The magnetic bearing using the High Temperature Superconductor (HTS) is developed. The 2-layer ring type rotor consists of the cylinder type and the ring type permanent magnet. In this rotor, the part of the flux from the permanent magnet does not interlink to the HTS. Thus, the yoke equipped cylinder type rotor is introduced. In this rotor, the iron is installed around the permanent magnet to concentrate the flux on the HTS. The flux distribution on the surface of the HTS is related to the stability of the rotor during rotation. When the magnetic flux is concentrated in the outside of the HTS, stable rotation is maintained.

In order to achieve stable rotation, the yoke equipped ring type rotor is considered. This rotor is used the ring type permanent magnet equipped the yoke. The magnetic circuit of this rotor is designed using magnetic field analysis of the 3-dimensional finite element method. The table1 shows the specification of the HTS.

 Fig.1 shows the structure of the yoke equipped ring type rotor. The change in the linkage flux when the distance w between the yoke and the permanent magnet, the yoke thickness a and the yoke width b are changed is obtained. Fig.2 shows the dependence of distance w on the linkage flux. Fig.3 shows the flux line of the rotor. From the figures, as the distance w increases, the quantity of linkage flux increases. And the flux distribution is more concentrated on the outside of the HTS. The increment of linkage flux decreases at w = 6~8[mm]. When the diameter of the rotor is larger than the HTS, the linkage flux on the surface of the HTS decreases. Thus, w = 6 is adopted.

 Fig.4 shows the dependence of the yoke shape on the linkage flux. From the figure, as the yoke thickness a and the yoke width b increase, the quantity of linkage flux increases. The amount of linkage flux is maximum at a =6 [mm]. The linkage flux is almost same at a = 6 ~ 8[mm]. This is because the flux from the permanent magnet is same amount. It shows that the magnetic saturation is relaxed at a = 6 [mm]. Due to the relaxation of magnetic saturation at b = 5~8[mm], there is almost same in the amount of the flux. It shows that the magnetic saturation is relaxed at b = 5 [mm]. As each valueincreases, the rotor becomes large. It causes that the suppression force against vibration becomes small. In consideration of the factors, a = 6[mm], b=5 [mm] are adopted.

Keywords: Magnetic Bearing, HTS, Flywheel, Magnetic Circuit