Research on maximizing power transfer efficiency of wireless in-wheel motor by primary and load-side voltage control

The authors have developed a wireless power transfer (WPT) system for an in-wheel motor (IWM). It is called a wireless in-wheel motor (W-IWM). This paper presents a method that enhances the WPT efficiency in this system. Some methods that maximize the power transfer efficiency by power converter control have been proposed in past WPT research. In this research, a DC-DC converter is inserted on the receiver side to vary the load state. However, the space on the receiver side is very small for the W-IWM; therefore it is preferable to make the secondary circuit small. Therefore, a full bridge converter is used instead of a DC-DC converter in theW-IWM. In this paper, the authors propose a theoretical formula ofor the transfer efficiency of the W-IWM. From an analysis of this formula, there is a combination of a primary voltage and load voltage that maximizes the efficiency. The feasibility is validated by an experiment using a motor bench set.