280 Ë 8 New progress of HTS Maglev vehicle
bulk’s round-trip movement times on levitation forces was larger at higher tempera-
ture while it was smaller at lower temperature. On the other hand, when the bulk lay
atx=0 mm, the variation ofBzbecame small during the vertical movements which
led to a smaller induced current in the bulk. Therefore, reduction of the variation of
Bzduring movement was the main reason why the influence of the bulk’s round-trip
movement times on the levitation forces was so small at any temperature.
Considering the practical running situation of the HTS Maglev vehicle, we chose
four gap points in the experiment curves, i.e. 11, 12, 15, and 16 mm, respectively.
Figure 8.22 shows levitation forces under different movement speeds for the above
gaps for four working temperature conditions.
It is interesting to note that the levitation forces decreased with increasing move-
ment speeds from 1 mm/s to 6 mm/s for the gap atx= −25 mm when the temperature
of the bulk was held at 77 or 73 K. For example, when the gap was 11 mm and
the temperature was at 77 K, the levitation force of the bulk was 67 N at 1-mm/s
movement speed, while it decreased to 61 N at 6-mm/s movement speed. However,
at the lowest 63 K, the forces did not decrease with increasing movement speed for
the gap atx= −25 mm. The influence of movement speed on the levitation forces was
negligibly small at 63 K or lower. These conclusions were also obtained for a large
variation ofBzfield. Once the variation ofBzbecomes small, the influence of the bulk’s
round-trip movement times and speed on the levitation forces were very small at any
temperature. Withx=0 mm position, for example, the strength ofBzwas extremely
Fig. 8.22:Levitation forces under different movement speeds at the 11-, 12-, 15-, and 16-mm gap at
four working temperatures and at 35-mm FCH.