Research Papers: Applications

Dynamic Analysis of Rotor System With Misaligned Retainer Bearings

[+] Author and Article Information
Antti Kärkkäinen1

Department of Mechanical Engineering, Lappeenranta University of Technology, FI-53851 Lappeenranta, Finlandantti.karkkainen@lut.fi

Marlene Helfert

Department of Mechanical Engineering, Darmstadt University of Technology, D-64287 Darmstadt, Germany

Beat Aeschlimann

 MECOS Traxler AG, CH-8404 Winterthur, Switzerland

Aki Mikkola

Department of Mechanical Engineering, Lappeenranta University of Technology, FI-53851 Lappeenranta, Finland


Corresponding author.

J. Tribol 130(2), 021102 (Apr 22, 2008) (10 pages) doi:10.1115/1.2908921 History: Received July 31, 2007; Revised February 18, 2008; Published April 22, 2008

Active magnetic bearings present a technology that has many advantages compared to traditional bearing concepts. Active magnetic bearings, however, require retainer bearings in order to prevent damages in the event of a component, power, or a control system failure. In the drop-down, when the rotor drops from the magnetic field on the retainer bearings, the design of the retainer bearings has a significant influence on the dynamic behavior of the rotor. In this study, the dynamics of an active magnetic bearing supported rotor during the drop on retainer bearings is studied employing a simulation model. The retainer bearings are modeled using a detailed ball bearing model while the flexibility of the rotor is described using the finite element method with component mode synthesis. The model is verified by comparing measurements carried out using an existing test rig and simulation results. In this study, the verified simulation model is employed studying the effect of misalignment of retainer bearings during the rotor drop-down on the retainer bearings. It is concluded in this study that the misalignment of the retainer bearings is harmful and can lead to whirling motion of the rotor.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Ball-ring elliptical contact

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Figure 2

Axial cross section of a ball bearing

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Figure 3

Circle-in-circle contact

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Figure 4

Diagram of the electric motor under investigation (dimensions are in millimeters)

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Figure 5

Measured (M1–M3) and simulated (S1–S3) orbits of the rotor with various rotational velocities of the rotor: (M1 and S1) 150Hz, (M2 and S2) 300Hz, and (M3 and S3) 400Hz

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Figure 6

Misalignment of the retainer bearing in the vertical direction (cases (a)–(d))

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Figure 7

Misalignment of the retainer bearing in the horizontal direction (cases (e)–(h))

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Figure 8

Conical (a) and cylindrical (b) modes of the whirling motion

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Figure 9

Vertical displacement of the rotor during drop-down situation

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Figure 10

Contact forces between the rotor and the horizontally (a) and vertically (b) misaligned retainer bearing during the first contact

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Figure 11

Stability map of the rotor system including retainer bearings with misalignment.




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