Maximum Output Power Design Considering the Efficiency in Wireless Power Transfer Coils

Wireless power transfer has been attracting a lot of attention in recent years to improve our convenience. Wireless power transfer to electric vehicles is very important to contribute to the spread of electric vehicles and to reduce global warming. Since power supply to electric vehicles often requires high output power, it is essential to design coils to increase the output power by focusing on the coupler part in a specific frequency band from the viewpoint of practicality. In this study, based on SAE J2954 Test station GA-WPT1 and Test station VA-WPT1/Z3 at 85kHz band, we propose a coil design method to obtain the output power while maintaining the efficiency within the required coil size. Although the WPT1 requires 3.3 kW output, the highest efficiency of 99.2% was achieved at 10.9 kW with 600 V input in the simulation. It also achieved 99.0% efficiency at 20.2kW output. The simulation and measurement results show that the inductance of the coil on the transmission side has a significant effect on the output power, which is applied to all wireless power transfer in SS circuits.