278 Ë 8 New progress of HTS Maglev vehicle
Fig. 8.20:Maximum levitation forces dependence on the working temperature under different FCHs.
were dependent on not only the temperature of the HTS but also the original FCH.
When the FCH was less than 20 mm, the vertical component of the magnetic field
at FCH was strong. The훿 0 of the HTSC was large enough to disturb the invasion
of the magnetic field, so the effect of the working temperature on the levitation
forces was ultra-weak at the low FCH. This implied that the original FCH of an
HTS Maglev system was the key parameter for the enhancement of the levitation
forces. When the levitation gap was more than 40 mm, the PMG magnetic field was
less than 0.1 T. TheJcof the HTSC bulk was high enough to disturb the invasion
of the PMG magnetic field, so the potential of the working temperature to increase
the levitation forces was very small in the low magnetic field. It implied the need
to have a relatively high magnetic field for the levitation enhancement of an HTS
Maglev vehicle in addition to considering the improvement effect of a low working
temperature.
In addition, multi-time measurements of the working temperature effect on the
levitation forces were explored and an estimate of the effect of passengers leaving or
boarding the HTS Maglev vehicle, resulting in an up-and-down (vertical) round trip
movement (change of working position) of the on-board superconductor bulk, was
considered. The experimental procedure was designed based on the deep cryogenic
measurement system (see Fig. 8.18) as follows. First, the deep cryogenic measurement
system was initialized with the midline of the ring-shaped YBCO bulk in accordance
with the peakBxline,x=0 mm, of the Halbch PMG. Then the guideway was moved
down and stopped at a height of 35 mm over the upper surface of the ring-shaped
YBCO bulk in the K535 Stirling cryocooler. When the temperature of the YBCO bulk
reached the pre-set value (63–77 K), the Halbach PMG was moved at a pre-speed. At
the same time, levitation forces were measured continuously three times under the
control of the SCML-01. Then the next set of levitation experiments were performed