Induction Motor Diagnostics Using Vibration and Motor Current Signature Analysis

Diagnostics of an induction motor is a serious issue for improving plant reliability. Induction motors are workhorse of the world today. Motor current signature analysis (MCSA) and vibration data are commonly used for diagnosing induction motor problems. However, the fault signatures are complicated and lack consensus. The problem is further complicated by the loading effects of the defect signatures. This paper will present a comparison of vibration and motor current signals for induction motor subjected to different levels of torque, unbalance, and misalignment loadings. Experiments were performed on intentionally faulted motor with varying degrees of electro-mechanical defects. Different levels of mechanical torque, unbalance, and misalignment loadings were applied to the rotor side. The data were analyzed using both vibration and motor current sensors. Results indicate motor current signature provides better indication of certain electrical faults such as airgap eccentricity and broken rotos bars, and vibration signature is better indicator of mechanical defects. The results suggest that both motor current and vibration measurements are required for more complete diagnostics of induction motors.