Application of Vector Fitting to High Frequency Transformer Modeling

This paper describes a procedure for frequency dependent modeling of power transformers from measured terminal characteristics. The admittance matrix is measured in the frequency domain using a network analyzer and a dedi- cated measurement setup. Subsequent approximation of the admittance matrix with rational functions using Vector Fit- ting gives an EMTP-type compatible model suitable for tran- sient studies. The approach is demonstrated for a 3-winding rectifier transformer and for the calculation of internal volt- ages in a winding. It is shown that that highly accurate results can be obtained

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