Modeling and Evaluation of Ferrite Eddy Losses in High-Frequency Transformers Based on Loss-Effective Conductivity Extraction

The eddy effects of Mn Zn ferrites in high-frequency transformers become obvious and cause significant losses when the frequency becomes high. These eddy losses are analyzed in this research. An analytical calculation model of eddy losses is proposed for cores of rectangular cross sections based on a simple model and corrections according to limited simulations. This analytical calculation model consumes few computing resources while being close to precise simulations. The application scope of the proposed model is analyzed, requiring that the influences of the nonuniformity of the magnetic reluctance and the resonant effects need to be small enough. The apparent conductivity is significant for eddy loss estimation. In this study, it is proposed to analyze and measure the core losses of ferrite cores of different cross-sectional areas so that the eddy losses can be evaluated separately. On this basis, it is proposed to extract the apparent conductivity from the measured core loss to reflect the real working conditions of the cores. Experiments are performed to verify the accuracy of the proposed eddy loss model and the apparent conductivity extraction method based on toroidal core samples only for simplicity. The proposed eddy loss model and the corresponding experimental results are used to evaluate and improve eddy loss reduction methods.