Determination of Coupling Factor of Wireless Power Transfer Systems for Charging Electric Vehicles by using Measured Magnetic Near-Field

Abstract

In this paper, we determine the coupling factor of kHz-band wireless power transfer (WPT) systems for electric vehicles by using measured magnetic near-field. A near-field measurement system with in-house developed magnetic- field probes is constructed and used to measure the magnetic field distributions at the position close to the fabricated WPT systems. Then, the magnitude and phase of the magnetic near-field obtained by the developed system are used as an incident field in the numerical analyses by the impedance method in order to numerically derive induced electric fields inside various human body models. Finally, the coupling factor for both kHz-band WPT systems with and without ferrite tiles and mimic vehicle body is proved to be lower than 0.15, which is the coupling factor value for WPT systems of EVs, determined in the report by the Information and Communication Council, Japan.