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Journal ArticleDOI

Coupling misalignment in rotating machines: modelling, effects and monitoring

01 Jan 2009-Noise & Vibration Worldwide (SAGE Publications)-Vol. 40, Iss: 1, pp 17-39
TL;DR: In this article, the authors explore the research on coupling misalignment by briefly summarizing the research work done so far on different modelling techniques, effects on the system behaviour, fault identification and condition monitoring techniques.
Abstract: After unbalance, coupling misalignment is the most common fault present in rotating machines. However, limited research has been carried out on coupling misalignment and its effects. The present study aims to explore the research on coupling misalignment by briefly summarizing the research work done so far on different modelling techniques, effects on the system behaviour, fault identification and condition monitoring techniques.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a comparison between two approaches for modeling the forces and moments generated by a metallic disc coupling under angular misalignment is presented, where a well-established model based on the linear bending flexure of the disc packs is proposed.

51 citations

Journal ArticleDOI
TL;DR: In this paper, Fourier and wavelet transforms are used to detect the misalignment in rotating machinery shafts at different frequency of operation and the variation of the fault characteristics with respect to time are reported for sampled signals using wavelet transform.

48 citations

Journal ArticleDOI
17 Apr 2018-Energies
TL;DR: The diagnosis is achieved through spectral analysis of the stator currents, where fault frequency components related to rotor mechanical unbalance are identified and can be implemented in condition monitoring strategies, which is of great interest to optimise operation and maintenance costs of wind farms.
Abstract: The goal of the present paper is to achieve the diagnosis of an in-service 1.5 MW wind turbine equipped with a doubly-fed induction generator through current signature and vibration analyses. Real data from operating machines have rarely been analysed in the scientific literature through current signature analysis supported by vibrations. The wind turbine under study was originally misdiagnosed by the operator, where a healthy component was replaced and the actual failure continued progressing. The chronological evolution of both the electrical current and vibration spectra is presented to conduct an in-depth tracking of the fault. The diagnosis is achieved through spectral analysis of the stator currents, where fault frequency components related to rotor mechanical unbalance are identified. This is confirmed by the vibration analysis, which provides insightful information on the health of the drive train. These results can be implemented in condition monitoring strategies, which is of great interest to optimise operation and maintenance costs of wind farms.

32 citations


Cites background from "Coupling misalignment in rotating m..."

  • ...As a rule of thumb, when the vibration amplitude of the second harmonic of the rotational speed is more than 50% of the first harmonic, coupling damage has probably occurred [54]....

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Journal ArticleDOI
TL;DR: A new method, named variable weighted contribution rate of NOFRFs, is proposed, which enhances the ratio of high-order output frequency response to total output response of a rotor system and proposes a new index MR, which is more sensitive for the slight misalignment rotor system.
Abstract: Fault features extraction method for slight misalignment of rotor systems is researched in this paper. When a rotor system with faults is excited by harmonic inputs, system response will contain higher harmonic components. Phenomenon of these higher harmonics implies the presence of nonlinear features in a rotor system. When extracting these nonlinear features, traditional methods have certain limitations, and it is easy to ignore weak features of a rotor system. Nonlinear output frequency response functions (NOFRFs) can extract effectively nonlinear features of a rotor system from noise-containing vibration signals and are used in many fault diagnosis fields. However, as for weak damage to structures and in the early stages of a system faults, fault features reflected by high-order NOFRFs are not still obvious enough. Therefore, a new method, named variable weighted contribution rate of NOFRFs, is proposed in this paper. This method enhances the ratio of high-order output frequency response to total output response of a rotor system. Based on this method, a new index MR is proposed to detect the faults of a rotor system. In addition, lumped mass model is used in this paper to simulate misaligned rotor system with slight misalignment, and the sensitivities of the traditional methods and new index for slight misalignment fault features extraction are compared. The results indicate that the new index is more sensitive for the slight misalignment rotor system. Additionally, the rotor system with misalignment fault experiment table is built, and the effectiveness of this new index for detecting the slight misalignment fault of the rotor system is verified.

30 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of angular misalignment in a rotor-train-AMB system with two 4-dof simple rotors, each with an offset disc to have gyroscopic effects, is quantified by way of estimation of additive coupling stiffness.

