Investigation of rotor–gas foil bearing system and its application for an ultra-high-speed permanent magnet synchronous motor

In this study, an ultra-high-speed rotor–gas foil-bearing system is designed and applied to a permanent magnet synchronous motor. Gas foil journal bearings and gas foil thrust bearings are used to provide journal and axial support to the rotor, respectively. The bearings are analyzed theoretically considering the nonlinear deflection of the top foil, and the static and dynamic characteristics are obtained with which the rotor dynamic performances of the tested rotor are calculated using the finite element method. During the experiment, the permanent magnet synchronous motor can operate stably at 94,000 r/min, which demonstrates a great dynamic performance of the gas foil bearings and the stability that it provides to the entire system. The sub-synchronous vibration also occurs when the rotating speed reaches 60,000 r/min and as the speed keeps rising, the amplitude of such vibration increases, which will contribute to the destabilization of the rotor–gas foil-bearing system. Finally, the axial force of the rotor is calculated theoretically as well as measured directly by four micro force sensors mounted in the thrust end cover of the permanent magnet synchronous motor. The experimental results presented in this article are expected to provide a useful guide to the design and analysis of the rotor–gas foil-bearing system and high-speed permanent magnet synchronous motor.