Modeling of magnetizing and core-loss currents in single-phase transformers with voltage harmonics for use in power flow

Abstract

This paper presents two approaches for calculating the iron-core and copper losses of a 25 kVA single-phase pole transformer subjected to low-frequency voltage harmonics: an approximate calculation and a finite-element computer model. These methods can be applied to any transformer of similar construction by simply changing the input data, and they can be used for most other single-phase transformers with small modifications. The approximate method is a technique for calculating the change in iron-core losses which can be done without a computer. The finite element computer model performs a quasi three-dimensional field analysis on the iron-core region and calculates the flux density (B) and iron-core losses in each finite element, as well as the magnetizing and core-loss currents. The results of either method can be used at pre-processing for a (harmonic) power flow program.