Analysis and Design of Three-Coil Wireless Power Transfer System with Split Transmitting Coils

Wireless power transfer (WPT) technology is helping the electric vehicles (EVs) to solve several issues brought by cable charging. Three different WPT networks, namely series-series (SS), three-coil, and inductor-capacitor-capacitor-series (LCC-S), are the possibilities for different application scenarios. This paper analyzes the three-coil WPT system and compares it with the other two networks. We find that the three-coil network is combining the advantages of the other two networks, including high efficiency and better misalignment tolerance. Then, we have concluded several conditions to guide the design of three-coil WPT system. Next, we propose a design method, that is setting the turn ratio to split the transmitter coil of an SS network into two independent coils and the compensation capacitors to meet the conditions above. Finally, we obtain experimental results with 3.3kW output and 96.67% total efficiency, using a split transmitting three-coil network.