Optimization of ferrite core to reduce the core loss in double-D pad of wireless charging system for electric vehicles

In this paper, an optimized core structure is proposed for the double-D (DD) power pad to reduce its core loss in a wireless charging system for Electric and Plug-in Hybrid Electric Vehicle (EV/PHEV) application. At around 85 kHz operating frequency, the core loss is found to be one of the most significant loss in typical wireless charging system of high power application. The core loss in power ferrite mainly depends on the operating frequency and magnetic field density in the core. The frequency is usually fixed for certain application, therefore, the magnetic field density in the core is be to optimized to reduce the loss. The magnetic field density in core of a double-D (DD) pad has very different pattern compared to unpolar pad; therefore traditional bar or plate core does not provide the optimum performance considering core loss. In this paper, an optimized core structure is proposed to make the flux density uniform in the core and minimize its loss. The proposed optimized model is simulated in finite element analysis (FEA), and compared with traditional flat type core. Finally, the proposed model is verified through a 3.2 kW wireless Double-D (DD) type wireless charging pad.