Waveform Dependent AC-Losses of Power Ferrites by Hysteresis Loop Modelling

Abstract
The solution of the Hodgdon hysteresis differential equation starting from measured major loops is reviewed. The computation scheme derived for symmetric minor loops allows to express DC-losses in terms of the major loop functions and the initial permeability. An extension to the calculation of AC-losses is achieved by considering the equation of domain wall motion. Thus, expressions for the losses with different periodic voltage waveforms, i.e. sinusoidal and rectangular, are then derived for different power material grades. Since losses can be computed for all excitation levels by the procedure described, the performance factor, i.e. the product f-B_M for given dissipation level and waveform, can be calculated. The results are compared with experimental data showing good agreement.