How a linear motor works?

Question

How linear motor is useful in maglev trains?How it will be lifted&how it will be stopped at the destination?

Answer 1

The monorail is powered by a linear induction motor (LIM). LIMs have been around for some time. The monorails at Euro Disney are powered by LIMs, as is the Vancouver rapid transit system. The senatorial transit system in Washington DC, and many roller coasters and baggage handling systems, are all powered by LIMs. LIMs were used to propel test trains at speeds up to 250 mph at the Transportation Technology Center, Colorado, in the 1970s.

The LIM used on the monorail is a new and improved version, Seraphim (SEgmented RAil PHased Induction Motor), developed by Sandia National Laboratories. The Seraphim motor was originally designed to launch satellites into orbit. It can accelerate a one ton satellite up a 0.6 mile-long track with a 30% upward grade to a speed of 14,000 mph, sufficient to launch the satellite into low earth orbit.

How a Seraphim LIM Works


Step #1
Mount a permanent magnet to the underside of a vehicle. Now slide another magnet along the track and if the second magnet is oriented correctly, the magnets will repel, causing the vehicle to move.

Step #2
Instead of sliding a magnet along the track, put in a whole series of magnets. Change the magnet on the underside of the vehicle into an electromagnet so that you can turn it on and off. Now when the electromagnet is in the correct position relative to a magnet on the track (just beyond its center), turn it on so that the magnets repel and the vehicle is pushed along. Turn the electromagnet off before it gets too close to the next magnet (or it will brake the vehicle). Let the vehicle run on just past the next magnet, and then pulse the electromagnet again so that the vehicle continues moving forward. Continue this process. To brake the vehicle, pulse the electromagnet just before it reaches a magnet on the track.

Step #3
Instead of using permanent magnets in the track, use a segmented aluminum rail (a ladder-like structure) which will act as a series of electromagnets, but do not supply any power to the rail. Now when the electromagnet on the vehicle is in the correct position relative to a segment on the track, turn it on. It will induce surface currents in the segment, generating a magnetic field, so that the electromagnet on the vehicle will be repelled and the vehicle will move forward. Keep pulsing the electromagnet on the vehicle every time it is in the correct position relative to a rail segment on the track. The segmented rail along the track is called a "reaction rail".

Step #4
To go fast, mount a number of electromagnets to the underside of the vehicle so that any one time 40% of them are in the correct position relative to a rail segment on the track and are pushing forward smoothly. An alternative to using onboard power is to use a power pick-up to connect each electromagnet on the vehicle to the "third rail" which is connected to an external power supply.



The advantages of a LIM over conventional motors and drive systems are several:


Because there are no moving parts, a LIM is very quiet.
Propulsion is by electromagnetic forces between the active coils on the vehicle and the reaction rail - not through traction between the wheels and rail. This means a monorail with a LIM can climb steep grades and in rain, snow and ice without depending on wheel traction. The monorail's wheels carry the vehicle weight and provide guidance, not traction, minimizing wheel and track wear.
If the reaction rail is placed on top of the guideway beam, as is the case with the high-speed monorail, then there is a vertical component to the electromagnetic forces between the active coils and reaction rail. This uplift force can be as great as 90% of the weight of the vehicle. This magnetic lift can improve ride quality, make the monorail even quieter, reduce friction in the suspension system (static and rolling drag), and improve energy efficiency and acceleration.
Comparison of the Seraphim and Conventional LIMs

The Seraphim motor is a new form of LIM that generates thrust by pulsing an alternating current through each active coil mounted on the vehicle when it is properly positioned over the unpowered reaction rail. The reaction rail is not continuous as is the case with conventional LIMs, rather, it is a segmented structure. The magnetic flux from the driving coil induces currents in the segmented reaction structure, creating forces for propulsion or braking due to the interaction of the magnetic fluxes. This is unlike a conventional LIM where magnetic flux is embedded in the continuous reaction rail in order to create propulsive forces.

Since the Seraphim motor relies on the exclusion of flux from the reaction rail, it has the following advantages over conventional LIMs for use as a high-speed rail propulsion technology:


It permits a larger gap between the active coils on the vehicle and the reaction rail on the guideway, up to 1", and perhaps larger, which improves ride quality and relaxes guideway tolerances, significantly reducing construction and maintenance costs.
Very low magnetic drag is induced in the reaction rail (assuming proper motor control), which improves motor efficiency.
It is smaller, lighter, and more compact than a conventional LIM, and costs significantly less to build and operate.
The efficiency of the motor increases with speed.
The power of the Seraphim motor is limited only by the power available, the frequency of pulsing relative to the required energy input necessary for a desired speed of operation, and by the maximum acceleration/deceleration forces that can be comfortably accommodated by passengers.

Answer 2

achieveable defense force applications are submarine torpedo launchers and aircaft service catapults. an electric powered linear motor elements the capacity to regulate the stress of acceleration in the course of the launching part of the torpedo or airplane. It also elements for the managed deceleration (preventing) of the motor fairly of hitting a provide up as is easy with the at the moment used platforms. also, a linear motor elements the alternative of recuperating a number of the launch capacity in the course of the deceleration section. surely a linear motor works an same as any electric powered motor. An electrically generated, shifting magnetic container contained in the table certain winding of the device acts on a movable electromagnet or everlasting magnet employing the magnetic forces of repulsion or charm or both. For a linear motor the stator magnetic container pushes and pulls the movable coil/magnet down the size of the device. In a rotary electric powered motor, the rotor of the device magnetically follows the rotating container produced by employing the stator winding. even if the action is rotary or linear, the guidelines of operation are an same.

Answer 3

The magnetic field is pulsed to push the train. Much like your pulse moves blood. If you just keep pushing something on that pulse, you have made a linear motor.

Linear motor is kind of a new definition because a motor needs a non moving stator and a moving rotor. The train would be considered a rotor, but since the train does not rotate (under normal circumstances) it does not act like a rotor. It acts like a load in a resistive circuit.

Answer 4

Linear Induction Motor (LIM) is an asynchronous motor, working on the same prinicple an Induction motor works, but is designed to produce the rectilinear motion, unlike the rotary movement produces by a motor; hence the word 'linear'.LIM, in principle, is an Induction motor only.
Its construction can be envisaged thus: tear down the stator and rotor along its circumference, and lay down the structure on a falt surface.

Conventionally, when the stator (primary) is excited by applying 3 phase supply in an induction motor, rotating magnetic field is produced. Here, after laying down the stator flat, excitation with three phase supply would induce a 'travelling flux', a travelling magnetic field, which would linearly travel along the stator.
This would again induce emfs in the rotor, which produces a forward thrust force, and if the secondary (rotor) is fixed primary is free to move, it would travel across the length of the machine linearly, along the tracks provided.
These motors find their applications in maglev propulsion, linear cranes, automatic sliding doors in electric trains, conveyors et cetera.

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