Impact of DC Bias on the Magnetic Loading of Three Phase Three Limb Transformer Based on Finite Element Method

This article proposes a modelling mechanism based on Finite Element Method (FEM) to understand the impact of DC currents on the magnetic loading of the transformer. It details on the way magnetizing currents vary and harmonics develop in a transformer. The analysis is performed using ANSYS tool for generating the scaled transformer model and MATLAB for plotting the results. The analysis shows that on varying the primary voltage to different levels of voltages and injecting DC currents based on a weakly coupled multi harmonic approach the three phase three limb transformer is subjected to varying magnetizing currents with the development of odd harmonics based on the saturation level of transformer. The even harmonics are not observed owning to the structure of three phase three limb transformer which offers a high reluctance to DC flux. Furthermore the scaled transformer is observed in ANSYS and it is visualized that the stray fluxes and the saturation levels of the three limb transformer raises to a higher level on impact of DC currents of varying magnitudes.