An Improved Time Period FEM for Numerical Analysis of Electromagnetic Fields of Power Transformers under DC Bias

The DC bias of a power transformer will increase the noise level and additional losses of the transformer. It thus is essential to calculate the transient electromagnetic fields of a power transformer under DC Bias. In this respect, the time period finite element method (TPFEM) is a feasible solution. However, the standard constant time step TPFEM will encounter deficiencies in solving a field problem with a sharp change occurring in a relatively small interval. To address this issue and improve the convergence, an improved adaptive time step TPFEM is proposed and validated in this paper.