Analysis of an Eddy Current Journal Bearing

[+] Author and Article Information
K. A. Connor

Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180-3590

J. A. Tichy

Department of Mechanical Engineering, Aeronautical Engineering & Mechanics, Rensselaer Polytechnic Institute, Troy, New York 12180-3590

J. Tribol 110(2), 320-326 (Apr 01, 1988) (7 pages) doi:10.1115/1.3261619 History: Received March 05, 1987; Online October 29, 2009


Nearly all magnetic bearings which have found use in modern technology are based on the attractive force between a magnet and a magnetic material. A distinct disadvantage is that such devices are inherently unstable and require active feedback for operation. In the present study an eddy current bearing is analyzed which uses repulsive forces to levitate a rotor, as in proposed advanced rail transportation systems. The journal bearing is considered to be a series of one-dimensional pads wrapped around a shaft. Maxwell’s equations are solved for the equivalent Cartesian geometry pad and rotor. This system is modeled as a sinusoidally varying surface current backed with an infinitely permeable (magnetic) pad which is separated from a conductive nonmagnetic rotor by a free gap. The magnetic forces are found to vary inversely with gap size, a necessary condition for stability. The behavior of an eddy current journal bearing is calculated and compared to that of fluid film bearings. Load, “friction” (which may also serve as propulsion), and attitude angle are determined as a function of eccentricity ratio, a slip parameter, clearance ratio and a number of pads. The approximate results presented may serve as guidelines for development work and subsequent analysis.

Copyright © 1988 by ASME
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