.A NEW TRACK IN THE RUNNING
Engineers are constantly trying to improve on previous technology. Within the past few years the United States
This system uses an “arrangement of powerful permanent magnets, known as a Halbach array, to create the levitating force”. The Halbach array uses high field alloy magnetic bars. These bars are arranged so the magnetic fields of the bars are at 90º angles to the bars on either side, which causes a high powered magnetic field below the array.
The Inductrack is similar to that of the EDS system in that it uses repulsive forces. The magnetic field of the Halbach array on the train repels the magnetic field of the moving Halbach array in the guideway. The rails in the system are slightly different. The guideway is made from “two rows of tightly packed levitation coils”. The train itself has two Halbach arrays; one above the coils for levitation and the other for guidance. As with the EMS and EDS system, the Inductrack uses a linear synchronous motor. Below is a picture of the Halbach array and a model of the Inductrack system.
MODEL OF THE INDUCTRACK
A major benefit of this track is that even if a power failure occurs, the train can continue to levitate because of the use of permanent magnets. As a result, the train is able to slow to a stop during instances of power failure. In addition, the train is able to levitate without any power source involved. The only power needed for this system is for the linear synchronous motor and “the only power loss that occurs in this system is from aerodynamic drag and electrical resistance in the levitation circuits”.
Although this type of track is looking to be used, it has only been tested once on a 20-meter track. NASA is working together with the Inductrack team to build a larger test model of 100 meters in length. This testing could eventually lead to a “workable Maglev system for the future”. The Inductrack system could also be used for the launching of NASA’s space shuttles. The following picture displays side by side all three types of levitation systems.
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THREE TYPES OF LEVITATION TECHNIQUES
LATERAL GUIDANCE SYSTEMS
The Lateral guidance systems control the train’s ability to actually stay on the track. It stabilized the movement of the train from moving left and right of the train track by using the system of electromagnets found in the undercarriage of the MagLev train. The placement of the electromagnets in conjunction with a computer control system ensures that the train does not deviate more than 10mm from the actual train tracks.
The lateral guidance system used in the Japanese electrodynamic suspension system is able to use one “set of four superconducting magnets” to control lateral guidance from the magnetic propulsion of the null flux coils located on the guideways of the track as shown in Fig.[10]. Coils are used frequently in the design of MagLev trains because the magnetic fields created are perpendicular to the electric current, thus making the magnetic fields stronger. The Japanese Lateral Guidance system also uses a semi-active suspension system. This system dampens the effect of the side to side vibrations of the train car and allows for more comfortable train rides. This stable lateral motion caused from the magnetic propulsion is a joint operation from the acceleration sensor, control devive, to the actual air spring that dampens the lateral motion of the train car.
A SKETCH OF THE COMBINED LEVITATION, PROPULSION AND GUIDANCE SYSTEM
The lateral guidance system found in the German transrapid system(EMS ) is similar to the Japanese model. In a combination of attraction and repulsion, the MagLev train is able to remain centered on the railway. Once again levitation coils are used to control lateral movement in the German MagLev suspension system. The levitation coils are connected on both sides of the guideway and have opposite poles. The opposites poles of the guideway cause a repulsive force on one side of the train while creating an attractive force on the other side of the train. The location of the electromagnets on the Transrapid system is located in a different side of the guideways. To obtain electro magnetic suspension, the Transrapid system uses “the attractive forces between iron-core electromagnets and ferromagnetic rails.” In addition to guidance, these magnets also allow the train to tilt, pitch, and roll during turns. To keep all distances regulated during the ride, the magnets work together with sensors to keep the train centered.
.ADVANTAGES AND LIMITATIONS OF MAGLEV
ADVANTAGES
Magnetic Fields
· Intensity of magnetic field effects of Maglev is extremely low (below everyday household devices)
· Hair dryer, toaster, or sewing machine produce stronger magnetic fields
Energy Consumption
· Maglev uses 30% less energy than a highspeed train traveling at the same speed. (1/3 more power for the same amount of energy)
Speed | ICE Train | Maglev Train |
200 km/hr | 32 Wh/km | 32 Wh/km |
250 km/hr | 44 Wh/km | 37 Wh/km |
300 km/hr | 71 Wh/km | 47 Wh/km |
400 km/hr | - | 71 Wh/km |
Noise Levels
· No noise caused by wheel rolling or engine
· Maglev noise is lost among general ambient noise
· At 100m - Maglev produces noise at 69 dB
· At 100m - Typical city center road traffic is 80 dB
Vibrations
· Just below human threshold of perception
Power Supply
· 110kV lines fed separately via two substations
Power Failure
· Batteries on board automatically are activated to bring car to next station
· Batteries charged continuously
Fire Resistance of vehicles
· Latest non-PVC material used that is non-combustible and poor transmitter of heat
· Maglev vehicle carries no fuel to increase fire hazard
Safety
· 20 times safer than an airplane
· 250 times safer than other conventional railways
· 700 times safer than travel by road
· Collision is impossible because only sections of the track are activated as needed. The vehicles always travel in synchronization and at the same speed, further reducing the chances of a crash.
