An automated calorimetric method of loss measurement in electrical machines

Abstract

Traditionally the losses dissipated in an electrical machine have been determined from the difference between the measured input and output powers. However, the achievable accuracy is limited by the uncertainty of measurement errors, particularly if the machine is supplied with distorted voltage and current waveforms. Therefore, a more appropriate approach is to employ a calorimetric method in which the losses are determined by direct measurement of the dissipated heat. This paper describes the control and instrumentation of such an automated calorimetric system which has been commissioned to accomodate machines of up to 75 kW rating, and in which losses can be measured to an accuracy better than 10 W.