caused by the imbalance. This excessive heating can damage the motor windings and ultimately lead to motor failure. Additionally, imbalances can cause uneven mechanical stress on the motor's components, resulting in premature wear and a decrease in the overall lifespan of the motor.

In contrast, single-phase motors are designed to operate on a single-phase supply and do not face the same critical issues arising from a voltage imbalance. DC motors are unaffected by phase imbalances in the same way, as they operate on direct current. PSC (Permanent Split Capacitor) motors, although they are often single-phase, also do not experience significant problems from voltage imbalance in the same manner as three-phase systems. Thus, three-phase motors are