Modeling and Characterization of Natural-Convection Oil-Based Insulation for Medium Frequency Transformers

Due to its high value of dielectric strength, oil is often used for transformer insulation, especially when processing high powers. Nevertheless, its presence needs to be considered when determining thermal coordination of a converter system, which also includes the challenging modeling of fluid dynamics. This paper presents an analytical model for calculation of charac-teristic oil temperatures for medium frequency transformers with oil-immersed windings. The characterization and verification of the developed analytical model is performed based on a small-scale experimental setup. The paper demonstrates that the analytical model reasonably agrees with the selected verification method, and can aid design optimization.