Magnetic Levitation

Emerging Technologies

By Nick Presson

Introduction

Magnetic levitation has been around for years, but with advances in technology it may become a part of everyday life. The main emphasis for magnetic levitation is for transportation. Magnetically levitated ground transportation, or “Maglev”, is an advanced mode of surface high speed transportation whereby a vehicle gliding above a guideway is suspended, guided, and propelled by magnetic forces. Can you imagine a train that that actually floats in air 4 to 6 inches in the air and travels up to 300 mph. This technology can reduce air and highway congestion, air pollution, and petroleum use.

Traditional Systems

The transportation system in the United States has been much admired around the world. Our extensive highway and air systems have facilitated business and leisure travel and contributed to a high quality of life for many Americans. In 1990, 429 million passengers traveled 342 billion passenger miles on commercial airlines. Americans traveled 2 trillion passenger miles my car, truck, bus, and public transit, and 6.1 billion passenger miles on Amtrak. As population have grown and shifted, however, the traditional systems have become stressed. Congestion on highways and at airports, especially since September 11, not only wastes time and fuel increases, but also constrains mobility to the extent that economic growth and productivity are adversely affected. Some of the current concerns are the rising costs. Land is costly and becoming more scarce. Adding more highway lanes and building new airports in or near our larger cities is becoming increasingly difficult. Environmental issues are associated with building and operating air and highway systems (such as air and noise pollution) have become a major problem in expansion. The last one is increased oil dependence. Current transportation technologies are petroleum dependent, accounting for 64 percent of total petroleum use. Without transportation alternatives that reduce dependency, transportation petroleum use is expected to remain high. Due to this, it is possible that this situation will contribute to the U.S. trade deficit and dependence on oil imports, possibly creating a national security problem. Let’s look at how the technology of magnetic levitation, or Maglev, may decrease these current problems.

Basic Principles of Physics

Magnetism is a phenomenon that occurs when a moving charge exerts a force on other moving charges. The magnetic force caused by this moving charge sets up a field which in turn exerts a moving force on other moving charges. The magnetic field is found to be perpendicular to the velocity of the current.

Maglev History Timeline

1900 - Robert Goddard and Emile Bachelet conceived the concept of frictionless trains.

1930 - German scientist Hermann Kemper studied the use of magnetic fields in conjunction with airplanes and trains

1969 - American scientists James R. Powell and Gordan T. Danby patented the first design for magnetic levitational trains

1970 - Germans and Japanese start research and development towards their versions of maglev technology

1990 - U.S. Federal Government with FRA begins to support maglev technology and implements the National Maglev Imitative (NMI).

1991 - Germany's government certifies operation of first maglev train for the public

1998 - Hamburg to Berlin route will be complete

2005 - Tokyo-Osaka route scheduled to be finished

Magnetic levitation Train

Magnetic Levitation Train, also maglev train,is a high-speed ground transportation vehicle levitated above a track called a guideway and propelled by magnetic fields. Magnetic levitation train technology can be used for urban travel at relatively low speeds (less than 100 km/h, or less than 62 mph); a short-distance maglev shuttle operated for 11 years from 1984 to 1995 between the Birmingham, England, airport and the city train station. However, the greatest worldwide interest is in high-speed maglev systems. Train speeds of 552 km/h (343 mph) have been demonstrated by a full-size maglev vehicle in Japan, while in Germany a maglev train has run at 450 km/h (280 mph).

Types of Levitation

Two different approaches to magnetic levitation train systems have been developed. The first is called electromagnetic suspension. This is basically levitated by attraction. There are conventional electromagnets mounted at the ends of a pair of structures under the train; the structures wrap around and under either side of the guideway. The magnets attract up toward laminated iron rails in the guideway and lift the train. However, this system is inherently unstable; the distance between the electromagnets and the guideway, which is about 10 mm (3/8 in), must be continuously monitored and adjusted by computer to prevent the train from hitting the guideway.

There are 3 main components to the system that governs the functionality of Maglev Trains:

1) A large electrical power source

2) Metal coils lining a guideway or track

3) Large guidance magnets are attached to the underside of the train.

