Determination of Temperature Rise in a Dry Type Transformer using Finite Element Analysis G. H. Chitaliya* and S. K. Joshi** *-**Dept. of Electrical Engineering, Faculty of Tech. & Engineering, The M. S. University of Baroda, Baroda, Gujarat, India ghchitaliya@gmail.com, skjoshi@ieee.org Abstract: This paper represents the effectiveness of finite element method in designing a dry type transformer to determine the temperature rise. A 160 kVA Vacuum Pressure Impregnated (VPI) tap wound LT isolation transformer having nominal voltage ratio of 415 / 415 Volt has been designed and subjected to a temperature rise test by simulation load method. A 3D finite element method using Variational Approach was adopted in designing the transformer to estimate the temperature rise under full load condition for linear loads. Keywords: Transformer, Temperature rise, 3D Variational Approach, Finite Element Method (FEM). Introduction The finite element method is being used since long for different applications like to determine forces in a civil structure, to carry out stress analysis in a mechanical structure, to identify vibration and shocks effect on a structure or components, thermal analysis of an equipment or their part etc. The FEM has been utilized effectively for doing the analysis of various electrical equipments like inductors, generators, transformers, etc. A. G. Kladas, M. P. Papadopoulos and J. A. Tegopoulos [9], represent use of FEM for finding the leakage flux and force in a winding of a power transformer during short circuit condition. A. S. Reddy and M. Vijaykumar [3], have calculated the life of a power transformer by identifying the hottest spot in a winding using finite element method. M. Lee, H. A. Abdullah, J. C. Jofriet and D. Patel have adopted 2 Dimensional approach using Quasi-Static FEM and circuit based method [11, 12]. M. R. Barzegaram, M. Mirzaie and A. S. Akmal [2] did the analysis in a power transformer to detect the short circuits in winding because of inter-turn or disk to disk failures with the help of Frequency Response method. References [4], [5], [7] & [8] also discuss different methods to design transformer using Finite Element Method. The short circuit study of a transformer having a split winding has been represented by G. B. Kumbhar and S. V. Kulkarni [6] with an approach of coupled field circuit. In the study the estimation of forces due to short circuit on a winding has been found by FEM. However, they did not estimate an actual deformation due to mechanical forces. H. M. Ahn, Y. H. Oh, J. K. Kim, J. S. Song and S. C. Hahn, [1] have taken care of mechanical forces on a dry type transformer of 50 KVA with due verification through experiments. In present paper the main focus is on the determination of temperature rise in a dry type transformer. Finite Element Method has been used to determine the temperature rise in a 160 kVA, three phase, Dyn1, 415 V / 415 V, 50 Hz, dry type Vacuum Pressure Impregnated tap wound transformer, when being subjected to temperature rise by simulation load method in accordance to IS 11171 -1985 / IS 2026-2011 [20]. The hot spot in any electrical machine is due to losses in it. The hot spot temperature is to be determined for estimating the life of insulating material and consequently that of a machine. In a transformer the heat flow is through core and through winding and insulation. It mainly depends on its geometry and type of construction. The temperature distribution in core and winding has been estimated using 3D Variational approach and overall temperature rise has been calculated. Based on FEM results, a design modification has been done for better air circulation and a transformer has been manufactured which then sent to Electrical Research & Development Association (ERDA), Vadodara, Gujarat, India for an actual thermal run (temperature rise test). The transformer model has been shown in Fig. 1 and its specifications are as given in Table 1. Thermal Capacity of a Dry Type Transformer In a dry type transformer the construction is critical for maintaining the thermal capacity. Thermal capacity is defined by its ability to supply the rated load within predefined temperature rise limit in connection with the temperature rise limits of the insulating materials used. The parameters governing the temperature rise are no load losses, load losses and the space between core and winding. The volume of core and winding plays a vital role in heat dissipation.