The magnetic noise of inverter-fed three-phase induction motors with squirrel cage rotors

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-to-frequency 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.