Analysis of short circuit electromagnetic forces in transformer with asymmetrically placed windings using Finite Element Method

Abstract

Short circuit electromagnetic (EM) forces are considered as important factor and should be taken care of while designing a transformer. The effect of forces is more important in case of large transformers, but the procedure of analysis of forces is same for both power transformers and power distribution transformers. Therefore, a 630kVA, 11/.433kV power distribution transformer has been modeled for analyzing the forces using Finite Element Method (FEM). Windings are modeled into twenty three sections and short circuit EM force of each and every section of the winding is calculated. The forces are calculated under worst fault condition of three phase symmetrical short circuit current. In practical transformer, there is some axial asymmetry between the windings. Net axial force experienced by the windings because of absence of symmetry is calculated and effect of tapping on short circuit EM forces is also included in this study.