Major challenges of transformer designers are high energy-efficiency, high reliability, low cost and weight requirements. So they need advanced techniques and tools that lead to optimum design and improvement of product performance. A single conductor winding conventionally has been used which does not have any circulating current loss. This winding, however, has high electrical resistance due to the skin effect and the eddy currents from the leakage magnetic flux increase. As a result, the single conductor winding has big eddy current loss. In order to reduce the eddy loss, parallel multi-conductor winding is replacing the single-conductor winding. This winding, however, has circulating current loss instead of the eddy current loss. It is because the magnetic flux varies depending on the physical positions of the parallel windings, and each parallel winding has its own induced voltage and the voltage difference between the parallel conductors will generate circulating currents inside the winding. In order to minimize the circulating current loss, the parallel winding has transposition which changes the physical position of each conductor of the parallel winding.
In this thesis, circulating current loss of a power transformer is analyzed using finite element method. This dissertation is composed of as follows:
In oder to overcome the problem, firstly, a power transformer model has a layer winding at the low voltage of the transformer. The transposition that changes the physical position of the parallel windings is performed to reduce the circulating current loss. we proposed a transposition method. Secondary, we model a transformer in this dissertation has been carried out using an electromagnetic finite element analysis method(FEM) software, Ansys Maxwell. In the FEM, the model is analyzed by time stepping method to reduce computing time in nonlinear transient problem. And the equation of steady state estimation was defined. Finally, The equation of circulating current loss was analyzed with currents in each parallel conductors.