How does maglev train move forward

It may be that one day soon, maglev technology will be commonplace throughout the world. This article reviews the history of these trains, how they work, as well as their benefits and drawbacks. It also discusses the importance of electrical engineering in developing maglev, and how electrical engineers can make this technology the next transportation revolution.

Imagine a train without wheels. Instead of rolling along the track, it quietly floats above and glides smoothly from origin to destination without ever touching a rail. This may sound like science fiction, but instances of this technology already exist in a number of places in the world.

They are known as maglev trains derived from the term mag netic lev itation. These futuristic locomotives offer many new and exciting possibilities for travel.

They have the potential for being faster, safer, and more energy efficient than conventional transportation systems. Although such trains are few and far between as of now, they are a hotbed of research in the electrical engineering community.

The fundamental ideas behind maglev technology can be traced back to the early 20th century. Much work went into laying the groundwork for these trains, including the development of electric motors and research in magnetism. A few scientists, namely Robert Goddard and Emile Bachelet, even dared to propose a vehicle that would float using magnets Yadav, In , a German man by the name of Hermann Kemper was given a patent for the first concept of a magnetic, levitating train Yadav, At this time, Germany and Japan began researching the potential of maglev.

During the 70s and 80s, both countries made great progress in developing these trains. Germany built and tested a string of prototype maglev systems and called their design the TransRapid Figure 1.

The trains achieved speeds of over mph kph on the test track Luu, Their trains were able to exceed mph kph Luu, Transrapid on testing center in Germany near Bremen.

Japan continued development of its maglev technology into the 90s and beyond. They tested a new series, called the MLX, which broke mph kph in Yadav, No commercial lines have been established in the country, but they are still carrying out research.

However, in , the government shut down the project Luu, Not all was lost, though, as the Chinese took notice and commissioned the Germans to build a TransRapid train in Shanghai.

The Shanghai Maglev Figure 2 , which resulted from this venture, is now the only high-speed maglev train in commercial use. It carries passengers a distance of 19 miles 30km in 8 minutes, reaching a top speed of over mph kph Coates, Thus China has quickly become a large player in the worldwide maglev market.

The country plans to continue development of its maglev infrastructure. Maglev trains do not have wheels or rails. As shown in Figure 3, they have guideways, and they float down these guideways without ever touching them. Comparison of Wheel-Rail versus Guideways. Source: Author, derived from Lee There are three essential parts to achieving maglev functionality: levitation, propulsion and guidance as seen below.

Levitation, propulsion, and guidance in maglev. Levitation is the ability for the train to stay suspended above the track. There are two important types of levitation technology:. Electromagnetic Suspension EMS. Uses attractive magnetic forces. Electrodynamic Suspension EDS. Uses repulsive magnetic forces.

Propulsion is the force that drives the train forward. Maglev uses an electric linear motor to achieve propulsion.

A normal electric rotary motor uses magnetism to create torque and spin an axle. It has a stationary piece, the stator, which surrounds a rotating piece, the rotor.

The stator is used to generate a rotating magnetic field. This field induces a rotational force on the rotor, which causes it to spin. A linear motor is simply an unrolled version of this see Figure 7. The stator is laid flat and the rotor rests above it. Instead of a rotating magnetic field, the stator generates a field that travels down its length. Similarly, instead of a rotating force, the rotor experiences a linear force that pulls it down the stator.

Thus, an electric linear motor directly produces motion in a straight line. However, this motor can only produce a force while the rotor is above the stator. Once the rotor has reached the end, it stops moving.

So a magnetic field is sent down the guideway and it pulls the train along after it. It is so called because the magnetic field in the primary induces a magnetic field in the secondary. It is the interaction between the original field and the induced field that causes the secondary to be pulled along. However, in this configuration, the secondary always lags somewhat behind the moving field in the primary.

