A Simplified Dynamical Model of Mixed Eccentricity Fault in a Three-Phase Induction Motor

Abstract

Dynamical model of a three-phase induction motor helps in understanding the physical behavior of the motor system. In a healthy motor, the air gap between the stator and rotor phases remains constant. However, due to eccentricity related faults, this air gap is subjected to a harmonic variation. To study the effects of such eccentricity related faults, modified winding function theory is applied to calculate the inductance values of stator and rotor phases. The computational complexity of the model increases when the rotor bars come into picture since the number of inductance values to be calculated increases at every time step. This article proposes a simplified technique to reduce this computational effort. Instead of considering the rotor bars, the circumference of the rotor periphery is divided into three phases. A suitable turns function that explains the physical phenomenon of eccentricity has been used. The effect of rotor bars has been taken into account in the turns function. Also, saturation effects that arise due to different load conditions have been considered. Accordingly, a closed-form expression for inductances has been derived. Magnetic coupled circuit approach has been implemented to develop the dynamical model of the motor system. The proposed model has been validated by finite element method and experimental results.