Locked Rotor Amperage (LRA) in Motors

The Locked Rotor Amperage is a specification which specifies the current in the rotor of a motor when it is locked. 

When the motor is a standstill and the power is given to the terminals, the current is maximum in the rotor. As the speed increases, the current drops.  The Locked Rotor Amperage is typically 3 to 8 times of the Running Current Amperes.

The LRA is also dependent on the input voltage during start up.  As such, the Locked rotor Amperage value is used to select the type of starter for the motor.


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