7.5 Two-dimensional modelings and simulations Ë 229Fig. 7.4:Cross-sectional distribution of current in the HTSC in asymmetrical applied field with
levitation gap of 5 mm and lateral displacement of 30 mm drawn in 3D (a) and 2D (b) views.
Fig. 7.5:Comparison between the calculated and experimental levitation forces as functions of
levitation gap in the symmetrical field. Levitation force curve using actual (a) and normalized (b)
data.
to 5 mm above the PMG and went back to the original position. When the sample
vertically moved centrally above the PMG, the applied field was symmetrical and the
relationship between the levitation force and gap was approximately linear. Once the
HTSC sample was off, the center plane, the applied field became asymmetrical.
The difference between two levitation force curves in the symmetrical and asymme-
trical fields was obvious. In an asymmetrical applied field, the descending part of the
hysteresis curve was convex [6].
We have two cases for the use of the critical exponential description to take the
field-dependent properties of critical current density into account: without and with
the angle dependence (details can be found in Ref. 6). There are differences between