MAGNETIC LEVITATION BEYOND BULLET SPEED

Introduction
Understanding the secrets of the nature and unrevealing the hidden facts is an all time profession of mankind and the beauty of which lies in its diversified horizons, characterized by the discovery of mighty galaxies to the invisible atom. One such revelation has benefited human race in the form of high speed electric trains which have shortened the days long distances to merely a few hours. The magic behind this revolution is very simple and many of you might be knowing this from elementary school level physics, yes it is the magnetic field effect of the current flowing in a conductive path. More precisely it is the magnetic levitation principle that allows suspension of an object above a certain level, ground in case of bullet trains. The magnetic field is the only support to the lift against gravity and other forces tending to destabilize the object.



Principle of operation
It is a well recognized fact that like poles repel each other, if an object is placed between two such magnet poles, it will be repelled by both sides vertically and will try to escape sideways if it is not ties to any support. If this phenomena is taken on a large scale where instead of using permanent magnets, electromagnets are put to work and required amount of force is generated by controlling the magnetic field intensity from a remote end, MAGLEV can be used to drive vehicles having tons of weight such as in bullet trains which were a dream until recently when Japan and Germany introduced speeds in the range of approximately 270 to 290 mph.



Historical Facts
There are various applications of maglev but the ultimate application is found in bullet trains and two of the major systems, the German and Japanese systems are still not only in action but these are also evolving. In 1979, Germany produced its first bullet train known as Transrapid International, which was licensed to carry passengers but speed was less than 250 mph. The next version of Transrapid achieved the highest speed of its time approaching to 257 mph with its next iteration of 271 mph. The principle employed to achieve this speed is that the frame of car wraps with guideway and is lifted through attraction from underside of the path. Germany is still working on new technologies with even faster trains to connect cities hundreds of miles apart such as Berlin and Hamburg.

On the contrary the Japanese systems is divided into two major categories, the HSST (high speed surface transport) system initiated in 1974 and the Yamanashi system. The HSST works the same way as mentioned above about the German system whereas the later one fundamentally differs from the first that it uses on board superconducting electromagnets and a guideway with coils in base and side beams used to provide levitation, braking, guidance and propulsion. The cooling of magnets is provided by using the liquid helium and nitrogen with an inbuilt re-liquefaction system.

What is Superconducting Maglev
In superconducting Maglev systems, linear instead of a rotary motors are used and that is why these are also known as linear motor rail cars. To distinguish between rotary and linear motors, we can add that a linear motor exerts its energy in straight line instead of a circle. The rotor and stator of this motor is split in such a way that one part resides on train and other on guideway ( path followed by bullet train). The problem of carrying heavy equipment such as transformers and inverters is mitigated by mounting superconducting magnets on train and leaving energized coils for guideway mechanism. The pathway coils are energized by using power supply from utility grid and propulsive force is generated with superconducting magnets in conjunction with guide way coils. Apart from providing forward motion this method also ensures that there is no derailing risk and also as there are no wheels so rail adhesion problem is self resolved.

Pros and Cons
Bullet trains due to their environment friendly fuel and high speeds have become the prime source of transportation both in Europe , Asia and America. Governments have managed to keep this mode of travelling easily accessible at cheaper price and acts as a substitute to air travels between distant cities. From the safety point of view the risk of derailing is minimum due to its efficient working principle and friction power loss is also minimum as the whole vehicle is suspended in the air. The cons include operational cost as megawatts of electricity are consumed and moreover, dedicated transformers, power converters and cooling systems are needed for maintenance thus increasing the cost slightly higher.

Application of Maglev in Seismology
The application of maglev is not only restricted to bullet trains but also applied in other areas of daily life as well. One of the best example is the inverted pendulum which is kept balanced in inverted position by the magnetic field repulsion thus making it inherently unstable and a best suitable option for use in seismometers which are used to measure any type of disturbance that occurs in the nature such as volcanic eruptions and earthquake etc. Moreover this concept is used in control and robotics for industrial use.

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