Modeling of power transformers and realisation of electromagnetic field analysis

Transformer, which is one of the most important elements of energy transmission and distribution systems, is manufactured as a result of high cost and long studies. The mechanical, electrical and magnetic properties of a transformer need to be known before the manufacturing process. To satisfythe test criteria and to minimize the problems that may arise after the manufacturingand in operation it is important to model transformers with a reliable simulation program. By means of developing simulation techniques, design defects can be determined through a simulation program at the beginning, whichmakesthe necessary revisions possible. In this thesis, to investigate the magnetic field density, magnetic field intensity, magnetic flux lines, current density, vector distribution and losses in the coil and core of the transformerANSYS Maxwell 2D and 3D packages,which are widely used in transformer simulationwere used. Two different types of transformers were considered; one of them was single-phase 90 VA low powertransformer and the other was three-phase 15 MVA power transformer. Current, voltage, magnetic field values, current densities, losses and B-H curves of these transformers were investigated by using the Finite Element simulations of ANSYS Maxwell 2D and 3D models. Electrical and physical properties of the single-phase low power 90 VA transformer were taken into consideration in the laboratory environment and the necessary parameters were calculated by carriying out the measurements. The values which were derived by simple theoretically calculations, experimental measurements results and the ANSYS Maxwell program simulationresults were compared. Theresults of the model formed in the programwere verified by the laboratory tests. For three-phase 15 MVA transformer, the electromagnetic field distribution and losses in the cores and windings of the transformer were investigated by using the pre-design values. In the transformer model, M530-50A material was selected from the simulation program libraryas the core material. It wasshown that it was possible to decrease the core and copper losses by using the appropriate winding structure. KEYWORDS: Power transformers, finite elements method, electromagnetic analysis, transformer losses.