The magnetic noise of three-phase and single-phase induction motors with squirrel cage rotors

This paper presents a study of the magnetic noise in three-phase and single-phase cage rotor, totally enclosed, externally cooled induction motors. Investigations include three-phase and single-phase induction motors, with rated speeds of 3000, 1500, 1000, 750 r/min, and two-speed three-phase induction motors with Dahlander winding connection or separate windings, with rated speeds of 3000/1500, 1500/750, 1500/1000 r/min The investigated motors (manufactured by S.C. Electroprecizia S.A.) were placed in a 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 noise spectrograms. The work presents the importance of the pressure, which is applied for the stacking of the stator laminations to the level of the magnetic noise.