Commissioning of a Modular Active-Magnetic-Bearing-Suspended Rotor System

Traditional high-speed rotor configurations employing magnetic bearing technology, which typically integrates two radial bearings and one axial bearing to suspend the rotor, are sensitive to changes in impeller mass properties. This paper focuses on modular magnetically levitated rotor technology, which enables drivelines with two or more impellers and three or more radial active magnetic bearings (AMBs). This configuration ensures the reliability and robustness of the rotordynamic behavior by providing a structure that enables adaptable integration of components, such as compressors and turbines, onto the same long high-speed shaft. The structure considered here includes a 2 MW, 12 000 rpm induction machine with three radial magnetic bearings and a rotor system where the impeller is installed on a separate shaft and connected to the motor drive with a flexible coupling. The main focus of this paper is on the proof-of-concept testing and commissioning of such a technology, with particular attention given to modeling and control aspects. An $H_{\infty }$ loop-shaping approach is adopted for model-based control design, using a model that incorporates two flexible modes and adaptive notch structures to eliminate speed-synchronous components from the feedback signal. The AMB–rotor system modeling is validated through system identification routines. The experimental results demonstrate that the proposed modular technology provides improvements in rotordynamics despite the increased complexity of the system and control.