Investigation of the eddy-current anomaly in electrical sheet steels

Abstract

The well-known discrepancy between the calculated value of the eddy-current losses in electrical sheet steels at supply frequencies and the experimentally observed value is discussed. The effect of the flux waveform distortion due to magnetic non-uniformity of laminations is examined experimentally and found to be small. It is shown, however, from experiments on a model, that inside each lamination the flux waveform distortion with alternating magnetization is severe, and is sufficient to cause the hysteresis loss per cycle to be strongly frequency-dependent. On the other hand, the discrepancy which occurs with alternating magnetization is found to be absent with a pure rotational flux where there are no waveform effects. It is concluded that, without having recourse to more elaborate explanations, the observed anomaly might be largely accounted for by the increased hysteresis loss brought about by internal flux waveform distortion, the true eddy-current loss being, in fact, not appreciably different from its calculated value.