Temperature dependence of power loss anomalies in directional FeSi 3%

Abstract

Measurements as a function of temperature t were performed on directional FeSi 3%, in order to study the possible influence on the power loss anomalies of a change of intrinsic parameters, such as crystalline anisotropy energy K, without affecting the extrinsic ones, such as grain size and orientation. Power losses per cycle P/f were measured vs. frequency f, between d. c. and 50 Hz at various temperatures ranging from 25 to 650°C. The variation of K and of saturation induction B s with t were also determined up to the Curie point by means of a torque magnetometer. The results show that the excess loss anomaly at 50 Hz, measured by the ratio of experimental to classical eddy-current loss, and the non-linearity anomaly, determined from the renormalized P/f vs. f curves, are essentially independent of t. Analogies with the temperature dependence of the power density spectrum of the Barkhausen noise, which varies according to a B_{s}^{2} (t) law, are briefly discussed. These results seem to indirectly stress the role of extrinsic parameters in determining the anomalous loss behaviors in directional FeSi 3%. Kerr observations made up to 350°C on a (300 × 30)mm2strip did not detect any change of stripe domain widths and patterns.