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Sometimes referred to as a linear induction motor, the linear motor is a motor device that functions with the use of a multi-phase alternating current. As part of the design for the motor, the stator is in an unrolled position. This makes it possible for the linear motor to produce linear force along the length of the stator rather than the more common approach of producing rotation or torque.
Linear motors are usually classified as either low acceleration or high acceleration models. The low acceleration model works well for many ground transportation methods, such as with the use of commuter trains. In contrast, a high acceleration linear motor is ideal for locomotion that is not strictly considered ground transportation. The range of a high acceleration linear motor would include such entertainment devices as a roller coaster, as well as motors designed to aid in propelling spacecraft through the atmosphere of the earth and into open space.
The concept of electric drive linear motors actually precedes the invention of the automobile. The first designs for a working linear motor are attributed to Charles Wheatstone. Developed in the early 1840’s while Wheatstone was associated with King’s College in London, the model was workable but generally considered impractical for mass production.
Further technological advances in the 20th century made the idea of a linear motor for general usage more practical. During the first half of the century, designs were patented in the United States, the United Kingdom, Germany, and Japan. Along with use in transportation, the linear motor also proved to be workable in mining situations, as well as some manufacturing environments. The invention of a Lorentz-type actuator helped to broaden the usability and appeal of the linear motor as the century progressed.
Today, the linear motor is utilized as a matter of course in a number of settings. Aircraft commonly make use of the motor. In like manner, the motor is used with large aircraft carriers. Many companies around the world make use of the motor in digging operations, as well as some factory work. Even military weaponry may involve the use of a linear motor as part of the design.