Design of a High Speed Rotating Loss Test Rig for Radial Magnetic Bearings

This paper describes the design and operating characteristics of a vacuum rundown test rig for the measurement of rotating losses in radial magnetic bearings. These rotating losses are due to eddy currents, alternating hysteresis, rotating hysteresis, and windage which create drag on a rotating shaft. The rig consists of a shaft supported in two radial magnetic bearings. The shaft is accelerated by end-mounted electric motors. whose stators can be withdrawn from the shaft after run-up to eliminate any residual magnetic coupling, at which point coast down times due only to drag from the magnetic bearings will be measured. Temperature rises will also be monitored. Different levels of vacuum can be employed to quantify the windage losses. Losses will be measured in several different bearing configurations, both radial planar and homopolar, and the individual loss mechanisms identified and quantified wherever possible. The experimental results will be compared with theoretical models of loss mechanisms. An accurate characterization of the loss mechanisms will aid in calculations of losses and temperature rise in future applications.