What happens during plugging in an induction motor?

When an induction motor is plugged, which commonly occurs when the motor is suddenly disconnected from the power supply while it's still rotating, it experiences significant changes in operation. During this process, the rotor of the motor rapidly decelerates, creating a condition where the motor begins to generate negative torque.

This deceleration leads to an increase in power loss because the current flowing into the motor can substantially increase due to the braking action. The increase in current results in higher losses primarily through I²R losses (where I is the current and R is the resistance), which ultimately raises the overall power loss in the motor. This scenario can stress the motor's windings and is a crucial factor to consider in motor protection and operation.

The other options do not accurately describe the primary effect of plugging. While the motor's speed does decrease during this process and the rotor may nearly lock, the key distinguishing feature of plugging is the rise in power loss due to excessive current draw. Thus, the increase in power loss is a crucial characteristic that defines the plugging phenomenon in induction motors.