Operation Costs
· Virtually no wear. Main cause of mechanical wear is friction. Magnetic Levitation requires no contact, and hence no friction.
· Components normally subjected to mechanical wear are on the whole replaced by electronic components which do not suffer any wear
· Specific energy consumption is less than all other comparable means of transportation.
· Faster train turnaround time means fewer vehicles
LIMITATIONS
There are several disadvantages with maglev trains. Maglev guide paths are bound to be more costly than conventional steel railways. The other main disadvantage is lack with existing infrastructure. For example if a high speed line
between two cities it built, then high speed trains can serve both cities but more importantly they can serve other nearby cities by running on normal railways that branch off the high speed line. The high speed trains could go for a fast run on the high speed line, then come off it for the rest of the journey. Maglev trains wouldn't be able to do that, they would be limited to where maglev lines run. This would mean it would be very difficult to make construction of maglev lines commercially viable unless there were two very large destinations being connected. Of the 5000km that TGV trains serve in France
A possible solution
Although it is not seen anywhere a solution could be to put normal steel wheels onto the bottom of a maglev train, which would allow it to run on normal railway once it was off the floating guideway.
.CONCLUSION
Railways using MagLev technology are on the horizon. They have proven to be faster than traditional railway systems that use metal wheels and rails and are slowed by friction. The low maintenance of the MagLev is an advantage that should not be taken lightly. When you don’t have to deal with the wear and tear of contact friction you gain greater longevity of the vehicle. Energy saved by not using motors running on fossil fuels allow more energy efficiency and environmental friendliness.
Maglev will have a positive impact on sustainability. Using superconducting magnets instead of fossil fuels, it will not emit greenhouse gases into the atmosphere. Energy created by magnetic fields can be easily replenished. The track of a Maglev train is small compared to those of a conventional train and are elevated above the ground so the track itself will not have a large effect on the topography of a region. Since a Maglev train levitates above the track, it will experience no mechanical wear and thus will require very little maintenance.
Overall, the sustainability of Maglev is very positive. Although the relative costs of constructing Maglev trains are still expensive, there are many other positive factors that overshadow this. Maglev will contribute more to our society and our planet than it takes away. Considering everything Maglev has to offer, the transportation of our future and our children’s future is on very capable tracks.
.REFERENCES
Þ Sawada, Kazuo, "Magnetic Levitation (Maglev) Technologies 1. Supderconducting Maglev Developed by RTRI and JR Central", Japan
Þ He, J. L., Coffey, H. T., Rote, D.M. "Analysis of the Combined MagLev Levitation, Propulsion, and Guidance System", IEEE Transactions on Magnetics, Vol 31, No. # 2, March 1995, pp 981-987.
Þ Zhao, C. F., Zhai, W. M., "MagLev Vehicle/Guideway Vertical Random Response and Ride Quality", Vehicle System Dynamics, Vol 38, No # 3., 2002, pp 185-210.
Þ Cassat, A., Jufer, M. "MAGLEV Projects Technology Aspects and Choices", Transactions on Applied Superconductivity, Vol 12, No. # 1, March 2002, pp 915-925.
Þ Powell, J., Danby G. “Maglev: The New Mode of Transport for the 21st Century” 21st Century Science & Technology Summer Issue. http://www.21stcenturysciencetech.com/articles/Summer03/maglev2.
Þ Lever, J. H. “Technical Assessment of Maglev System Concepts”, Final Report by the Government Maglev System Assessment Team.
Þ Freeman, R. http://members.tripod.com/~american_almanac/maglev.htm.
Þ The Monorail Society Website Technical Pages http://www.monorails.org/tMspages/TPMagIntro.html
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