The RTRI promoted the development of a superconductive magnetic bearing that combines superconductive magnets and superconductive bulk bodies, and manufactured a small prototype magnetic bearing with a view to being applied to the support of flywheels for power storage.

The prototype bearing has superconductive magnets on the stator side and superconductive bulk bodies on the rotor side (Fig. 1). Two superconductive magnets are arranged in series around a rotating shaft, and are energized to opposite polarities to generate a strong electromagnetic force. Two superconductive bulk bodies, each 60 mm in diameter and 20 mm in thickness, are cooled with liquid nitrogen.

This bearing can support a static load of 10 kN, which is the limit load for support by superconductive magnets, or over. It has a load-carrying capacity per unit area 10 times that of conventional magnetic bearings that combine superconductive bodies and permanent magnets or iron members. The RTRI also manufactured a test apparatus to support a rotating body with the use of this bearing (Fig. 2) and confirmed that it can stably support a 500-kg flywheel rotating at 3,000 rpm.

The RTRI plans to increase the bearing’s load-carrying capacity by changing the arrangement of the superconductive bulk bodies and cooling them to a lower temperature and also to propose a new flywheel power storage system.