Modeling Core Losses under Exciting Waveforms with Zero Voltage Period in Power Converters

When the exciting waveform contains the period of zero voltage, additional core losses have been observed, but lack of a clear physical explains. These additional losses may come from two aspects. The first one is the released energy caused by the interfacial dielectric loss between the isolation layers and grains. A function with two extracted relaxation coefficients is used to model the interfacial dielectric loss. The less important one is the released energy from the parasitic inductance of core materials. Based on the micro-scale material structure, an equivalent eddy current loss circuit model is proposed to include these two aspects. Based on the proposed model, core losses in N87 and 3C90 materials have been predicted successfully. The experimental results are in agreement with both theoretical analyses and simulation results.