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.
Electromagnetic Suspension(EMS)
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 Maglev Train
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 310 mph (500 kph), 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 562 mph (905 kph). Developers say that maglev trains will eventually link cities that are up to 1,000 miles (1,609 km) apart. At 310 mph, you could travel from Paris to Rome in just over two hours.
Germany and Japan are both developing maglev train technology, and both are currently testing prototypes of their trains. (The German company "Transrapid International" also has a train in 
commercial use -- more about that in the next section.) Although based on similar concepts, the German and Japanese trains have distinct differences. In Germany, engineers have developed anelectrodynamic suspension (EMS) system, calledTransrapid. In this system, the bottom of the train wraps around a steel guideway. Electromagnets attached to the train's undercarriage are directed up toward the guideway, which levitates the train about 1/3 of an inch (1 cm) above the guideway and keeps the train levitated even when it's not moving. Other guidance magnets embedded in the train's body keep it stable during travel. Germany has demonstrated that the Transrapid maglev train can reach 300 mph with people onboard.
Electrodynamic Suspension
Japanese engineers are developing a competing version of maglev trains that use anelectrodynamic suspension (EDS) system, which is based on the repelling force of magnets. The key difference between Japanese and German maglev trains is that the Japanese trains use super-cooled, superconducting electromagnets. This kind of electromagnet can conduct electricity even after the power supply has been shut off. In the EMS system, which uses standard electromagnets, the coils only conduct electricity when a power supply is present. By chilling the coils at frigid temperatures, Japan's system saves energy. However, the cryogenic system uses to cool the coils can be expensive.
Another difference between the systems is that the Japanese trains levitate nearly 4 inches (10 cm) above the guideway. One potential drawback in using the EDS system is that maglev trains must roll on rubber tires until they reach a liftoff speed of about 62 mph (100 kph). Japanese engineers say the wheels are an advantage if a power failure caused a shutdown of the system. Germany's Transrapid train is equipped with an emergency battery power supply. Also, passengers with pacemakers would have to be shielded from the magnetic fields generated by the superconducting electromagnets.[more...]
Maglev Technology in use
While maglev transportation was first proposed more than a century ago, the first commercial maglev train made its test debut in Shanghai, China, in 2002 , using the train developed by 
German company Transrapid International. The same line made its first open-to-the-public commercial run about a year later in December of 2003. The Shanghai Transrapid line currently runs to and from the Longyang Road station at the city's center and Pudong airport. Traveling at an average speed of 267 mph (430 kmh), the 19 mile (30 km) journey takes less than 10 minutes on the maglev train as opposed to an hour-long taxi ride. China is building an extension of the Shanghai line that will run 99 miles (160 km) to Hangzhou. Construction is scheduled to begin in fall 2006 and should be completed by the 2010 Shanghai Expo. This line will be the first Maglev rail line to run between two cities.[more...]
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