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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Negative Stiffness Coefficients for Magnetic Actuators Using Laplace’s Equation

[+] Author and Article Information
L. S. Stephens

Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506-0108   e-mail: stephens@engr.uky.edu

M. A. Casemore

Mechanical Engineering Department Louisiana State University, 2508 CEBA Baton Rouge, LA 70803

J. Eng. Gas Turbines Power 123(3), 612-618 (Oct 01, 2000) (7 pages) doi:10.1115/1.1377874 History: Received October 01, 1999; Revised October 01, 2000
Copyright © 2001 by ASME
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References

Schultz, R. R., Bornstein, K. R., Jayawant, R. C., and Leung, R., 1995, “Applications of Active Magnetic Bearings to High Speed Turbomachinery with Aerodynamic Rotor Disturbance,” Proceedings of Mag ’95, Technomic, Lancaster, PA, pp. 14–23.
Iannello, V., 1995, “Magnetic Bearing Systems for Gas Turbine Engines,” Proceedings of Mag ’95, Technomic, Lancaster, PA, 1995, pp. 77–86.
Kelleher, W. P., and Kondoleon, A. S., 1997, “A Magnetic Bearing Suspension System for High Temperature Gas Turbine Applications,” Proceedings of MAG ’97, Technomic, Lancaster, PA, pp. 15–24.
Maslen,  E. , 1989, “Practical Limits to the Performance of Magnetic Bearings: Peak Force, Slew Rate, and Displacement Sensitivity,” ASME J. Tribol., 111, pp. 331–336.
Okada,  Y., Miyamoto,  S., and Ohishi,  T., 1996, “Levitation and Torque Control of Internal Permanent Magnet Type Bearingless Motor,” IEEE Trans. on Control Systems Technology,4, No. 5, pp. 565–571.
Bischel, J., 1991, “The Bearingless Electrical Machine,” Proceedings of the International Symposium on Magnetic Suspension Technology ’91, NASA Langley Research Center, p. 561.
Maslen,  E. , 1996, “Magnetic Bearing Design for Reduced Power Consumption,” ASME J. Tribol., 118, pp. 839–845.
Meeks, C., 1993, “Magnetic Bearing Structure Providing Radial, Axial, and Moment Load Bearing Support for a Rotating Shaft,” U.S. Patent No. 5,216,308.
Sortore, C., Allaire, P., Maslen, E., Humphris, R., and Studer, P., 1990, “Permanent Magnet Biased Magnetic Bearings—Design, Construction, and Testing,” Proceedings of 2nd International Symposium on Magnetic Bearings, Tokyo, July 12–14, University of Tokyo, Tokyo.
Knospe,  C. R., and Stephens,  L. S., 1996, “Side-Pull and Stiffness of Magnetic Bearing Radial Flux Return Paths,” ASME J. Tribol., 118, pp. 98–101.
Walowit,  J. A., and Pinkus,  O., 1982, “Analytical and Experimental Investigation of Magnetic Support Systems. Part 1: Analysis,” ASME J. Lubr. Technol., 104, pp. 418–428.
Happel, J., and Brenner, H., 1986, Low Reynolds Number Hydrodynamics, Matrinus Nijhoff, Boston, pp. 474–499.

Figures

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Typical magnetic actuators
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Annular magnetic actuator air gap region
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Bipolar coordinate transformation of air gap
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Graphical representation of boundary conditions
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Magnetomotive force for centered journal: Case 1
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Flux density for centered journal: Case 1
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Flux density for eccentric journal: Case 1
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Negative stiffness coefficient: Case 1
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Flux density for eccentric journal: Case 2
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Negative stiffness coefficient: Case 2
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Flux density for eccentric journal: Case 3
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Negative stiffness coefficient: Case 3
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Flux density for eccentric journal: Case 4
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Negative stiffness coefficient: Case 4

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