Coupling factor analysis for an inductive power transfer system using a quasi-Helmholtz primary coil

We present an analysis of the coupling factor profile of an inductive link formed by a quasi-Helmholtz primary coil and a smaller single secondary coil for wireless power transfer (WPT) applications. Using the quasi-Helmholtz coil configuration allows us to reduce the intrinsic position limitations of standard inductive power transfer applications by providing a more homogeneous magnetic field along the primary coil axis. We analyze the correlation of the distance between the primary coils and the coupling factor of the inductive link along a movement of the secondary coil in the z-direction and observe excellent agreement between our simulations and measurements.We examine the advantages of coupling response by decreasing the distance between the primary coils and the tradeoff of the coupling factor by covering long transmission sections with multiple primary coils at larger distances.