Low-Frequency Medium Power Capacitor-Free Self-Resonant Wireless Power Transfer

With the rapid development of wireless power transfer (WPT), the self-resonant WPT system without using additional compensation capacitors has attracted attentions. However, most of reported self-resonant WPT systems have low power transfer (less than 100 W) and high operating frequencies at megahertz. In this paper, four multiple-layer, self-resonant WPT coil pads with different dielectrics are designed and experimentally validated. The aim is to increase the power rating and decrease the operating frequency for capacitor-free WPT system. Analysis of integrated compensation capacitance, inductance, and parasitic capacitance of the coil is provided. Finite Element Analysis (FEA) is used to evaluate four dielectric materials, mica, polypropylene, polyimide, and fiberglass. An experimental setup has been developed, which can achieve more than 360 W power transfer for a 120 mm air gap with an efficiency of 82% and an operating frequency of near 80 kHz.