An Extensively Applicable Equivalent Air Gap Method for Mutual Inductance Calculation Between Coils With Finite Magnetic Cores in WPT Systems

Coils are the key elements in wireless power transfer (WPT) systems. Performing magnetic field analysis, especially the mutual inductance analysis of the coils, is of great significance for the predesign and performance evaluation of the systems. To enhance transmission power and reduce magnetic leakage, magnetic cores of finite size are typically installed within the coils. However, this installation significantly complicates the calculation of magnetic fields. Generally, simulation analysis using finite element analysis (FEA) tools is required, which is time-consuming and unable to optimize the performance of WPT systems efficiently. This article introduces the concept of equivalent air gap (EAG) based on Ohm’s law for magnetic circuits, allowing coils with finite magnetic cores to be equivalently modeled as coils without cores. The method facilitates rapid and efficient calculations of mutual inductance, remains unaffected by the specific configurations of the coil and core, and therefore offers wide applicability. The effectiveness of the proposed method is validated through both simulation and experimental results.