Abstract
This paper describes a micro-magnetic bearing (MMB) motor, in which, for the miniaturization, the rotor is supported by a one-axis-controlled magnetic bearing and the axial displacement is measured using capacitance variation between electromagnet cores and the rotor to stabilize the system. To drive the MMB rotor, an induction motor is chosen from the viewpoint of easy-to-integration. The induction motor is designed so that influences of magnetic and electrical interferences on the magnetic stiffness and the accuracy of the measured axial displacement can be reduced. The experimental results for an MMB motor with 6-mm-diameter rotor show that the rotor could levitate and rotate at 10,000 rpm stably. Magnetic stiffness of the MMB in the radial and angular directions were 1.32 N/mm and 0.64 Nm/rad, respectively and vibration amplitude of the rotor in the radial and angular directions were 2.3 μm and 3.5×10-4 rad at 5,000 rpm, respectively.
