8.3 Methods to improve Maglev performances Ë 293Fig. 8.35:Levitation (a) and guidance force curves (b) of the individual and double-layer of HTS bulk
levitation unit above the PMG in 30-mm FCH conditions.
by adding the upper-layer HTS bulk so that the double-layer HTS bulk levitation unit
obtained the biggest levitation force at the smallest gap.
In the 30-mm FCH condition, the profiles of levitation force curves in Fig. 8.35a
are similar to those of the ZFC case in Fig. 8.34. Only the maximum levitation forces
at the smallest gap showed some decrease due to the trapped flux in the FC case.
The double-layer HTS bulk levitation unit still obtained the biggest levitation force
at the smallest gap in the FC case, followed by the lower layer and then the upper
layer. The guidance force curves in 30-mm FCH cases, shown in Fig. 8.35b, exhibited
the stable levitation feature, i.e. a restoring force would be generated against any
displacements to either side [4]. The maximum guidance force was found at the
maximum lateral displacement of 10 mm. In the figure, the guidance force curves of
the lower-layer and double-layer HTS bulk were very close to each other and showed
some improvement in the latter. As the measurement height of the upper-layer HTS
bulk was 28 mm due to the thickness of the lower-layer HTS bulk, the guidance forces
of the upper levitation unit were obviously smaller than the other two.
To compare quantitatively, Tab. 8.3 shows the maximum levitation forces and gui-
dance forces of the individual and double-layer of HTS bulk levitation unit above the
Tab. 8.3:Maximum levitation forces of the individual and double-layer of HTS bulk levitation unit
above the PMG at the smallest gap of 6 mm.
Conditions Upper Lower Sum.a Double- Double Upper
layer layer layer increase.b eflciencyc
ZFC FLevd(N) 239 690 929 870 26.1% 75.3%
FC FLev(N) 200 587 787 701 19.4% 57.0%
aSum=Upper layer+Lower layer;bDouble increase=(Double-layer−Lower layer)/Lower layer;c
Upper eflciency=(Double-layer−Lower layer)/Upper layer;dFLevis levitation force.