High Speed Rotor Losses in a Radial 8-Pole Magnetic Bearing: Part 1 — Experimental Measurement FREE

[+] Author Affiliations
M. E. F. Kasarda, P. E. Allaire, E. H. Maslen, G. T. Gillies

University of Virginia, Charlottesville, VA

G. R. Brown

University of Virginia, Charlottesville, VANASA Lewis Research Center, Cleveland, OH

Paper No. 96-GT-470, pp. V005T14A055; 6 pages
  • ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition
  • Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; General
  • Birmingham, UK, June 10–13, 1996
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-7876-7
  • Copyright © 1996 by ASME


The continual increase in the use of magnetic bearings in various capacities, including high speed aerospace applications such as jet engine prototypes, dictates the need to quantify power losses in this type of bearing. The goal of this study is to present experimentally measured power losses during the high speed nperatinn nf a pair of magnetic bearings. A large scale test rotor has been designed and built to obtain unambiguous power loss measurements while varying a variety of test parameters. The test apparatus consists of a shaft supported in two radial magnetic bearings and driven by two electric motors also mounted nn the shaft. The power losses of the spinning rotor are determined from the time rate of change of the kinetic energy of the rotor as its angular speed decays during free rotatinn. Measured results for the first set of magnetic bearings, a pair of 8-pole planar radial bearings, are presented here. Data from three different parameter studies including the effect of the hias flux density, the effect of the bearing pole configuration, and the effect of the motor stator on the power loss are presented. Rundown pints of the test with the bearings in the paired pole (NNSS) versus the alternating (NSNS) pole configuration shnw only small differences, with losses only slightly higher when the poles are in the alternating pole (NSNS) configuration. Loss data was also taken with the motor statnrs axially removed from the mntnr rotors for comparison with the case where the mntor stators are kept in place. No measurable difference was observed between the two cases, indicating negligible windage and residual magnetic effects. Throughout mnst of the speed range the dominant loss mechanism appears to be eddy currents.

Copyright © 1996 by ASME
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