Detection of Eccentricity Faults in Three-Phase Reluctance Synchronous Motor

Reluctance synchronous machines, particularly the newer ones with axially laminated anisotropic rotor, are being employed increasingly in many industrial applications as they offer energy efficient solutions along with low-cost rugged construction and zero speed regulation. High-performance requirements of the machine demand a high saliency ratio resulting in low air-gap length along the direct axis. Air-gap eccentricity diagnosis therefore becomes very significant. In this paper, the effects of different types of eccentricity faults in a commercially available reluctance synchronous motor (RSM) are first analyzed to identify the fault-specific frequency components in the line current spectrum. For validating the analyses, a modified-winding-function-based model and a finite-element-based model are built to simulate the motor under different eccentricity conditions. Experiments are then carried out on a three-phase RSM with a moderate to high level of eccentricity to confirm the theoretical prediction and simulation results. Finally, by applying residue-elimination technique, the effects of supply unbalance and internal asymmetry are minimized, and eccentricity is detected very reliably. These results will help noninvasive eccentricity fault detection in larger power salient-pole synchronous machines in the long run.