International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 12 Issue: 06 | Jun 2025
p-ISSN: 2395-0072
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A thermal simulation of a power transformer using a 3D model with two oil inlets and two oil outlets Alejandro Roberto Tello Campos 1, Saúl García Hernández2, William Vicente Rodríguez1, Rodrigo Ocon Valdez3 1Researcher, Instituto de Ingeniería, Universidad Nacional Autónoma de México, CDMX, 04510, México. 2Researcher, TecNM–Instituto Tecnológico de Morelia, Maestría en Ciencias en Metalurgia, Morelia, Michoacán,
58120, México.
3Professor, Facultad de Estudios Superiores Aragón, Universidad Nacional Autónoma de México, Nezahualcóyotl,
57171, México. ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract – In this study, a 3D thermal simulation of an
During the past decades, a lot of research has been done to investigate the hot spot within transformer windings. From advanced mathematical techniques [1,2,3] that are employed to solve the energy equations that represent the heat transfer occurring in windings and obtain the windings temperatures. Also, other researchers have solved the momentum, energy, and continuity equations in a simplified 2D CFD model, which employ numerical techniques to solve these equations and obtain a more detailed view of oil velocities and temperatures in simplified versions of a winding. In this study [4], a lot of simplification in the winding’s geometry has been done to simplify the computational time and identify the maximum windings and oil temperatures and their exact location.
ONAN power transformer using two oil inlets and two oil outlets was performed. A similar simulation was performed in a previous paper using only one oil inlet and one oil outlet. The benefits of this simulation are that the oil velocity vector graphics show an oil circuit that forms at the inlets, which prevents oil from flowing smoothly through the windings of the transformer, guiding oil directly from inlets to outlets. Furthermore, as oil velocity increases, the transformer is cooled more efficiently. Also maps of oil being heated were found to be illustrative as the inner surfaces of the LV windings were hotter than the ones of the HV windings. This kind of simulation also helps to understand the fluid dynamics of oil within the windings and core.
In this study, a graphical representation of oil flow within transformers is presented. Contours of oil velocities and temperatures along with windings and core temperatures were calculated. A power transformer model with two oil inlets and two oil outlets was considered for use.
Keywords: transformer; CFD; oil flow; 3D Model; temperature
1. INTRODUCTION
A 3D model was employed to capture the physics of oil flow within windings and core, comparing it with the one obtained in another study [5], which uses only one oil inlet and one oil outlet. This helps to understand the oil flow dynamics obtained at low oil flowrates which are observed in ONAN power transformers. Final remarks include an analysis of the benefits obtained from this study and the possible improvements that can be made to the 3D model in order to optimize the cooling of the power transformer.
Power transformers are electrical equipment that are necessary to transform voltages from one level to another. They have been designed to connect one electrical circuit at a high voltage to another at a lower voltage. They are elements that have to perform their function for at least 25 years. In this regard, as they are constructed out of windings which are embedded in a core forming an electromagnetic coupling of the high and low voltage circuits, they produce an amount of heat due to the Joule effect generated by the circulating current in the conductors of windings. The transformer itself has to be cooled down by oil circulating through the windings and core. This helps to increase its lifetime and performance. These power transformers are large in numbers, so they must be efficient. The electrical efficiency of this device is high, but it could still be increased by optimizing the cooling of this apparatus. That is the main reason for studying the flow phenomena that occur, which are directly related to the oil being circulated in a natural way or being forced by using a pump, which employs a radiator to dissipate the heat produced in the electrical conductors.
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2. 3D MODEL The power transformer is composed basically of windings surrounding a central core. This assembly is contained in a tank and immersed in mineral oil. Supporting structures are other components that help maintain the assembly in a vertical position within the tank. Also, the whole power transformer uses external air-cooled radiators that help cool down the hot oil coming from the windings and core. This effect of heat generation produced by the circulation of electrical currents within the windings and core is what is normally called Joule effect.
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