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Adjustable Speed Drive
Armature
Ball Bearing Motor
Brush
Brushed DC Motor
Brushless DC Motor
Commutator
DC motor
Direct Torque Control
Direct on Line Starter
Doubly-fed machine
ESC
Electrostatic Motor
Enameled Wire
Induction Motor
Inverter AC/DC
Linear Motor
Lynch Motor
Motor Controllers
Motor Soft Starter
Outrunner
Parvalux
Piezoelectric Motor
Repulsion motor
Shaded Pole Motor
Slip Ring
Squirrel-Cage Rotor
Stepper Motor
Traction Motor
Ultrasonic Motor
Vibrators
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Linear Motors
Many designs have been
put forward for linear motors, falling into two major categories,
low-acceleration and high-acceleration linear motors. Low-acceleration
linear motors are suitable for maglev trains and other ground-based
transportation applications.
High-acceleration linear motors are normally quite short, and are
designed to accelerate an object up to a very high speed and then
release the object. They are usually used for studies of hypervelocity
collisions, as weapons, or as mass drivers for spacecraft propulsion.
The high-acceleration motors are usually of the linear induction
design (LIM) with an active three-phase winding on one side of the
air-gap and a passive conductor plate on the other side.
The low-acceleration, high speed and high power motors are usually of
the linear synchronous design (LSM), with an active winding on one
side of the air-gap and an array of alternate-pole magnets on the
other side. These magnets can be permanent magnets or energized
magnets. The Transrapid Shangai motor is an LSM.
High-acceleration linear motors have been suggested for a number of
uses. They have been considered for use as weapons, since current
armor-piercing ammunition tends to consist of small rounds with very
high kinetic energy, for which just such motors are suitable. Many
amusement park roller coasters now use linear induction motors to
propel the train at a high speed, as an alternative to using a lift
hill.
The United States Navy is also using linear induction motors in the
Electromagnetic Aircraft Launch System that will replace traditional
steam catapults on future aircraft carriers. They have also been
suggested for use in spacecraft propulsion. In this context they are
usually called mass drivers. The simplest way to use mass drivers for
spacecraft propulsion would be to build a large mass driver that can
accelerate cargo up to escape velocity.
High-acceleration linear motors are difficult to design for a number
of reasons. They require large amounts of energy in very short periods
of time. One rocket launcher design calls for 300 GJ for each launch
in the space of less than a second. Normal electrical generators are
not designed for this kind of load, but short-term electrical energy
storage methods can be used.
Capacitors are bulky and expensive but can supply large amounts of
energy quickly. Homopolar generators can be used to convert the
kinetic energy of a flywheel into electric energy very rapidly.
High-acceleration linear motors also require very strong magnetic
fields; in fact, the magnetic fields are often too strong to permit
the use of superconductors. However, with careful design this need not
be a major problem.
Two different basic designs have been invented for high-acceleration
linear motors: railguns and coilguns.
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