292 Ë 8 New progress of HTS Maglev vehicle
Fig. 8.33:Schematic diagram of the double-layer
HTS bulk array with a width of 32 mm×4 and a
height of 13 mm×2 working above the applied
Halbach PMG.adding a new bulk layer. In this section, the performance improvement from adding
a new layer of HTS bulk above the original on-board HTS bulk is examined. It is
reasonable to believe that some flux can go through and be trapped by pinning centers
of the new upper bulk layer based on the following exploration.
As shown in Fig. 8.33, eight HTS bulk samples were used to investigate the
Maglev performance of the double-layered HTS bulk array. Either layer of HTS bulk
levitation unit was composed of four bulk samples, denoted as the upper and lower
layers, respectively, where the upper layer of four HTS bulks were directly put at the
upper surface of the lower layer. Both ZFC and FC conditions were performed on the
double-layer HTS bulk in the experiments. In the FC condition, a representative FCH of
30 mm was chosen. After about 20 minutes, when the bulks were cooled completely,
levitation and guidance forces between the HTS bulk levitation unit and the PMG were
measured by the SCML-01 [26]. It should be noticed that the smallest measurement
gap was 6 mm for the lower-layer HTS bulk, while it was 19 mm for the upper-layer
HTS bulk due to the thickness of the lower-layer HTS bulk.
In the ZFC condition (Fig. 8.34), the levitation force curves of the individual and
double-layer of HTS bulk levitation unit above the PMG were a big hysteresis loop
composed of two branches, descending and ascending. The levitation forces showed
an approximate exponential increase with the decrease of the levitation gap, and
reached a maximum value at the lowest measurement gap. It was observed that the
levitation capability of the single-layer HTS bulk levitation unit had been improved
Fig. 8.34:Levitation forces of the individual
and double-layer of the HTS bulk levitation
unit above the PMG in ZFC conditions.