Rotational loss separation in grain-oriented Fe–Si

Rotational and alternating magnetic losses have been investigated in high permeability grain-oriented laminations as a function of frequency (2.5 Hz⩽f⩽150 Hz) and peak magnetization (0.15 T⩽Ip⩽1.7 T). The results have been analyzed according to the concept of loss separation. The rotational hysteresis Whrot and excess Wexcrot energy loss components exhibit a similar increasing behavior with the magnetization Ip and reach a maximum value around 1.5–1.6 T. Wexcrot shows, in particular, a definite f1/2 dependence. The ratios between rotational and alternating hysteresis and excess losses (Rh=Whrot/Whalt, Rexc=Wexcrot/Wexcalt) follow similar trends with Ip, with their values depending, however, on the testing configuration adopted for the alternating loss measurements (single strip versus X-stacked strips). The 90° domain wall transitions between the in-plane [001] and the out-of-plane [100] and [01̄0] directions are the basic loss producing mechanism under rotational fields, but, on approaching the saturation, the magnetization can eventually rotate only through coherent spin rotations and the classical loss term Wclrot alone survives.