4.2 LTS Maglev Ë 91small-scale current-carrying superconducting coils, placed near a large rotating disk.
Most of the experimental results were compared with exact calculations based upon
the general theory given by Miericke and Urankar [35, 36] for infinitely wide but
arbitrarily thick sheet tracks. The agreement between experiment and theory was
generally good. All numerical results based on these approximate formulae also
agreed well with the exact expressions (see Fig. 4.1) [35]. Iwasa [38] detailed the
various problems of EDS Maglev, including these theories referred to above.
Lift forceFLcan also be understood as the magnetic pressure between the magne-
tic field of the induced current and the superconducting magnet. Any magnetic field
has an associated magnetic pressurePBand is given by
PB=B
2
2 휇 0, (4.6)
i.e., the magnetic pressure is proportional to the square of magnetic field.
In addition to the above theoretical study, in the early 1970s, several groups
[39–42] in the USA began some experimental research work on the superconducting
Maglev. By the mid-1970s, the effort in the USA had ended with no implementation
of a Maglev system. Nearly 20 years after, the US Federal Railway Administration
Fig. 4.1:Comparison of experimental results of lift forcesFL, drag forcesFD, and speedvwith
theoretical values calculated with the exact and approximate equation [36]. The values were
calculated with the exact equation, whereas the values were calculated with approximate
equation. Experimental measurement results.