300 Ë 8 New progress of HTS Maglev vehicle
Fig. 8.40:Levitation (a) and guidance force (b) curves of the bulk levitation unit with and without
introducing iron plates on its surface.
the PMG. For the guidance forces (see Fig. 8.40b), there is some increase when adding
the iron plate. The maximum guidance force increases from 109.0 to 112.0 N when
a full iron plate is added on the bulk surface. However, it is not feasible to add a
full iron plate on the bulk surface considering the obvious decrease of the levitation
forces.
To find a suitable position to add the iron plate, the force behavior was investiga-
ted with an iron plate of the same size as one bulk sample at the two typical working
positions, i.e., above the field pole and in the middle of the PMG. It was found that
the attractive forces always exist at the two measured positions, but a stable guidance
force can be obtained only at the middle of the PMG. This stable guidance force will be
useful for practical applications, so in the following measurements, the influence of an
added iron plate on a bulk sample laid above the middle of the PMG was investigated
in the typical FC condition with the SCML-02 [35] (see Section 5.5).
When adding the iron plate on the bulk sample above the middle of the PMG,
the magnetic field distribution would be changed at the bulk position (see Fig. 8.41a).
The horizontal component of the magnetic field decreased obviously at the middle
of the PMG, while, the vertical component of the magnetic field increased at the two
field-pole positions (see Fig. 8.41b). As a result, the levitation forces and guidance
forces of the bulk also changed. As shown in Fig. 8.42a, there was also some decrease
of the levitation force when adding the iron plate. The maximum levitation force
at the minimum gap of 10 mm decreased from 92.1 to 78.7 N, decreasing by 14%.
However, for the guidance forces in Fig. 8.42b, the maximum guidance force increased
from−20.3 to−30.4 N, increasing by 50% at the maximum lateral displacement of
5 mm. These data meant that with a reasonable introduction position, the positive
benefit in the guidance forces brought by the ferromagnetic materials would sur-
pass the negative influence on the levitation forces. This method of introducing the