In contactless power transformers, the electric power is transmitted at a high frequency. Therefore, the skin and proximity effects much increase the AC resistance. In this paper, the influence of the magnetic field and frequency on the equivalent resistance of the coils is evaluated. In addition, the iron loss characteristics are evaluated by considering the excitation voltage. The iron and copper losses due to the skin and proximity effects in a 300 kW CPT transformer were estimated. Based on the results, the temperature rise characteristics were predictively studied using heat equivalent circuits. The results of this study contribute to the thermal design efforts of high power contactless power transformer coils.
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