Magnetic Flux Uniformity Analysis of the Magnetic Core in the Wireless Power Transfer System

The magnetic flux uniformity in the core is an important figure of merit to design a compact and high efficiency magnetic coupler in a high power wireless power transfer (WPT) system. In this paper, the asymmetrical DD pads are studied which is widely adopted in the electric vehicle (EV) charging WPT system. The equivalent magnetic circuit model is derived to establish an equivalent model for the selected reference DD coil structure and provide theoretical guidance for obtaining magnetic core losses. The magnetic flux uniformity of the DD pad core on the transmitter side is investigated by the finite element analysis (FEA) model. The coefficient of variation (CV) with respect to magnetic flux density is proposed to quantitatively analyze the magnetic field distribution inside the core. It is found that the magnetic core utilization is low on the transmitter side due to the magnetic flux is concentrated in the middle of the core. This method is useful for the magnetic core optimization in order to obtain a high power density magnetic coupler structure.