A Coil Positioning Method Integrated With an Orthogonal Decoupled Transformer for Inductive Power Transfer Systems

Misalignment between primary and secondary coils in inductive power transfer systems decreases power capacity and efficiency. In this article, a secondary coil positioning method integrated with an orthogonal decoupled transformer is proposed. This nested rectangular and solenoidal structure consists of a pair of double-D coils and a pair of solenoidal coils. The coils are integrated spatially and decoupled magnetically. Based on their directional selectivity characteristics, a coil positioning method is proposed prior to the power path activation. Coordinates can be obtained with polynomial fit calculations. The positioning method is compatible with power transfer and has merits of less auxiliary equipment, higher compatibility, and higher positioning precision considering both horizontal and vertical misalignment cases. The transformer performance is simulated with a three-dimensional finite element modeling tool and verified experimentally on a 3.2-kW prototype. In the preactivation sensing process, points distributed throughout a ±180 mm × 180 mm positioning range were tested. Experimental results show that 92% of tested points are accurate to within 10 mm given a 210 mm vertical distance. When air gap variations are taken into consideration, 90% of tested points are accurate to within 12 mm over the tested range. In the power transfer stage, the maximum full-power dc-dc system efficiency is 94.6%.