Design and optimizations of solenoid magnetic structure for inductive power transfer in EV applications

Based on magnetic induction, wireless power transfer have been proved to be promising in many applications, especially in EV charging systems. The coupling performance of loosely coupled transformers determines the overall feasibility of the whole systems. Considering volume, cost and coupling properties, a solenoid magnetic structure of 400mm*600mm with a 200mm air gap is utilized to transfer power in this study. By FEM simulation tools, the distance of wires and the coverage length are discussed to find the best coupling design. In addition, the position of the magnetic stripe cores is analyzed when taking account of the system cost. Moreover, additional shielding devices, which are made of aluminum, are designed to eliminate the back leakage magnetic flux. In order to improve the coupling performance, flux guiding ferrites are also added into the shielding devices to guide more leakage to flow to the secondary windings. Simulation results indicate the proposed design can increase the coupling coefficient k dramatically. Also, experimental results show great agreement with the simulation results.