TPC 3-Phase Practice Test 2025 – Complete Exam Prep

In an induction motor, plugging refers to a method of braking that involves reversing the motor's rotation by momentarily applying the supply voltage in the opposite phase. During this process, the rotor is forced to decelerate rapidly, which induces a current in the stator that opposes the applied voltage.

When plugging occurs, the slip of the motor increases significantly, which means the rotor is effectively at a standstill while the stator continues to apply the voltage. This condition results in a high amount of slip, leading to a significant increase in induction current. The current drawn increases because the motor now operates under conditions that generate a higher torque demand, necessitating a larger current to create sufficient electromagnetic forces.

The induction current during plugging can indeed become higher than the locked-rotor current because the rotor is attempting to generate enough torque to counteract the applied force. In locked-rotor conditions, the rotor is stationary, and the slip is at its maximum; however, during plugging, the motor generates torque in the opposite direction, resulting in an even higher current in some cases.

This understanding highlights the dynamics of how the induction motor behaves under various conditions, particularly during braking scenarios like plugging, where the electrical and mechanical systems interact to produce significant