Abstract
The measurement of the iron loss in ferrites is an important work for developing high efficiency switching power supplies. The authors have proposed the dynamic magnetic loss parameter, λf, for evaluating the iron loss in ferrites. In the previous studies, the parameter was assumed to be a constant value for an individual ferrite material and defined for one period of a small B-H loop. In this paper, assuming that λf is a function of the time derivative of the magnetic flux density, dB/dt, a novel measurement method of λf of a Ni-Zn ferrite is proposed using rectangular wave voltage excitation and the Fourier expansion of the exciting current. In order to realize an iron loss measurement system with the rectangular wave voltage excitation, a high frequency FET inverter has been developed. The results of measuring λf show that it is uniquely determined by dB/dt regardless of B-H loop size. The measured dB/dt characteristics of λf are applied to practical examples for switching power supplies and sinusoidal wave voltage excitations. Their experimental and computational results coincide and it is clarified that the measured dB/dt characteristics are effective and useful.
