Numerical Simulation And Research On Winding Leakage Magnetic Fields And Characteristic Parameters Of Special Transformers

The special transformers which are analyzed in this paper mainly include dry foil winding transformers and high-capacity phase-shifting rectifier transformers.Dry foil winding transformer is characterized by environment protection, energy saving and material saving, thus, its market demand and capacity continuously increase. However, with the increasing transformer capacity, the extremely uneven eddy current loss caused by leakage magnetic field in the foil winding conductor will be more and more serious, and the traditional design method of additional loss is based on the multiplication of DC resistance loss and coefficient. Clearly, the method is difficult to accurately reflect the influence of winding arrangement structure and conductive material (wire or foil conductor winding) on additional loss distribution characteristics, therefore, using numerical method to research the leakage magnetic field and eddy current loss distribution has practical significance. In this paper, the numerical calculation and statistical analysis on short circuit impedance, winding eddy current loss and electromagnetic parameters for the same series of dry-type transformers are carried out by using finite element method(FEM), which provides a design reference for additional loss calculation of the same kind of dry type transformers.As a power device, high-capacity phase-shifting rectifier transformer is an important equipment. The common transformer usually adopts Y/Δ connection, and the phase-shifting rectifier transformer uses delta or Z connection. The net side winding of this transformer has parallel branches, but the branch currents are unknown. At the valve side, under the condition of half through operation and split operation, the distribution of winding ampere-turn and leakage magnetic field is asymmetric. Therefore, the3D FEM model coupling with the equivalent electric-circuit is well established for a large capacity phase-shifting rectifier transformer (PSRT). Then, short-circuit impedances and branch currents of different operating conditions are calculated and validated by the field-circuit coupled method (FCCM) respectively. Thus the current distribution and some conclusions are obtained, which provide reliable analysis method for product design of phase-shifting rectifier transformer.