Calculating Leakage Reactance of 9-Winding Transformer using Time-Dependent 3D FEM analysis

Calculating leakage reactance of transformers is a very important factor in designing transformers. It is difficult to calculate the leakage reactance in multiple-winding transformers, because their structures are more complicated. The finite element method (FEM) is useful to obtain the leakage reactance in such a complex case. Using a 3D FEM analysis, leakage reactances have been calculated and compared to experimental results. But, there were differences between the results of FEM analysis and the experimental results. In this paper, the leakage reactance is calculated by using a coupled-field analysis, which combined electromagnetic field analysis and electric circuit analysis, for simulation of short-circuit test in multiple-winding transformer. The results of this analysis showed that current values of parallelly connected primary windings are very different by the physical geometry of the secondary winding. The leakage reactances calculated by using the coupled-field analysis are qualitatively the same as experimental results.