Abstract:

The sound radiated by large power transformers found in electric utility substations is an annoyance to nearby residents. Noise barriers are not effective at 120 Hz, the most prominent harmonic radiated by the transformers, and active control with loudspeakers and microphones is very sensitive to environmental conditions. Thus the active structural acoustic control is an attractive alternative because this strategy controls the sound at the source. However, efficient actuators are needed to generate antivibrations. This paper describes an experimental investigation conducted in order to select and test a piezoceramic actuator for the active control of large power transformer vibrations. It presents experimental measurements of transverse displacements on the various sides of a transformer, together with simulation and experimentation of a selected piezoceramic actuator bonded to a test structure and to the transformer. Vibration levels obtained with a (0.0075x2.5x1.5 in.) PZT piezoceramic actuator bonded to the transformer are generally larger than the primary vibration field at 240 Hz and at higher harmonics, but smaller at 120 Hz. Guidelines for the design of appropriate piezoceramic actuators to control power transformer vibrations are given. [Work supported by Hydro-Quebec.]