Evaluation of different measurement methods to determine stray load losses in induction machines

Five different test methods for the determination of stray load losses of tine-operated induction machines are compared and the results obtained are discussed. The five experimental measurement procedures are: input-output tests acc. to IEC 61972 (A) and IEEE 112-method B (B), reverse rotation test (RRT) (C) acc. to the standard IEEE 112, eh-star-circuit (D) and equivalent no-load method (E). The advantages and disadvantages of these measurement methods are shown. Nineteen cage induction motors (2-, 4- and 6-pole) with current design of six European manufacturers with rated power 1.1 kW, 5.5 kW and 11 kW are investigated. RRT method yields higher stray load losses, whereas results of EEC 61972, IEEE 112-Method B and eh-star-circuit results correlate quite well. The results of equivalent no-load method are either greater or less than values of IEEE 112-Method B, and only in some cases are fitting quite well. The eh-star method seems to be a good, lower cost alternative for determination of stray load losses of induction machines.