98 Ë 4 Superconducting magnetic levitation
per pound. The HTS Maglev is the right choice that best meets the requirements
of reusable cold launch technology compared to other Maglev alternatives.4.5 HTS wire Maglev train
A cryogen-free HTS magnet has been developed in Japan. The magnet coil is wound
with HTS tape instead of Nb-Ti wire and it uses a conductive cooling method with
direct cooling by refrigeration [65]. Further reduction of operation cost will be expec-
ted when the HTS magnet replaces of the LTS magnet.
The R&D project for BSCCO HTS magnets has been in development for the
superconducting Maglev trains since 1999. In 2001, JR Central was entrusted with the
national project to develop of a trial HTS magnet that contains one “racetrack”-shaped
coil. The first trial HTS magnet can be cooled by a cryocooler, using a conduction
cooling method. The Ag-sheathed Bi2223 coil is connected with a HTS persistent
current switch and cooled by a pulse tube cryocooler below 20 K. The current decay
rate is 0.44%/day. This means that the HTS magnet can be operated virtually in the
persistent current mode for Maglev use [65]. Schematic view and appearance of HTS
magnet using Ag-sheathed Bi2223 coil for the EDS Maglev train in Japan is shown in
Figs. 4.6 and 4.7, respectively.
A second HTS magnet consisting of four persistent current HTS coils was
developed. The HTS coils were installed in a cryostat and cooled to approximately 15 K
by conduction cooling, using two sets of two-stage G-M-type pulse tube cryocoolers.
The HTS magnet was operated in a persistent current mode at a rated magneto-motive
force of 750 kAt which was the same as that used with LTS magnets. The running tests
were executed in the Maglev vehicle “Series L0” on the Yamanashi Maglev Test line,
with a top speed of 553 km/h achieved on December 2, 2005 [74, 75]. The running trial
Fig. 4.6:Schematic view of HTS magnet using Ag-sheathed Bi2223 coil of the EDS Maglev train in
Japan [65].