3D modelling of metal shield on circular coil pad for contactless electric vehicle charging using finite element analysis

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Abstract
Inductive power transfer (IPT) is a practical and preferable method for contactless electric vehicle (EV) charging which proved to be safe, convenient and reliable. Due to the air gap between transfer coil pad and receive coil pad, the magnetic field coupling decreases and the magnetic leakage increases significantly compared to traditional transformer, and this may lead to the magnetic flux density around the coil pads more than the safety limit for human. The coil pad for contactless EV charging is usually composed of winding made from copper litz wires and ferrite strips to enhance magnetic field coupling and reduce the magnetic flux leakage. However, in order to ensure electromagnetic radiation around the EV under safety standards, metal shield may be added to the coil pad in some applications. The adding of metal shield will have influence on power output, coupling coefficient and self-inductance of coil pad. So it is necessary to model and investigate the influence of metal shield on coil pad to provide reference for coil pad design. Finite element analysis (FEA) software is often used to design coil and model IPT system. In this paper, four structures of circular coil pad with different metal shield are modeled and compared from several different aspects using FEA software to study metal shield design of coil pad.