A coil structure optimal method based on vertical coupling for inductive power transfer

An optimization method of coil structure based on vertical coupling for inductive power transfer system is proposed in this paper to achieve high coupling coefficient of loosely coupled transformer, which ensures high efficiency of system. With the help of analyzing vertical coupling, relation of different coil structures wound in clockwise or anticlockwise directions is researched. 3D finite element simulations and a set of experiments are performed to draw a conclusion that a combination of a clockwise wound coil and an anticlockwise wound coil can get higher coupling coefficient. Furthermore, a method based on calculating area of vertical coupling is proposed to optimize the configuration of secondary coil to improve the coupling coefficient. Assignment of turns of secondary coil is discussed in detail to find an optimal coil structure to get higher coupling coefficient. Finally, a 1.4 kW ICPT system is built and tested to verify the effectiveness of the proposed system. The results prove that the optimized coil can achieve a coupling coefficient of 0.271 and a system efficiency of 93%, when those of a conventional coil wound in clockwise direction are 0.268 and 92%.