Maglev

MAGLEV, or magnetically levitating train is a form of transportation that suspends, guides and (usually) propels vehicles, predominantly trains, using magnetic forces. This method has the potential to be faster, quieter and smoother than wheeled mass transit systems, potentially reaching velocities comparable to turboprop and jet aircraft (900 km/h, 600 mph). The highest recorded speed of a maglev train is 581 km/h (361 mph), achieved in Japan in 2003, 6 km/h faster than the conventional TGV speed record. If you've been to an airport lately, you've probably noticed that air travel is becoming more and more congested. Despite frequent delays, airplanes still provide the fastest way to travel hundreds or thousands of miles. Passenger air travel revolutionized the transportation industry in the last century, letting people traverse great distances in a matter of hours instead of days or weeks. The only alternatives to airplanes -- feet, cars, buses, boats and conventional trains -- are just too slow for today's fastpaced society. However, there is a new form of transportation that could revolutionize transportation of the 21st century the way airplanes did in the 20th century.

Photo courtesy Railway Technical Research Institute

Maglev trains can travel at speeds of up to 310 mph (500 kph). See more electricity pictures.

A few countries are using powerful electromagnets to develop high-speed trains, called maglev trains. Maglev is short for magnetic levitation, which means that these trains will float over a guideway using the basic principles of magnets to replace the old steel wheel and track trains. In this article, you will learn how electromagnetic propulsion works, how three specific types of maglev trains work and where you can ride one of these trains. If you've ever played with magnets, you know that opposite poles attract and like poles repel each other. This is the basic principle behind electromagnetic propulsion. Electromagnets are similar to other magnets in that they attract metal objects, but the magnetic pull is temporary. As you can read about in How Electromagnets Work, you can easily create a small electromagnet yourself by connecting the ends of a copper wire to the positive and negative ends of an AA, C or D-cell battery. This creates a small magnetic field. If you disconnect either end of the wire from the battery, the magnetic field is taken away. The magnetic field created in this wire-and-battery experiment is the simple idea behind a maglev train rail system. There are three components to this system: • A large electrical power source • Metal coils lining a guideway or track • Large guidance magnets attached to the underside of the train The big difference between a maglev train and a conventional train is that maglev trains do not have an engine -- at least not the kind of engine used to pull typical train cars along steel tracks. The engine for maglev trains is rather inconspicuous. Instead of using fossil fuels, the magnetic field created by the electrified coils in the guideway walls and the track combine to propel the train.

Photos courtesy Railway Technical Research Institute

Above is an image of the guideway for the Yamanashi maglev test line in Japan.

Pros and cons of different technologies Each implementation of the magnetic levitation principle for train-type travel involves advantages and disadvantages. Time will tell us which principle, and whose implementation, wins out commercially.

Technology Pros Cons

EMS (Electromagnetic suspension) Magnetic fields inside and outside the vehicle are insignificant; proven, commercially available technology that can attain very high speeds (500 km/h); no wheels or secondary propulsion system needed The separation between the vehicle and the guideway must be constantly monitored and corrected by computer systems to avoid collision due to the unstable nature of electromagnetic attraction; due to the system's inherent instability and the required constant corrections by outside systems, vibration issues may occur.

EDS (Electrodynamic) Onboard magnets and large margin between rail and train enable highest recorded train speeds (581 km/h) and heavy load capacity; has recently demonstrated (December 2005) successful operations using high temperature superconductors in its onboard magnets, cooled with inexpensive liquid nitrogen 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; limitations on guideway inductivity limit the maximum speed of the vehicle; vehicle must be wheeled for travel at low speeds; used in JRMaglev.

Pros and cons of maglev

Maglev vs. conventional trains Maglev trains are not compatible with conventional track, and therefore require all new infrastructure for their entire route. By contrast conventional high speed trains such as the TGV are able to run at reduced speeds on existing rail infrastructure, thus reducing expenditure where new infrastructure would be particularly expensive (such as the final approaches to city terminals), or on extensions where traffic does not justify new infrastructure. Due to the lack of physical contact between the track and the vehicle, maglev trains experience no rolling friction, leaving only air resistance and electromagnetic drag, potentially improving power efficiency.[ The weight of the large electromagnets in EMS and EDS designs is a major design issue. A very strong magnetic field is required to levitate a massive train. For this reason one research path is using superconductors to improve the efficiency of the electromagnets. The high speed of some maglev trains translates to more sound due to air displacement, which gets louder as the trains go faster. A study found that high speed maglev trains are 5 dB noisier than traditional trains. At low speeds, however, maglev trains are nearly silent. However, two trains passing at a combined 1,000 km/h has been successfully demonstrated without major problems in Japan. Braking issues and overhead wire wear are problems for the Fastech 360 railed Shinkansen. Maglev would eliminate these issues, but not the noise pollution issue. Issues relating to magnets are also a factor. See suspension types. As linear motors must fit within or straddle their track over the full length of the train, track design is challenging for anything other than point-to-point services. Curves must be gentle, while switches are very long and need care to avoid breaks in current. Maglev needs very fast-responding control systems to maintain a stable height above the track; this needs careful design in the event of a failure in order to avoid crashing into the track during a power fluctuation.

Maglev vs aircraft One advantage of maglev's higher speed would be extension of the serviceable area (3 hours radius) that can outcompete subsonic commercial aircraft.

For many systems, it is possible to define a lift-to-drag ratio. These ratios can exceed that of aircraft (for example Inductrack can approach 200:1 at high speed, far higher than any aircraft). This can make it more efficient per mile, and potentially give greater range. Aircraft travel at high altitude where the airdrag is lower, and hence can travel faster, and can service more destinations. Maglev can transport larger numbers of people far more efficiently in large urban areas. Unlike airports, one need not arrive early at the train stations to go through numerous