Investigation of Core Loss Calculation Methods for Nanocrystalline Core in Medium Frequency Range

Abstract

Nanocrystalline core is often adopted in high-power medium-frequency transformer, whose excitation voltage is usually a rectangular wave with an adjustable duty ratio. In this paper, several kinds of methods are proposed for core loss calculation under non-sinusoidal voltage excitation by modifying the original Steinmetz equation (OSE). Firstly, these correction methods are compared in theory, and their analytical equations under rectangular voltage with an adjustable duty ratio are deduced. Then, a hysteresis loop measurement system is established to measure the core loss density of a nanocrystalline core. Based on the measured results of the core loss density under sinusoidal voltage excitation, the coefficients of OSE for the core are fitted. Finally, core loss calculation results using the proposed correction methods under different amplitudes and duty ratios are analyzed and compared with the measured values. The results verify the correctness of the theoretical analysis, that waveform-coefficient Steinmetz equation is the most suitable method for loss calculation of nanocrystalline core in medium frequency range when the excitation voltage is a rectangular wave with an adjustable duty ratio.