Jia-Su Wang and Su-Yu Wang
4 Superconducting magnetic levitation
Superconducting technology has many advantages, such as being environment
friendly and energy efficient [1]. In the future field of energy, traffic, and information,
it is very competitive. In addition to the advantages of PM and normal conductive
Maglev, superconducting Maglev has new advantages, for example, more energy
savings, environmental protection, higher speed, especially the possibility of ultra-
high speed. The superconducting Maglev types, LTS and HTS Maglev, will be discussed
in this chapter. Various Maglev versions have different unique performance. In the
constant pursuit for the “perfect” Maglev transportation, the new HTS Maglev train
may be one of the best candidates.
4.1 Introduction
Powell and Danby [2, 3] are the inventors of the superconducting Maglev trans-
portation systems. They filed a patent application (No. 684775) of electromagnetic
inductive suspension and stabilization system for a ground vehicle on November 21,
1967, and the patent was granted (No. 3470828) on October 7, 1969. This magnetic levi-
tation is called the LTS Maglev. The time-varying magnetic fields induce eddy currents
in the conductors and create a mutually expulsive magnetic field. The time-varying
magnetic fields can be produced by moving a constant magnet. Their inventions,
including the inductive levitation and stabilization guideway, null flux geometry, and
the linear synchronous motor for vehicle propulsion, and this invention of the EDS
using LTS magnets is the basis for the 500-km/h LTS Maglev train line from Tokyo to
Osaka now under construction. Additional comments on the LTS EDS Maglev vehicle
can be found in Ref. [4].
In 1945, the stable levitation of a permanent magnet over a superconductor was
demonstrated first for a magnet above a concave lead (lowTcsuperconductor) disk by
Arkadiev [5, 6], at the University of Moscow.
For both diamagnetic materials [7, 8] and highTcsuperconductors [9, 10],
stable levitation is possible in static magnetic fields. It is really static (requires no
energy input), quiet, and extraordinarily stable, and it is called the unique self-
stable levitation. A high-Tcsuperconductor can be levitated either above or below a
permanent magnet.
The levitation of a NdFeB PM of volume 0.7 cm^3 above a disk of YBCO bulk
superconductor of 2.5 cm diameter and 0.6 cm thickness bathed in liquid nitrogen was
observed by Hellman et al. [9] Peter et al. [10] observed a very stable suspension of
YBCO samples in the magnetic field below the PM. Soon after, Brandt [11] presented
that a HTS bulk could realize stable levitation without any active control. The physical