Engines with low acceleration

The first development of electric linear motors dates back to 1840, with the work of Charles Wheatstone at King's College in London,[1] but Wheatstone's model was very inefficient which made it impractical. A possible linear induction motor is described in US patent US 782312 (1905 - inventor Alfred Zehden of Frankfurt-am-Main), for moving trains or elevators. The German engineer Hermann Kemper built a working model in 1935.[2] In the late 1940s Professor Eric Laithwaite of Imperial College in London developed the first full-scale working model. In a single-sided version the magnetic repulsive forces push the conductor away from the stator, making it levitate, and moving it in the direction of the moving magnetic field. These versions were later called the "magnetic river").

Because of these characteristics, linear motors have often been used for magnetic levitation (maglev) propulsion of railways, such as in the Japanese Linimo maglev train near Nagoya. However, linear motors have been used independently of magnetic levitation, such as in Bombardier's Advanced Rapid Transit systems and in several modern Japanese subways including the Toei Oedo line in Tokyo.

A similar technology, although with some modifications, is used in some roller coasters, but currently it is still little used in urban trams, although this would be possible to implement if the linear motor were located in a duct hidden in a slot in the pavement.

In addition to public transportation, the use of vertical linear motors has been proposed for climbing devices in deep mines, and the use of linear motors is growing for motion control devices. They are often used in sliding doors, such as those found on low-floor trams such as the Citadis and Eurotram. There are also dual-axis linear motors. These specialized devices have been used to enable direct X-Y travel for fabric and metal plate cutting using precision lasers, automated drawing, and cable assembly. The most used linear motors are the LIM (linear induction motor) and the LSM (linear synchronous motor). DC linear motors are not used since their cost is higher and linear SRMs have low power.

Engines with high acceleration

The use of high acceleration linear motors has been proposed for several applications.

They have been evaluated for use in weapons to propel projectiles, since current armor-piercing "AP (ammunition)" munitions consist of small projectiles with very high kinetic energy, for which these motors are suitable. Many amusement park roller coasters now use linear induction motors to propel the train at high speed, as an alternative to lifting the train by mechanical means at the start of the ride. The US Navy also uses linear induction motors in the Electromagnetic Aircraft Launch System, which will replace traditional steam catapults on aircraft carriers. Its use has also been proposed for spacecraft propulsion. In this context they are called mass drivers. The simplest way to use mass drives for spacecraft propulsion is to build a large mass drive capable of accelerating cargo to escape velocity, although launching a reusable launch system (RLV) such as StarTram into low Earth orbit has also been considered.

High acceleration linear motors are difficult to design for a variety of reasons. These engines require releasing large amounts of energy for very short periods of time. The design of a rocket launcher[3]​ requires 300 Giga Joules in each launch into space in a period of time less than 1 second. Normal electrical generators cannot cope with this type of demand, but it is possible to use quick release electrical energy storage methods. Capacitors are bulky and expensive but can deliver large amounts of power quickly. Homopolar generators" can be used to rapidly convert the kinetic energy of a flywheel into electrical energy. High-acceleration linear motors also require very high magnetic fields; the magnetic fields are often too strong for superconductors to be possible. However, through proper design, this can be solved.

There are two basic designs for high acceleration linear motors: railguns and coilguns.

The operation of the railgun is based on the principle of the homopolar motor: a pair of parallel conductors (the rails) are powered by an electric current. The projectile is placed making contact with both, to close the circuit. The current that is produced interacts with the strong magnetic fields generated by the passage of electricity through the conductors and this accelerates the projectile linearly in the direction of the rails.

Engines with low acceleration

The first development of electric linear motors dates back to 1840, with the work of Charles Wheatstone at King's College in London,[1] but Wheatstone's model was very inefficient which made it impractical. A possible linear induction motor is described in US patent US 782312 (1905 - inventor Alfred Zehden of Frankfurt-am-Main), for moving trains or elevators. The German engineer Hermann Kemper built a working model in 1935.[2] In the late 1940s Professor Eric Laithwaite of Imperial College in London developed the first full-scale working model. In a single-sided version the magnetic repulsive forces push the conductor away from the stator, making it levitate, and moving it in the direction of the moving magnetic field. These versions were later called the "magnetic river").

Because of these characteristics, linear motors have often been used for magnetic levitation (maglev) propulsion of railways, such as in the Japanese Linimo maglev train near Nagoya. However, linear motors have been used independently of magnetic levitation, such as in Bombardier's Advanced Rapid Transit systems and in several modern Japanese subways including the Toei Oedo line in Tokyo.

A similar technology, although with some modifications, is used in some roller coasters, but currently it is still little used in urban trams, although this would be possible to implement if the linear motor were located in a duct hidden in a slot in the pavement.

In addition to public transportation, the use of vertical linear motors has been proposed for climbing devices in deep mines, and the use of linear motors is growing for motion control devices. They are often used in sliding doors, such as those found on low-floor trams such as the Citadis and Eurotram. There are also dual-axis linear motors. These specialized devices have been used to enable direct X-Y travel for fabric and metal plate cutting using precision lasers, automated drawing, and cable assembly. The most used linear motors are the LIM (linear induction motor) and the LSM (linear synchronous motor). DC linear motors are not used since their cost is higher and linear SRMs have low power.

Engines with high acceleration

The use of high acceleration linear motors has been proposed for several applications.

They have been evaluated for use in weapons to propel projectiles, since current armor-piercing "AP (ammunition)" munitions consist of small projectiles with very high kinetic energy, for which these motors are suitable. Many amusement park roller coasters now use linear induction motors to propel the train at high speed, as an alternative to lifting the train by mechanical means at the start of the ride. The US Navy also uses linear induction motors in the Electromagnetic Aircraft Launch System, which will replace traditional steam catapults on aircraft carriers. Its use has also been proposed for spacecraft propulsion. In this context they are called mass drivers. The simplest way to use mass drives for spacecraft propulsion is to build a large mass drive capable of accelerating cargo to escape velocity, although launching a reusable launch system (RLV) such as StarTram into low Earth orbit has also been considered.

High acceleration linear motors are difficult to design for a variety of reasons. These engines require releasing large amounts of energy for very short periods of time. The design of a rocket launcher[3]​ requires 300 Giga Joules in each launch into space in a period of time less than 1 second. Normal electrical generators cannot cope with this type of demand, but it is possible to use quick release electrical energy storage methods. Capacitors are bulky and expensive but can deliver large amounts of power quickly. Homopolar generators" can be used to rapidly convert the kinetic energy of a flywheel into electrical energy. High-acceleration linear motors also require very high magnetic fields; the magnetic fields are often too strong for superconductors to be possible. However, through proper design, this can be solved.

There are two basic designs for high acceleration linear motors: railguns and coilguns.

The operation of the railgun is based on the principle of the homopolar motor: a pair of parallel conductors (the rails) are powered by an electric current. The projectile is placed making contact with both, to close the circuit. The current that is produced interacts with the strong magnetic fields generated by the passage of electricity through the conductors and this accelerates the projectile linearly in the direction of the rails.