This lag is a source of energy and speed loss. Because the secondary is now producing its own stationary magnetic field, it travels down the primary in sync with the moving field—hence the name for this variant of motor Gieras, Because LSMs are faster and more efficient, they are the motor of choice in high-speed maglev trains Lee, Guidance is what keeps the train centered over the guideway. For high-speed maglev, repulsive magnetic forces are used to achieve this Figure 8. Superconducting magnets are electromagnets that are cooled to extreme temperatures during use, which dramatically increases the power of the magnetic field.

The first commercially operated high-speed superconducting Maglev train opened in Shanghai in , while others are in operation in Japan and South Korea. In the United States, a number of routes are being explored to connect cities such as Baltimore and Washington, D. In Maglev, superconducting magnets suspend a train car above a U-shaped concrete guideway. Like ordinary magnets, these magnets repel one another when matching poles face each other. The magnets employed are superconducting, which means that when they are cooled to less than degrees Fahrenheit below zero, they can generate magnetic fields up to 10 times stronger than ordinary electromagnets, enough to suspend and propel a train.

These magnetic fields interact with simple metallic loops set into the concrete walls of the Maglev guideway. The loops are made of conductive materials, like aluminum, and when a magnetic field moves past, it creates an electric current that generates another magnetic field. Three types of loops are set into the guideway at specific intervals to do three important tasks: one creates a field that makes the train hover about 5 inches above the guideway; a second keeps the train stable horizontally.

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:. 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.

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 mph kph , or twice as fast as Amtrak's fastest commuter train [source: Boslaugh ]. In comparison, a Boeing commercial airplane used for long-range flights can reach a top speed of about mph kph. Developers say that maglev trains will eventually link cities that are up to 1, miles 1, kilometers apart.

At mph, you could travel from Paris to Rome in just over two hours. Some maglev trains are capable of even greater speeds. In October , a Japan Railway maglev bullet train blazed all the way to mph kph during a short run. Those kinds of speeds give engineers hope that the technology will prove useful for routes that are hundreds of miles long. Germany and Japan both have developed maglev train technology, and tested prototypes of their trains. Although based on similar concepts, the German and Japanese trains have distinct differences.

In this system, the bottom of the train wraps around a steel guideway. Other guidance magnets embedded in the train's body keep it stable during travel. Germany demonstrated that the Transrapid maglev train can reach mph with people onboard. However, after an accident in see sidebar and huge cost overruns on a proposed Munich Central Station-to-airport route, plans to build a maglev train in Germany were scrapped in [source: DW ].

Since then, Asia has become the hub for maglev activity. On Aug. There were no injuries, and investigators believe that the fire was caused by an electrical problem. On Sept. The train was going at least mph kph at the time. Some 23 passengers were killed and 11 injured. A court ruled that human error was to blame for incident, which would have been avoided had employees followed established regulations and procedures.

No further maglev accidents have been reported since However, the test trains in Germany were eventually discontinued while the Shanghai maglev train still runs. Japanese engineers have developed a competing version of maglev trains that use an electrodynamic suspension EDS system, which is based on the repelling force of magnets.

The key difference between Japanese and German maglev train technology 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 used to cool the coils can be expensive and add significantly to construction and maintenance costs. Another difference between the systems is that the Japanese trains levitate nearly 4 inches 10 centimeters 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 93 mph kph. Japanese engineers say the wheels are an advantage if a power failure caused a shutdown of the system.

Also, passengers with pacemakers would have to be shielded from the magnetic fields generated by the superconducting electromagnets. The Inductrack is a newer type of EDS that uses permanent room-temperature magnets to produce the magnetic fields instead of powered electromagnets or cooled superconducting magnets.

Inductrack uses a power source to accelerate the train only until it begins to levitate. If the power fails, the train can slow down gradually and stop on its auxillary wheels. The track is actually an array of electrically shorted circuits containing insulated wire.

In one design, these circuits are aligned like rungs in a ladder.