Design of Wireless Power Transfer Coils for High Efficiency and Low Leakage Magnetic Fields

Electromagnetic fields (EMFs) around the wireless power transfer (WPT) coils should be lower than the limits set by standards. In this paper, a design of the WPT coils for a reduced level of leakage magnetic fields (LMFs) and constant efficiency is proposed. A hemicylinder-cylinder joint structure is given. Transmitting coil (TX-C) was wound on a hemicylindrical structure and receiving Rx coil (RX-C) was wound on a cylindrical structure. Thus, the RX-C can rotate around its axis between 0° and 85°. Design procedures are discussed in detail. EMF analysis is investigated under different rotation angles. The chosen design reduced the variation of the mutual inductance (M). Therefore, it maintained a constant power transfer efficiency (PTE) while rotating the RX-C. In addition, LMFs near the WPT windings of the selected design were reduced by 63.6% compared with other coil methods that have similar values of PTE.