Magnetic Levitation Trains

This paper involves the design, hardware, technology, application and future uses of “Magnetic levitation trains.” The maglev transportation system is more stable, faster, efficient and economic. Maglev systems are currently in use for applications such as bearings, high- speed trains, and manufacturing. Maglev is a method of propulsion that uses magnetic levitation to propel vehicles with magnets rather than with wheels, axles, and bearings. With maglev, a vehicle is levitated a short distance away from a guideway using magnets to create both lift and thrust. In future, these High-speed maglev trains would give a huge competition to the aviation industry.

Research methodology

I have chosen a very trending topic which is, the “Magnetic Levitation Trains”.

My report is based on the basic information from the internet further adding on, research from the newspaper as well as from the websites which made my work easier. All the information was readily available which added further to my interest in doing the project with utmost sincerity and honesty. Therefore my work is a combination of primary and secondary data.

Maglev trains are the new technology which is a breakthrough for the world. Maglev or magnetic levitation is exactly how it sounds, which is the levitation of objects or vehicle. Unlike the conventional vehicles with tires for cars or rails for trains, the whole system is changed. In the maglev system, there is no contact between the roads and tires the object remains levitated hence traction and friction doesn’t come into the picture. Friction and traction play a major role deciding the speed of the vehicle, without those the speed considerably increases. Maglev trains don’t get affected by weather, unlike the conventional trains. Countries like India where most citizens travel through the train and having a huge area of land this idea of maglev needs to be introduced so that the time taken for travel can be incredibly reduced.

Magnet

A magnet is an object that has a magnetic field. It attracts ferrous objects like pieces of iron, steel, nickel, and cobalt. These day’s magnets are made artificially in various shapes and sizes depending on their use. One of the most common magnets the bar magnet is a long, rectangular bar of uniform cross-section that attracts pieces of ferrous objects. The magnetic compass needle is also commonly used. The compass needle is a tiny magnet which is free to move horizontally on a pivot. One end of the compass needle points in the North direction and the other endpoints in the South direction. The end of a freely pivoted magnet will always point in the North-South direction. The end that points in the North are called the North Pole of the magnet and the end that points south is called the South Pole of the magnet. It has been proven by experiments that like magnetic poles repel each other whereas unlike poles attract each other.

Magnetic field and field lines

Magnetic Field

The space surrounding a magnet, in which magnetic force is exerted, is called a magnetic field. If a bar magnet is placed in such a field, it will experience magnetic forces.

Magnetic Lines of Force

When a small north magnetic pole is placed in the magnetic field created by a magnet, it will experience a force. The magnetic lines of force are the lines drawn in a magnetic field along which a north magnetic pole would move. The direction of a magnetic line of force at any point gives the direction of the magnetic force on a north pole placed at that point. Since the direction of the magnetic line of force is the direction of the force on the North Pole, so the magnetic lines of force always begin on the N-pole of a magnet and end on the S-pole of the magnet. A small magnetic compass when moved along a line of force always sets itself along the line tangential to it. So, a line drawn from the South Pole of the compass to its the North Pole indicates the direction of the magnetic field.

Maglev technology

This technology uses monorail track with linear motors, these trains move on special tracks rather than the mainstream conventional train tracks. They use very powerful electromagnets to reach higher velocities, they float about 1- 10 cms above the guideway on a magnetic field.These trains are propelled by the guideways. Once the train is pulled into the next section the magnetism switches so that the train is pulled on again. The electromagnets run the length of the guideway.

The mechanics of maglev train

Magnetic levitation trains operate through the use of electromagnets, which are magnets created by electric current. An electromagnet is defined as “a coil of insulated wire wound around an iron or steel cylinder”, and functions when current flows through the coil a magnetic field is produced. These electromagnets are used to lift the train above its track, as well as propel it forward.

There are three main types of Maglev trains:

1. 1. Electromagnetic suspension

It is the magnetic levitation of an object achieved by constantly altering the strength of a magnetic field produced by electromagnets using a feedback loop. In most cases, the levitation effect is mostly due to permanent magnets as they don't have any power dissipation, with electromagnets only used to stabilize the effect. In these kinds of fields, an unstable equilibrium condition exists. Although static fields cannot give stability, EMS works by continually altering the current sent to electromagnets to change the strength of the magnetic field and allows a stable levitation to occur. In EMS a feedback loop which continuously adjusts one or more electromagnets to correct the object's motion is used to cancel the instability. In this system, Electromagnets are attached to the train and also attached to the guideway track. They have ferromagnetic stators on the track and they help them to levitate the train. They have guidance magnets on the sides of the track they are laid complete along the track A computer is used to control the height of levitation of train they make us levitate about ( 1 – 15 cms ). The Max speed these trains could reach is about 438km/hr. They have an onboard battery power supply which gives a surplus amount of energy required to run a cabin.

