An Experimental Model for Extraction of the Natural Frequencies influencing on the Acoustic Noise of Synchronous Motors

Acoustic noise analysis of electrical machines is of special interest due to their numerous and miscellaneous applications. The analytical and numerical approaches for prediction and calculation of acoustic noise radiated from electrical machines usually yield considerable errors. Therefore, the accurate investigation of acoustic noise in electrical machines necessitates exact experimental noise measurements. In this paper, an efficient experimental model is developed to analyze the acoustic noise radiated from a synchronous motor, identify the noise sources, and extract the significant natural frequencies. At first, the motor mechanical speed is raised from zero up to a maximum value by use of a Variable Frequency Drive (VFD). During the motor acceleration period, its radiated acoustic noise is measured by means of a "measurement microphone" in a standard test condition. The measurement results are then analyzed via developing and utilizing an Image Processing Algorithm, and thereby, the prominent noise sources of the synchronous motor and its significant natural frequencies are finally identified.