Electric motors are a crucial components in virtually every industrial automation application or environment. Therefore optimizing their performance and reliability can play a major role in reducing costs and improving overall plant efficiency. Electric motors fail and about half of them fail because of overheating through overload, phase failure or insulation breakdown. There are wide ranges of motors and motor characteristics in existence, because of numerous duties for which they are used and all of them need protection. Fortunately, the more fundamental problems affecting the choice of protection are independent of the type of motor and the type of load to which it is connected. Motor characteristics must be carefully considered when applying for protection. It is emphasized because it applies more to the motor than other items of power system plant. Protection of motor exists in any form, a variety of designs & either packaged individually or in different combinations. The fundamental and basic aim should be to permit the motor to operate up to, but not to exceed its thermal and mechanical limits for overloads and abnormal operating conditions and to provide maximum sensitivity to faults.