Optimization of the Ferrite Bars in Power Pads for Inductive Power Transfer Systems Based on Penalty Function

The efficiency of an inductive power transfer (IPT) system is closely related to the mutual inductance between its coupled coils. This paper proposes a design method to optimize the configuration of ferrite bars for IPT systems based on a penalty function. The research shows that the growth rate of mutual inductance reaches a maximum point with the increase in the ferrite bar length, and the optimum lengths of ferrite bars decrease with the number of ferrite bars. By taking the bar length and position as variables, an interior penalty function method is proposed to achieve an optimal arrangement for ferrite bars. Subsequently, a mathematical relationship is established among the length, position, and mutual inductance based on the constraint rules of practical designs and Max-well simulation data. Finally, the objective penalty function is obtained by fitting the established surface using Matlab, and the best position and length are accurately determined under a certain number of ferrite bars. Two power pads with diameters of 200 mm and 300 mm are constructed, and the results demonstrate the effectiveness of the proposed optimization method.