Design and Experimental Verification of an Oil-Cooled Medium-Frequency Transformer for a 250 kW Half-Bridge Series Resonant Converter

This paper describes the conceptualization of an oil-cooled, medium-frequency transformer (MFT) characterized by a toroidal core and foil windings. Compared to conventional foil transformers, the proposed MFT achieves a single layer for each winding due to its unique structure, thereby reducing losses attributed to eddy currents, particularly in the part affected by proximity effects. Verification of the design’s losses is accomplished within a 250 kW back-to-back converter configuration.