Loss Analysis of Circular Wireless EV Charging Coupler

With the demand for mass-produced commercial electric vehicles (EVs) growing over the last few years, the requirement for EV charging will increase, with continued growth as the number of on-road EVs increases. The EV wireless charging technology offers more flexibility than traditional plug-in charging technology for the following reasons: 1) full automation; 2) fast response; 3) high-power capacity; and 4) safety. The charging coupler is the key component in an inductive wireless charging system. This is a medium to high-frequency transformer (20 kHz), the core loss and the copper loss have to be considered carefully since these will affect the efficiency of the coupler. This paper presents the analysis of a circular coupler with ferrite bar cores and includes the analysis of the core loss considers the sizing of the device. The device is circular on a vertical axis and the air gap is large since there has to be a gap between the charger and vehicle. Therefore, the variation of the transformer coupler diameter is considered in terms of primary/secondary linkage for a fixed air gap. Resonance is used to improve the power factor and boost the transformer output voltage. The core loss is analyzed using finite element analysis in ANSYS Maxwell and the copper loss assumed the use of Litz wire.