Permanent magnet pulse motor with high-temperature superconducting levitation

A simple but stable noncontact high T-c superconducting levitation system with a vertical shaft has been presented. The levitation system consists of a superconductor and permanent magnets. In the system, a high T-c superconductor supports a lower end of the shaft, and a pair of permanent magnets supports the other end. Although a levitation is stable when the levitation system is used, since the restoring force is small in the horizontal direction, the levitation stability is small in the horizontal direction. Hence, it is difficult to drive the shaft by electromagnetic forces in using such motors. This paper describes a driving system consisting of six coils and a permanent magnet with eight poles, in which balance forces act on two opposite sides of the disc type rotor in the axial direction. The system has no unbalance force, and stable rotation is obtained without control. To validate the proposed system, experimental tests have been carried out. The experimental motor achieved stable rotation at speeds up to 1250 rpm.