Study of Transformer Loss and Temperature Rise Under DC Bias Magnetism Based on Finite Element Method

In order to analyze the temperature rise of the transformer body under AC-DC conditions, this paper investigates the transformer losses under DC bias magnetism based on the finite element method. The electric-magnetic-thermal coupling model of the three-phase three-column transformer is established, and the transient electromagnetic field is calculated by using COMSOL software, and the electromagnetic calculation results are coupled to the temperature field cell by cell according to the grid to obtain the distribution of transformer core and winding losses and three-dimensional temperature field under different DC bias magnetization. The results show that the DC bias leads to the increase of core and winding losses, and the losses in the area where the core column meets the upper and lower yoke are most affected by the DC bias, and the losses in the horizontal path of the core are more affected by the DC bias than the vertical path; the winding losses are unevenly distributed, and the DC bias has more influence on the winding losses than the core losses. With the increase of DC bias current to 5A, the maximum temperature of transformer winding rises to 147.3°C.