Finite Element Calculation of Leakage Reactance in Distribution Transformer Wound Core Type Using Energy Method

Abstract

This paper presents the accurate energy method for calculation of leakage reactance of wound core transformers. It takes into consideration the curvature of the winding. The energy technique procedures for computing the leakage reactance are based on finite element analysis. This method is very efficient compared with the classical design methodology which based on magnetic circuit theory. The electromagnetic stored energy is obtained by leakage magnetic flux computing based on finite element method (FEM), and then leakage inductance can be computed. The Finite Element model of distribution transformer with non-linear magnetic characteristic for iron core is built using software "ANSYS".Two dimensional (2D) and three dimensional (3D) finite element modeling of distribution transformer have been used to analyze the leakage field, The obtained results have shown that the 3D model provides higher accuracy in the prediction of the leakage reactance than 2D model, with respect to the test value, due to the better representation of the transformer geometry especially the portions of the coil out of the core window(End and Curvature region),Therefore, the adoption of this energy technique during the design phase is able to enhance transformer manufacturer ability to predict the transformer leakage reactance, thus resulting to better performance and reducing the design time and cost before manufacturing.