Zhang, W. and Malhan, R., "Center-Tapped Loosely Coupled Transformer Design for iCab and EV Interoperable Wireless Charger," SAE Technical Paper 2017-01-1241, 2017, doi:10.4271/2017-01-1241.
Wireless power transfer (WPT) technology has started to be applied in charging electrical vehicles (EV). EV models with built-in wireless charging capability is expected to be available from several major automakers in the next few years. Meanwhile, problems associated with the massive adoption of automobiles require new format of vehicles, especially the form with compact size and electric power. An inductively charged autonomous bicycle (iCab) is proposed, which has both the automotive driving and wireless charging features. It is designed to be compatible with an EV wireless charger. The wireless charging interoperability issue of the single transmitting coil capable to charge both the EV and iCab is studied in this paper. The receiving coil of a wireless charger is usually designed to match with single transmitting coil and to have a fixed power level output. To solve this problem, a center-tapped loosely coupled transformer (LCT) is proposed for interoperability between the iCab and EV chargers. Both iCab and EV wireless charging applications are realized with a center-tapped primary coil; multiple power levels output is achieved with a center-tapped secondary coil. A transmitting coil is designed to charge an EV with low power of 3.3 kW and high power of 7.7 kW. The same transmitting coil is also able to charge the iCab with low and high power of 510 W and 1.1 kW respectively. The wireless chargers with the universal transmitting pad can achieve the required power level, the maximum efficiency and the soft-switching at the same time..