Design of Loosely Coupled Transformer of Wireless Power Transfer for Higher Misalignment Tolerance of System Efficiency

The offset between the primary and secondary couplers of the Loose-Coupled Transformer (LCT) results in deviation in the efficiency of the wireless transmission system. In order to obtain higher efficiency deviation tolerances, a three-loop LCT structure is proposed. The LCT's intermediate couplers are slightly larger than primary and secondary couplers. A 30mm air gap between primary and intermediate couplers exists. The compensation capacitance of the proposed intermediate coupler is variable. Moreover, when the horizontal or vertical offset between the primary and secondary couplers reaches 200 mm or 50 mm, respectively, the intermediate couplers can move with the secondary couplers. At the same time, the proposed LCT control strategy is optimized. A 3-kW prototype was developed for experimental verification, which proved the effectiveness of proposed LCT and control strategy.