Improving Transmission Efficiency with Magnetic Coating Technology for Lightweight Wireless Power Transfer Coil Using Aluminum Plate

As a power supply method for electric vehicles (EVs), wireless power transmission is attracting attention because it allows to charge stationary EVs seamlessly and is not associated with cable-related problems such as forgetting to charge or leakage1-3). Wireless power transmission for EVs operates at a high frequency of 85 kHz. Since a high-frequency loss typically occurs in wireless power transfer coils4), the litz copper wire (LCW) with good high-frequency characteristics is generally used in wireless power transfer coils for EVs5-11). To improve the fuel efficiency of EVs, a weight reduction of the embedded coil is highly desirable. Furthermore, a coil that is inexpensive and easy to manufacture is required. To meet these requirements, we examined a relatively facile fabrication of a coil using an aluminum plate. However, the aluminum plate (AP) coil has a large AC resistance due to the proximity effect12). At the same time, this resistance can be reduced by coating the coil with a magnetic layer13-15). Therefore, we coated the AP coil with a magnetic composite material using a low-loss amorphous alloy powder achieving a magnetically coated plate (MCP) coil. In this study, the optimal magnetic composite material was analyzed using the finite element method (FEM). Furthermore, the impedance characteristics of the coil were evaluated, and the transmission efficiencies of the AP and MCP coils were measured using the double-LCC resonant circuit. (b) (a)