An Electrical Circuit based 3-D Steady State Thermal Model of a Fan Cooled 60 Hz, 20 kW 3-Phase Plasma Cutting Power Supply Transformer

This paper presents an electric circuit based 3-D steady state thermal model of a 3-phase, 60 Hz, 20 kW transformer operating under forced air cooled conditions. The model is developed using a cost effective approach and consists of current sources that represent the power loss, voltage sources for the temperature and resistors for the associated conduction and convective heat transfer terms to solve the underlying heat transfer equation. The paper includes a procedure for deriving these components. Simulation results using a standard circuit simulator are then compared with experimental data. These show that the trends in various temperatures predicted by simulation are in good agreement with those from experiment. Thus the model can be used to comparatively evaluate potential transformer designs during a design optimization process. Finally, the paper discusses limitations and advantages of the proposed method and identifies ways to further improve the model performance.