Design and numerical analysis of thermal capability of power transformer using coupled electromagnetic field-thermal model

Abstract

In this study, by using the co-simulation technique, the dry-type transformer is designed for a wind turbine with 3.8 MVA, 690 V/36 kV power, and voltages. Dry-type transformers used in wind turbines require extra effort at the design stage concerning oil-immersed type because of the limited cooling capacity of air, possible higher inrush currents, resonant overvoltage, higher voltage, and load fluctuations that degrade thermal behavior. Furthermore, transformer design and analysis of their thermal behavior cannot be realized through one simulation software. Therefore, another approach using different simulation software simultaneously is needed, called co-simulation or multi-physics solution. This paper investigates transformer design and its effect on the system using a co-simulation technique including ANSYS Maxwell 3D, Simplorer, and Mechanical. After realizing the three-dimensional transformer design, its lumped parameter consisting of inductance matrix, leakage inductances, and resistances are determined analytically and using an eddy current solver. Core losses of the transformer, high- and low-voltage windings voltages, and their harmonic spectrums under different load conditions, including ohmic and inductive loads, are defined, the steady-state thermal solution is performed, and conclusions are made. It is proved that the transformer design works as desired.