What does a 'locked rotor' condition indicate?

A 'locked rotor' condition indicates that the rotor of the motor is unable to turn while electrical power is applied. This situation typically occurs when the motor is initially started and cannot overcome the inertia of the load it is trying to drive or when there is a mechanical binding or fault preventing the rotor from rotating.

Being in a locked rotor condition results in high current being drawn from the power supply, often significantly exceeding the full-load current of the motor, which can lead to overheating and potential damage if the condition persists. This status is critical for motor protection designs, as it prompts protective devices such as overload relays or circuit breakers to intervene and disconnect power to the motor.

Understanding this condition is essential for diagnosing motor issues and ensuring proper implementation of protection mechanisms to safeguard the motor against damage caused by prolonged locked rotor scenarios.