Influence of the Power Transformer Tank Design on the Sound Level.

Low noise levels are today requested for power transformers in order to comply with customer specifications and environmental legislations. Manufacturers have to improve the acoustic performances of their products and also reduce the costs in the same time. Therefore it is necessary to predict sound levels with a sufficient accuracy for each transformer design. Sound radiation of transformer tanks is influenced by a wide variety of parameters including placement, type, arrangement and dimensions of stiffeners, tank thickness, tank shape and type, insulating fluid or gas (mineral oil, ester or air). The vibration sources in transformers are located within an oil-immersed rib-stiffened transformer tank vessels made of thin and flexible steel plates. The vibrations generate sound pressure waves which are iteratively reflected from structural boundaries and discontinuities. They form standing patterns of vibrations, structural modes of the vessel and standing waves inside the fluid-filled acoustic cavity. If the corresponding natural frequencies of the structures are in the vicinity of the forcing frequencies, unexpectedly high sound levels are regularly observed, [1]. In order to avoid these unexpectedly high sound levels caused by the natural frequencies of the tank, optimization of the tank and tank stiffeners arrangement, dimensions and design has to be carried out. [ABSTRACT FROM AUTHOR]