The Experts below are selected from a list of 1215 Experts worldwide ranked by ideXlab platform

N. Yazdandoost - One of the best experts on this subject based on the ideXlab platform.

  • Oil-Whirl Fault Modeling, Simulation, and Detection in Sleeve Bearings of Squirrel Cage Induction Motors
    IEEE Transactions on Energy Conversion, 2015
    Co-Authors: M. Ojaghi, N. Yazdandoost
    Abstract:

    Bearings are divided into two main categories: rolling Bearings and Sleeve Bearings. The Sleeve Bearings are normally used in electrical machines above 200-hp rating. In this paper, dynamic modeling and simulation of a squirrel cage induction motor with Sleeve Bearings under oil-whirl fault is performed. The required air gap function under the fault is defined using earlier experimental results. Then, a winding function approach is used for modeling and simulation of the motor with faulty Sleeve Bearings. Accuracy of the simulation is approved by comparison to the corresponding experimental results. The stator line current harmonics produced by the Bearing oil-whirl fault are identified, and the best harmonics as the fault index are chosen considering sensitivity of the harmonics to the fault severity, as well as the load level change and supply voltage unbalance. Selected index is used to determine the severity of oil-whirl fault in Sleeve Bearing of an induction motor working in a real production line.

Li-li Wang - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Spiral Angle on the Performance of Spiral Oil Wedge Sleeve Bearing
    Hindawi Limited, 2018
    Co-Authors: Li-li Wang, Qing-liang Zeng, Xin Zhang
    Abstract:

    Spiral angel is an important structure parameter of spiral oil wedge Sleeve Bearing, which produces greater impact on Bearing performance. Based on JFO boundary condition, the generalized Reynolds equations considering four slip conditions are established. Using the concept of partial derivatives, stiffness and damping coefficients of Sleeve Bearing are calculated. The results show that carrying capacity and friction drag of oil film decrease, temperature rise decreases first and then increases, and end leakage rate, stiffness, and damping coefficients generally increase first and then decrease with the increase of spiral angle. The carrying capacity, friction drag, temperature rise, stiffness, and damping coefficients are smaller and the end leakage rate is higher considering wall slip and JFO condition compared with reckoning with no slip and Reynolds boundary condition

  • numerical analysis of spiral oil wedge Sleeve Bearing including cavitation and wall slip effects
    Lubrication Science, 2015
    Co-Authors: Li-li Wang
    Abstract:

    The modified Reynolds equation is established on the basis of critical shear stress model, in which the circumferential and axial wall slip of Sleeve and journal surface is considered. Cavitation is treated using modified Elrod algorithm that simplifies the solution of modified Reynolds equation in the full-film region. The modified Reynolds equations considering wall slip and cavitation effect for two-dimensional Sleeve Bearing are established. The results show that wall slip decreases oil film pressure, carrying capacity, friction drag and temperature rise but increases end leakage and cavitation region. The obtained results using the mass-conserving boundary condition are compared with the Reynolds boundary condition. Copyright © 2014 John Wiley & Sons, Ltd.

  • study on the influence of critical shear stress on wall slip of spiral oil wedge journal Bearing
    Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2012
    Co-Authors: Li-li Wang, Shujiang Chen
    Abstract:

    With the application of Sleeve Bearing in high speed, super-high speed and narrow-gap conditions, and the emergence of non-metallic Bearing materials, the conventional no-slip boundary condition can be broken down. Critical shear stress is a main parameter in the numerical computation of wall slip. The four modified Reynolds equations for the two-dimensional spiral oil wedge Sleeve Bearing is established based on the critical shear stress model, in which the circumferential and axial wall slip of the Sleeve and axial surface are considered. The shear stress angle is used to compute the circumferential and axial shear stress component and slip velocity. The results show the special structure of spiral oil wedge and the increase of eccentricity ratio make slip more difficult to occur. With the decrease of initial limiting shear stress, pressure, carrying capacity and friction drag decrease. Wall slip has an effect on the oil film rupture position, positive pressure area, and pressure peak. Wall slip occurs ...

  • The numerical analysis of the radial Sleeve Bearing with combined surface slip
    Tribology International, 2012
    Co-Authors: Li-li Wang, Min Wang
    Abstract:

    Abstract In order to improve the carrying capacity and reduce the temperature rise in high speed and precise spindle systems, a combined surface radial Sleeve Bearing using the interfacial slip technique was discussed. An extended Reynolds equation was derived based on the modified slip length model considering the limiting shear stress. By means of the finite differential methods, the characteristic analysis and optimization of the slip region of the combined surface Sleeve Bearing were carried out, and it has been proved that there is still a considerable large load support in a parallel sliding gap. Comparing with the general journal Bearing, the load capacity and end leakage rate of the combined surface Sleeve Bearing can be increased greatly and the load capacity can be increased by 1.75 times. The attitude angle, friction drag, temperature rise of the combined Bearing can be decreased distinctly and the temperature rise can be decreased by 92.4%.

