Eddy-Current Reduction Structure of Copper Foil Winding for Medium-Frequency Transformer in DC-grid Applications

As a differentiating technology from the conventional technology utilizing a Litz wire, a low-cost and simple structure that reduces in-plane eddy-current loss due to the leakage magnetic flux generated in the copper-foil windings of a medium-frequency transformer (MFT) was devised. An MFT based on this structure was prototyped by processing a tapered cross-section at both ends of the copper foil. The frequency-versus-AC-resistance (R
ac
) performance of the winding was evaluated by short-circuit test. According to the results of the test, R
ac
of the prototyped MFT can be reduced by up to 8% at around 1 kHz compared that of an MFT with conventional copper-foil winding.