74 Ë 3 Magnetic levitation
It showed that three-dimensional analyses are more effective than two-dimensional
ones.
In general, the PMs in Maglev are the traditional ones, for example, NdFeB.
HTS PMs have much larger magnetic energy products than the traditional PMs and
may be better candidates for future Maglev applications. When the HTS bulk is
magnetized to a high magnetic field, part of this field is trapped in the bulk to
create the superconducting PM. The trapped magnetic field of the superconducting
bulk magnet has been reported to be better than that of a conventional PM (for
example, NdFeB). The maximum trapped fields were 16 T [76] (at 24 K) and 11.2 T
(at 47 K), and trapped fields of 9 T (at 46 K) and 17.24 T [77] (at 29 K) were recorded.
Even a large HTS bulk magnet is believed to trap a very high magnetic field of 5 T at
77 K [78].
Fujimoto et al. [79] describes a superconducting bulk magnet for a Maglev train
with liquid nitrogen refrigeration, instead of Nb-Ti superconducting racetrack coils
which require liquid helium as a coolant. If this is successful, it will have a great impact
on the future transport systems.
3.7 Normal-conductive Maglev
In 1934, Hermann Kemper was awarded a patent for a “monorail vehicle with no
wheels attached” [19]. This invention eventually led to the development of the Transra-
pid Maglev train program begun in 1969 in Germany and high-speed surface transport
(HSST) Maglev train program in Japan. This magnetic levitation is called the EMS. EMS
is achieved by the attraction forces between the electromagnet and the iron rail, and
stable levitation is produced by electromagnets with an active feedback loop. EMS
systems of the Transrapid in Germany and the HSST in Japan use on-board normal-
conductive magnets, and the EMS systems of AMT and MagneMotion in the USA use
on-board PMs (see Section 3.6).
In the EMS, vertical suspension, lateral guidance, and propulsion are achieved
without direct mechanical contact between the vehicle and guideway. Both vertical
suspension and lateral guidance are produced by attractive forces between on-board
normal conductive electromagnets and the steel rails. Control of both vertical and
lateral forces is achieved by checking the gap change and adjusting the corresponding
magnetic fields. This method is similar to that of conventional active control.
The EMS is a basic type of magnetic suspensions. The technology is mature
and has already begun trial operation and development. In the early 1970s, the
developments of EMS Maglev transportation technology began in Germany, Japan, the
USA, and Great Britain.
The first commercial automated EMS Maglev (Fig. 3.4) system in the world [81] was
a low-speed vehicle that ran from the airport terminal of Birmingham International
Airport to the nearby Birmingham International Railway Station in 1984. The length