176 Ë 6 First manned HTS Maglev vehicle in the world
Section 5.3). The average force densities (AFD) were calculated and compared. The
melt-textured single-domain YBCO cylinder bulk Beijing 207 (17×휙30 mm) was fabri-
cated by the Beijing General Research Institute for Nonferrous Metals. Another rectan-
gular bulk TG 208-7 (30×35.6×15.5 mm) was made by IFW. In all the experiments, the
c-axis of the HTS bulk was oriented perpendicular to the surface of the PMG.
The actual vehicle “Century” was designed based on the above measurement
results. For the full-scale HTS Maglev vehicle “Century”, 43 pieces of cylindrical YBCO
bulks were used in each rectangular-shaped on-board the HTS Maglev equipment (see
Section 6.15) in ASCLab. The inside size of the liquid nitrogen vessel equipment was
102 mm wide, 470 mm long, and 168 mm high. The levitation forces of two HTS Maglev
vessels composed of rectangular and cylindrical bulks were calculated. The results
indicated that an asymmetric field applied about the axes of bulks had more of an
effect on the average force density of the rectangular bulk than on the cylindrical
bulk. Particularly for the full-scale HTS Maglev vehicle “Century”, the total levitation
force was increased from 1092 N to 1282 N at a gap of 20 mm, if a rectangular bulk was
employed rather than cylindrical bulk. Arranging rectangular bulks rather than cylin-
drical bulks in the same vessel equipment increased the number of YBCO bulks, thus
strengthened the levitation force to 1320 N at a gap of 20 mm [41]. These measured data
had great significance for practical application. The conclusion of this experiment
study has also been used in subsequent development of the HTS Maglev vehicle.
6.9.2Influence of HTS bulk size on the properties
Ren et al. [42] researched the influence of the size of the HTS bulks on the levi-
tation forces. Three top-seeded MTG YBCO bulks were used in the levitation force
measurement. These samples were made in the Beijing General Research Institute
for Nonferrous Metals. All the levitation forces were measured at 77 K by the HTS
Maglev measurement system SCML-01 (see Fig. 5.7). Table 6.8 lists the parameters and
levitation forces over the PMG in ZFC at 77 K at different gaps.
Table 6.8 lists the levitation forces of the three samples at different gaps. The
diameters of samples 2 and 3 are 16.6% and 33.3% larger than the diameter of sample 1,
respectively, but their levitation forces are increased 30.5% and 69.9% at a gap of
5 mm and 39.4% and 90.1% at a gap of 20 mm, respectively, than that of sample 1.
This implies that the larger the sample, the more rapidly levitation forces increase for
larger gaps. Figure 6.30 shows the levitation forces over the PMG of samples 1, 2, and 3
in ZFC at 77 K. As shown in Fig. 6.30, levitation forces of sample 3 are obviously larger
than that of sample 2, but the difference between the thicknesses of the two samples
is very small. The influence of thickness on levitation forces in this case is negligible.
However, the thickness must reach a certain value (see Section 6.9.3).
Fourteen years ago, “Century” was built with cylindrical shaped HTS bulks,
because that was what we had. Of course, the larger the size of YBCO HTS bulks, the