Abstract: Rolling-element bearings are commonly used to protect the magnetic bearing system as auxiliary bearings. On the basis of the thermal transfer theory, tribology of rolling-element bearing and rotor dynamics, a new thermal structure of double-decker auxiliary bearing (DDAB) is established, and then the thermal characteristics are analyzed through building the heat transfer equations and computing the friction heat and temperature. Details of studies are as follows: after the establishment of the heat transfer model of double-decker rolling bearing (DDRB) and the derivation of heat transfer resistance and equations, the temperature rising of DDRB is analyzed under normal conditions when gets heat balance. The effects on temperature rise of DDRB concerning various structures, loads, speeds, viscosities of lubricant as well as material properties are discussed. And the calculation results are compared with those of the traditional bearings under the same operation conditions. Test rig is built to measure the temperature rises for different structures and lubricant conditions, and then the main measures to reduce heat generation are illustrated. The following results can be obtained: The radial load and the rotational speed of inner race directly influence the bearing friction torque which ulteriorly influence the heat generation, and the temperature rising of the inner race of DDRB is 5%-20% smaller than that of traditional bearings and 10%-30% smaller of the outer race; Viscosities of lubricant and thermal properties of material have great influence on the temperature distribution of inner and outer race. 1/3 lubrication amount of the space of the bearing, Z-structure, aluminum middle ring, ceramics balls can make the bearing obtain better thermal characteristics and a lower temperature rise under high speed.

Key words: Active magnetic bearing, Auxiliary bearing, Heat generation, Rolling-element bearing