What does the term “locked rotor” condition refer to?

The term “locked rotor” condition refers to a situation where the rotor of an electric motor is not able to turn due to mechanical resistance or an external load that prevents it from rotating. This typically occurs at the moment the motor is starting, where the rotor is effectively "locked" in place and cannot overcome the inertia or resistive forces acting upon it.

In this state, the motor draws a significantly higher current, known as locked rotor current, which is much greater than the normal operating current. This condition can occur if the motor is overloaded, if there is a mechanical failure, or if there is a fault in the drive train. Understanding the locked rotor condition is essential for troubleshooting motor performance and ensuring the motor is not subjected to prolonged duration under this condition, as it can lead to overheating and damage.

The other options describe scenarios that do not accurately depict the locked rotor condition, such as the rotor spinning at maximum speed, being free of obstructions, or running under normal operating conditions. Each of these scenarios indicates a functioning motor, in contrast to the locked rotor state, where the motor is effectively stalled.