| With the limitation to transportation conditions of railroad and highway, the volume of the transformers can’t be increased without any limitation. Thus, the structure of the transformers has to be adjusted by carrying out some measurements, such as pressing the upper and lower iron yoke and decomposing the iron core column. However, it will cause some problems such as disorders of magnetic field distributions and uncertainty of field current with the structures of transformers changed. In this paper, two transformers with special structure, i.e. single-phase three-limb yoke-pressing transformer and the three-phase five-limb disintegrating transformer, were presented. Based on the field-circuit coupled method, two-dimensional (2D) and three-dimensional (3D) magnetic field in these two transformers were simulated numerically and the field distribution and field current waveform were discussed. The main contents are as follows:Firstly, the development situation of electromagnetic field calculation methods and product design of the power transformers at home and abroad are reviewed on the basis of understanding the special structure characteristics of the transformer and operation characteristics. The principle about the field-circuit coupled finite element calculation was studied and its application in commercial software was mastered.Secondly, the simulation analysis of no-load operation experiment in single-phase three-limb yoke-pressing transformer with DSP-241000kVA/500kV was accomplished. The2D and3D simulation model and external circuit model of this transformer were established based on the commercial software, and the main magnetic field distribution and excitation current were calculated with transient field solving module through. The calculation results of flux linkage and ampere turns are analyzed to verify reliability of results of magnetic field calculation.Finally, the main magnetic field analysis in three-phase five-limb disintegrating transformer with OSFPS9-360000kVA/330kV was accomplished. The2D simulation model was analyzed with field-circuit coupling, firstly, because of its complicated structure, and the change of magnetic field about air gap in iron core was discussed. In order to obtain the magnetic field distribution in core and no-load current, the3D simulation was implemented with transient finite element method with respect to2D simulation model. The influence on computational efficiency from different phases of excitation voltage was discussed in order to reduce overlong computation time resulted from large time constant value. |
