ABSTRACT
Faults in an electric motor are due to three important components-the rotor, stator, and the motor bearings. The rotor in an electrical motor is designed to have a uniform air gap all around it with the stator of the motor. When bearings have defects, the shaft is bent, or if during installation the rotor is not positioned at the center, the air gap becomes eccentric. This air gap eccentricity leads to pulsating radial electromagnetic forces, which leads to an increase in the mechanical vibration of the motor as well as an increase in the presence of additional frequency components and their harmonics in the stator current. The air gap eccentricity can be static or dynamic. The static eccentricity is a result of the fact that the position of the minimum air gap is fixed in space. In dynamic eccentricity, the position changes with time. In dynamic eccentricity, the center of the rotor is not at the center of the rotation.
