The Effect of Load Impedance on the Efficiency of a Wireless Power Transfer System with an Additional Resonant Coil

Abstract:
Modern wireless power transfer systems (WPTS) are complex electromechanical devices, in the development of which mathematical analysis and computer-simulated models often fail to fully replicate the complex processes occurring within them. These processes can be categorized into three main groups: mechanical, electrical, and electromagnetic.To verify the analytical results obtained in [1,2], a laboratory mockup of a wireless charging system (WCS) for electric vehicle (EV) was developed at a 1:4 scale. The main goal is to simulate the real operating conditions of a wireless charging station with the following parameters: a transmitter coil (TX), a resonant coil (RC), and a receiver coil (RX) with a diameter of 600 mm, as well as an EV clearance ranging from 100 to 350 mm.The possibility of efficient energy transfer over a distance greater than D/4 (D- diameter of the transmitter coil) has been investigated. A series of experiments are made under different load resistances, representing the battery discharge level at the beginning of the charging process- from fully discharged battery to an fully charged battery. The results of the study are presented in graphic form, showing that the system's efficiency remains within very good limits (above 80%), regardless of the battery discharge level (load resistance).