Comparison of Acoustic Noise and Vibration in Ball-Bearing-Supported Motors and One-Axis Actively Positioned Single-Drive Bearingless Motor With Two Radial Permanent-Magnet Passive Magnetic Bearings

This study experimentally investigates the acoustic noise, vibration, and power consumption in a one-degree-of-freedom actively positioned single-drive bearingless motor, which has radial passive magnetic bearings (RPMBs) and compared to an identical stator part and rotor shaft with radial mechanical ball bearings. For the experiment, three test motors were set up: (a) a bearingless motor with two RPMB, (b) a motor with two ball bearings without an axial preload, and (c) a motor with two ball bearings with an axial preload. Motor (a) under test had one-axis active positioning and the radial movements were supported by RPMB made of cylindrical permanent magnets. Conversely, in motors (b) and (c), the radial and axial movements were supported by ball bearings, and there was no production of active axial force. The experimental results confirmed that the levels of acoustic noise, stator vibration, and input power consumption were significantly lower in motor (a) than those in motors (b) and (c). In the analysis section, dynamic models of the bearingless motor with RPMB and motor with ball bearings were designed and simulated using MATLAB $\backslash$ Simulink. The low radial stiffness in RPMB was found to contribute to acoustic noise and vibration reductions. Thus, this article presents an example of a one-degree-of-freedom actively positioned bearingless motor with RPMB that realizes reductions of acoustic noise, stator vibration, and input power consumption.