A Topological Design Optimization Approach for Winding Oil Flow Paths in ONAN Transformers Based on a Fluidic-Thermal Coupled Model

A power transformer is one of the most critical components in transmission and distribution systems. To extend the life-cycle while operating with enough reliability and controllability, thermal concerns of a transformer have attracted extensive research attentions. In this paper, a topology optimization (TO) methodology is presented for designing the coolant flow paths in a prototype oil-natural air-natural (ONAN) power transformer to maximize the winding heat dissipation capacity without any compromise on the flow resistance. First, the thermal and fluid flow characteristics in both the winding and the radiator of the prototype transformer are numerically investigated through a fluidic-thermal coupled field approach. The preliminary cooling effectiveness of the oil circulation system is initialized. Second, a material-density-based TO scheme is employed to realize the optimal design of the oil baffle structures. In the TO optimization, artificial Darcy frictional forces are applied to the solidified cells to block their internal flows in the fluidic calculations, while the thermal conduction coefficients in those cells are enhanced to separate the baffles from the flowing oil in thermal analyses. Finally, the fluid flow and thermal coupled fields of the prototype transformer winding region with structurally optimized oil baffles are numerically calculated to validate the TO effectiveness.