ABSTRACT
Design of magnetic bearings (MBs) requires a good understanding of rotordynamics, controls, electronics, and electromagnetics. MBs were developed in the 1940s by Jesse Beams [1,2] of the University of Virginia for ultracentrifuge application. ˜ese devices have since been applied to an ever widening scope of commercial applications such as vacuum pumps, industrial compressors, pumps and turbines, energy storage ¨ywheels, machine tools, and even artiŸcial hearts [3]. Other potential applications include ultrahigh-temperature gas turbines [4] and satellite attitude control ¨ywheels [5]. MBs oµer some key advantages over oil or gas Ÿlm passive bearings such as (a) environmentally friendly, (b) oilfree operation, (c) elimination of process contamination, (d) reduced footprint from eliminating lube system, (e) reduced maintenance, (f) reduced power losses, (g) no minimum speed requirement, (h) DN values (D is the diameter in mm and N is the rotation rate in RPM) greater than 3,000,000, and (i) adaptive adjustment of stiµness and damping. Some disadvantages include lower unit load capacity relative to oil Ÿlm bearings: (150-200 psi) vs. 600-1000 psi, and generally higher initial cost.
