Calculation of Losses in PCB Windings for Multi-Coil Contactless Charging Systems

This work presents a method for calculating losses in PCB windings used in multi-coil contactless charging systems. This includes an electromagnetic model which combines analytical developments with FEM simulations in order to calculate the frequency-dependent resistance in a rectangular cross-sectional conductor. The obtained resistance per unit length is then applied to a PCB winding composed of multi-stranded turns in which strands rotate their positions building a Litz structure. The proposed model considers a generic case of a multi-coil assembly in which one of the inductors is supplying power to the load. As other coils may be positioned in the immediate vicinity of an alternating magnetic field source, these coils will produce a loss contribution due to proximity effect. The model has been experimentally validated and the results present consistence when compared with the calculations.