Design of Metal Object Detection Coil Set with Positioning Function for WPT System

In this paper, an metal object detection (MOD) method based on balanced coil sets is proposed to prevent wireless power transfer (WPT) system from the risk of fire and charging failure. First, the influence of eddy current induced by foreign metal objects on the symmetrically distributed magnetic field of the WPT system is analyzed. Then a double-layered balanced MOD coil set with positioning function is proposed. All mutual inductance values between each detection coil and transmitter coil are measured and the differences are calculated, as indicator of the presence and location of the metal foreign object. Finally, a 1:1 scale 3D model is established by ANSYS MAXWELL software to test the working condition of the coil set, and a coin sized copper plate is used as the metal foreign object. The simulation results indicate that the proposed method can effectively response to the presence of metal foreign object and accurately locate the center point of the metal object.