INVESTIGATION INTO EFFECT OF INCLINED AIR GAP ECCENTRICITY ON dq COMPONENTS OF STATOR CURRENTS IN INDUCTION MOTOR

Abstract

Induction motor controller design is very complex as it requires a coordinated control of magnitudes, frequencies and phases. Controller design is made simple by converting three phase quantities (voltage and current) into two phase quantities (dq quantities) as they turn out to be dc quantities. Any oscillations produced in these quantities are either attributed to the use of inverter at the supply end or to the fluctuations in the load. In this paper, it is shown that these oscillations in dq components of stator currents may be due to the mixed eccentricity fault developed in an induction motor. Mathematical expressions are derived to show the presence of eccentricity fault related harmonics in these components. A dynamic model of a machine suffering from air gap eccentricity is developed and simulated to obtain stator phase current spectra and dq component current spectra and the results show the presence of eccentricity related harmonics in both current and its dq components. Experimental results are presented to validate the results obtained by modeling and simulation.