Influence of Active Part Stiffness on Radiated Sound Power Level in Power Transformers

Power transformers are associated with the radiation of unwanted noise in many circumstances due to its low frequency and relative high power, which reduction and mitigation is imperative. It is known that the main source of this noise are originated by the vibrations induced in the active part, namely the core, primarily due to electromagnetic forces and magnetomechanical effects. On the other hand, the laminated design of the core is indispensable in order to reduce the Foucault currents losses. Thus, in addition to the electrical requirements, the development of an appropriate model of the core dynamic behavior taking into account its segmented structure is urgent, in order to avoid resonances at any of the excitation frequencies. In the current proceeding, the influence of the core equivalent dynamic mechanical properties on a power transformer radiated noise was studied by performing a numerical parametric analysis. It was concluded that the active part stiffness properties, namely the directional component related to the out of lamination plane bending, ruled the vibroacoustic behavior of the transformer for the studied frequency range.