Minimizing printed spiral coil losses for inductive link wireless power transfer

This work aims for the design of printed spiral coils (PSC) with high quality factors. This consists in minimizing coil losses represented by proximity and eddy currents losses. For this purpose, specific geometric parameters characterizing spiral coils are shown to have a direct impact on increasing such losses. As a result, to minimize proximity effect, high ratios between the interspace separating two adjacent traces and the trace width are recommended to be used. In addition, to reduce eddy current losses, an empirical equation is developed to determine the optimal inner diameter sizes of the coils. The obtained numerical results confirmed that, using the proposed design constraints, the quality factor of the coils improves by 40 % in average with only 12 % decrease of the coil inductance value. Analytical formulation of the coil quality factor is obtained. Comparing analytical to simulation results, the obtained errors are reduced from 43 % to only 5 % when the recommended design constraints are applied.