Modeling of Eccentricity and Performance of Three-Phase Induction Motors

This paper modelled the eccentricity in three-phase induction motors and the accompanying performance. The geometry of three-phase asynchronous induction motor was utilized to calculate dynamic electromagnetic torque and inductances for the purpose of performance improvement. The position-dependent variation of the mechanical energy was applied to the rotor through the air gap which generates the mutual inductance across the stator-rotor circuitry. The entire six-by-six inductance matrix modelled for the non concentric three-phase induction motor was analytically differentiated and used to model the torque equation for the eccentric motor. The approach was simulated in MATLAB and ratified with an eccentricity degree of zero (non-existent) which tallied and rhymed with that gotten for a healthy induction motor. Results obtained show that an eccentric motor rotor does not accelerate uniformly, but glitches and flickers intermittently until it attains a maximum speed of about 320 rad/sec, whereas for the healthy motor, the rotor accelerates uniformly from rest to peak giving rise to a load-less motor speed of 0.33sec. For eccentricity degrees greater than 0.7, the air gap function for a non-concentric three-phase induction motor goes higher than 1.0 at some points and hits zero at lowest values thereby validating that the displacement of the rotor position from the normal is directly proportional to the degree of eccentricity.