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A high efficiency 3.3 kW loosely-coupled wireless power transfer system without magnetic material

This paper proposes a loosely-coupled wireless power transfer (WPT) system without magnetic material, which has 95.0% dc-to-dc efficiency working at 1MHz and 3.3kW output power. The coil size is 320mm×320mm, and the coupling coefficient k is 14.0% at 150mm air-gap distance. The magnetic material is removed to increase system switching frequency to MHz level and eliminate the magnetic losses. Power loss models of the circuit components are presented to calculate the total losses and the system efficiency. It shows that, through designing the circuit parameters to minimize the power losses, the maximum achievable efficiency can be higher than 95% even at a coupling coefficient of 10%. This paper provides the guideline for high-frequency and high efficiency WPT system design.