Analysis of air gap eccentricity in closed-loop drive-connected induction motors

This paper analyzes the effect of current-regulated indirect field-oriented drives on the diagnostics of air gap eccentricity in three-phase induction motors. It points out that the bandwidths of speed and current PI controllers determine the harmonic distribution in stator currents and voltages. Thus, for the accurate and sensitive prediction, particular electrical variables should be monitored for different faults. A motor-drive system with static and mixed eccentricity is simulated by the finite element method respectively. Meanwhile, the results of two experiments on a drive-connected 7.5-hp induction motor operating under no load and part load conditions are discussed. The simulation and experimental results verify the theoretical analysis and the feasibility of the proposed diagnostic method.