MAGNETIC LEVITATION
Overcoming the pull off gravity and fighting acceleration are some of the major challenges for scientists who are looking to achieve flight and/or high-speed transportation face. One way to overcome this is the modern and growing technology known as Magnetic Levitation.
Magnetic levitation (aka. maglev or magnetic suspension) is the method by which an object is suspended with no support other than magnetic fields. More easily said, Maglev is the means of floating one magnet over another. Here magnetic force is used to counteract the effects of the gravitational acceleration and any other counter acceleration.
What happens when you keep a diamagnetic material in an external magnetic field?
Well, it floats or rather levitates. This happens because the external magnetic field forces the electron around the atom of a diamagnet to change course, and their new motion generates an opposing magnetic field and temporarily expels a portion of an external magnetic field. Even though this is a weak magnetic field, it does cause the material to repel from the magnet. With a strong enough magnetic field, diamagnetic materials can levitate. As mentioned before, this repulsive force is very weak compared with the attractive force a ferromagnetic material such as iron will experience due to a magnetic field.
According to a theorem attributed to Earnshaw, it is impossible to achieve static levitation using any combination of fixed magnets and electric charges. There are, however, ways to levitate by getting round the assumptions of the theorem. Magnetic levitation employs diamagnetism.
Then… Can we levitate?!
The answer is yes!! Humans can also levitate, though the magnetic field required would be enormous.
In magnetic levitation, there is lack of contact and thus no wear and friction. This increases efficiency, reduces maintenance costs, and increases the useful life of the system. Cool right! This technology can be an efficient and useful tool in various industries.
One of the most important and popular applications of magnetic levitation is in Maglev Trains.
There are already many countries that are attracted to maglev systems. Many systems have been proposed in different parts of the world.
Maglev vehicles use non-contact magnetic levitation, guidance, and propulsion systems and have no wheels, axles, and transmission. Contrary to traditional railroad vehicles, there is no direct physical contact between the maglev vehicle and its guideway. These vehicles move along magnetic fields that are established between the vehicle and its guideway. Conditions of no mechanical contact and no friction provided by such technology make it feasible to reach higher speeds of travel, which are attributed to such trains.
These trains float over guideways using the basic principles of magnets and hence are a good replacement for the old steel wheel and track trains. There’s no rail friction to speak of, meaning these trains can hit speeds of hundreds of miles per hour. Yet high speed is just one major benefit of maglev trains. Because the trains rarely (if ever) touches the track, there’s far less noise and vibration than typical, earth-shaking trains. Less vibration and friction results in fewer mechanical breakdowns, meaning that maglev trains are less likely to encounter weather-related delays.
Levitation technologies
Electromagnetic levitation(EML) uses the attractive force between electromagnets on the levitated object and the circuit on the ground.
Electrodynamic levitation(EDL) makes use of the repulsive force between magnets (superconductive magnets) on the levitated object and induced current in the secondary circuit on the ground.
Thus, we may classify magnetic levitation systems into two groups: attractive systems and repulsive systems. The former is referred to as electromagnetic suspension(EMS) while the latter is referred to as electrodynamic suspension(EDS).
In an attractive system, the moving component, or carrier, is suspended under the fixed component, or guide track. It uses feed- back control, which is complicated, and requires power to levitate a carrier.
The repulsive system utilizes permanent magnets and air-core electromagnet coils running constant current to provide repulsive force. It has a simple configuration and does not require power to levitate a carrier.
EDS is more popularly used.
The Maglev system uses two sets of magnets: one set to repel and push the train up off the track, and another set to move the elevated train ahead. Here, both magnetic attraction and repulsion are used to move the train car along the guideway.
The magnets employed are superconducting, which means that when they are cooled to less than 450 degrees Fahrenheit below zero, they can generate magnetic fields up to 10 times stronger than ordinary electromagnets, enough to suspend and propel a train. 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 cooling the coils at frigid temperatures, the system saves energy. However, the cryogenic system used to cool the coils can be expensive and add significantly to construction and maintenance costs.
Any maglev system consists of the following three subsystems:
- a magnetic suspension,
- a propulsion motor, and
- a power system.
The magnetic suspension is supposed to ensure a stable suspension of a vehicle in its own magnetic field. The propulsion motor should produce a propulsion force sufficient for continuous flight of the vehicle along an assigned track with a given speed. If you’ve ever played with magnets, you know that opposite poles attract and like poles repel each other. This is the basic principle behind electromagnetic propulsion. The power system provides uninterrupted power supply. A source of energy (an engine or a battery, at least) is always required to keep an object afloat.
Electrifying the propulsion loops generates magnetic fields that both pull the train forward from the front and push it forward from behind.
Another big benefit is safety. Maglev trains are “driven” by the powered guideway. Any two trains traveling on the same route cannot catch up and crash into one another because they’re all being powered to move at the same speed. Similarly, traditional train derailments that occur because of cornering too quickly can’t happen with Maglev. The further a Maglev train gets from its normal position between the guideway walls, the stronger the magnetic force required for pushing it back into place.
The big difference between a maglev train and a conventional train is that maglev trains do not have an engine — at least not the kind of engine used to pull typical train cars along steel tracks. The engine for maglev trains is rather inconspicuous. Instead of using fossil fuels, the magnetic field created by the electrified coils in the guideway walls and the track combine to propel the train.
