FERRITE CORE LOSS FOR POWER MAGNETIC COMPONENTS DESIGN

A practical method is presented for computing high-frequency ferrite core losses in the magnetic component for arbitrary voltage waveforms. The model presented requires only a few material parameters as input. The voltage waveforms are assumed to be symmetric, and a piecewise-linear model is used to represent them. To calculate ferrite hysteresis losses, a model based on empirical rules is employed. For high-frequency eddy current losses, a bulk phenomenon is assumed. The excess (anomalous) eddy current loss due to the existence of domains is approximately taken into account by adjusting the value of resistivity of the ferrite material. It is demonstrated that the hysteresis model reproduces all of the important known features of the soft ferrites. These features include hysteresis loop shapes for low- and high-field excitations, the nonlinear permeability behavior, and hysteresis loss dependence on the amplitude of the exciting field. It is found that the total calculated core loss as a function of frequency and flux density correctly describes the observed soft ferrite behavior. The theoretical results are compared with available data for two commercial ferrites, and good agreement is found up to fairly high frequencies (approximately 500 kHz).