Electric vehicles numbers are increasing but they still have issues with range between charges. Battery pack energy density is still low compared to the density of fossil fuel so it is advantageous to offer more recharging windows. This will also reduce consumer “range anxiety”. Automatic inductive charging technology can connect the vehicle to the grid during very short stops, or even during on-road use. The core system device is the charging coupler which transfers power from grid to vehicle. It is a medium-frequency loosely-coupled transformer and the efficiency is critical to the charging process. The loss in the coupler can be categorized into core loss and copper loss. Litz-wire can be used to reduce eddy current loss. This paper analyzes this loss and the AC resistance of multiconductor wires and calculates the magnetic field within the winding. The copper loss of the coupler is then estimated.