Method for Calculating Mutual Inductance at Any Position Between Circular Coils With Bilateral Magnetic Medium in Wireless Power Transfer Systems

ABSTRACT Accurately calculating the mutual inductance between coils is crucial for achieving an efficient and reliable wireless power transmission system. However, when a double‐sided magnetic medium coil undergoes any positional change, it typically relies on simulation software to obtain the mutual inductance value, lacking a straightforward calculation method. To address this, this paper proposes a unilateral mirror current equivalent method to derive the mutual inductance formula for coils with double‐sided magnetic medium at arbitrary positions. This method replaces the magnetic medium on the receiving side with a mirror current coil, equating the mutual inductance to the sum of the mutual inductance when only the transmitting side magnetic medium is present and the mutual inductance when the mirror current is acting without magnetic media. By analyzing the variation of the mirror current coefficient, a formula for the mutual inductance between coils with double‐sided magnetic medium during positional changes is derived. An experimental setup with the same parameters as the simulation model was built using acrylic plates, copper wires, and other materials. The mutual inductance experimental values were measured using an impedance analyzer. Simulation and experimental results indicate that the calculated mutual inductance values have an error of no more than 5.30% compared to experimental values. This method remains applicable even when the parameters of the coils and magnetic media change, and it is 70 times faster than simulation, thereby validating the effectiveness and speed of the calculation method.