Comparison of standards for determining efficiency of three phase induction motors

The paper describes a set of experiments and discusses their results for de termining the efficiency of low voltage, three phase squirrel cage inductio n motors. The measured efficiency of an induction motor directly connected to the grid, strongly depends on the method used to evaluate the results an d the standard according to which the measurements are performed. Different standards as IEEE 112 and IEC 32 are mentioned and their similarities and differences are discussed. The main discrepancies between the various stand ards is the way in which the values for the stray load losses are obtained at different load levels. A short description of the measurement setup is given and measurement resul ts for motors of several manufacturers accounting for different standards a re proposed. The results clearly demonstrate the necessity to handle the ef ficiency data given by the manufacturer with a lot of care.