302 Ë 8 New progress of HTS Maglev vehicle
Fig. 8.43:Schematic diagram of a new HTS Maglev design using thec-axis direction of bulk
superconductors and iron introduction for better guidance performance.
8.4 Some developed designs of the HTS Maglev vehicle system
8.4.1Multi-pole PM guideway structure
The monopole PMG is most popular in HTS Maglev vehicle systems [5–15]. The most
popular structure, similar to the “Century” PMG, is that of two PMs with opposite
horizontal magnetization direction connected by a flux-concentration iron with a
single peak in the vertical component of magnetic field. However, an axially symmetric
HTS magnetic bearing with only a 200-mm diameter realized about 1-ton load in two
representative applications [49, 50]. It is reasonable to believe that high load capability
of the axially symmetric HTS bearing is mainly due to the PM rotor structure [49–51].
In the general HTS-bearing design, the PM rotor is composed of multi-pole PMs for
larger force stiffness because one pole can create one higher magnetic field region.
More poles are effective in enhancing the stability [52]. Application of the multi-pole
magnetic field to the HTS Maglev PMG design, the expected to be improved is efficiency
under the same PM material cost through the reasonable design and arrangement of
HTS bulk.
Figure 8.44 illustrates a double-pole PMG with Halbach array that is designed and
fabricated to verify its improved capability for use in a HTS Maglev vehicle system. Two
vertical magnetic field peaks appear at the two poles. In comparison, the double-pole
Halbach PMG has nearly the same PM cross-section area of a traditional monopole
PMG, 3900 mm^2 and 4000 mm^2 , respectively. More details about the two PMGs can be
found in Ref. 25.
Figure 8.45 shows the levitation force comparison of this unit above two PMGs at
the 30-mm FCH. The bulk unit with the double-pole Halbach PMG had a bigger levi-
tation force and hysteresis loop than the traditional monopole PMG. At the smallest
gap of 7 mm, the maximal levitation force was 231.5 N for the former, which was 1.73
times larger than that of the latter, 133.7 N. The bigger force and hysteresis indicated
that the double-pole Halbach PMG produces a better magnetic field distribution at
the interacting range with the bulk. In Fig. 8.44, it shows that the average magnetic