286 Ë 8 New progress of HTS Maglev vehicle
Fig. 8.27:Maximum trapped flux density dependence on the external static magnetization field
density of the Lakeshore electromagnet.
power supply (Model 647, Lakeshore) to magnetize a cylindrical melt-processed
YBCO superconductor withc-axis oriented grain with 30 mm in diameter and 18 mm
height.
In the inset of Fig. 8.27, the arrow shows the magnetization direction which
was parallel to thec-axis direction of the YBCO sample for obtaining a better HTS
bulk magnet based on theJcanisotropy of the YBCO superconductor. The maximum
trapped field at the surface of the bulk was measured by a Lakeshore low-temperature
Hall probe and a Lakeshore model 450 gauss meter. Every magnetic measurement
was conducted after 15 minutes when the magnetization was completed according
to IEC 61788–9: 2005. In such static magnetization, the maximum external static ma-
gnetization field could be up to 0.836 T, and the maximum surface trapped field of the
YBCO HTSCM was 0.620 T when the distance between the two electromagnet poles was
55 mm with a small LN2 cryostat just clamped between the poles. Figure 8.27 shows
that the maximum trapped field of the YBCO HTSCM increased approximately linearly
with the external magnetization field, and that the magnetization ratio was around
77.8% for this YBCO superconductor in the static magnetization field environment.
That was higher than after a pulsed-field magnetization.
More specific levitation performance of the HTS bulk magnet was further inves-
tigated over the Halbach PMG [25] (see Section 8.4.1). Both levitation and guidance
forces, two important levitation parameters of the HTS Maglev vehicle system, were
measured in the SCML-02 [35] (see Section 5.5). During the experiments, the levitation
force measurement was conducted after the guidance force measurement. It aimed
to avoid the PMG magnetic field affecting the original trapped field in the HTS bulk