Analysis of incipient fault signatures in inductive loads energized by a common voltage bus

摘要

Recent research has demonstrated the use of electrical signature analysis (ESA),that is, the use of induction motor currents and voltages, for early detection of motorfaults in the form of embedded algorithms. In the event of multiple motors energizedby a common voltage bus, the cost of installing and maintaining fault monitoring anddetection devices on each motor may be avoided, by using bus level aggregate electricalmeasurements to assess the health of the entire population of motors. In this researchan approach for detecting commonly encountered induction motor mechanical faultsfrom bus level aggregate electrical measurements is investigated.A mechanical fault indicator is computed processing the raw electrical measurementsthrough a series of signal processing algorithms. Inference of an incipient faultis made by the percentage relative change of the fault indicator from the ??healthy??baseline, thus defining a Fault Indicator Change (FIC).To investigate the posed research problem, healthy and faulty motors with brokenrotor bar faults are simulated using a detailed transient motor model. The FICbased on aggregate electrical measurements is studied through simulations of differentmotor banks containing the same faulty motor. The degradation in the FIC whenusing aggregate measurements, as compared to using individual motor measurements,is investigated. For a given motor bank configuration, the variation in FIC withincreasing number of faulty motors is also studied. In addition to simulation studiesexperimental results from a two-motor setup are analyzed. The FIC and degradationin the FIC in the case of load eccentricity fault, and a combination of shaft loosenessand bearing damage is studied through staged fault experiments in the laboratorysetup.In this research, the viability of using bus level aggregate electrical measurementsfor detecting incipient faults in motors energized by a common voltage bus isdemonstrated. The proposed approach is limited in that as the power rating fractionof faulty motors to healthy motors in a given configuration decreases, it becomes farmore difficult to detect the presence of incipient faults at very early stages.