10.7 Studies on HTS linear induction motors Ë 383Fig. 10.9:Schematic arrangement of the high-temperature superconductor (HTS) above the 3-phase
copper windings [30].
respectively. The magnetic field along they-axis is approximately to zero due to the
sample symmetry and the direction of travel of the magnetic waves. The space-phase훼
component does not contribute in our case since the sample was fixed during the static
force measurements. Hence, the static vertical and thrust forces between the HTS
magnet and the traveling magnetic field were only dependent on the time-phase훽.
Figure 10.9 shows the schematic arrangement of the high-temperature superconductor
(HTS) above the 3-phase copper windings at a working gap.
10.7 Studies on HTS linear induction motors
LIMs are mostly used for rapid acceleration systems, when large thrust output is
needed in short time, such as roller coaster rides or the recently developed EMALS
(Electromagnetic Aircraft Launching System) system that can launch a 45-ton aircraft
to over 200 km/h on a 91-m runway [31]. To Launch heavy items into orbit such as
satellites, rockets and spacecraft, a magnetic launching system will be a cleaner
and safer alternative compared with the conventional launching method of burning
rocket fuel. It has been estimated that the cost of launching a rocket into orbit can be
decreased by tenfold if an LIM launching system is employed. Magnetic launchers are
also reusable and can be modified to launch different types of projectiles.
One of the simplest designs of an LIM involve the use of a series of flat, racetrack-
shaped copper wire coils wound on a ferromagnetic armature acting as the primary
and a conducting plate as the secondary [32]. As alternating current passes through
the copper wire in the primary, an alternating magnetic field is generated to induce
currents inside the secondary conducting plate. The induced currents (eddy currents)
have an associated magnetic field that interacts with the magnetic field generated by
the primary creating large forces along the direction of the traveling magnetic field
of the primary. Thus, if the secondary can move freely only along the direction of the
traveling magnetic field, then the secondary can act as a vehicle to launch projectiles.