The Development of a Flexible Rotor Active Magnetic Bearing System

A design process comprising aspects of modelling and analysis is developed, implemented and verified for a flexible rotor active magnetic bearing system. The system is specified to experience the first three critical frequencies up to an operating speed of 10,000 rpm. Rotor stability at critical frequencies places specific constraints on the equivalent stiffness and damping parameters of the active magnetic bearing. An iterative design process is then initiated by an electromagnetic design of the radial active magnetic bearings resulting in parameters used in the detailed modelling of the system. Stiffness and damping parameters as well as system dynamic response are verified and used to design a flexible rotor. The magnetic bearing locations, displacement sensor locations and rotordynamic response are verified using finite element analysis. The design of the rotor stands central to the iterative design process since it impacts on the forces experienced by the active magnetic bearings as well as the critical frequencies of the active magnetic bearing system. Once constructed the actual active magnetic bearing system stiffness and damping parameters as well as dynamic response are compared to modelled results. The rotordynamic response is characterised by measuring the rotor displacement at pre-defined locations as the rotor traverses the critical frequencies. These results are compared with the predicted rotordynamic response.