A Novel Loosely Coupled Transformer With Nanocrystalline Cores for Omnidirectional Misalignment Tolerance and Receiver Compactness for Wireless Power Transfer System

To solve the poor tolerance of the conventional loosely coupled transformers (LCTs) to misalignment in certain directions, as well as achieve a lightweight receiver of a wireless power transfer system, this paper proposes a nanocrystalline‐core LCT with omnidirectional misalignment tolerance. Finite element analysis (FEA) is employed to study the directional efficiency characteristics and field distribution of the LCT with the classic double D (DD)‐DD quadrature (DDQ) pads under different misalignment conditions. On this basis, a magnetically equivalent structure to the section of DD‐DDQ pads is developed and further constructed for omnidirectional misalignment tolerance and receiver compactness. The nanocrystalline core is also applied to improve the power density of the onboard receiver. Then, a design flowchart is given for the proposed LCT and a case study is accordingly conducted. Mutual inductance variations, transmission efficiency and field distribution are analysed by FEA. Finally, an LCT prototype is developed for experimental verification and the results under 3‐kW output power show that, regardless of the misalignment direction, AC–AC efficiency only decreases by 3.728% compared to the aligned position and reaches 91.524% at a misalignment of 275 mm, which reaches 82.583% of the transmitting coil radius.