Unilateral Route Method to Estimate Practical Mutual Inductance for Multi-Coil WPT System

Abstract

Multi-coil WPT systems require mutual inductance information between coils to increase the power transmission efficiency. However, in the high frequency (HF) bands such as 6.78 MHz and 13.56 MHz, the presence of surrounding coils changes the value of the mutual inductance between the two coils due to the parasitic element effect of the coils. These parasitic effects make it harder to estimate the mutual inductance among three or more coils. In contrast to ideal mutual inductance, which has a constant value regardless of frequency and surrounding coils, we define the practical mutual inductance as the mutual inductance varied by parasitic elements. In this paper, a new method is presented to estimate the practical mutual inductance between multiple coils in the HF band. The proposed method simply configures the expression of practical mutual inductance formula because only one of two bilateral dependent voltage sources generated by mutual inductance is considered. For several coils placed along the same axis, the practical mutual inductances between coils were measured with respect to the distance between them to validate the proposed method. The practical mutual inductance obtained from the proposed method was consistent with the simulated and measured values in HF band.

On-Line Foreign Object Detection Using Double DD Coils in an Inductive Wireless Power Transfer System

“…These methods cannot be used during wireless power transfer. It is possible to estimate mutual inductance using measurements of voltages and currents in primary and secondary circuits [9][10][11][12][13][14][15]. Estimations are based on simple circuit equations that describe the compensated resonant IPT.…”