Influence of Rotor Slot Number on Magnetic Noise in a Squirrel-cage Induction Motor for Traction Applications

Abstract

In this paper, the influence of rotor slot number on the magnetic noise of a squirrel cage motor for traction applications is analyzed. The introductory part explains the importance of noise analysis and measurement and gives an overview of the types of noise that occur in this type of motor. The dominance of a particular type of noise depending on the design of the induction motor (number of poles, type of cooling) and the operating range of the motor is also commented. The cause and occurrence of magnetic noise are explained by analytical expressions. Methods are listed that can be used to effectively influence the magnetic noise level at the design stage. The difference between sound pressure level and sound power level is explained as noise level is expressed in both forms. The dominant stress components due to the radial forces acting on the stator teeth and the resulting sound power maxima are calculated for three combinations of stator and rotor slot numbers using the software package MANATEE.