Dynamic Responses of Rotor Drops onto Double-decker Catcher Bearing

In an active magnetic bearing （AMB） system, the catcher bearings （CBs） are indispensable to protect the rotor and stator in case the magnetic bearings fail. Most of the former researches associated with CBs are mainly focused on the dynamic responses of the rotor drops onto traditional single-decker catcher bearings （SDCBs）. But because of the lower limited speed of SDCB, it cannot withstand the ultra high speed rotation after rotor drop. In this paper, based on the analysis of the disadvantages of SDCBs, a new type of double-decker catcher bearings （DDCBs） is proposed to enhance the CB work performance in AMB system. In order to obtain thc accurate rotor movements before AMB failure, the dynamic characteristics of AMB are theoretically derived. Detailed simulation models containing rigid rotor model, contact model between rotor and inner race, DDCB force model as well as heating model after rotor drop are established. Then, using those established models the dynamic responses of rotor drops onto DDCBs and SDCBs are respectively simulated. The rotor orbits, contact forces, spin speeds of various parts and heat energies after AMB failure are mainly analyzed. The simulation results show that DDCBs can effectively improve the CBs limit rotational speed and reduce the following vibrations, impacts and heating. Finally, rotor drop experiments choosing different types of CBs are carried out on the established AMB test bench. Rotor orbits, inner race temperatures as well as the rotating speeds of both inner race and intermediate races after rotor drop are synchronously measured. The experiment results verify the advantages of DDCB and the correctness of theoretical analysis. The studies provide certain theoretical and experimental references for the application of DDCBs in AMB system.

Dynamics of Rotor Drop on New Type Catcher Bearing

In an active magnetic bearing(AMB)system,the catcher bearings(CBs)are indispensable to protect the rotor and stator in case the magnetic bearings fail or overload.A new CB structure composed of two ball bearings is introduced.Detailed simulation models containing contact model between rotor and inner race,double-decker catcher bearing(DDCB)model as well as single-decker catcher bearing(SDCB)model are established using multibody dynamics simulation software MSC.ADAMS.Then,using those established models,the rotor orbits and the contact forces between rotor and inner race are simulated respectively after rotor drop on DDCBs and SDCBs.The simulation result shows that the rotor vibration range using DDCBs is significantly smaller than that using SDCBs;the maximum contact forces drop about 15%—27% compared with the contact forces using SDCBs.Finally,the test bench for the rotor drop experiments is built and the rotor drop experiments for different types of CBs are carried out.Labview data acquisition system is utilized to collect the displacement of rotor and the rotating frequencies of both inner race and intermediate races after rotor drop.The experimental results are comparatively analyzed,and the conclusion that DDCB can help to reduce vibration amplitude and collision force is obtained.The studies can provide certain theoretical and experimental references for the application of DDCBs in AMB system.