Rotor power losses in planar radial magnetic bearings -- Effects of number of stator poles, air gas thickness, and magnetic flux density

Journal Article · Fri Oct 01 04:00:00 EDT 1999 · Journal of Engineering for Gas Turbines and Power

DOI:https://doi.org/10.1115/1.2818528· OSTI ID:20006110

Allaire, P E; Kasarda, M E.F.; Fujita, L K

Rotor power losses in magnetic bearings cannot be accurately calculated at this time because of the complexity of the magnetic field distribution and several other effects. The losses are due to eddy currents, hysteresis, and windage. This paper presents measured results in radial magnetic bearing configurations with eight pole and 16 pole stators and two laminated rotors. Two different air gaps were tested. The rotor power losses were determined by measuring the rundown speed of the rotor after the rotor was spun up to speeds of approximately 30,000 rpm, DN + 2,670,000 mm-rpm, in atmospheric air. The kinetic energy of the rotor is converted to heat by magnetic and air drag power loss mechanisms during the run down. Given past publications and the opinions of researchers in the field, the results were quite unexpected. The measured power losses were found to be nearly independent of the number of poles in the bearing. Also, the overall measured rotor power loss increased significantly as the magnetic flux density increased and also increased significantly as the air gap thickness decreased. A method of separating the hysteresis, eddy current and windage losses is presented. Eddy current effect were found to be the most important loss mechanism in the data analysis, for large clearance bearings. Hysteresis and windage effects did not change much from one configuration to the other.

• Research Organization: Univ. of Virginia, Charlottesville, VA (US)
• OSTI ID: 20006110
• Journal Information: Journal of Engineering for Gas Turbines and Power, Journal Name: Journal of Engineering for Gas Turbines and Power Journal Issue: 4 Vol. 121; ISSN JETPEZ; ISSN 0742-4795
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
EDDY CURRENTS
ENERGY EFFICIENCY
HYSTERESIS
MAGNETIC BEARINGS
PERFORMANCE
POWER LOSSES