Modern induction motors tend to operate at higher temperatures continuously to give maximum power utilization. The net effect is that there is a fast rise of temperatures say of the order 10^o C per second under overload conditions.Thus to achieve a compromise between minimum motor cost and its maximum life, a need for New Motor protecting Technique is felt which can offer the protection against overheating of Motor windings owing to overloading  (both sustained and momentary), Locked or stalled rotor, Variations in supply, Single phasing, Chocked ventilations, Faulty bearings and other mechanical over load conditions etc.