Model for Loss Calculation of Wireless In-Wheel Motor Concept Based on Magnetic Resonant Coupling

Adopting the In-Wheel Motor technology (IWM) for the traction system of electric vehicles (EVs) leads to several advantages. Since the motors can drive each wheel in the vehicle independently, the EV can take full advantages of technologies such as anti-slip control of tires for enhanced safety and performance, and optimal torque distribution for extension of the vehicle mileage. However, a major problem of conventional IWM is that the power cables and signal wires from the vehicle body to the wheel are exposed to harsh environment, and may be damaged due to continuous bending, impact with debris from the road, or become brittle because of the freezing in snowy areas. To overcome this problem, a system in which the IWM receives its power wirelessly from the vehicle body has been proposed, resulting in the Wireless In-Wheel Motor (W-IWM) concept. This cutting-edge technology eliminates the risk of cable disconnection of IWM and therefore raises the reliability of the whole vehicle system. Due to steering and to the operation of suspensions, the relative position between the car body and the wheel assembly changes during driving. Therefore, the wireless power transfer has been implemented using the principle of magnetic resonant coupling, which is robust to misalignment between the transmitter and receiver coils. A single phase inverter is installed in the car body side (transmitter side). Single phase converter is also installed the wheel side (receiver side). This paper discusses two control schemes on transmitter side and three control schemes on receiver side. The loss analysis of each converter aims to verify the most efficient control combination. Eventually, the DC/DC chopper control regulating the inverter output voltage amplitude is selected because of its better efficiency compared to other control schemes on transmitter side. In addition, this paper proposes symmetric synchronous rectification control on receiver side. The proposed control effectiveness is confirmed by numerical analysis considering its efficiency and total harmonic distortion.