8.3 Methods to improve Maglev performances Ë 297Fig. 8.37:Levitation force curves of the bulk sample with horizontal or vertical laying modes
measured at the PMG middle and field-pole positions in the cases of ZFC (a) and 30 mm FCH (b).
In the ZFC case, the levitation force of two bulks with a vertical laying mode was
approximately 125.5 N× 2 =251.0 N at a measurement gap of 10 mm, which was larger
than 108.2 N for the horizontal laying mode. In the case of 30-mm FCH, the levitation
force of the vertical mode was 104.6 N× 2 =209.2 N, also larger than 92.1 N in the
horizontal mode. Moreover, the estimated levitation force by a vertical mode was
also larger than that when the bulk is put horizontally above the field-pole of the
PMG. These results indicated that by adopting a vertical bulk-laying mode at the
middle of the PMG, the levitation forces of the bulk could be improved significantly,
because in such mode, the induced current in thea-bplane could interact with
the horizontal component of the applied magnetic field efficiently, as shown in
Fig. 8.36b.
Next, the stability (guidance force) of the bulk sample with different laying modes
at the two measurement positions was compared. Figure 8.38 shows the guidance
force curves of the bulk sample with different laying modes measured at the PMG
middle and field-pole positions at the 30-mm FCH. All guidance force curves exhibited
the stable feature of a levitation system. It notes that when the bulk was laid at the
field-pole position, the magnetic field at the two sides of the measurement position
was asymmetric. Correspondingly, the guidance force curves measured above the
field-pole position were not symmetric either. When the bulk was put horizontally, the
maximum guidance force was obtained at the middle of the PMG, and the minimum
at the field-pole position. When the bulk was laid vertically, it was just reversed.
The maximum guidance force at the field-pole position was larger than that at the
middle of the PMG. These results were consistent with the former conclusions, i.e.
the horizontal bulk-laying mode can generate the maximum guidance force at the
middle of the PMG. Meantime, it was implied that the stability of the levitation system
can be improved by changing the horizontal bulk-laying mode to the vertical mode at
the field-pole position. At the maximum lateral displacement of 5 mm, the maximum
guidance force increased from−3.4 to−17.3 N when changing the horizontal bulk