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 attention. However, most of reported self-resonant WPT systems have low power transfer (less than 100 W) and high operating frequencies at megahertz. In this article, four multilayer, self-resonant WPT coil pads with different dielectrics are designed and experimentally validated. The aim of this article is to increase the power rating and decrease the operating frequency for capacitor-free WPT system compared to reported systems used in consumer electronics. Analysis of integrated compensation capacitance, inductance, and parasitic capacitance of the coil is provided. Finite-element analysis 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.