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the purpose of this paper is to study the influence of the type of winding -double layer or single layer -to the global noise level of the machine. For this purpose, two variable speed induction motors have been studied, of the type M3AA 71 B4/8 manufactured by Electroprecizia S.A. Săcele, Romania, with Dahlander windings, star connected -for the low speed and double star connected -for the high speed. The motors are modelled from magnetic and mechanical point of view with finite element softwares. The investigated motors were placed in the semi-anechoic chamber in order to determine the noise-tofrequency characteristics (spectrograms).

the paper analyzes the magnetic noise in inverted-fed single speed three-phase induction motors with squirrel cage rotor. The motors are totally enclosed and externally cooled. Investigation includes motors with the rated speeds of 3000, 1500, 1000 and 750 r/min. The investigated motors were placed in the semi-anechoic chamber in order to determine the noise-tofrequency characteristics (spectrograms). This paper is based on the results and conclusions obtained after analyzing these spectrograms. The importance of the pressure, which is applied for the stacking of the stator laminations to the level of the magnetic noise, is presented as well.