Detection of Eccentricity Faults in Induction Machines Based on Nameplate Parameters
ABSTRACT Eccentricity-related faults in induction motors have been studied extensively over the last few decades. They can exist in the form of static or dynamic eccentricity or both, in which case it is called a mixed eccentricity fault. These faults cause bearing damage, excessive vibration and noise, unbalanced magnetic pull, and under extreme conditions, stator-rotor rub which may seriously damage the motors. Since eccentricity faults are often associated with large induction machines, the repair or replacement costs arising out of such a scenario may easily run into tens and thousands of dollars. Previous research works have shown that it is extremely difficult to detect such faults if they appear individually, rather than in mixed form, unless the number of rotor bars and the pole-pair number conform to certain relationships. In this paper, it is shown that the terminal voltages of induction machines at switch-off reveal certain features that can lead to the detection of these faults in individual form, even in machines that do not show these signatures in line-current spectrum in steady state, or to the detection of the main contributory factor in case of mixed eccentricity.
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ABSTRACT: The fault diagnosis of rotating electrical machines has received an intense amount of research interest during the last 30 years. Reducing maintenance costs and preventing unscheduled downtimes, which result in losses of production and financial incomes, are the priorities of electrical drives manufacturers and operators. In fact, both correct diagnosis and early detection of incipient faults lead to fast unscheduled maintenance and short downtime for the process under consideration. They also prevent the harmful and sometimes devastating consequences of faults and failures. This topic has become far more attractive and critical as the population of electric machines has greatly increased in recent years. The total number of operating electrical machines in the world was around 16.1 billion in 2011, with a growth rate of about 50% in the last five years .IEEE Industrial Electronics Magazine 06/2014; 8(2):31-42. DOI:10.1109/MIE.2013.2287651
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ABSTRACT: A 1130kW squirrel-cage induction motor used for railway traction is analyzed in this paper in case of eccentric rotor. Since the motor has parallel-connected windings, the air-gap unbalance makes rise unbalanced currents in the stator branches, and the split-phase current signature analysis can be attempted for fault detection. The split-phase currents are better analyzed when transposed in the complex domain, by using symmetrical components. Moreover, the rotor cage currents must be carefully taken in account in the model, since they develop a powerful damping effect on the signature of static eccentricity. This paper shows that the faulted machine can be represented by the superimposition of five equivalent circuits corresponding to five centered-rotor virtual machines, useful for fault-related split-phase current calculation. The mathematical modeling shown in this paper is useful to carry out a diagnostic method, as shown in a companion paper. The latter also reports confirmatory simulations of the faulted 1130kW motor, based on winding function approach.EPECS’13 3rd International Conference on Electric Power and Energy Conversion Systems, Istanbul, Turkey; 10/2013
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ABSTRACT: Unfortunately, motor current signature analysis (MCSA) cannot detect the small degrees of the purely static eccentricity (SE) defects, while the air-gap magnetic flux signature analysis (FSA) is applied successfully. The simulation results are obtained by using time stepping finite elements (TSFE) method. In order to show the impact of magnetic saturation upon the diagnosis of SE fault, the analysis is carried out for saturated induction motors. The index signatures of static eccentricity fault around fundamental and PSHs are detected successfully for saturated motor.