9.3 Application of HTSB Ë 337
worry about wear and generated heat present with conventional bearings. A RSB
was designed to support the 1 ton shaft of a 4-MW HTS generator of Siemens. This
application was claimed as the first industrial application of HTSB [19]. The HTS
stator was composed of 270 YBCO bulks which were arranged in nine rings and
was subdivided into an upper half shell and a lower half shell. Its inside diameter
was 325 mm and length was 305 mm. PM rotor had an outer diameter of 319 mm,
so the working gap of RSB was 3 mm. During activation, the upper half shell of
the HTS stator was fixed and the lower half shell moved upward. By this method,
radial force of the RSB reached 6900 N at 28 K and 5000 N at 65 K, and the radial
stiffness reached 5.1 kN/mm at 28 K. Its maximum speed was 4400 rpm and the
shaft oscillation was less than 0.01 mm at 3600 rpm.
- Laser beam deflection polygon scanner [36]: A light beam scanner can be used
to deflect a laser not beam in xerographic printers or laser display units. Fluid
and gas suspension bearing can not be accelerated to above 120,000 rpm for
a 60-mm diameter rotor due to friction, so a RSB has chosen for the scanner.
The main advantages of introduction of the RSB are its high speed with good
optical resolution, low power consumption due to elimination of wear and heat,
no need for electronic control and safety during power failure. In the scanner,
a 0.2-kg rotor was suspended by two RSBs with 36-mm-outer diameter, 20-mm-
inter-diameter, 15-mm-thick YBCO rings and 18-mm-outer diameter, 10-mm-inter-
diameter, 5-mm-thick PM rings. The maximum speed of the rotor was 174,000 rpm.
When the magnetic inhomogeneity of the PM ring was less than 2%, rotational
loss per rotation is 3.8× 10 −^4 J.
- Centrifuge [37]: A centrifuge can separate different materials quickly by the
centrifugal force. It has been used in chemical engineering, oil industry, food
processing, pharmaceuticals, etc. In a centrifuge, the motor generates torque
and transfers it to the centrifuge rotor through shafts, couplers and spindles.
This structure often causes breakdowns and a whirling up of the sediments. RSB
can solve these problems, because it can handle much higher imbalance mass
compared to conventional bearings. During resonance, an extreme eccentricity of
2 mm is safely accommodated by introduction of the RSB. A centrifuge with 1 kg
titanium rotor levitated by two RSBs with inner PM rotors was developed [37]. PM
rings were selected with a magnetic inhomogeneity of the PM rings less than 2%,
and the magnetic field was 0.5–0.8 T in the gap center. HTS stators were cooled
by a 15-W/80-K Stirling cryocooler, and the working temperature of the upper and
lower RSB was typically 68 and 65 K, respectively. A 250-W motor between two
RSBs drove the rotor to 30,000 rpm. A radial emergency bearing was placed under
the upper RSB and an axial emergency bearing was placed in the bottom of the
rotor.
- Liquid hydrogen tank [38–40]: Hydrogen can provide environmentally friendly
energy. It is usually stored as liquid hydrogen in a tank. Heat loss through
convection and radiation is reduced by vacuum and radiation shields between
