Improvement of Magnetic Shielding for Transformers Based on the Magnetic Flux Characteristics at Shielding Ends

Magnetic shielding is generally laid on the transformer tank and clamps to reduce the eddy current loss in the tank, yet designers did not pay attention to the phenomenon of flux concentration caused by magnetic shielding. According to the simulation results of the accustomed shielding structures, we noticed that the flux density near the end of shielding plates is relatively high. Thus, an idea is proposed that regions with lower flux density before shielding construction may also need to be shielded, and the shielding should be made to closed path or loop, i.e., the shielding plates in different directions should be connected to each other, or the end of the plates should be bent to the core surface. The aim of all these measures is to avoid the flux entering the transformer tank. The improved structure of the shielding can significantly reduce the loss of the tank, thus mitigating the extent of local overheating. As for the lower clamps, adding necessary shields can dramatically reduce the loss. Furthermore, in consideration of saving materials, adjustment on shielding geometry is performed. A final shielding design is achieved, which reduces the loss, mitigates local overheating, and saves materials. The effect of the magnetic shielding is verified by the finite-element analysis.