General properties of power losses in soft ferromagnetic materials

Measurements are reported of the loss per cycle (sinusoidal flux waveform) versus magnetizing frequency f_m(0⩽f_m⩽100 or 400 Hz) and peak magnetization I_max, performed on 3% SiFe alloys (both grain-oriented and nonoriented), Armco iron, NiFe alloys, and amorphous ribbons. Using a novel theoretical framework, the microscopic origin of the observed dynamic losses is discussed, and a physical interpretation is given of the general fact that the loss per cycle is always a nonlinear function of f_m. A theoretical procedure is discussed by which it is possible, for a generic material, given a single loss curve at a certain value of I _max, to predict the dependence of dynamic losses on both I_max and f_m, with an approximation within ±10% in all the investigated cases. The behaviour of grain-oriented SiFe, which presents some specific complexities, is discussed in particular detail