FEA-Assisted Optimization Design of Asymmetric DD Type Structure Magnetic Coupler for Wireless Electric Vehicle Charger

In an inductive power transfer system, the coupling coefficient of the magnetic coupler is the key for high power capacity and high transmission efficiency. In this paper, the issue of asymmetrical DD type magnetic coupler design is discussed. The relationship between the coupling coefficient of the asymmetrical DD coils and the size ratio of the transmitter coil to the receiver coil is analyzed. A numerical modeling method by fitting the simulation data based on the Dagum distribution is presented. Given the size of the receiver coil, the optimal coil size for the maximum coupling coefficient can be obtained and improved by considering the misalignments. Based on the theoretical analysis and simulation results, the asymmetric DD coils with different numbers of turns and sizes are experimentally fabricated, which validates the accuracy of the proposed modeling method. When the vertical gap is 150 mm and the size of the receiver coil is 400 mm × 400 mm, the transmitter coil size for optimum coupling is designed as 679 mm × 679 mm according to the proposed design method, which achieves a coupling coefficient of 0.1922 when aligned.