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Active and Passive Electronic Components
Volume 2014 (2014), Article ID 951624, 6 pages
Research Article

Analysis of the Coupling Coefficient in Inductive Energy Transfer Systems

The University of Melbourne, Parkville, VIC 3010, Australia

Received 8 January 2014; Accepted 4 June 2014; Published 17 June 2014

Academic Editor: Gerard Ghibaudo

Copyright © 2014 Rafael Mendes Duarte and Gordana Klaric Felic. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In wireless energy transfer systems, the energy is transferred from a power source to an electrical load without the need of physical connections. In this scope, inductive links have been widely studied as a way of implementing these systems. Although high efficiency can be achieved when the system is operating in a static state, it can drastically decrease if changes in the relative position and in the coupling coefficient between the coils occur. In this paper, we analyze the coupling coefficient as a function of the distance between two planar and coaxial coils in wireless energy transfer systems. A simple equation is derived from Neumann’s equation for mutual inductance, which is then used to calculate the coupling coefficient. The coupling coefficient is computed using CST Microwave Studio and compared to calculation and experimental results for two coils with an excitation signal of up to 10 MHz. The results showed that the equation presents good accuracy for geometric parameters that do not lead the solution of the elliptic integral of the first kind to infinity.