Noise problems of the induction motors

Abstract

The audible noise produced by electrical machines is developed depending on the various energy sources that generally appear during the rotation of the rotor. Usually the main energy source in the electrical machines is the magnetic field. Maxwell stresses act on the stator core, armature, and stator laminations, and generally exhibit spectral distribution as a function of time. These forces may provide excitation on the mechanical resonances of the machine’s mechanical system that have a distributed mass, stiffness, and damping. The force waves and their possible contribution to overall machine noise can be predicted by analysis of the electrical design, which can be optimized to reduce their effect. Careful analysis and design are required, with perhaps additional magnetic core material to keep flux levels low, and air gap large, without compromising good performance. Behind the features of the magnetic and mechanical structure, the aerodynamic features and excitations provided by the air circulation and the movement can also gain significance when the similar interaction appears with the machine structure. Interaction might be amplified during the coincidence of the mechanical resonances and the provided excitation on similar frequencies.