Electromagnetic acoustic noise and vibrations of electrical machines; their production and means of reduction

Abstract

Detailed theoretical and experimental investigations were conducted to determine the resonant frequencies and the vibrational behaviour of electrical machine stators of different sizes. During the course of the study of resonant frequencies and the nature of the vibration at resonance, the effects of the frame, laminations, dynamics of the teeth and windings were critically examined. Further, investigations were conducted on the electromagnetic excitation forces that induce vibrations in the machine during its operation. These forces produce cyclic deformations of the stator and the rotor, and they generally occur at predictable frequencies. The electromagnetic radial-forces depend on the nature of the magnetic field in the air-gap of a machine. A detailed study was done to examine the effects of various parameters on the magnetic field and the radial-forces. A simple and elegant technique is developed to predict the various frequency components in the audible noise spectrum