Metal Object Detection in a Wireless Power Transfer System Based on Double-Layer Symmetric Sensing Coils

The intrusion of a metal object into a wireless charging system could cause safety issues, such as temperature rise and even combustion. This paper proposes a double-layer symmetric sensing coil design for metal object detection (MOD) of wireless electric vehicle charging to prevent the detection blind area. First, the magnetic effect and the eddy current effect of a metal object in high-frequency magnetic fields are analyzed. Second, the principle of the proposed double-layer symmetric sensing coils is detailed. Finally, the finite element simulation is implemented in order to test the performance of the proposed sensing coil design. The simulation results show that the proposed double-layer symmetric sensing coils can effectively detect the presence and position of the metal object simultaneously.