M. Ojaghi - One of the best experts on this subject based on the ideXlab platform.

  • modeling induction motors under mixed radial axial asymmetry of the air gap produced by oil whirl fault in a Sleeve Bearing
    IEEE Transactions on Magnetics, 2018
    Co-Authors: M. Ojaghi, Reza Akhondi
    Abstract:

    High-power rating three-phase squirrel cage induction motors (SCIMs) may be equipped with Sleeve Bearings (SBs). Oil-whirl fault (OWF) is an important fault mode of the SBs, which can lead to their serious damage. On-line condition monitoring is recommended to detect possible incipient OWFs in the SBs before total failure of them and catastrophic stop of the machine. The OWF usually happens only in one of the motor SBs and introduces time-variant mixed radial–axial asymmetry to the air gap distribution. To study the SCIM performance under the OWF in one of its SBs, this paper proposes an analytical modeling and simulation approach. Multiple coupled circuit modeling along with the 2-D modified winding function theory is used for this purpose. The modeling and simulation results show novel harmonic components in the stator line currents, as well as the self-inductances of the stator windings due to the fault. The latter harmonics can be used as indices for diagnosing the Bearing OWFs as well. Regarding the sensitivity to the fault severity and robustness against the load level change and the mains voltage unbalance degree change, simulation-based studies are used to determine the most appropriate inductance harmonic as the OWF index.

  • Oil-Whirl Fault Modeling, Simulation, and Detection in Sleeve Bearings of Squirrel Cage Induction Motors
    IEEE Transactions on Energy Conversion, 2015
    Co-Authors: M. Ojaghi, N. Yazdandoost
    Abstract:

    Bearings are divided into two main categories: rolling Bearings and Sleeve Bearings. The Sleeve Bearings are normally used in electrical machines above 200-hp rating. In this paper, dynamic modeling and simulation of a squirrel cage induction motor with Sleeve Bearings under oil-whirl fault is performed. The required air gap function under the fault is defined using earlier experimental results. Then, a winding function approach is used for modeling and simulation of the motor with faulty Sleeve Bearings. Accuracy of the simulation is approved by comparison to the corresponding experimental results. The stator line current harmonics produced by the Bearing oil-whirl fault are identified, and the best harmonics as the fault index are chosen considering sensitivity of the harmonics to the fault severity, as well as the load level change and supply voltage unbalance. Selected index is used to determine the severity of oil-whirl fault in Sleeve Bearing of an induction motor working in a real production line.

Sang Bin Lee - One of the best experts on this subject based on the ideXlab platform.

  • discussion of oil whirl fault modeling simulation and detection in Sleeve Bearings of squirrel cage induction motors
    IEEE Transactions on Energy Conversion, 2016
    Co-Authors: Sang Bin Lee, Junyeong Jung, Youngsig Park
    Abstract:

    The discussers are in agreement with the authors that research on analysis and detection of Sleeve Bearing faults is an important area that has not been investigated in the literature due to the difficulties of testing involved. We also have recently started the investigation with requests from industry for remote, electrical signal based detection of Sleeve Bearing faults. Electrical monitoring of Sleeve Bearing faults is meaningful for medium-high voltage motors that do not have proximity probes installed, especially for cases where the motor operating environment is unfavorable for vibration analysis. It can also contribute to monitoring of low voltage motors with Sleeve Bearings used in applications such as seal-less pumps or compressors (appliances), where the cost of vibration analysis cannot be justified.

  • electrical monitoring of mechanical looseness for induction motors with Sleeve Bearings
    IEEE Transactions on Energy Conversion, 2016
    Co-Authors: Junyeong Jung, Sang Bin Lee, Chaewoong Lim, Chang Hee Cho, Kwonhee Kim
    Abstract:

    Mechanical looseness in induction motors is a common problem caused by loose bolts, structural damage, improper fit, or increased clearance between components, and results in increased vibration and wear. Detection of mechanical looseness in the Sleeve Bearing of industrial motors mainly relies on vibration analysis. However, there are many motor applications in the field where vibration analysis cannot be applied due to cost, environmental, and/or sensitivity limitations. The feasibility of using existing voltage/current measurements available in the motor control center for remote, low-cost monitoring of mechanical looseness due to improper fit between the Bearing-housing and Bearing-shaft is evaluated in this paper. It is shown through experimental testing on a custom built Sleeve Bearing test setup and on a 6.6 kV, 2250 hp motor that monitoring of the one-half and one-third subsynchronous components in the instantaneous power spectrum can serve as a reliable indicator of mechanical looseness.

Youngsig Park - One of the best experts on this subject based on the ideXlab platform.

  • discussion of oil whirl fault modeling simulation and detection in Sleeve Bearings of squirrel cage induction motors
    IEEE Transactions on Energy Conversion, 2016
    Co-Authors: Sang Bin Lee, Junyeong Jung, Youngsig Park
    Abstract:

    The discussers are in agreement with the authors that research on analysis and detection of Sleeve Bearing faults is an important area that has not been investigated in the literature due to the difficulties of testing involved. We also have recently started the investigation with requests from industry for remote, electrical signal based detection of Sleeve Bearing faults. Electrical monitoring of Sleeve Bearing faults is meaningful for medium-high voltage motors that do not have proximity probes installed, especially for cases where the motor operating environment is unfavorable for vibration analysis. It can also contribute to monitoring of low voltage motors with Sleeve Bearings used in applications such as seal-less pumps or compressors (appliances), where the cost of vibration analysis cannot be justified.