Determination of three phase induction machine efficiency from start up data

There are various methods to determine the efficiency of three phase induction machines. But all of them have in common that they are to inaccurate or they are impracticable. In this paper the machine efficiency will be derived from start up data. For that purpose the variation with time of all stator currents and all stator voltages have to been measured. Normally it isn't possible to mount a speed sensor on the machine. For this reason only the speed at the end of the start up can be determined. Practical results with three phase induction machines with different power ranges are presented.