Modelagem de transformadores de núcleo amorfo usando método de elementos finitos

Abstract

The amorphous materials are becoming broadly used in transformers industry, due to the low losses in its core, since they have a hysteresis loop narrower compared to the traditionals cores of silicon steel. However, its cost of these materials is a great factor against its use in electric power systems. Study the cost / benefit in terms of technical performance and robustness must be considered when we want to design transformers which use this material type. The main contribution of this work is the performance analysis of the transformer in short-circuits, since the equipment failures cause a reduction in revenue, not only for expenses maintenance, but also because the concessionaire does not sell its product, electric energy, and it could be submitted to penalties by regulatory agency in the electricity sector. Under short-circuit conditions, the windings of transformers are submitted to mechanical efforts produced by Lorentz forces, these forces arise as a flux result produced by conductors in parallel that carry current in the same direction. In this case, study the electromagnetic behavior of the transformer is essential for obtaining such forces. To develop this work, the software Finite Element Method Magnetics (FEMM) was used. This tool is based on the finite element method in the calculations of the electromechanical magnitudes and, consequently, the calculation of forces acting in the spires, which allow the calculations of the strain. Finally, this paper deals with the application of the FEMM tool to calculate the mechanical effort and the simulation of the electromagnetic behavior of a distribution transformer.