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This paper discusses rotational losses and how they are produced in the core materials of induction motors. These losses are largely caused by flux that rotates in the plane of the machine laminations. l h s suggests that steel specification for applications to rotating machines should be given in terms of rotational loss data as a material characteristic, in much the same fashion as Epstein test results are provided for alternating losses. If a standardized test for rotational losses were to be used, steel producers could rationally investigate the effects of composition and processing variables. l h s is necessary in order to produce low loss steels for motor applications. Reduction of rotational losses in motor cores could significantly lower ac machine operating costs and contribute to the growing interest and design of highefficiency induction motors.The paper describes a test procedure for determining rotational losses in a sample. It then compares the results with standardized tests from an Epstein test procedure. It is seen that there are significant differences in loss results obtained for the rotational test versus the alternating current test.The development of analysis tools for determining the amount of rotational flux and degree of polarization in a machine core is also assuming greater importance as a tool for machine designers. The authors have investigated a time harmonic finite element formulation utilizing Magnet 2D, a commercially available package. The paper includes a brief analysis of a typical problem using th~s tool.

A large portion of the stator core of a rotating electric machine is subjected to magnetic flux that rotates in the plane of the laminations. Iron losses under rotating flux conditions can differ considerably from those due to alternating fields. It has long been suspected that this difference may be responsible for some of the discrepancy between predictions of no-load core loss at the design stage and values obtained by factory test. At present, no international standard exists for determining iron losses due to rotational flux. This paper describes an apparatus capable of making such measurements and briefly reviews the state of the art in this area of research. Measured loss curves are given for seven grades of nonoriented (NO) electrical sheet.

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