A Study on the Design Process of Noise Reduction in Induction Motors

Noise of induction motors can be classified in three main parts, which consist of mechanical source, aerodynamic source, and magnetic source. The magnetic noise is defined as noise generated from vibrations due to electromagnetic excitation force. In this paper, the electromagnetic excitation force is analyzed and design process of noise reduction is proposed. Firstly, the harmonic components which are generated from combination of pole and slot are analyzed in the initial design. Moreover, the lower space harmonic components are reduced in this design stage. Secondly, 2-D transient analysis is conducted to consider the saturation effect and harmonic components of current in detail design. Fourier series has been addressed according to time and space considering harmonic component of electromagnetic excitation force. In the mechanical part, the natural frequency modes of motor components such as bracket, stator and rotor cores are calculated using finite element analysis (FEA) to avoid resonance. Lastly, the skewed rotor is adjusted to reduce the harmonic components of force, and the spectrums of motor according to skew effect are analyzed. The noise of skewed model is analyzed using FEA and compared with experimental result. In order to verify proposed method, the skewed model is manufactured and experimented at no-load condition.