Modeling and design of a wireless power transfer cell with planar spiral structures

As an emerging technology of wireless power transfer, an electromagnetic resonant coupling technique, also known as witricity, has been widely discussed. In this paper, a prototype with square planar spiral structure based on witricity is proposed. To compute the resonant frequency, an equivalent circuit model is presented. The inductance is calculated based on Wheeler formula. The accuracy of the equivalent circuit model is verified both experimentally and numerically using Ansoft HFSS which is a three-dimensional (3-D) finite element (FE) software. The developed equivalent model is used to optimize the design of the coils to realize resonance at the lowest resonanting frequency.