An Efficient Method for Litz-Wire AC Loss Computation in Transient Finite Element Analysis
D. Lin, Chuan Lu, N. Chen, Ping Zhou
Abstract
An efficient method is proposed to predict eddy current loss of Litz wire coils, or completely transposed multi-strand coils, in transient finite element analysis (FEA). The method is based on analytical solutions of eddy current loss in a solid wire due to skin effects and proximity effects. The bundle of Litz or solid wires is homogenized by introducing a fill factor to describe the conducting area ratio. The analytical solutions in the frequency domain for round, square, and rectangular wires are further expanded to those in the time domain. The wire length direction in each 3-D mesh is automatically detected so that the flux density vector in each mesh can be correctly decomposed to the orthogonal and tangential components for anisotropic proximity effect loss computation. The method is applied to calculating eddy current loss of a gapped inductor in both 2-D and 3-D, and the results are compared with that using real solid wires.