Numerical Calculation of the AC Resistance in a Litz Wire Applying the MTL Theory

The performance of a Litz wire for wireless power transfer (WPT) applications is investigated by a new prediction model. The litz wire composed of many insulated strands is assumed to be a multiconductor transmission line (MTL). The MTL impedance and admittance matrices are extracted respectively from a numerical solution of electrostatic and eddy current equations. The variable position of the strands in the cross section of the wire is taken into account to evaluate the electrical performance in terms of the AC resistance. Different litz cable configurations are analyzed at different frequencies and the ratio between AC resistance and DC resistance is predicted.