Finite Element Based Modelling of the Thermal Behaviour of Converter Transformers influenced by DC Bias

The work emphasises on the thermal behaviour of a High Voltage DC transformer on the occurrence of DC bias in the system. The DC bias can lead to temperature rise in the transformer and can form hotspot in the windings which may result in various issues including thermal breakdown among others. A two-dimensional design of the core and windings of the converter transformer is modelled using Finite Element Method and is considered for studying the thermal behaviour due to the presence of DC bias. The results are curve fitted to obtain a sigmoidal function describing the variation of hotspot temperature with respect to applied DC bias. The developed function is validated by choosing different values of DC biases. Besides, the statistical significance of the function has also been evaluated. The obtained results are encouraging in the prediction of the hottest spot temperature.