A universal mathematical model of a three-phase transformer with a single magnetic core

Abstract

A universal mathematical model of a three-phase transformer with a single magnetic core for different variants of primary and secondary winding connections using wye and delta schemes at each of 12 phase shifts using clock notation is described. Such a model design is necessitated by the requirements of GOST (State Standard) 30830-2002 (IEC 60076-1-93) and by the wide use of phase-shifting transformers as elements of schemes for feeding power semiconductor converters. Examples of simulation results for cases of three-phase transformers of Y/Y-8 and Y/Y-4 schemes and vector groups are shown. The proposed model allows the working regimes to be investigated of a three-phase transformer with unbalanced sets of parameters for its phases or phases of load, as well as in cases of feeding from a source with an asymmetrical voltage, including a nonsinusoidal one. Taking into into account nonlinearity of magnetization curve at each phase separately allows one to correctly simulate the harmonic composition of currents and voltages.