Superconducting Wireless Power Transfer Beyond 5 kW at High Power Density for Industrial Applications and Fast Battery Charging

State-of-the-art wireless power transfer (WPT) systems, based on conventional copper coils, are known to exhibit efficiencies well above 90% when operated in the resonantly coupled mid-range regime. Besides full system efficiency, the area- and weight-related power densities of the transmission coils are key figures of merit for high power applications. This article reports on a fully functional WPT system, consisting of single pancake high-temperature superconducting (HTS) coils on the transmitter and the receiver side, which exceeds the power density of most conventional systems. Despite a compact coil size, a dc-to-dc efficiency above 97% is achieved at 6 kW output power. Next to the fundamental coil design, analytical and numerical simulations of the ac loss in the HTS coils are shown, taking into account both hysteresis and eddy current contributions. The results are validated by experimental ac loss measurements of single coils, obtained by a standard lock-in technique up to frequencies of 4 kHz. Finally, experimental results of the full system performance at different frequencies and load conditions are presented.