engleski

Fast Hybrid Approach for Calculation of Losses in Outer Packages of Transformer Core due to Perpendicular Stray Flux

Stray flux in a transformer enters the outer packages of a core perpendicularly and induces significant eddy currents which cause ohmic losses. Local thermal conditions near the core are affected by these losses which dissipate as heat and can cause local overheating in the oil near the outer packages. Stray losses in the outer packages should be considered during the power transformer design process, and it is therefore important to model them properly. This type of losses can be solved using 3D FEM ; however, that approach is time-consuming which makes it impractical for the loss calculation in real-time. Another approach is 2D modelling, which is faster, but it is limited to axisymmetric and planar geometries only. Due to its complex geometry, a transformer cannot be modelled using a single 2D model. Instead, each quantity of interest, such as a magnetic field or eddy currents, can be obtained from a suitable 2D model. These models include certain simplifications, which should not affect the accuracy of the results. In this paper, a hybrid approach that utilizes various 2D models for the calculation of stray losses in the outer packages is proposed. The advantage of the proposed methodology is in obtaining the same level of accuracy while considerably reducing the calculation time when comparing to the 3D FEM approach. The estimation of the temperature rise of the outer packages, based on the calculated losses, will be a part of further research.

2D FEM, Rabins’ method, transformer, laminations, stray losses.

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