304 Ë 8 New progress of HTS Maglev vehicle
Fig. 8.46:Levitation stiffness comparison of the levitation unit above two PMGs under the
30-mm FCH.
Fig. 8.47:Guidance force comparison of the levitation unit above two PMGs under the 30-mm FCH
and 15-mm WH.
close and even cross each other. That is, the double-pole Halbach PMG did not have
an advantage over the monopole PMG at large levitation gap.
For HTS levitation system, the guidance forces are used to evaluate whether
the system is stable in the lateral direction and determine its restoring capability.
Figure 8.47 shows the guidance force comparison of a seven-bulk levitation unit above
two PMGs at the 30-mm FCH and 15-mm MH. Due to the field cooling condition, the two
guidance force curves both imply a stable Maglev system where a restoring force was
generated against lateral displacement. The bulk unit above the double-pole Halbach
PMG had a better guidance performance and bigger hysteresis loop than that above
the monopole PMG. At the maximum lateral displacement of−10 mm, the maximum
guidance force was 47.0 and 21.1 N, respectively, for the two PMGs. The guidance force
ratio was 2.2, which was larger than the levitation force ratio. Figure 8.48 shows