Vibration Control for a Rotor Supported by Oil-Film Bearings Using a Bearingless Motor

Rotors of large turbomachinery are usually supported by oil-film bearings, because an oil-film bearing has a simple structure, high load capacity, and large damping. However, an oil-film bearing induces self-excited vibration at high rotational speeds. Therefore, a suppression method for the self-excited vibration is needed. This study proposes the application of a bearingless motor (BELM) for a rotor supported by oil-film bearings. To realize the proposed rotor system, an experimental rotor, supported by the oil-film bearings and equipped with a BELM, is designed and fabricated. This study illustrates the winding configuration and the controller design of the BELM for a stable suspension system. The test rotor with the oil-film bearings and the BELM exhibited stable rotation at rotational speeds higher than the onset speed of the self-excited vibration. Furthermore, the radial force required to suppress the self-excited vibration is discussed. Because it is desirable for the radial force of the BELM to be small in the actual machine, we realized a stable and high-speed rotation with a small radial force. Thus, we demonstrate the feasibility of a compact, stable, and high-speed rotor-oil-film bearing system.