Asymmetric Coil Sets for Wireless Stationary EV Chargers With Large Lateral Tolerance by Dominant Field Analysis

Asymmetric coil sets for wireless stationary electric vehicle (EV) chargers, which has significantly larger lateral tolerance than previous ones, is proposed. The pick-up coil set is much smaller than the power supply coil set, thereby allowing large lateral and longitudinal displacements as well as robustness to air-gap displacement. Electromagnetic field (EMF) is reasonably reduced by arranging magnetic poles along the EV´s moving direction so that alternating magnetic flux through adjacent poles cancels each other. A dominant field analysis useful for complex vector magnetic flux simulation is newly proposed, which is applicable to any resonating coils of an inductive power transfer system (IPTS). Furthermore, a hysteresis loss model is suggested, which appropriately reflects the partial core saturation on a system analysis. A prototype IPTS including the proposed coil sets were designed and successfully verified by experiments. In the quick charging mode, maximum output power of 15 kW, large lateral displacement of 40 cm, longitudinal displacement of 20 cm, air gap of 15 cm were achieved, and low EMF of 6.1 μT at 20 kHz was achieved in the normal charging mode of 5 kW.