Comprehensive Thermal Analysis of Oil-Immersed Auto-Transformer Based on Multi-Physics Analyses

Thermal design of large oil-immersed transformer is the key to guarantee its safe operation. However, the thermal design is a coupled problem including electromagnetic, oil flow and thermal performance of the transformer. Consequently, thermal design is a comprehensive multi-physics fields design process. In this paper, the comprehensive thermal analysis of the structure parts and winding area are respectively carried on. An electromagnetic-fluid-thermal coupled approach is proposed. In addition, the use of an arrangement of wall shunts and winding oil baffles are proposed to reduce significantly the transformer temperature rises. The temperature rises of the transformer with the improved structure are computed by multi-physics coupled analyses to verify the structural modifications. Finally, an experimental prototype is established, the multi-physics analysis results are verified with the experimental ones. By analyzing the electromagnetic, thermal, and fluidic characteristics comprehensively, the synthetic performance and calculation accuracy of the whole transformer can thus be guaranteed.