228 Ë 7 Numerical simulations of HTS Maglev
Fig. 7.3:Cross-sectional distribution of the current in the HTSC in symmetrical applied field with
levitation gap of 5 mm drawn in 3D (a) and 2D (b) views.
The magnetic forces generated by the interaction between the induced current and
the external magnetic field of PMG are calculated by the Lorentz equation,
F=XJ×BdV. (7.44)7.5.1.2Example of applications
Assuming a HTSC with 30 mm in width and 15 mm in height, numerical simulations
using this method have been performed by quadratic programming [5].
When the HTSC is centrally above the PMG, the applied magnetic field is sym-
metrical about the axis of the HTSC. Once the HTSC is off the central position, the
applied magnetic field will become asymmetrical. Supposing the HTSC is subjected to
a ZFC condition at a position of 130 mm above the PMG, Figs 7.3 and 7.4 present the
current distribution on the vertical cross section inx-yplane (the infinite direction
is on thez-axis in thesedrawings) when the HTSC moves to the height of 5 mm, i.e.
the smallest levitation gap. As shown in Fig. 7.3, the current distribution is anti-
symmetrical about the center plane of the HTSC in the symmetrical applied field.
However, the current distribution becomes asymmetrical when a lateral displacement
of 30 mm is applied to the HTSC, resulting from the titled field in asymmetrical applied
field as depicted in Fig. 7.4.
Figures 7.5 and 7.6 compare the calculated and experimental levitation forces in
both symmetrical and asymmetrical applied fields. The details of the measurement
rigs used in the experiment have been described in Section 5.3. The sample of HTSC
had a dimension of 36 mm in length, 30 mm in width and 15 mm in thickness. After
the sample was cooled in liquid nitrogen with the absence of the magnetic field, the
levitation forces were collected real-time while the sample was moved from 130 mm