Investigation into effect of mixed air gap eccentricity on dq components of currents in induction motor

Dq components of currents are extensively used in the controller applications of industrial drives as they are dc quantities. In this paper, it is shown that these components will no longer remain as dc quantities, if they are extracted from the induction motor suffering from mixed air gap eccentricity. A dynamic model of an induction motor suffering from mixed air gap eccentricity is developed and simulated to show the presence of eccentricity characteristic harmonics in dq components of the stator currents in synchronous reference frame. In this paper, it is also shown that the frequency analysis of dq currents helps in the detection of air gap non uniformity in the machine. The results obtained by modeling and simulation are also validated experimentally.