Metallic object detection in inductive power transfer systems

Abstract

Due to the conductive nature of Metal Objects (MO), the presence of foreign MO can cause complications in an Inductive Power Transfer (IPT) system. In IPT system, strong magnetic fields are generated to achieve contactless electric power transmission. When a foreign MO interacts with the generated magnetic fields, it gets heated up due to the induced eddy current in the MO. This may lead to ignition hazards. Therefore, to ensure the safe operation of IPT, a Metal Object Detection (MOD) System is essential to alert the IPT system when the presence of MO is recognized. Different types of MOD methods were studied and a MO detection coil prototype utilizing the Sensing Pattern-Based Detection Method was proposed. The proposed detection coil was divided into multiple rows of two separate coils (D-coil and Q-coil). Experiments were conducted to verify the effectiveness, sensitivity, and reliability of the detection coil in identifying MO. The test MO used in the experiment was a 10-cents Singapore Dollar Coin. The experiment includes Induced Voltage variation test and Inductance & Impedance variation test.