Rotational Speed Limit of Non-controlled Magnetic Levitation Motor with Composite HOPG Disk

Abstract

　The subject of this paper is to realize high-speed rotation by stabilizing the rotation of an non-controlled magnetic levitation motor using a diamagnetic disc. The non-controlled magnetic levitation motor has a small rigidity of the magnetic bearing, and it is difficult to rotate at a stable high speed. As a countermeasure, the permanent magnets attached to the upper and lower parts of the levitated rotor are surrounded by copper blocks, and the eddy current generated inside the copper blocks stabilizes the levitated rotor. As a result, the levitation rotor can rotate at high speed. However, as the rotational speed of the levitation rotor increases, the aerodynamic attractive force between the permanent magnet array for floating the diamagnetic disc and the diamagnetic disc increases. Above 4800 rpm, it was found that the permanent magnet array and the diamagnetic disc were in contact due to the attractive force.