Maglev Train

Background:

Transportation is the direct product of the social link and social relationship of the people. Revolutionary changes have taken place in the life of the mankind since human beings acquired the capability of walking upright as a result of evolution from the ape. Human being’s vision was widened to enable itself to better observe the surroundings and to be watchful against any possible crises. But due to the low productive forces and constraints on people by the conditions of the nature in the primitive times, usually they could not but live by hunting animals or gathering plants within a certain region to maintain the lease of life by making use of a few elements of the nature, let alone any act of transport for the commercial intercourse among the peasants, workers and merchants. Nevertheless, with the development of human society, people gradually widened their vision in the geographic space through several forms of lateral social contact in their production activities and injected active seeking factor into the passive man, environment relationship. Gradually, human being mastered the use of tools and other special at his service. Among others, the horse, an animal which changed the speed of human transportation, enabled a cart to run at some 10km/h, thus the region scoped varied and the link between city and city became closer, enhancing the progress of culture and civilization in various places.

Magnetic levitation (maglev) is an innovative transportation technology. It is sometimes said to be the first fundamental innovation in the field of railroad technology since the invention

of the railway. A high speed maglev train uses non-contact magnetic levitation, guidance and propulsion systems and has no wheels, axles and transmission. The replacement of mechanical components by wear-free electronics overcomes the technical restrictions of wheel-on-rail technology. Compared with traditional railways, maglev systems have features that could constitute an attractive transportation alternative:

1. High Speed

2. High Safety

3. Less Pollution

4. Low Energy Consumption

The Principle behind Maglev trains:

A method of supporting and transporting objects or vehicles which is based on the physical property that the force between two magnetized bodies is inversely proportional to their distance. By using this magnetic force to counterbalance the gravitational pull, a stable and contactless suspension between a magnet (magnetic body) and a fixed guide way (magnetized body) may be obtained. In magnetic levitation (Maglev), also known as magnetic suspension, this basic principle is used to suspend (or levitate) vehicles weighing 40 tons or more by generating a controlled magnetic force. By removing friction, these vehicles can travel at speeds higher than wheeled trains, with considerably improved propulsion efficiency (thrust energy/input energy) and reduced noise. In Maglev vehicles, chassis-mounted magnets are either suspended underneath a ferromagnetic guide way (track) or levitated above an aluminum track. the three primary functions basic to Maglev technology:

(1) levitation or suspension;

(2) propulsion; and

(3) guidance.

In most current designs, magnetic forces are used to perform all three functions, although a nonmagnetic source of propulsion could be used. No consensus exists on an optimum design to perform each of the primary functions.

In the attraction-type system, a magnet-guide way geometry is used to attract a direct-current electromagnet toward the track. This system, also known as the electromagnetic suspension (EMS) system, is suitable for low- and high-speed passenger-carrying vehicles and a wide range of magnetic bearings. The electromagnetic suspension system is inherently nonlinear and unstable, requiring an active feedback to maintain an upward lift force equal to the weight of the suspended magnet and its payload (vehicle).

In the repulsion-type system, also known as the electro dynamic levitation system (EDS or EDL), a superconducting coil operating in persistent-current mode is moved longitudinally

along a conducting surface (an aluminum plate fixed on the ground and acting as the guide way) to induce circulating eddy currents in the aluminum plate. These eddy currents create a magnetic field which, by Lenz’s law, opposes the magnetic field generated by the travelling coil. This interaction produces a repulsion force on the moving coil. At lower speeds, this vertical force is not sufficient to lift the coil (and its payload), so supporting auxiliary wheels are needed until the net repulsion force is positive. The speed at which the net upward lift force is positive (critical speed) is dependent on the magnetic field in the air gap and payload, and is typically around 80 km/h (50 mi/h). To produce high flux from the traveling coils, hard superconductors (type II) with relatively high values of the critical field (the magnetic field strength of the coil at 0 K) are used to yield air gap flux densities of over 4 tesla. With this choice, the strong eddy-current induced magnetic field is rejected by the superconducting field, giving a self-stabilizing levitation force at high speeds (though additional control circuitry is required for adequate damping and ride quality.

The Types of Maglev Methods

• Repulsion between like poles of permanent magnets or electromagnets.

• Repulsion between a magnet and a metallic conductor induced by relative motion.

• Repulsion between a metallic conductor and an AC electromagnet.

• Repulsion between a magnetic field and a diamagnetic substance.

• Repulsion between a magnet and a superconductor.

• Attraction between unlike poles of permanent magnets or electromagnets.

• Attraction between the open core of an electromagnetic solenoid and a piece of iron or a magnet.

• Attraction between a permanent magnet or electromagnet and a piece of iron.

• Attraction between an electromagnet and a piece of iron or a magnet, with sensors and active control of the current to the electromagnet used to maintain some distance between them.

• Repulsion between an electromagnet and a magnet, with sensors and active control of the current to the electromagnet used to maintain some distance between them.

Summary

High-speed magnetically levitated ground transportation (maglev) is a new surface mode of transportation, in which vehicles glide above their guide ways, suspended, guided, and propelled by magnetic forces. Capable of travelling at speeds of 250 to 300 miles-per-hour or higher, maglev would offer an attractive and convenient alternative for travelers between large urban areas for trips of up to 600 miles. It would also help relieve current and projected air and highway congestion by substituting for short-haul air trips, thus releasing capacity for more efficient long-haul service at crowded airports, and by diverting a portion of highway trips. Finally, it gives a peek into the future expansions of maglev trains and thus undoubtedly assures its readers that maglev trains are no longer a science fiction, and are in fact the future of world transportation.