• Title/Summary/Keyword: Rotating machinery

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Theory and Experiment for Electromagnetic Shaft Current in Rotating Machinery

  • Kim, Chaesil;Park, Jong-Kweon
    • International Journal of Precision Engineering and Manufacturing
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    • v.3 no.1
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    • pp.20-25
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    • 2002
  • Electrical damages to critical parts in rotating machinery have caused many machinery failures and hours of costly downtime. The problem of shaft currents generated in non-electrical machines has puzzled both users and manufacturers of these machines. The main solution for preventing electromagnetic type damage is to demagnetize all of the machinery parts, however this is costly and time consuming. Therefore a thorough investigation into the causes and physical characteristics of electromagnetic shaft currents is needed. In this paper, the self excitation theory was developed far a simple model, an axial flux Faraday disk machine surrounded by a long solenoid. Experimental tests were conducted to investigate the physical characteristics on an electromagnetic self excitation rig. The theory showed that the directions of both the shaft rotation and the coil turns should be identical if self excitation is to occur. From the tests, the electromagnetic type shaft current had both AC and DC components occurred at all vibration frequencies. This could point to a way to detect small instabilities or natural frequency locations by monitoring shaft currents.

On-Line Condition Monitoring for Rotating Machinery Using Multivariate Statistical Analysis (다변량 통계 분석 방법을 이용한 회전기계 이상 온라인 감시)

  • Kim, Heung-Mook;Lim, Eun-Seop
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1108-1113
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    • 2000
  • A condition monitoring methodology for rotating machinery is proposed based on multivariate statistical analysis. The CMS usually are using the vibration signal amplitude such as acceleration RMS, peak and velocity RMS to detect machine faults but the information is not so enough that CMS cannot perform reliable monitoring. So new parameters are added such as shape factor, crest factor, kurtosis and skewness as time domain parameters and spectrum amplitude of rotating frequency, $2^{nd}$ harmonics and gear mesh frequency etc. as frequency domain parameters. Many parameters are combined to represent the machine state using the Hotelling's $T^2$ statistics. The proposed methodology is tested in laboratory and the on-line experiment has shown that the proposed methodology offers a reliable monitoring for rotating machinery.

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Numerical Simulation of Turbulent Flows Under a Plane Rate of Strain Condition in a Rotating $90^{\circ}$ Curved Duct (평면변형율 조건 하의 회전하는 $90^{\circ}$ 곡덕트 내 난류유동의 전산해석)

  • Kwon, Hyung-Joong;An, Jung-Soo;Choi, Young-Don
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.485-490
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    • 2000
  • The effect of curvature, rotation, variable cross-section can make very complex flow pattern in turbo-machinery such as Pumps, compressors, turbines, In this study of turbulent flow characteristics rotating $90^{\circ}$ curved duct under a Plane rate of strain condition is computationally analyzed. The objective of this study is to understand the complex turbulent flow phenomena in turbo-machinery passage by analyzing the modeled rotating $90^{\circ}$ curved duct flow. RSM(Reynolds Stress Model) was employed for the turbulence modeling of Reynolds stress in momentum equations proposed by Shin(1995). The three dimensional computational code which adopts RSM for trubulence modeling was newly developed for the generalized curvilinear coordinate.

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Fault Diagnosis of Rotating Machinery Using Multi-class Support Vector Machines (Multi-class SVM을 이용한 회전기계의 결함 진단)

  • Hwang, Won-Woo;Yang, Bo-Suk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.12
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    • pp.1233-1240
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    • 2004
  • Condition monitoring and fault diagnosis of machines are gaining importance in the industry because of the need to increase reliability and to decrease possible loss of production due to machine breakdown. By comparing the nitration signals of a machine running in normal and faulty conditions, detection of faults like mass unbalance, shaft misalignment and bearing defects is possible. This paper presents a novel approach for applying the fault diagnosis of rotating machinery. To detect multiple faults in rotating machinery, a feature selection method and support vector machine (SVM) based multi-class classifier are constructed and used in the faults diagnosis. The results in experiments prove that fault types can be diagnosed by the above method.

