Abstract
Due to increase of capacity and weight saving, bigger electrostatic and magnetic energy is stored in transformer, compared with conventional transformer. Because of these, Vibration and noise are likely produced. In the field of noise reduction of transformer, core vibration by magnetic-striction, winding vibration and sound proof of transformer and tank have been studied. Winding vibration due to the currents produce sound wave in the insulation oil. This wave spreads in the oil and vibrates tank of transformer. The transformer tank yields a fluid elastic vibration hitherto, two-dimensional fluid is analyzed by FEM with dis placement method. However, the fluid-structural analysis of a coil and a tank of transformer have not been studied by a three-dimensional FEM. In this paper, the method of calculating the character frequency which took the influence of oil into consideration from the fluid-structural analysis by three-dimensional FEM which is not in the former with sufficient accuracy was found out. Since it showed clearly that it changes with modes of vibration, the decreasing rate of character frequency and oscillating attenuation by oil are reported.
