Time-Domain Homogenization of Foil Windings in 2-D Axisymmetric Finite-Element Models

In this paper, an approach for the time-domain homogenization of foil windings in axisymmetric finite-element (FE) models is presented. The homogenized formulation is characterized by an axial current redistribution due to the skin effect and a radial inter-turn voltage given by the insulation in-between the turns. The method is successfully applied to an axisymmetric 20-turn foil-winding inductor. At low frequencies, the local and global results present an excellent agreement with those obtained by an accurate but expensive FE model in which all turns are explicitly discretized. The air-gap effect and the frequency limitations are studied as well.