8.3 Methods to improve Maglev performances Ë 281small, 20 times smaller than that at 25 mm, and the influence of the bulk’s movement
speed on the levitation forces was very small at any temperature.
Hence, if more magnetic energy with strong field and a lower temperature con-
dition are utilized, the enhanced of levitation performance will directly promote the
development of HTS Maglev vehicle applications.
8.3 Methods to improve Maglev performances
8.3.1Pre-loading method
The pre-load method is an effective improvement to suppress the levitation height and
force decay and enhance the stability of the HTS Maglev vehicle system. The typical
pre-load execution steps include:
- Lower the levitation height of the on-board HTS bulks after the FC initialization
by adding additional load or other ways. - Keep the levitation system, including the on-board HTS bulk, staying at this above
lower levitation position for some time. - Release the levitation system to the working height before running.
Finally, it will be found that better Maglev performance could be obtained for HTS
Maglev vehicle application. As to the pre-load method, because more magnetic flux
is trapped at a lower height (larger applied magnetic field) than at the working height
before any movement, the magnetism of the HTS bulk is enhanced during vertical
movement and the probability of the HTS bulk to trap more magnetic flux during
lateral movement is reduced. That is why the pre-load method can suppress not only
the levitation forces decay but also the guidance force decay.
The following implementation of the pre-load method was applied to the scaled
HTS Maglev vehicle model (see Fig. 8.1 and Section 8.2.1) before running to verify
the improvement effect on the levitation stability of the HTS Maglev vehicle system.
Figure 8.23 shows the schematic procedures for the pre-load method carried on HTS
Maglev vehicle.
The pre-load was added to the vehicle step by step, with 10 kg every time. The new
WH was measured after each loading as shown in Fig. 8.24. The maximal pre-load was
set at 130 kg due to an ideal acceptable levitation height from 10 mm to 15 mm for the
HTS Maglev vehicle. Then unloaded the vehicle model, so that it returned to a new
equilibrium position. Figure 8.24 shows that the levitation height linearly decreased
with the increase of the load. The slope of the curve after the pre-load was smaller
than that before the pre-load. It indicated that the HTS Maglev vehicle was an elastic
system, so that an elastic restoring force would act when the vehicle is pulled down
or up. However, the restoring force was limited, and the vehicle would not return to
the original position if the load was too big. The levitation height reduced by 8 mm