In this digest, an optimized Litz wire is proposed for high-power wireless charging systems operating at 85kHz frequency. Litz wire in a wireless charging system causes more than half of the loss of a high-power wireless charging system, making it a critical design component. In this study, the Litz wire is optimized through Finite Element Analysis (FEA) considering electrical and mechanical design aspects, and the tested through experimental tests on different Litz wire with various strand-diameters, twisting ratio, and number of strands. The proposed optimal Litz wire maximizes the system efficiency considering the tradeoff between coil resistance and mutual inductance. The optimal Litz wire shows that Litz wire the 63µm strand significantly outperform the traditionally used Litz wire with 100µm strand diameter. Additionally, the coil with optimal Litz shows 60% reduction in the copper volume for the same loss, and at the same time increase the coil-to-coil efficiency by more than 2% by increasing the mutual inductance. The optimized Litz wire was implemented in a 22 kW wireless charging system achieving 95.5% efficiency.
