Experimental Results Passing Through Critical Speeds of Radial and Tilting Motions in a One-Axis Actively Positioned Single-Drive Bearingless Motor

Abstract

One-axis actively positioned bearingless motors have been studied for industry applications such as pumps and cooling fans. In particular, single-drive bearingless motors have a great advantage of simple regulation system. Only one three-phase inverter is required for generating torque and active axial force by q- and d-axis currents. On the other hand, radial and tilting motions of the rotor shaft are passively stabilized by passive magnetic bearings. These passive force and torque are just spring force. Inherently, damping force and torque are not generated. As a result, the rotor vibrations in the radial and tilting directions are considerable high at resonant frequencies. In this paper, a novel strategy is proposed to pass through the critical speed by the motor acceleration with a fan blade. In the experiment, it is verified that the single-drive bearingless motor successfully pass through the critical speed without touch-down.