Measurement of vibrations and radiated acoustic noise of electrical machines

The investigations reported in this paper mainly concern the vibration and noise aspects of polyphase induction motors. Although the investigations are focused on induction machines, the fundamental results presented in the paper will be applicable to other types of rotating electrical machines. The maximum allowable noise levels associated with the operation of electrical machines of different sizes and speeds are stipulated in the various standards. Although these noise levels represent the upper limits, they do not necessarily reflect upon the achievable levels with the present state of art in the design of electrical machines. Considering the physiological characteristics of the human ear, magnetic noise of electrical machines is particularly troublesome since it is characterised by many pure tones. The conventional methods for the measurement of resonant frequencies, vibrations and noise are laborious and very time consuming. This paper presents the laboratory-techniques which have been developed for the measurement of resonant frequencies, vibrations and noise based on digital processing of signals. The measurement set-up acquires and processes signals from several transducers with the help of a data-acquisition system and a personal-computer.