SAE J2954 specifies a contactless power transfer in which the electric vehicle is automatically aligned over the primary coil by magnetic triangulation. The primary coil is located in the ground and the secondary coil is located under the vehicle.
The J2954 standard specifies the criteria for interoperability, electromagnetic compatibility( EMC), transmissible power, charging and safety. The standard recognizes three different charging processes - WPT1, WPT2 and WPT3 - which differ in charging power. The charging power of WPT1 is 3.7 kW, that of WPT2 7.7 kW and that of WPT3 11 kW.