Abstract
This paper introduces a small displacement sensor for active magnetic bearings. A magnetic bearing has merits of low loss supporting capability, maintenance-free drive and so on. However, active magnetic bearings require feedback control for stabilization of the magnetic force, and needs many expensive sensors, amplifiers and control devices. In recent years, the demand of a small high speed-rotating machine is growing, and development of a small and low-cost magnetic bearing is required. In this paper, a small and low-cost displacement sensor suitable for a small magnetic bearing is proposed. The proposed sensor consists of the sensor target made from ferromagnetic material, and four double coils placed around the sensor target. The displacement is measured by the principle of a differential transformer. In this paper, a simple analysis shows that the sensor output is proportional to the displacement. Then it is confirmed by results obtained by simple experiment.
