Fast Numerical Power Loss Calculation for High-Frequency Litz Wires

This article presents a fast numerical calculation method of realistic power losses for high-frequency litz wires. Explicitly, the imperfect structure of litz wires is considered when calculating losses due to an excitation current (skin losses) and external magnetic fields (proximity losses). Calculations of litz wires with more than 1000 strands were performed on a personal computer and have been validated by measurements up to 10 MHz. In the calculation, the impact of the bundle structure on skin and proximity losses is examined. The method allows to select a suitable litz wire for a specific application or to design a litz wire considering realistic twisting structures.