Suppression of Leakage Magnetic Fields in Wireless Power Transfer Using a Sandwich Structure

This study proposes a wireless power transfer (WPT) system using a sandwich structure comprising two transmitter coils and two receiver coils with distinct magnetic field configuration modes. The primary objective of this research is to suppress leakage magnetic fields while maintaining high power transfer efficiency. The results of the electromagnetic field analysis and experimental tests demonstrated that the magnetic field leakage of the differential-differential (DD) mode of the sandwich structure was significantly lower than that of the conventional structure, which employs a single coil pair and the cumulative-cumulative (CC) mode of the sandwich structure. Compared to the conventional and CC modes, the leakage magnetic field of the DD mode decreased by 10.1-12.3 dB at 1 m from the coils. This corresponds to suppressing the magnetic field leakage by approximately 76.0% compared to the conventional mode and 68.7% compared to the CC mode. These reductions were attributed to antiphase magnetic fields canceling each other in the DD mode. Moreover, the power transfer efficiency in the DD mode exceeds 95%. The proposed system was shown to effectively suppress electromagnetic interference without compromising transmission efficiency.