306 Ë 8 New progress of HTS Maglev vehicle
Fig. 8.49:Guidance forces of the seven-bulk levitation unit above the double-pole Halbach PMG
under ZFC and the 15-mm WH.
Fig. 8.44, was formed between the two peaks of the vertical magnetic field component.
At the same time, the three middle bulks just fell into the potential-well area. When
a lateral displacement on any side happened to the bulks in the potential-well, the
vertical magnetic field at the bulk position would be larger. According to Faraday’s
law of electromagnetic induction, the shielding current would be induced in the bulk
material, and a corresponding repulsive Lorentz force would result from the interac-
tion of induced current and the applied PMG field to resist the lateral displacement.
Thus, the levitation was stable. This was also the reason why more poles were effective
in enhancing he levitation stability [52]. This experiment indicated another way to
realize stable superconducting levitation beyond the FC condition by PMG design. It
is very attractive to use the potential-well field configuration to enhance the guidance
performance in the multi-pole PMG design.
As listed in Tabs. 8.6 and 8.7, the values of the dynamic parameters measured
in the vibration experiment procedure (see Section 8.2.1) are consistent with the
above quasi-static force research. The dynamic stiffness of the bulk unit is thought
to correlate with the quantity of trapped flux inside it. At lower FCH, higher trapped
flux can bring a bigger dynamic stiffness, which is a benefit to the HTS Maglev system.
At the same FCH, the dynamic stiffness of the bulk unit above the double-pole PMG
Tab. 8.6:Vertical and lateral dynamic stiffness above two PMGs at different FCHs.
FCH (mm) Dynamic stiffness in verticalkz(N/mm) Dynamic stiffness in lateralkx(N/mm)
Monopole PMG Double-pole PMG Monopole PMG Double-pole PMG
40 5.54 7.44 3.96 7.44
30 6.42 11.03 6.42 13.62
20 10.62 20.97 13.11 32.25