The Differential Principle Applied to the Measurement of Stray Load Losses in Squirrel-Cage Induction Motors

The paper demonstrates how the differential principle may be used to measure stray load losses in squirrel-cage induction motors under full-load conditions, while only a fraction of full-load power is drawn from the supply. A full analysis together with the test results for a mechanical differential are included in this paper and, in addition, the results obtained by using an electrical differential are given, showing the close correlation between the measurements obtained from these two types of differential device. The particular advantages of each arrangement are discussed, and it is concluded that the mechanical differential is likely to prove the more suitable for large-scale industrial use.