Induction Motor Efficiency Test Methods

Electric motor drives are significant to the overall energy requirements of the country and the world. The majority of these electric motors are squirrel cage induction motors, and it is to the efficiency testing of these motors that this paper is directed. It is essential that motor efficiencies be determined accurately to allow true comparisons to be made between alternate offerings and to assess correctly the motor´s share of system energy consumption. IEEE Standard 112, the recognized test procedure in the United States, has recently been revised. This paper presents the revised methods and compares this Test Procedure with IEC 34-2 and JEC-37. Each of these specifications includes a variety of basic methods for determining efficiency based on motor size and availability of test equipment. The National Electrical Manufacturers´ Association has recommended the use of IEEE Standard 112, Method B for ac motors of 1-125 hp. Ranking of different methods in order of desirability and practicality of use is presented.