6.5 Levitation forces vs. temperature Ë 161Tab. 6.5:Levitation stiffness at a gap of 20 mm with the FC height of 40 mm [29].
Displacement (mm) Stiffness (N/mm) Displacement (mm) Stiffness (N/mm)
0 2.29 50 0.32
5 2.21 55 0.37
10 1.76 60 0.45
15 1.29 65 0.55
20 0.98 70 0.69
25 0.64 75 0.74
30 0.48 80 0.76
35 0.38 85 0.71
40 0.35 90 0.58
45 0.34 95 0.38the levitation height when the load varies on the suspended carrier. When the load
changes in the Maglev system, bigger levitation stiffness corresponds to a smaller
change of the levitation height.
Generally, levitation force and stiffness at an operation gap of 20 mm is
essential for the practical operation of the vehicle “Century”. Song et al. [29]
measured the minor loops upon the major hysteresis loop from the gap of 22–18 mm
in field cooling (FC). The rectangle-shaped single-domain melt-textured bulk
(30×35.6×15.5 mm) was fabricated by IFW. According to the minor loops upon the
major hysteresis loop, the levitation stiffness in both symmetrical and unsymmetrical
applied field was calculated. The associated levitation stiffness in the descending and
ascending processes (from 22 mm to 18 mm and back to 22 mm) of minor loops were
2.63 and 2.75 N/mm, respectively. These in the descending and ascending processes of
the major loop (from 22 to 18 mm and back to 22 mm again) were 2.28 and 2.18 N/mm.
For the same minor loop, the stiffness in the descending process was slightly different
from the stiffness for the ascending process. The stiffness upon the descending process
of the major hysteresis loop was larger than that in the ascending process of the
major hysteresis loop. The levitation stiffness was measured with the HTS Maglev
measurement system (see Section 5.3).
Table 6.5 lists the levitation stiffness of the rectangular bulk at a gap of 20 mm
with the FC height of 40 mm. Figure 6.10 shows the levitation force versus gap for the
rectangle bulk at a displacement of 5 mm.
6.5 Levitation forces vs. temperature [30–32]
In order to study the influence of temperature on levitation force, Jiang et al. [30] desi-
gned a test device (Fig. 6.11) using the GM refrigerator in the HTS Maglev measurement
system SCML-01 (see Section 5.3), and they compiled a temperature control program.