The Shanghai maglev train, also known as the Shanghai Transrapid, has a top speed of 430 km/h (270 mph). The line is the fastest operational high-speed maglev train, designed to connect Shanghai Pudong International Airport and the outskirts of Central Pudong, Shanghai. It covers a distance of 30.5 km (19 mi) in just over 8 minutes! The launch generated wide public interest and media attention, which propelled the popularity of the mode of transportation. Despite over a century of research and development, currently high-speed maglev is only available in China and maglev transport systems are now operational in just three countries (Japan, South Korea and China).
Evolution of Magnetic Levitation
Levitation of a permanent magnet over a superconductor was first demonstrated by V. Arkadiev in 1945, and the levitation of magnets above superconductors became much easier and more common after the discovery of high-temperature superconductors and materials superconducting at liquid-nitrogen temperature in 1987. Magnetic bearings based on repulsive forces between permanent magnets and high-temperature superconductors have been developed for a number of potential applications, including energy-storage flywheels and model maglev trains (carrying nitrogen-cooled superconductors on cars floating above permanent-magnet tracks).
Another means of using a moving magnet to circumvent Earnshaw’s rule and achieve full levitation is to move the magnet in the presence of an electrical conductor, thereby inducing Eddy currents in the conductor and associated repulsive forces on the magnet. This is the basis of the electrodynamic approach to maglev trains proposed by James Powell and Gordon Danby in the 1960s and developed most extensively by Japan National Railway. Strong superconducting electromagnets on the cars induce Eddy currents in the conducting track that produce levitation once the cars reach sufficient speed. Levitation via induction and eddy-current repulsion can also be achieved with AC fields.
In 1983, Roy Harrigan received a patent for a “levitation device” that consisted of a small spinning magnet floating above a large base magnet, and Bill Hones of Fascinations, Inc., later developed Harrigan’s idea into a successful commercial product called the Levitron. As with the rotor of the electric meter, the spinning magnet of the Levitron was pushed upward by the repulsion forces between like poles. But it floated fully contact-free, getting around Earnshaw’s rule because it was not a static magnet — it was spinning. At first glance, it seems that it is simple gyroscopic action that keeps the spinning magnet from tipping over, but detailed mathematical analysis by several prominent scientists soon showed that the stability of the Levitron is a bit more complicated than that.
In the 1930s, German scientists demonstrated levitation of highly diamagnetic graphite and bismuth, and after the development of high-field superconducting electromagnets, levitation of even much weaker diamagnets like water, wood, and plastic was accomplished. This was little noticed until 1997, when Andre Geim and his colleagues used a 16 Tesla superconducting magnet to magnetically levitate a small living frog, their “flying frog” finally drawing worldwide attention to the wonder of diamagnetic levitation.
Geim, winner of the 2010 Nobel Prize in Physics for research on graphene, was awarded an Ig Nobel Prize ten years earlier for frog levitation, an award he and co recipient Sir Michael Berry accepted, with a call for “more science with a smile.”
Today, maglev transportation is one of the fastest growing means of transportation in industrialized countries. This method has the potential to be faster, quieter and smoother than wheeled mass transit systems and the power needed for levitation is usually not a particularly large percentage of the overall consumption — most of it being used to overcome air drag.
Other applications
But though magnetically levitated trains have been the focus of much of the worldwide interest in maglev, the technology is not limited to train travel. Other applications of this technology include:
Launching Rockets
A magnetic levitation track is up and running at NASA’s Marshall Space Flight Center in Huntsville, Ala, USA. The experimental track is installed inside a high-bay facility at the Marshall Center. Marshall’s Advanced Space Transportation Program is developing magnetic levitation or Maglev technologies that could give a space launch vehicle a “running start” to break free from Earth’s gravity. A Maglev launch system would use magnetic fields to levitate and accelerate a vehicle along a track at speeds up to 600 mph. The vehicle would shift to rocket engines for launch to orbit. Maglev systems could dramatically reduce the cost of getting to space because they are powered by electricity, an inexpensive energy source that stays on the ground — unlike rocket fuel that adds weight and cost to a launch vehicle.
Maglev Fan
The maglev fan provides superior performance, low noise, and long life. By using magnetic levitation forces, these fans feature zero friction with no contact between shaft and bearing. With excellent rotational stability, the maglev fan eliminates vibration and typical wobble and shaking typically experienced in fan motors. The maglev fan also provides excellent high temperature endurance that results in long life. The models also feature all-plastic manufacture of major items for optimal insulation resistance and electrostatic discharge (ESD) performance.
Feasibility of Maglev trains in India
India has one of the largest train networks in the world. But Indian railways doesn’t have any train running with a more than 160 kmph. High speed corridors have been proposed but still not Implemented.
The fastest train in India is the Bhopal Shatabdi which runs at a speed of 150 kmph.
In India, thousands of people travel daily to and from metro cities like Delhi , Mumbai, Kolkata, Bangalore etc. Keeping in mind the need of passengers, increasing air traffic and fuel price hiking, we should focus on any alternative which can improve and help in travelling between the cities in minimum time, and in a more convenient and safer way. Rail transport creates least problems to the environment as compared to other transport systems. Maglev doesn’t use any fossil fuel — it uses magnets to run. As fossil fuels are available in limited amounts, the unavailability of fuel will not harm the maglev transport system.
BHEL (Bharat Heavy Electronics Limited) has tied up with SwissRapide AG (centre for the planning, construction and operation of ultra-fast, high-performance and highly reliable Maglev rail systems and projects around the globe) to bring Maglev high-speed trains to India. The agreement has been signed in the backdrop of the Prime Minister’s ‘Make in India’ and ‘Aatmanirbhar Bharat’ initiatives, and will enable BHEL to bring the latest, world-class technology to India and manufacture state-of-the-art Maglev trains indigenously. This can very well prove to be a big boost to travelers all across the country.
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