Proposal of Ferrite-less and Capacitor-less 85 kHz Four-Layer Coil for Stationary Wireless Power Transfer

In recent years, there have been many studies on wireless power transfer. In particular, it is expected to be applied to electric vehicles, such as stationary and dynamic wireless power transfer. However, power transfer coils for electric vehicles are high cost due to the use of resonant capacitors and ferrites. In previous research, self-resonant coils without ferrite core and capacitors have been proposed to reduce the cost. However, there is not yet a self-resonant coil for electric vehicles that complies with the coil size and power class of international standards. In this paper, we propose a four-layer ferrite-less and capacitor-less coil with self-resonance in the 85 kHz band. As a result of the power transmission experiment, even without ferrites and capacitors, 5.8 kW power in conversion value was obtained with an efficiency of over 90% at a 250 mm air gap.