Computation Of Leakage Magnetic Field And Tank Eddy Current Loss Of Transformer

With the development of capacity of transformer, the leakage magnetic is increasing which may enlarge the stray loss in the tank and structure. The complex and irregularity structure of transformer results in the uneven distribution in the component of the stray loss, which may lead to local overheating and the transformer accident etc. Therefore the running reliability of transformer may be affected. Controlling the quantity of the stray loss and temperature rise of hot spot may be the most important ways to assure the normal operation of transformer. The proportion of eddy current loss is very large among the stray loss. It is quite necessary to deeply and accurately study the magnetic leakage and eddy current loss.This thesis is faced with the complicated physical models of large capacity power transformer. Two-dimensional (2D) and three-dimensional (3D) calculation models for leakage magnetic field and leakage reactance are presented through reasonable simplification by the software ANSYS/Emag. Kinds of typical transformers are calculated. By contrasting the calculation results with the measured values, the two-dimensional model is feasible and the results can meet the engineering requirements dependence the ax symmetric on structure of transformer.The three-dimensional tank eddy current loss calculation model is also defined (model 1). Tank shells are considered the single layer and the reinforce iron plates are ignored in creating the model. The material of tank is ferromagnetic substance and the depth of tank wall is much more than the skin depth. Therefore, tank wall would be subdivided to several layers by FEM in order to get accurate results. It is computed that the tank eddy current loss is numerous and the distribution is uneven in the tank wall of large capacity transformer by ANSYS/Emag. To reduce the eddy current loss, the model with shield plate (model 2) is given based on the model 1. By changing the shield material and the depth, the electromagnetic shield and magnetic shield are researched. With the comparison of the two shield materials, it draws significative conclusions.The study in this thesis is a practice application of finite-element method. Conclusions are drawn by the thesis may instruct engineering practice.