Estimation of Core Loss of High Frequency Nanocrystalline Transformer for Non-sinusoidal Excitation

Abstract

This paper proposes a method to estimate the core loss of a high frequency transformer with non sinusoidal excitation. The voltage waveform obtained across a high frequency transformer, in a solid state transformer made using direct AC/AC converters is an example of a non-sinusoidal waveform. The correct estimation of core loss for such a non-sinusoidal excitation is difficult. The difficulty in estimation of core loss stems from the non applicability of the Steinmetz Equation to non-sinusoidal excitations. Manufacturers do not typically provide the core loss data for non-sinusoidal excitation. A number of improvements on the Steinmetz Equation have led to increased accuracy but in turn have increased the complexity of calculation. This paper proposes a simple method to estimate the core loss. The method combines experimental and modeling approach. The estimation of core loss is performed for a high frequency transformer made from nanocrystalline material, for non-sinusoidal excitations. The method presented in this paper reduces the dependence of the estimation on Steinmetz parameters, the material of the core involved and the type of excitation. The method involves measuring the core loss for square excitation and using the obtained data to model the transformer in MATLAB/Simulink. This model can then be used to estimate the core loss for non-sinusoidal excitation of the given transformer. The proposed method is implemented by estimating the core loss of a 10.5kVA high frequency transformer with non-sinusoidal excitation. The non-sinusoidal excitations are obtained from a direct AC-AC matrix converter.