Design of a Box-Shape Coil Structure to Achieve Uniform Magnetic Field Distribution for WPT

A box-shape coil structure is proposed for the wireless power transfer (WPT) system. The assist coils parallel with the transmission direction are added around the primary coil. The proposed coil structure could achieve a more uniform magnetic field distribution, which enhances the ability of anti-misalignment. The uniform field is also beneficial to the realization of multi-receiver WPT. Calculations by Biot-Savart Law are adopted for field evaluation and further coil design. The results prove that the magnetic field uniformity of the proposed coil improves more than 20 times compared with an existing designed structure. The result of the proposed design is verified by FEM simulation, and the calculation result matches well with FEM simulation.