10.4 Prototypes of HTS Maglev launch system Ë 375Another HTS Maglev assist launch system was demonstrated by Yang et al., at
Beihang University (BUAA) [20]. The PMG of BUAA had a different configuration from
that of ASCLab. It consisted of three PMs with opposite directions two iron plates. The
maximum field values for these two iron plates were up to−1.5 T and 1.5 T respectively.
The configuration of three PMs with opposite directions also brought a great lateral
magnetic gradient which benefits the lateral stability of HTS Maglev system.
The entire PMG of BUAA was 10.05 m long and 0.68 m wide. The propulsion system
was a linear induction motor (LIM), which is set between these two PMGs. The LIM
consisted of 15 segments with the total length 10.4 m. The LIM was automatically
controlled and could switch quickly between the acceleration and deceleration state.
By the control of input current, the acceleration of the linear motor could be adjusted
to be 1–4g.
The vehicle of HTS Maglev launch system was 1.0 m long and 1.0 m wide. The
launch vehicle contained four levitation cryostats with 36 YBCO bulks fixed inside.
The YBCO bulk had a diameter of 30 mm and thickness of 18 mm. At a levitation gap
of 15 mm, the total levitation force of the launch vehicle was 422 N and 743 N, at FCH of
30 mm and ZFC, respectively. At the levitation gap of 10 mm, the total levitation force
of the launch vehicle was 743 N and 1097 N, at FCH of 30 mm and ZFC, respectively. At
FCH of 35 mm, the total guidance force of the launch vehicle was 66 N and 86 N, at the
levitation gap of 15 mm and 10 mm, respectively. The vehicle of the HTS Maglev launch
system had a weight of 140 kg, which could reach a levitation gap of 6 mm at the 35 mm
FCH. The maximal lateral force of the launch vehicle was 150 N at the levitation gap of
6 mm and the lateral displacement of 5 mm.
The group of Yang studied the effect of the FCH and the load weight on the
dynamic force properties of a HTS Maglev system, including the resonant frequency
and the stiffness in both horizontal and vertical vibrations [21]. Experimental results
showed that the resonant frequency increased with decrease of the FCH or the load
weight. At the 25-mm FCH, the resonant frequency approached a maximum value of
10 Hz. The analyses and discussions showed that the dynamic properties of the test
vehicle were closely related to the motion process and the flux history in the super-
conductors. The effectiveness of lower FCH and preloading method to increase the
dynamic stability of HTS Maglev system was tested and verified by this group.
Yang’s group also investigated the damping properties of the HTS Maglev launch
system at different operation conditions [22]. The experimental results showed a weak
damping behavior of the HTS Maglev vehicle, and indicated that the damping of the
Maglev vehicle was almost unaffected by the trapped flux of the bulks HTSC. The
analyses indicated that the weak damping behavior of the HTS Maglev system derived
from the strong flux pinning ability of the melt-textured bulk HTSC. In practical
applications, it is better to introduce an additional damping device to increase the
operation stability of the HTS Maglev system.
Although the muzzle velocities of the HTS Maglev launch test systems at the
ASC Lab and BUAA are not very high, the basic application characteristics have