Determination of Forces in a Magnetic Bearing Actuator: Numerical Computation With Comparison to Experiment

[+] Author and Article Information
J. D. Knight, Z. Xia, E. McCaul

Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27706

H. Hacker

Department of Electrical Engineering, Duke University, Durham, NC 27706

J. Tribol 114(4), 796-801 (Oct 01, 1992) (6 pages) doi:10.1115/1.2920951 History: Received February 15, 1991; Revised October 01, 1991; Online June 05, 2008


Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and free space, using finite but constant permeability in the metals. Above a relative permeability of 104 the effects of changes in permeability are negligible, but below 104 decreases in permeability cause significant decreases in the force. The calculated forces are shown to depend on the metal permeability more strongly when the journal is displaced from its centered position. The predicted forces in the principal attractive direction are in good agreement with experiment when a relatively low value of permeability is chosen. The forces measured normal to the axis of symmetry when the journal is displaced from that axis, however, are significantly higher than predicted by theory, even with a value of relative permeability larger than 5000. These results indicate a need for futher work including nonlinear permeability distributions.

Copyright © 1992 by The American Society of Mechanical Engineers
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