Hybrid loop-array design for high efficiency and low EMF level in wireless high power transfer

Abstract

Current wireless power transfer(WPT) technology is widely used for various applications because of convenience and safety. One of those emerging application is high power charging system such as electric vehicle, bus, and train. However, unlike previous WPT system, transferring high power wirelessly causes efficiency and EMF issues. The fundamental cause of these issues is switching frequency limitation of power transistor in inverter, so several solutions including using magnetic field forming, are proposed for settling the problem. The previous solutions have fragmentarily resolved the weakness of high power charging system, but they did not make high power charging system have high efficiency and low EMF level simultaneously. Our research has proposed the solution, which is hybrid loop-array, for high power charging system with high efficiency and low EMF level simultaneously, and we analytically propose the design procedure for maximum efficiency and minimum EMF level. Moreover, for the validity of the proposed hybrid loop-array, we have proved the same tendency with simulation result and measurement result. With the proposed design process and equations, hybrid loop-array can be designed for other WPT system with high efficiency and low EMF.