Acceleration Challenge from 0 to 60,000 r/min in 1DOF Single-Drive Bearingless Motor with Pure Magnetic Suspension

One degree-of-freedom actively positioned bearingless motors and magnetic bearing motors have been studied to reduce costs and simplify the regulation system by reducing active positioning axes. Only axial direction of the rotor shaft is actively positioned, and the other axes of radial and tilting directions are passively stabilized with passive magnetic bearings. It has critical speeds that depend on the passive stiffness, and high acceleration is required to pass through the critical speed. This paper verifies the acceleration requirement in the experiment. In addition, this paper presents an adjustment method of a coefficient of time-delay compensation to reduce d-axis current that controls active axial forces. It is a key parameter to accelerate the bearingless motor up to 60,000 r/min with stable magnetic suspension. In the experiment, it is validated that the estimated optimal coefficient succeeds non-contact stable operations from the acceleration to the steady-state at 60,000 r/min.