6.9 Influence of HTS bulk geometry on the properties Ë 177Tab. 6.8:Parameters and levitation forces over the PMG in ZFC at 77 K and different gaps [42].
Sample No. Sample 1 Sample 2 Sample 3
Diameter (mm) 3.0 3.5 4.0
Weight (g) 77.6 101.4 133.2
Height (mm) 17.5 18.6 19.1
F 5 (N) 103.0 134.5 175.0
F 10 (N) 72.8 97.0 129.5
F 15 (N) 50.4 69.2 92.9
F 20 (N) 35.5 49.5 67.5
Fig. 6.30:Levitation forces over the NdFeB PMG of sampled 1, 2, and 3 vs. gap in ZFC at 77 K [42].
better, since the larger shielding current area gives the greater levitation force. The test
results for the levitation forces of 30 and 26 mm diameter showed that the levitation
force on the 30-mm diameter was much larger than that of the 26-mm diameter
one. The batch preparation of HTS bulks of diameter larger than that of 30 mm
was difficult when “Century” was developed. Therefore, we selected the sample of
diameter 30 mm.
Ren [43] researched the influence of HTS bulk size on the guidance force. In
order to study the influence of HTS bulk size on the guidance forces, three different
cylindrical samples with different diameters (Tab. 6.9) were used in the experiment.
The field cooling height and the measured height was 15 mm. The maximum lateral
displacement was 20 mm, and the sampling interval was 1 mm. The guidance forces
were measured at 77 K with the HTS Maglev measurement system SCML-01.