254 Ë 7 Numerical simulations of HTS Maglev
Fig. 7.23:Changing curve of the guidance forces on HTSCs at a lateral displacement of 6 mm with
the growth of the width ratio. The corresponding relationship between the width ratio and the order
(abscissa) can be found in Tab. 7.5. The total number of width ratios considered in this calculation is
reduced and thus the order starts at 6 and ends at 16.
the levitation forces at all positions, increases with the growth of the width ratio,
and reaches a maximum value when the width ratio is∼0.83 for Rail_A and is∼ 1
for Rail_B and then drops with continuous growth of the width ratio. This finding
indicates that the Halbach array has a better performance because the levitation
forces in the extreme case are always the smallest as has been verified by experiment.
On the other hand, the optimized structure for Rail_A is that the width of the PMs
magnetized in the horizontal direction is slightly larger than those magnetized in
vertical direction, but for Rail_B, the two types of PMs have an identical width
ratio.
For the case of transverse movement, only 11 different width ratios around 1 are
considered because a larger levitation force can be obtained in this range according
to the above computed results of levitation forces. The HTSCs have an FC height of
12 mm and then are driven transversely at the same height with a maximum lateral
displacement of 6 mm. Fig. 7.23 presents the guidance forces with respect to the width
ratio for Rail_A and Rail_B. We can find from this figure that the guidance forces
exhibit the same tendency with the growth of the width ratio as that found in the case
of the levitation forces, but the width ratio where the largest guidance force occurs is
found to be 1.22–1.5 for Rail_A and is still∼1 for Rail_B.
As a whole, this suggests that for the Halbach array as the PMG to the HTS Maglev
vehicle, the optimized width ratio between the vertical and transverse magnetized
PMs is∼1.