Enhanced numerical model of performance of an encapsulated three-phase transformer in laboratory environment

The paper presents a numerical thermal model of an encapsulated three-phase electrical transformer. This model is based on the coupled approach and involves a heat transfer analysis coupled with the examination of the specific power losses within the coils and the core, determined from a detailed analysis of the electromagnetic field. The thermal boundary conditions, i.e. local heat fluxes, are determined by considering a numerical model of the surrounding air. Additionally, the device is cooled via forced convection (water cooling system) and radiation (from the external walls). Moreover, for stranded coils and the core, anisotropic material properties were assumed. Results of the presented coupled analysis show that the temperature distribution within the transformer is more realistic and closer to the measurements when compared to the previous analysis limited to heat transfer problems with uniform internal heat sources and isotropic material properties only. The total heat transfer rate indicates that forced convection is the most important heat dissipation mechanism in this model. (C) 2006 Elsevier Ltd. All rights reserved.