Active magnetic bearing systems have many advantages for rotating machinery. However, one of the drawbacks is potential loss of levitation due to loss of power in the active magnetic bearing system. The rotor then drops, and an auxiliary bearing system is needed to protect vital system components from damage.
Auxiliary bearing systems usually consist of ball bearings to catch the rotor, and a spring and damper system to absorb the impact. Design of the auxiliary bearing system requires careful analysis. The rotor drop requires a non-linear model to properly capture friction and ball effects, and this has to be coupled with the rotordynamics and the spring-damper system. Typical spring-dampers use friction damping to remove energy from the system, which adds another non-linear element to the analysis.
RBSI has developed advanced analysis tools for rotor drop analysis. These tools accurately predict rotor behavior, bearing behavior, and can be used as inputs to perform ball bearing stress analysis. Dr. Jianming Cao, RBSI’s Director of Rotordynamics, has worked on developing these tools for general non-linear rotordynamics and for rotor drop analyses in particular.
For more details on RBSI auxiliary bearing analysis tools, see our paper presented at ISMB 15.
In a future post, we’ll discuss comparing Dr. Cao’s model to experimental data.
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