Novel Process of Precision Nickel Mesh Fabrication for EMI Shielding Using Continuous Electroforming Technique (연속전주공정을 이용한 전자파 차폐용 정밀니켈메쉬 제조 신공정)

  • Lee Joo-Yul;Kim Man;Kwon Sik-Chol;Hue Nguyen Viet;Kim In-gon
    • Journal of the Korean institute of surface engineering
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    • v.38 no.6
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    • pp.212-215
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    • 2005
  • Novel continuous electroforming process equipped with a rotating patterned mandrel, soluble/insoluble anode and multiple stage of rolling wheels was proposed to produce precision nickel mesh, which is known as a very efficient electromagnetic interference (EMI) shielding material. Continuously electroformed nickel deposits showed a tendency to form small-sized particles as the plating solution temperature increased and mandrel rotation speeded up and the applied current density decreased. Along the honeycomb patterns of mandrel, nickel was accurately electrodeposited on the surface of rotating mandrel, but quite different visual/structural characteristics were measured on both sides.

Development of a System for Diagnosing Faults in Rotating Machinery using Vibration Signals

  • Oh, Jae-Eung;Lee, Choong-Hwi;Sim, Hyoun-Jin;Lee, Hae-Jin;Kim, Seong-Hyeon;Lee, Jung-Youn
    • International Journal of Precision Engineering and Manufacturing
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    • v.8 no.3
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    • pp.54-59
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    • 2007
  • It is widely recognized that increasing the accuracy and diversity of rotating machinery necessitates an appropriate diagnostic technique and maintenance system. Until now, operators have monitored machinery using their senses or by analyzing simple changes to root mean square output values. We developed an expert diagnostic system that uses fuzzy inference to expertly assess the condition of a machine and allow operators to make accurate judgments. This paper describes the hardware and software of the expert diagnostic system. An assessment of the diagnostic performance for five fault phenomena typically found in pumps is also described.

Directional Wigner-Ville Distribution and Its Application for Rotating- Machinery Condition Monitoring

  • Kim, Dong-Wan;Ha, Jae-Hong;Shin, Hae-Gon;Lee, Yoon-Hee;Kim, Young-Baik
    • Proceedings of the Korean Nuclear Society Conference
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    • 1996.05a
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    • pp.587-593
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    • 1996
  • Vibration analysis is one of the most powerful tools available for the detection and isolation of incipient faults in mechanical systems. The methods of vibration analysis in use today and under continuous study are broad band vibration monitoring, time domain analysis, and frequency domain analysis. In recent years, great interest has been generated concerning the use of time-frequency representation and its application for a machinery diagnostics and condition monitoring system. The objective of the research described in this paper was to develop a new diagnostic tool for the rotating machinery. This paper introduces a new time-frequency representation, Directional Wigner-Ville Distribution, which analyses the time- frequency structure of the rotating machinery vibration.

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Design and Performance Evaluation of a 10kW Scale Counter-Rotating Tidal Turbine (10kW급 상반전 조류터빈의 설계와 성능에 관한 연구)

  • Hoang, Anh Dung;Yang, Chang-Jo
    • The KSFM Journal of Fluid Machinery
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    • v.17 no.1
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    • pp.47-53
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    • 2014
  • This paper aims to present the design and performance evaluation of a counter-rotating tidal turbine using CFD and to compare its performance with single rotor. The device scale is 10kW and the rotating part consists of two rotors which rotate in opposite direction. Compared with conventional single rotor, the counter-rotating system shows higher power efficiency at high stream velocity but lower efficiency at low stream velocity. The added counter-rotated rotor together helps improve the energy absorption capacity but has influence on the upstream rotor that reduces its performance. In terms of power capture, the designed counter-rotating tidal turbine is more advantageous in high speed tidal condition.