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Bearing faults account for approximately half of all electric machine failures. Bearing condition monitoring is of practical importance. In this paper, up to seven different bearing condition monitoring methods in terms of the measuring medium are reviewed, with an emphasis on their implementation considerations. The major advantages and disadvantages of those methods are also summarized. This paper...
Compared to conventional monitoring techniques such as vibration monitoring or temperature monitoring, stator current-based monitoring offers significant economic savings and implementation advantages. Consequently, stator current-based bearing fault detection has received more and more attention in research. Further more, according to a recent study, bearing faults can be categorized into two classes:...
Current-based monitoring can offer significant economic savings and implementation advantages over traditional vibration monitoring for bearing fault detection. A key issue in current-based bearing fault detection is to extract bearing fault signature from motor stator current. In this paper bearing fault signature in motor stator current is detected by estimating and removing non-bearing fault components...
Planning for an upcoming refueling shutdown at Limerick Nuclear Power Station, sixteen vane axial fans were analyzed to determine which ones need maintenance. Vibration and torque signature technologies were employed. Vibration technology is the standard bearing diagnostic approach; however, the need of physical proximity limits the usability to low radiation areas. Lacking this drawback, torque signature...
In this paper, we propose to perform early fault diagnosis using high-resolution spectral analysis of the stator current to detect bearing faults in electrical induction machine. While most research works focus on mechanical vibration analysis, the originality of our work relies on the use of high-resolution methods to detect modulations in the stator current. We present the results obtained for real...
This paper deals with a new diagnosis method for detecting bearing faults. The diagnosis is carried out based on frequency response analysis. The detection of bearing damages on motor and load side of a mechanical drive system is addressed. The mechanics are assumed to be a two-inertia-system with one dominant resonant frequency. The frequency response of the mechanical system of the drive is obtained...
The detection of non-catastrophic faults in conjunction with other factors can be used to determine the condition and remaining life of an electric drive. As the frequency and severity of these faults increase, the working life of the drive decreases, leading to eventual failure. In this work, four methods to identify developing electrical faults are presented and compared. They are based on the short-time...
Fault diagnosis of electrical machines has primarily been focused on steady state operation of the machine due to the limitations in signal processing techniques. However, the advancement in this area has led to the development of a new class of algorithms which are time-frequency based signal processing techniques. In this paper we explore the concept of identifying faults by analyzing the transient...
This paper presents the spectral analysis of the stator phase current and its dq0 components, in a 42V fault-tolerant six-phase induction machine (6PIM) fed by a voltage source inverter (VSI). This machine has symmetrical 60 degrees displacement winding allowing fault-tolerant modes for an electric power steering (EPS) application. The influence of the loss of stator phases in the stator current spectrum...
Condition monitoring of adjustable speed drives (ASDs) gives the ability to prevent catastrophic failures of the electromechanical system. In case of standstills, fast and accurate fault diagnosis is necessary in order to reduce the downtime and consequently the production and revenue losses. For the above mentioned reasons, the investigation of the ASDs behaviour during the presence of faults in...
The paper deals with some problems concerning fault analysis in multilevel V.S.I. converters. With reference to cascaded H-bridge topology, first the possible conditions of "single fault" are classified by analyzing the modification of output voltages when a generic power device is damaged ("short-circuited" or "definitely open"). Then a procedure for on-line quick identification...
A novel method is presented for the detection and isolation of open-transistor faults in voltage-source inverters feeding low-power AC motors. The method is based on monitoring two diagnostic signals, one indicating sustained near-zero values of output current and thus permitting fault detection, the other permitting the isolation of the particular transistor which went faulty. The latter signal is...
This paper investigates the impact of inertia on the fault signatures of squirrel cage induction machines. Rotor faults give rise to harmonic side band currents and double slip frequency shaft torque oscillations, however. The total drive inertia thus influences the speed ripple which, again, influences the balance of the magnitudes of the lower and upper side band current. Considering certain assumptions,...
Single phase stator current spectrum is usually monitored to examine rotor eccentricities in mains-fed induction motors. However, a rotor-position-dependent load torque oscillation introduces exactly the same side-band harmonics in the stator currents with larger magnitudes, leading to an ambiguity in the online rotor eccentricity diagnostics in the presence of a load torque oscillation. This paper...
System reliability is getting more and more important in modern industrial drives. Currently the most frequent source of a drive breakdown is a defect of the bearings, which at the same time is most difficult to detect especially under inverter operation. The exploitation of the transient current slope was shown to give an accurate means to identify the machines transient reactances and thus also...
This paper presents a study of the permanent magnet synchronous machine (PMSM) running under eccentricity fault. To carry out the study a two-dimensional (2-D) finite element analysis (FEA) is used. Relationships between stator current induced harmonics and dynamic air-gap eccentricity were investigated. Advanced signal analysis by means of continuous wavelet transforms was performed. Simulation were...
This paper presents a diagnostic method of the eccentricity of the rotor of the cage induction motor, using a diagnostic inference block, based on ANFIS (adaptive-network-based fuzzy inference system). A construction and principle of work of the diagnostic inference block for a selected induction motor will be provided, in order to assess the eccentricity of the rotor. The input data for the proposed...
This paper presents an intelligent method for diagnosing broken bars in induction motors. The method is based on training a neural network using new features extracted from vibration spectrum. These fault related features depend on slip. The exact value of slip can be determined using vibration spectrum; therefore, a vibration sensor is the only required sensor. The method has been able to diagnose...
Dependability and safety of a system are topical subjects, which have found the proper assessment in two formal corpuses: the dependability theory and the functional safety standards. The purpose of this paper is to explicate the two corpuses, showing how one corpus supplements the other one. At first the dependability theory is introduced and the related concepts of threatens, attributes and techniques...
Mathematical modeling is a basic way to simulate electric machines under various faulty conditions because it is to dangerous and/or to expensive to recognize properties of faulty machines by tests in the field or even on specialized test beds. Nowadays, signature analysis of measurable currents of machine windings is the most permissible way to characterize and to compare various faulty conditions...
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