Experimental Comparison of Circular Test Station Devices for Interoperable 22 kW Inductive Charging of Light-Duty EVs

Public and semi-public EV charging are demanding for higher power levels and seamless infrastructure integration. After completing SAE J2954s' WPT3 11 kW charging class, the WPT4 22 kW class now offers to introduce flush-ground-mounted coil assemblies. However, the increased air gap between vehicle assembly (VA) and ground assembly (GA) exhibits a physical limit in the magnetic flux linkage, such that the sizing of new WPT4 reference coils should be discussed. Based on the WPT3 test device system, a concept for WPT4 assemblies with circular coils is shown in this article. For this purpose, four VA and three GA prototypes were built and measured on a threeaxis test bench. The tolerated coil alignment range was sampled at 189 discrete spots such that for all tested coil combinations a total data set with 3.402 evaluated spots was generated. In each spot the inductance of both primary and secondary coil was measured with the opposing coil in short-circuit and open-circuit state, i.e. four measurements were taken in each spot such that the data presented in this article covers a remarkable number of 13.608 measurement samples in total. The objective of this article is to contribute to the standardization of 22 kW inductive light-duty EV charging by means of quantitative measurement data which can be used for further system level investigations for both G2V and V2G operation or for comparison to other potential test devices concepts.