1. 1. Electrodynamic suspension

Superconducting magnets are placed under the train. By this system, the train could levitate about 10 cm from the guideway. The magnetic field which helps the train to levitate is due to the using of superconducting magnets. The force in the track is created by an induced magnetic field in wires or conducting strips in the track.

In electrodynamic suspension (EDS), both the guideway and the train exert a magnetic field, and the train is levitated by the repulsive and attractive force between these magnetic fields. EDS systems have a major downside as well. At slow speeds, the current induced in these coils and the resultant magnetic flux is not large enough to support the weight of the train. For this reason, the train must have wheels or some other form of landing gear to support the train until it reaches a speed that can sustain levitation. Since a train may stop at any location, due to equipment problems, for instance, the entire track must be able to support both low-speed and high-speed operation. Another downside is that the EDS system naturally creates a field in the track in front and to the rear of the lift magnets, which acts against the magnets and creates a form of drag.

1. 1. Inductrack system

It is a suspension fail system, no power is required to activate magnets. The magnetic field is located below the car, they can generate enough force at low speeds (around 5 km/h) to levitate maglev train. In case of power failure cars slow down on their own safely, permanent magnets are arranged in an array which helps in the propulsion of the trains. They require either wheels or track segments that move for when the vehicle is stopped. Neither Inductrack nor the Superconducting EDS is able to levitate vehicles at a standstill, although Inductrack provides levitation down to a much lower speed, wheels are required for these systems. EMS systems are wheel-less.

The maglev track

The magnetized coil running along the track, called a guideway, repels the large magnets on the train's undercarriage, allowing the train to levitate between 0.39 and 3.93 inches (1 to 10 cm) above the guideway. Once the train is levitated, power is supplied to the coils within the guideway walls to create a unique system of magnetic fields that pull and push the train along the guideway. The electric current supplied to the coils in the guideway walls is constantly alternating to change the polarity of the magnetized coils. This change in polarity causes the magnetic field in front of the train to pull the vehicle forward, while the magnetic field behind the train adds more forward thrust. Maglev trains float on a cushion of air, eliminating friction. This lack of friction and the trains' aerodynamic designs allow these trains to reach unprecedented ground transportation speeds of more than 500 kmph, or twice as fast as Amtrak's fastest commuter train. In comparison, a Boeing-777 commercial airplane used for long-range flights can reach a top speed of about 905 kmph. Developers say that maglev trains will eventually link cities that are up to 1,609 km apart. At 500 km, you could travel from Paris to Rome in just over two hours.

Development of maglev trains:

There are different factors which are used in the development of maglev trains, these help in movement, stability, guidance etc of a train.

Propulsion:

Some EMS systems can provide both levitation and propulsion using an onboard linear motor. But some EDS systems are like they can levitate the train using the magnets on board but cannot propel it forward. As such, vehicles need some other technology for propulsion. A linear motor (propulsion coils) mounted in the track is one solution

Stability:

Any combination of static magnets cannot be in a stable equilibrium. Therefore a dynamic magnetic field is required to achieve stabilization. EMS systems rely on active electronic stabilization which constantly measures the bearing distance and adjust the electromagnet current accordingly. All EDS systems rely on changing magnetic fields creating electrical currents, and these can give passive stability. Because maglev vehicles essentially fly, stabilization of pitch, roll, and yaw is required by magnetic technology. In addition to the rotation, move forward and backward, sway (sideways motion) or heave (up and down motions) can be problematic with some technologies.

Guidance

Some systems use Null Current systems (also sometimes called Null Flux systems); they use a coil which is wound so that it enters two opposing, alternating fields so that the average flux in the loop is zero. When the vehicle is in the straight ahead position, no current flows, but if it moves off-line this creates a changing flux that generates a field that naturally pushes and pulls it back into line. This is the guidance system of maglev trains.

Evacuated tubes

Some systems (notably the Swissmetro system) propose the use of (vactrain ) maglev train technology used in evacuated (airless) tubes, which is used to remove air drag. This has the potential to increase speed and efficiency greatly, as most of the energy for conventional maglev trains is lost due to aerodynamic drag. One potential risk for passengers of trains operating in evacuated tubes is that they could be exposed to the risk of cabin depressurization unless tunnel safety monitoring systems can repressurize the tube in the event of a train malfunction or accident.