7.6 Three-dimensional modeling and simulations Ë 253Fig. 7.22:Changing curves of the levitation forces on the HTSCs at position of 5, 10, 15, and 20 mm
above Rail_A (a) and Rail_B (b) with the growth of the width ratio. The width ratio is replaced by an
order and the corresponding relationship between the width ratio and the order (abscissa) is given
in Tab. 7.5.
For the case of vertical movement, 21 different width ratios from zero to infinity are
considered and the changing curves of the levitation forces along with the width ratio
at position of 5, 10, 15, and 20 mm above Rail_A and Rail_B are shown in Figs. 7.22a
and b, respectively. Note that the extreme case with a width ratio of zero or infinity
denotes that Halbach structure disappears and PMs employed in the PMG only have
one magnetized direction (vertical or horizontal). Both Figs. 7.22a and b display that