The measurement of induction-motor stray loss and its effect on performance

Stray losses are shown to affect the performance of induction motors to a very considerable extent¿far greater than is indicated in B.S. 269. The sources of loss and methods for isolating the contribution of each to the whole are discussed. It is suggested that the total loss should be taken as the sum of the components, and this proposal is shown to be accurate except at small negative slips when the loss is much greater than such a calculation indicates. A single easy test, the reverserotation test, extrapolated according to simple rules, is shown to be sufficient to predict the stray loss under all conditions (including d.c. excitation) with sufficient accuracy for the majority of purposes, and it is proposed that such a test should replace the existing recommendations of B.S. 269.