Calculation of losses in structural parts of transformers by FE method

Abstract

Using commercially available finite element analysis software, a customised user-friendly macro routine has been developed to calculate power losses and associated temperature rises in power transformer core clamps, tanks and magnetic shields. This macro, with few input data, generates the geometric entities to build a model, sets material properties, meshes, applies loads and boundary conditions, solves sets of equations, plots results and calculates power losses and temperature rises. Magnetic and magnetic-thermal coupled field finite element analysis models are used to calculate losses and temperature rises. A simplified iterative method has been developed to deal with nonlinear magnetic material properties. The general understanding of finer mesh resulting in a better accuracy may not always be true, especially when considering the maximum values of magnetic flux density, current density and power loss density in geometries with sharp corners. Because of numerical singularities, as the mesh size decreases the maximum field values increase, leading to an overestimated values and incur unnecessary expenses in the design of equipment.