Alternating Hysteresis Loss in Electrical Sheet Steels

The paper describes a direct method of measuring alternating hysteresis loss in sheet materials utilizing small disc specimens. The loss may be measured in any desired direction in the sheet on the same samples, utilizing simple apparatus. No eddy-current losses are involved in the measurement. The observed results on four electrical sheet materials are given. The Steinmetz law is found to hold approximately for the lower portion of the loss curves, and a straight-line law for the upper portion. The change is found to occur near the knee of the magnetization curve where, according to theory, the mechanism of the magnetization process also changes. A definite correspondence between the loss and magnetization curves for different directions in the sheet is found. It is concluded that hysteresis loss is a function not only of the magnetization but also of the field strength, and a qualitative explanation is given. The general relation of alternating hysteresis loss in a single crystal of silicon iron to the principal crystal directions is inferred from the observations on one of the samples. The alternating hysteresis loss is compared with the rotational hysteresis loss previously determined on the same samples. The ratio between them is found to be approximately the same for all the four materials investigated.