Evaluation of stray load loss in induction motors, a comparison of input-output and calorimetric methods

This paper is concerned with the problems of accurately measuring stray load loss in induction motors and thereby declaring the correct machine efficiency. The standard experimental approach of input-output power measurement, using the IEEE 112 or C390 technique is well used but has limitations. The objective of this paper is to consider possible sources of error and to provide indications of how some of these errors may be mitigated. Results obtained by calorimetric methods are used to validate the standard test methods. Additional experimental work is used to highlight common sources of error. The value of the work is in improving measurement techniques. EASA and IEMT sponsor the work as part of research into the influence of electric motor repair upon machine losses.