Electro-mechanical analysis of the audible noise of an inverter-fed squirrel-cage induction motor

The audible noise emitted by a three-phase squirrel cage induction motor fed by a frequency inverter is determined by the electromagnetic and mechanical behavior of the components of the drive. A computerized analysis method is described that uses theoretical and experimental data for predicting the audible noise spectrum components. Starting from the inverter voltage and the motor data, the electromagnetic forces are predicted and analyzed. The mechanical natural frequencies are considered, either in a theoretical (finite element calculation) or in an experimental (modal analysis) methodology, to predict the vibrational behavior of the machine. The scheme contains the following steps: analysis of the frequency spectrum of the inverter used; synthesis of the magnetic force spectrum accounting for the motor data: calculation or measurement of the resonant data of the stator assembly; and comparison of the force spectrum and the resonant data. These various steps are discussed