A study of additional losses of low-voltage asynchronous motors by the asymmetric power-supply method

A new edition of IEC 34-2 part 1 laying out methods for determination of losses and electric engine efficiency, as well as demands placed on gauges, was introduced in September 2007. The method for determination of additional losses was published in the last edition of IEC, but missing in GOST (State Standard) 7217. The method is for carrying out tests for asymmetric power supply of asynchronous motors. The essence of the method lies in producing a reversely rotating field, which allows one to avoid experiments with reverse rotation. Supply voltage asymmetry is produced using an additional resistor connected with one of the phase. It is recommended to carry out the experiments with a cold engine to avoid overheating the winding due to asymmetry of phase currents. Linear voltages and currents, as well as power and skidding, are measured during the experiments. Data processing is reduced to determination of current and voltages of the direct and reverse sequence. A functional dependence of additional losses on the reverse sequence current is obtained, and the additional losses under the nominal regime are determined. Application of new test methods and determination of power efficiency will allow one to create prerequisites for increasing the technological level of modern low-voltage asynchronous motors. © 2015, Allerton Press, Inc.