Hot and Cold Condition of Motor

Hot and Cold condition of the motor refer to state of the temperature of the motor as a whole (especially the stator and rotor winding) when the motor is started.

Cold condition: When the temperature of the motor stator and rotor winding is at ambient temperature, the motor is considered 'cold condition'. If a motor remains stopped for relatively long period of time (generally half an hour - depends on motor size), it is considered cold condition and the start of a motor at this condition is called cold start.

Hot Condition: When the temperature of the motor stator and rotor winding is above the ambient temperature, the motor is considered 'hot condition'. If a motor is already hot from either an initial start or a period of recent full-load operation, it is considered hot condition and the start of a motor at this condition is called hot start. The hot start of the motor further raises its temperature to a higher level due to the subsequent restart and cause the motor damage. The motor protection relay generally prevents motor damage by limiting the number of start per hour and/or from further hot starting of the motor.

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- MS