Numerical and Experimental Evaluation and Heat Transfer Characteristics of a Soft Magnetic Transformer Built from Laminated Steel Plates

Abstract

The present work evaluates, both experimentally and numerically, the heat transfer characteristics of a 5 kW three-phase transformer built from laminated steel sheets. The transformer is operated at different powers, and its temperature distribution is monitored using 108 thermocouples. The experimental measurements are used firstly to determine the heat dissipated at the core and the windings of the transformer. This information is used as an input for a finite element numerical model, which evaluates the heat transfer characteristics of the transformer. The model proposed in this work simply solves the diffusion equation inside the transformer, accounting for the anisotropic thermal conductivity of the different components of the transformer, together with well-known correlations at its boundaries. The results reveal that the proposed numerical model can correctly reproduce the maximum temperature, the temperature distribution, and the time-evolution of the temperature at specific points of the transformer measured during the experimental campaign. These results are of great use for the subsequent development of transformers of the same type in lab-scale or industrial-scale size and reveal the applicability of simplified numerical models to accurately predict the heat transfer characteristics of this kind of transformers.

Review of Modeling Approaches for Conjugate Heat Transfer Processes in Oil-Immersed Transformers

“…In addition, the analysis of condition is complicated by the fact that the transformer load is not constant during the day and throughout the year. Mathematical models for transformer thermal simulation can be broadly classified into two categories: those based on circuit theory [39][40][41][42], and those that solve field problems using numerical methods [116][117][118][119][120][121][122][123]. The first group has the advantage of allowing for real-time calculations, as they do not require significant computational resources.…”

“…This conclusion highlights the importance of developing numerical conjugate heat transfer models or conducting experimental tests to define the hydrodynamic parameters of power transformer systems. In [119], a numerical model is developed based on the finite element method, considering only heat transfer equations. The model is correlated using measurements from 108 thermocouples and is asserted to have an accuracy of ±1 °C by the authors.…”

The Tools and Parameters to Consider in the Design of Power Transformer Cooling Systems

“…In the case of fluids such as mineral oil or air, this property is the heat transfer coefficient α. According to studies in the literature, the value of the mineral oil coefficient α is equal to 100 W•m −2 •K −1 [1][2][3][4]. The authors' research shows that the coefficient α of an insulating liquid can have different values.…”