02-07-2013, 01:08 PM
DRIVING WITHOUT WHEELS, FLYING WITHOUT WINGS
DRIVING WITHOUT.doc (Size: 488 KB / Downloads: 57)
Abstract
This paper “Driving without wheels, Flying without wings” deals with the present scenario of magnetic levitation (maglev) with Linear induction motor (LIM) .The magnetically levitated train has no wheels, but floats-- or surfs-- on an electromagnetic wave, enabling rides at 330 miles per hour. By employing no wheels, maglev eliminates the friction, and concomitant heat, associated with conventional wheel-on-rail train configurations. There are two basic types of non-contact Maglev systems Electro Dynamic Suspension (EDS), and Electro Magnetic Suspension (EMS). EDS is commonly know as "Repulsive Levitation," and EMS is commonly known as "Attractive Levitation." Each type of Maglev system requires propulsion as well as "levitation." The various projects above use different techniques for propulsion, but they are all variations of the Linear Induction Motor (LIM) or Linear Synchronous Motor (LSM).The conversion to a linear geometry has a far greater effect on induction motor performance than on that of synchronous motors. The cost of making the guideway is a high percentage of the total investment for a maglev system. The comparison looks even better for maglev when the terrain becomes difficult. Many of the tunnels, embankments, and cuttings necessary for roads and railroads are avoided because maglev guideways can be easily adapted to the topography. The Maglev system requires a slightly larger start-up capital construction cost, its operating cost-- because it deploys electricity in electromagnets in an extraordinarily efficient manner, rather than using as a fuel source coal, gas or oil-- can be one-half that of conventional rail. The crucial point is that maglev will set off a transportation and broader scientific explosion.
Introduction:
Air flights are and will remain beyond the reach of a major section of society, particularly in India. Moreover there are problems of wastage of time in air traffic delays and growing safety concerns. Trends in increased mobility of large masses with changing lifestyle for more comfort are leading to congestion on roads with automobiles. Besides, increasing pollution levels from automobiles, depleting fuel resources, critical dependence on the fuel import and due to a limited range of mobility of buses and cars the need for fast and reliable transportation is increasing throughout the world. High-speed rail has been the solution for many countries. Trains are fast, comfortable, and energy-efficient and magnetic levitation may be an even better solution.
Development of magnetic levitated transport systems is under progress in developed countries and it is just a matter of time they make inroads to India as well. Therefore, it will be interesting to know about the science and technology behind mass ground transport system known as "magnetic flight".
Magnetic levitation
Magnetic levitation is the use of magnetic fields to levitate a (usually) metallic object. Manipulating magnetic fields and controlling their forces can levitate an object. In this process an object is suspended above another with no other support but magnetic fields. The electromagnetic force is used to counteract the effects of gravitation. . The forces acting on an object in any combination of gravitational, electrostatic, and magnetostatic fields will make the object's position unstable. The reason a permanent magnet suspended above another magnet is unstable is because the levitated magnet will easily overturn and the force will become attractive. If the levitated magnet is rotated, the gyroscopic forces can prevent the magnet from overturning. Several possibilities exist to make levitation viable.
Linear induction motor(LIM) in magnetic levitation
The High Speed Surface Transport (HSST) sysem is propelled by linear induction motor.The HSST primary coils are attached to the carriag body and the track configuration is simple, using the steel rails and aluminum reaction plates.The HSST levitation system uses ordinary electromagnets that excerts an attractive force and levitate the vehicle.The electromagnetsare attached to the car, but are positioned facing the under side of the guide way's steel rails.They provide an attractive force from brlow,levitating the car.
This attractive force is controlled by a gap sensor that measures the distance brtween the rails and electromagnets. A control circuit continually regulates the current to the electromagnet , ensuring that the gap remains at a fixed distance of about 8 mm, the current is decreased. This action is computer controlled at 4000 times per second to ensure the levitation.
As shown in figure, the levtation magnets and rail are both U shaped (with rail being an inverted U ). The mouths of U face one another. This configuation ensures that when ever a levitational force is excerted, a lateal guidance force occurs as well. if the electromagnet starts to shift laterally from the center of the rail, the lateral guidance force is excerted in proportion to the extent of the shift , bringing the electromagnet back into alignment. Theuseofanelecromagnetic attractive force to both levitatie and guide the car is a significant feature of HSST the system
we cna visulize an HSST linear motor as an ordinary electric induction motor that has been split open and flattend. This of linear motor has recently been used in various fields the fig illustrates in the HSST, the primary side coils of motor are attached to the car body in the secondary side reaction plates are installed along the guide way .this component acts as induction motor and ensures both propulsion and breaking force without any contact between car and guide way. This system a car mounted primary linear induction system. The ground side requires only a steel plate backed by an aluminum or copper plate, meaning that the rail source is simple.
Conclusion
The MagLev Train: Research on this ‘dream train’ has been going on for the last 30 odd years in various parts of the world. The chief advantages of this type of train are: 1. Non-contact and non-wearing propulsion, independent of friction, no mechanical components like wheel, axle. Maintenance costs decrease. Low noise emission and vibrations at all speeds (again due to non-contact nature). Low specific energy consumption. Faster turnaround times, which means fewer vehicles. All in all, low operating costs.Speeds of upto 500kmph..Low pollutant emissions. Hence environmentally friendly