24 citations

References
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Book
23 Jul 1990
TL;DR: In this paper, the authors present a simple model of a simple rotor with three disc bearing elements for industrial applications and derive the minimum shaft radius branched systems in torsion analysis for industrial electric motor centrifugal compressor unit.
Abstract: Part 1 Characteristics of rotor elements: disc shaft bearings and seals mass unbalance. Part 2 Simple models - basic phenomena: determination of the model symmetric rotor dissymmetric rotor instability damped rotors. Part 3 Rotor equations - solutions of equations: finite elements of rotor elements equations for monorotors equations for coaxial multirotors solution of equations computer program. Part 4 Towards industrial applications: pseudo-modal method influence of modeling natural frequencies - bearing stiffness diagram transmissibility dual rotor. Part 5 Industrial applications: steam compressor high pressure centrifugal compressor low pressure centrifugal compressor centrifugal compressor fitted with active magnetic bearings power gas turbine industrial steam turbine textile machine spindle jet engine. Part 6 Transient motions: equations and solutions speed of rotation law behaviour of a simple rotor experimental and theoretical results for a three disc rotor behaviour of an industrial rotor. Part 7 Torsion: determination from statics of the minimum shaft radius branched systems in torsion analysis of a branched system in torsion industrial electric motor-centrifugal compressor unit. Part 8 Miscellaneous topics: dissymmetric shaft equations with periodic coefficients axial torque influence.

419 citations


"Coupling misalignment in rotating m..." refers background in this paper

  • ...There are several preliminary researches [3-8], that proposed equations to determine the forces and moments generated in the coupling....

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BookDOI
01 Jan 1993
TL;DR: In this article, the one degree of freedom system is described in detail, including the Short and the Long Rotors, with oil-film bearing and rolling-element bearing, as well as the Shaft Seals and non-circular Shafts.
Abstract: 1 Introduction.- 2 The one Degree of Freedom System.- 3 Shaft with Central Disc.- 4 Shaft with Non Central Disc.- 5 The Short and the Long Rotor.- 6 Oil-Film Bearings.- 7 Rotors with Oil-film Bearings.- 8 Vertical Rotors.- 9 Rolling-element Bearings.- 10 Shaft Seals.- 11 Steam Whirl.- 12 Internal Damping.- 13 Non-circular Shafts.- 14 Computer Model.- 15 Influence Coefficients.- 16 Equation of Motion.- 17 Results.- 18 Static Bearing Loads.- 19 Foundation.- 20 Rotor and Foundation.- 21 Rough Calculations.- 22 Bending Stresses in Rotors.- 23 Cracked Rotors.- 24 Solution of the Equation of Motion.- 25 Program MADYN.- References.

388 citations


"Coupling misalignment in rotating m..." refers methods in this paper

  • ...The second model suggested by Kramer [9], considers the rotational stiffness (kr) and damping (cr) of the coupling....

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  • ...1 Flexible Coupling The first model suggested by Kramer [9], considers the flexibility of mechanical couplings and is defined as a non friction coupling that is rigid in the radial direction....

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  • ...Tadeo and Cavalca [11] analyzed a rotorbearings-coupling system using FEM for the rigid coupling, for the flexible coupling models developed by Kramer [9]; Nelson and Crandall [10], discussed in the previous section....

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  • ...The models of Kramer [9] and Nelson and Crandall [10], take into account the inherent flexibility of the couplings....

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Journal Article

341 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical model of a complete motor-flexible coupling-rotor system capable of describing the mechanical vibration resulting from misalignment and unbalance was developed.

229 citations

Journal ArticleDOI
TL;DR: In this paper, the rotor bearing system is modelled using higher order finite elements by considering deflection, slope, shear force, bending moment with eight degrees of freedom per node.

205 citations


"Coupling misalignment in rotating m..." refers background or methods in this paper

  • ...Sekhar and Prabhu [16] used a model of the rotor-bearing system with higher order finite elements by considering deflection, slope, shear force, bending moment with...

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  • ...Sekhar and Prabhu [16] numerically evaluated the effects of coupling misalignment on the 2 x vibration response of a rotor-coupling-bearing system....

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  • ...Sekhar and Prabhu [16] used a model of the rotor-bearing system with higher order finite elements by considering deflection, slope, shear force, bending moment with degrees of freedom per node....

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  • ...7) has been modelled and the misaligned forces and moments have been estimated and are applied at the coupling nodes using the modelling techniques given in [16]....

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  • ...Coupling co-ordinate system: (a) Parallel misalignment [3]; (b) Angular misalignment [16] MX MX K MY MY Tq...

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