Unit-wave response-based modeling of electromechanical noise and vibration of electrical machines

Abstract

The primary aim of the thesis is to develop a method for the rapid electromechanical sound power calculation of electrical machines to be used in industry. The core idea is that the numerical simulation of sound radiation is carried out only once. Then, a number of characterizing curves, known as unit-wave responses, are extracted from the results and stored. Finally, the unit-wave responses, together with the magnetic excitation force waves, are used for fast sound power estimation. An experimental method for the determination of unit-wave responses is also developed, which serves especially the process of model verification. The secondary aim is to study the items crucial for the modeling of the sound radiation of electrical machines, such as the effect of tangential force waves on the vibration response, the correlation of force waves in the case of a DTC converter supply, the effect of impregnation on the material properties of the stator core, and the feasibility of the approximate methods for sound power calculation. The most important results of the work done in the thesis include the following: 1) the unit-wave-based sound power calculation performs well, provided that force waves with different wave numbers are weakly correlated, which was verified for the case of a machine supplied by a DTC converter; 2) tangential force waves may have a remarkable effect on the response, which is observed as either an increased or decreased response level, depending on the phase difference of the radial and tangential force waves; 3) the VPI impregnation affects the structural material properties of the stator core considerably, which manifests itself as increased stiffness and decreased damping of the stator core, and 4) the high-frequency boundary element method seems appropriate for the fast and approximate sound power calculation of electrical machinery.