A Method for Computing the Load Performance of Separate-Type Transformers

Abstract

This paper proposes a method for computing the load performance of separate-type transformers, employing 2-D FEM to take account of the terminal voltage. Separate-type transformers, whose primary core is separated from the secondary one by air gaps, cannot be treated as 2-D models, because of the leakage flux in the neighborhood of the air gaps. Therefore, in this method, 3-D static FEM analysis is used to calculate the leakage flux which cannot be considered in 2-D analysis, and the leakage inductances are calculated from the leakage flux. In the next step, the load performance is computed by 2-D FEM taking into account of the above leakage inductance inserted into primary and secondary circuits. Thus, the load performance of separate-type transformers can be easily and accurately obtained without 3-D dynamic analysis. Here, this method is applied to C−C- and C−I-type transformers. The results of the calculations agree well with measured results.