Maglev trains By Vishal Dubey
Agenda Introduction Fast facts How it works Maglev technology Electromagnetic suspension Electrodynamic suspension Stability Power and energy usage Advantages and disadvantages of Maglev Train
Introduction Magnetic levitation transport is a form of transportation that suspends guides and propels vehicles through the harnessing of electromagnetic force. The term "maglev" refers not only to the vehicles but also to the railway system. Maglev train uses magnetic levitation from a very large number of magnets for lift and propulsion. Has the potential to be faster, quieter and smoother than wheeled mass transit systems
Introduction Power needed for levitation is usually not a large percentage of the overall consumption In the present moment there are several countries working on the development of Magnetic Levitating trains: Japan and Germany were pioneers; USA and Australia are working in on it now. China is not a pioneer having build a maglev train from Shanghai to its city
Did you Know? Maglev trains can attain speeds of 250 mph easily (the speed of a jet aircraft). The Japanese Maglev's last record was of 581km/h. The Shanghai Maglev Train can speed up to 431 km/h, or 267 mph. The first commercial Maglev was opened in 1984 in Birmingham, England, covering some 600 meters between its airport and rail hub
How it works A maglev train floats about 10mm above the guideway on a magnetic field. It is propelled by the guideway itself rather than an onboard engine by changing magnetic fields Once the train is pulled into the next section the magnetism switches so that the train is pulled on again. The Electro-magnets run the length of the guideway.
How it works The train cars use gigantic magnets to hover above their tracks, decreasing the negative impact friction has on a train's speed and allowing the cars to achieve much greater speeds than normal railroad cars.
Maglev technology There are two primary types of maglev technology: electromagnetic suspension (EMS) electrodynamic suspension (EDS)
Electromagnetic suspension In current EMS systems, the train levitates above a steel rail while electromagnets, attached to the train, are oriented toward the rail from below. The electromagnets use feedback control to maintain a train at a constant distance from the track.
Advantage Proven, commercially available technology that can attain very high speeds (500 km/h) No wheels or secondary propulsion system needed
Disadvantage The separation between the vehicle and the guide way must be constantly monitored and corrected by computer systems to avoid collision due to the unstable nature of electromagnetic attraction.
Electrodynamic suspension In Electrodynamic suspension, both the rail and the train exert a magnetic field, and the train is levitated by the repulsive force between these magnetic fields The magnetic field in the train is produced by either electromagnets or by an array of permanent magnets. The repulsive force in the track is created by an induced magnetic field in wires or other conducting strips in the track.
Electrodynamic suspension 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.
Electrodynamic suspension Propulsion coils on the guideway are used to exert a force on the magnets in the train and make the train move forward. The propulsion coils that exert a force on the train are effectively a linear motor. An alternating current flowing through the coils generates a continuously varying magnetic field that moves forward along the track.
Electrodynamic suspension The frequency of the alternating current is synchronized to match the speed of the train. The offset between the field exerted by magnets on the train and the applied field create a force moving the train forward.
Advantage Onboard magnets and large margin between rail and train enable highest recorded train speeds (581 km/h) and heavy load capacity Successful operations using high temperature superconductors in its onboard magnets, cooled with inexpensive liquid nitrogen.
Disadvantage Strong magnetic fields onboard the train would make the train inaccessible to passengers with pacemakers or magnetic data storage media such as hard drives and credit cards, necessitating the use of magnetic shielding; vehicle must be wheeled for travel at low speeds; system per mile cost still considered prohibitive; the system is not yet out of prototype phase.
Stability EMS systems rely on active electronic stabilization. As Maglev vehicles essentially fly, stabilisation of pitch, roll and yaw is required by magnetic technology.
Power and energy usage Energy for maglev trains is used to accelerate the train, and may be regained when the train slows down. Also used to make the train levitate and to stabilise the movement of the train Main part of the energy is needed to force the train through the air Some energy is used for air conditioning, heating, lighting.
Power and energy usage At very low speeds the percentage of power used for levitation can be significant. Also for very short distances the energy used for acceleration might be considered. The power used to overcome air drag increases with the cube of the velocity, and hence dominates at high speed
Advantages of Maglev A Maglev is way faster than your usual bullet train. Maglevs can reach speeds up to 500 kilometres per hour. Due to its lack of wheels, MagLevs are quieter than normal trains, or sometimes even traffic. Maglevs use 30% less energy than normal trains. In theory, a Maglev and its track would require very little maintenance since the train never touches the track there is virtually no wear and tear.
Disadvantages of Maglev The Maglev's track is much more expensive than railroad tracks. Whole new sets of tracks would have to be built for the Maglev to run. Many Transportation vehicles in Europe run on existing track, like the TGV trains in France. Although Maglevs are pretty quiet, noise caused by air disturbance still occurs.
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