Asymmetric Coils for Large Tolerance EV Chargers

As discussed in the previous chapter, large tolerance is one of the best characteristics of a static electric vehicle (EV) charger, but only if no severe penalty for the larger tolerance is found. In this chapter, an explanation is given of asymmetric coil sets for wireless stationary EV chargers, which have a significantly larger lateral tolerance than any others in the world.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 airgap displacement. EMF is reasonably reduced by arranging magnetic poles along the EV's moving direction so that alternating magnetic flux through adjacent poles cancel each other. A dominant field analysis (DoFA) useful for complex vector magnetic flux simulation is used, which was introduced in Chapter 15 and is applicable to any resonating coils of inductive power transfer systems (IPTSs). Furthermore, a hysteresis loss model is suggested, which appropriately reflects the partial core saturation in 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, and an airgap 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.This chapter is written based on the paper by S.Y. Choi, B.W. Gu, J. Huh, W.Y. Lee, J.G. Cho, and C.T. Rim, “Asymmetric coil sets for wireless stationary EV chargers with large lateral tolerance by dominant field analysis,”
IEEE Trans. on Power Electronics
, vol. 29, no. 12, pp. 6406–6420, December 2014.