A key difference between the maglev train and a conventional train is the structure of the engine. Unlike trains in the past that used fossil fuels to pull the engine across steel tracks, the magnetic field created by the electrified coils in the guideway track walls propel the Maglev Train.

Here is a fundamental description of how Maglev operates. The guideway, which is a magnetized coil running along the track, repels the large magnets on the train's undercarriage, allowing the train to levitate above the guideway between .39 and 3.93 inches (1 to 10 cm). Subsequently, 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. To change the polarity of the magnetized coils, the electric current supplied to the coils in the guideway walls is constantly alternated. 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.

Currently, two prototypes of the Maglev Train are being tested: one using electromagnetic suspension (EMS) and the other using electrodynamic suspension (EDS). While both incorporate the same fundamentals into their design, there is one distinct difference in the two models.

Electromagnetic Suspension

In Germany, engineers are building an electromagnetic suspension (EMS) system in which electromagnets are attached to the train’s undercarriage and are directed up towards the guideway, which levitates the train called Transrapid. In this system, the bottom of the train wraps around a steel guideway. Electromagnets that are attached to the train's undercarriage are directed up toward the guideway, which levitates the train about one-third of an inch (1 cm) keeping the train levitated even when it's not moving. Other guidance magnets embedded in the train body keep it stable during travel. Germany has demonstrated that the Transrapid maglev train can reach 300 mph with people on board.

Here is a picture of how the EMS train operates. The magnets located on the side of the track elevate the train while the bottom magnets propel it forward.

Electrodynamic Suspension 

Japanese engineers are developing a competing version of maglev trains that use an electrodynamic suspension (EDS) system, which is based on the repelling force of magnets and not the attracting force. The key difference between Japanese and German maglev trains is that the Japanese trains use super-cooled superconducting electromagnets. These electromagnets 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 more energy.

The cylindrical unit at the top, is a tank holding liquefied helium and nitrogen. The bottom unit is a SC coil alternately generating N poles and S poles. At one end of the tank is the integrally-attached on-board refrigerator, which serves to re-liquefy the helium gas once vaporized by regular heat absorption and external disturbances during running.

contact, so it may be possible in the future to run speeds in excess of 500mph. All Maglev investigated could reach speeds of 300mph.

Guideway System

The guideway is constructed where the vehicle wraps around a Tshaped guideway of steel or concrete beams constructed and erected to very tight tolerances, as shown in the illustrations above. The attraction by magnets and the propulsion stator packs on the underside of the guideway generates lift; attraction between a second set of vehicle magnets and the edgemounted guideway rails provides guidance.

Linear Synchronous Motor

The linear Synchronus motor is the motor that is used by all Maglev operations. It basically energizes discrete guideway coils through individual inverters, thereby powering the maglev vehicle. A computer controls each set of coils and synthesizes a 3 phase wave form, using pulswidth modulation of a direct supply voltage. Its advantages include a very high overall efficiency, a significant operating capability, very flexible vehicle control, and use of the same coils and inverters for power transfer.

Advantages of Maglev

The main advantage for Maglev is the high capacity in which it can hold. The maglev concepts that have been studied so far can deliver 12,000 passengers per hour in each direction. An equivalent air capacity would be 60 Boeing 767’s per hour in each direction at 1 minute intervals. Weather conditions is another major advantage of maglev. Conditions that would normally slow travel would not be an issue because of the noncontact propulsion and braking render make it less susceptible to the restrictions of ice, snow, and rain.

There are further advantages that stem from the fact that maglev is not dependent on petroleum. While aircraft must rely exclusively on petroleum, maglev’s electric power can be supplied from various sources. Maglev’s low energy consumption, low maintenance potential offer very low operating expenses.

Conclusion

Magnetic levitation of trains offers many advantages for the public. With the research conducted it shows that maglev is a cost-effective, environmentally sound, alternative transportation system with significant public benefits. If the U.S. wants to keep up with the newest means of transportation, we all may be getting aboard a maglev in the years to come.

Webliography

www.American-maglev.com

www.Calmaglev.org

www.rti.or.jp/rd/maglev/html/english/maglev_fram_Ehtml

www.maglev2000.com

http://faculty.washington.edu/~jbs/itrans/maglev.html

www.bwmaglev.com

www.csmonitor.com/2001/1213/p15s1-stct.html