Analytical Magnetic Field Analysis of Misalignment Tolerance Characteristic of Double D Pad and Bipolar Pad

摘要

Wireless power transfer (WPT) is an emerging technology for electric vehicles. The unavoidable misalignment impact on the system performance is a critical issue which needs to be considered. Bipolar Pad (BPP) is a coil structure proposed recently to reduce the impact of misalignment. Although experimental results have shown the effectiveness of this structure, there is still a lack of general theoretical analysis. In this paper, an analytical magnetic field analysis method is used to show the advantage of BPP compared with the commonly used double D pads (DDP) when the primary pad and secondary pad are misaligned. Firstly, the expression of the output power when using BPP with double-sided LCC compensation topology is given. By using Biot-Savart Law, the flux distributions of both BPP and DDP are derived, and the magnetic flux is calculated by integrating the corresponding area of the coils. The results confirm that with properly controlling the phase angle of the two adjacent coils, BPP exhibits superior misalignment tolerance over DDP. Finally, a Finite Element Analysis (FEA) simulation is used to verify the accuracy of the proposed method, which shows that the error of the proposed method is less than 8%. However, it only needs several seconds to finish a calculation while FEA needs about twenty minutes.