Numerical Modelling of AC Loss in Coated Conductors by Finite Element Software Using H Formulation

This paper proposes a practical and memory efficient method to model YBCO coated conductors by commercial finite element software. This method uses the H formulation to directly solve a magnetic field in a two-dimensional space. This model has been successfully used for bulk materials and thick wires, and is extended in this article to solve geometries with high aspect ratios such as coated conductors. The effect of mesh quality and order of element on the performance and accuracy of the model is discussed. A model using 2nd order single layer elements is chosen as the optimal setting for solving AC loss in coated conductors. Based on this setting, a series of simulations with the thickness of the tape varying from 1 mu m (the actual thickness) to 120 mu m have been performed to investigate the effect of artificially expanding tape thickness. The results obtained from our FEM model are compared with the classical analytical solutions. The discrepancies between the two are discussed and explained. The model proposed in this paper is able to give an accurate solution of AC loss for simple geometry (such as a single tape with expanded thickness) within just a few minutes. Even in the case of dealing with complex problems (such as a tape in its actual dimension or a stack of tapes under complicated magnetic conditions), the model would only require a few hours to solve the problems with excellent convergence properties.