Causes and reduction techniques of electromagnetic noise in induction motors

Induction motors are the most common prime mover used in pulp and paper mills. Noise in a paper mill is not only annoying but also harmful. Prolonged exposure to loud noise can lead to permanent hearing damage. Noise in induction motors may be airborne or electromagnetic in nature. Most of the induction motors used in pulp and paper mills have four or more poles, hence the noise in these induction motors is primarily electromagnetic in nature. It is imperative to have reliable prediction tools to accurately calculate the magnetic noise generation during the motor design phase, thus avoiding expensive rework cost. Stator-rotor mechanical design, careful stator winding design, and tight manufacturing processes can significantly reduce electromagnetic noise in an induction motor. This paper discusses the theoretical foundations for various causes of electromagnetic noise generation, and practical reduction techniques for new or existing motors.