Motor protections vary widely depending on the size of the motor and voltage level involved, thus only the more common ones are discussed.
Instantaneous over-current is usually the result of fault conditions (phase to phase, phase to ground), in which current flow will greatly exceed normal values. Damage due to winding overheating and burning damage associated with large fault currents can occur without this type of protection.
These types of faults can be rapidly detected by a differential protection scheme using Core Balance CTs as will be discussed later and cleared before major damage results. In these situations, fast acting electromagnetic relays will be used to trip the affected motor.