Magnetic levitation how does it work

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.

In the TransRapid, there are two electromagnetic rails placed on the train facing either side of the guideway. These rails keep the train from moving too far off course Lee, In the MLX, guidance is coupled with the levitation system.

The levitation rails on either side of the train are connected to each other. Through this connection, when the train moves closer to one side a restoring force is induced which pushes it back towards the center.

Thus the MLX is both levitated and guided at the same time Lee, Guidance system of Transrapid and MLX. Both use repulsive magnets. The most obvious attraction of maglev trains is that they can travel faster than traditional rail trains. The only commercial high-speed maglev, the Shanghai Maglev, is now the fastest train in existence. It travels over 50 mph 80 kph faster than the fastest high-speed wheel-rail kph Hayabusa , And it is only the first.

The lack of friction between the train and the guideway removes many limits that bound traditional trains. Maglev will only get faster from here Luu, There are other, more subtle qualities that also make maglev attractive:.

Although there are many upsides, there are still reasons why maglev trains are not being built everywhere. Perhaps the biggest reason is that maglev guideways are not compatible with existing rail infrastructure. Any organization attempting to implement a maglev system must start from scratch and build a completely new set of tracks.

This involves a very high initial investment Coates, Even though guideways cost less than rails over time Powell, , it is hard to justify spending so much upfront. Another problem is that maglev trains travel fast, but they might not travel quite fast enough. It is hard to dispute that these trains are superior to standard ones.

Regardless, more work needs to be done before it is worth implementing them worldwide. Ever since the steam engine, trains have traditionally been in the domain of mechanical engineers. They were all motors and axles, wheels and engines. However, the introduction of maglev technology has broken that tradition. Developing these trains has required input from a number of different fields other than mechanical engineering, including physics and chemistry.

Most importantly, though, it has brought electrical engineers to the table. See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter.

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Subscribe Now You may cancel at any time. 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. As the train moves, a magnetic field repels the magnets, causing the train to levitate. Inductrack I is designed for high speeds, while Inductrack II is suited for slow speeds. Inductrack III is specifically designed for very heavy cargo loads moved at slow speeds.

Inductrack trains could levitate higher with greater stability. As long as it's moving a few miles per hour, an Inductrack train will levitate nearly an inch 2. A greater gap above the track means that the train would not require complex sensing systems to maintain stability. Permanent magnets had not been used before because scientists thought that they would not create enough levitating force.

The Inductrack design bypasses this problem by arranging the magnets in a Halbach array. The magnets are configured so that the intensity of the magnetic field concentrates above the array instead of below it.

They are made from a newer material comprising a neodymium-iron-boron alloy, which generates a higher magnetic field. The Inductrack II design incorporates two Halbach arrays to generate a stronger magnetic field at lower speeds.

Notably, the passive magnetic levitation concept is a core feature of proposed hyperloop transportation systems, which is essentially an Inductrack-style train that blasts through a sealed tube that encases the entire track. It's possible that hyperloops may become the approach of choice, in part because they dodge the issue of air resistance in the way the regular maglevs cannot, and thus, should be able to achieve supersonic speeds.

Some say that a hyperloop might cost even less than a traditional high-speed rail line. But whereas maglev trains are already a proven technology with years of operational history, no one has yet built a commercial hyperloop anywhere in the world [source: Davies ]. While maglev transportation was first proposed more than a century ago, the first commercial maglev train didn't become a reality until , when a low-speed maglev shuttle became operational between the United Kingdom's Birmingham International railway station and an airport terminal of Birmingham International Airport.

Since then, various maglev projects have started, stalled, or been outright abandoned. However, there are currently six commercial maglev lines, and they're all located in South Korea, Japan and China.

The fact that maglev systems are fast, smooth and efficient doesn't change one crippling fact — these systems are incredibly expensive to build. Some critics lambast maglev projects as costs perhaps five times as much as traditional rail lines. But proponents point out that the cost of operating these trains is, in some cases, up to 70 percent less than with old-school train technology [sources: Hall , Hidekazu and Nobuo ].