MAGNET

 

A magnet is any object that has a magnetic field. It attracts
ferrous objects like pieces of iron, steel, nickel and cobalt. These day’s
magnets are made artificially in various shapes and sizes depending on their
use. One of the most common magnets the bar magnet is a long, rectangular bar
of uniform cross-section that attracts pieces of ferrous objects. The magnetic
compass needle is also commonly used. The compass needle is a tiny magnet which
is free to move horizontally on a pivot. One end of the compass needle points
in the North direction and the other end points in the South direction. The end
of a freely pivoted magnet will always point in the North-South direction. The
end that points in the North is called the North Pole of the magnet and the end
that points south is called the South Pole of the magnet. It has been proven by
experiments that like magnetic poles repel each other whereas unlike poles
attract each other.

 

 

 

 

MAGNETIC
FIELD AND FIELD LINES

 

Magnetic Field

The space surrounding
a magnet, in which magnetic force is exerted, is called a magnetic field. If a bar
magnet is placed in such a field, it will experience magnetic forces.

 

Magnetic Lines of Force

When a small north
magnetic pole is placed in the magnetic field created by a magnet, it will
experience a force. The magnetic lines of force are the lines drawn in a
magnetic field along which a north magnetic pole would move. The direction of a
magnetic line of force at any point gives the direction of the magnetic force
on a north pole placed at that point. Since the direction of magnetic line of
force is the direction of force on a North Pole, so the magnetic lines of force
always begin on the N-pole of a magnet and end on the S-pole of the magnet. A
small magnetic compass when moved along a line of force always sets itself
along the line tangential to it. So, a line drawn from the South Pole of the
compass to its North Pole indicates the direction of the magnetic field.

 

 

 

 

MAGLEV TECHNOLOGY

 

This
technology uses monorail track with linear motors, these trains move on special
tracks rather than the mainstream conventional train tracks. They use very
powerful electromagnets to reach higher velocities, they float about 1- 10 cms
above the guide way on a magnetic field .These trains are propelled by the
guide ways. Once the train is pulled into the next section the magnetism
switches so that the train is pulled on again. The electro magnets run the
length of the guide way.

 

 

THE MECHANICS OF MAGLEV TRAIN

Magnetic levitation trains operate through the use of electro
magnets, which are magnets created by electric current. An electromagnet is
defined as “a coil of insulated wire wound around an iron or steel cylinder”,
and functions when current flows through the coil a magnetic field is produced.
These electromagnets are used to lift the train above its track, as well as
propel it forward.

 

There are three main types of Maglev trains:

 

i)                  
ELECTROMAGNETIC
SUSPENSION

It is
the magnetic levitation of an object achieved by constantly altering
the strength of a magnetic field produced by electromagnets using
a feedback loop. In most cases the levitation effect is mostly due to
permanent magnets as they don’t have any power dissipation, with electromagnets
only used to stabilize the effect. In these kinds of fields an unstable
equilibrium condition exists. Although static fields cannot give stability, EMS
works by continually altering the current sent to electromagnets to change the
strength of the magnetic field and allows a stable levitation to occur. In EMS
a feedback loop which continuously adjusts one or more electromagnets
to correct the object’s motion is used to cancel the instability. In this system Electromagnets are attached to the
train and also attached to the guide way track. They have ferromagnetic stators
on the track and they help them to levitate the train. They have guidance
magnets on the sides of the track they are laid complete along the track A
computer is used to control the height of levitation of train they make us
levitate about ( 1 – 15 cms ).The Max speed these trains could reach is about
438km/hr. They have on-board battery power supply which gives surplus amount of
energy required to run a cabin.

                   

ii)               
ELECTRODYNAMIC SUSPENSION

 

Superconducting magnets are placed under the train. By this system
the train could levitate about 10 cm from the guide way. The magnetic field
which helps the train to levitate is due to use of superconducting magnets. The force in the track is created by
induced magnetic field in wires or conducting strips in the track.

In electrodynamic suspension (EDS), both the guide way and the
train exert a magnetic field, and the train is levitated by the repulsive and
attractive force between these magnetic fields. EDS systems have a major
downside as well. At slow speeds, the current induced in these coils and the
resultant magnetic flux is not large enough to support the weight of the train.
For this reason, the train must have wheels or some other form of landing gear
to support the train until it reaches a speed that can sustain levitation.
Since a train may stop at any location, due to equipment problems for instance,
the entire track must be able to support both low-speed and high-speed
operation. Another downside is that the EDS system naturally creates a field in
the track in front and to the rear of the lift magnets, which acts against the
magnets and creates a form of drag. .          

 

iii)             
INDUCTRACK SYSTEM

 

It is a suspension fail system, no power is required to activate
magnets. Magnetic field is located below the car, they can generate enough
force at low speeds (around 5 km/h) to levitate maglev train. In case of power
failure cars slow down on their own safely, permanent magnets are arranged in
an array which helps in propulsion of the trains. They require either wheels or
track segments that move for when the vehicle is stopped. Neither Inductrack
nor the Superconducting EDS are able to levitate vehicles at a standstill,
although Inductrack provides levitation down to a much lower speed, wheels are
required for these systems. EMS systems are wheel-less.

 

THE MAGLEV TRACK

 

The
magnetized coil running along the track, called a guideway, repels the large
magnets on the train’s undercarriage, allowing the train to levitate between
0.39 and 3.93 inches (1 to 10 cm) above the guideway. Once the train is
levitated, 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. The electric current supplied to the coils in the guideway walls is
constantly alternating to change the polarity of the magnetized coils. 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. Maglev trains float on a cushion of air, eliminating friction. This
lack of friction and the trains’ aerodynamic designs allow these trains to
reach unprecedented ground transportation speeds of more than 500 kmph, or
twice as fast as Amtrak’s fastest commuter train. In comparison, a Boeing-777
commercial airplane used for long range flights can reach a top speed of about
905 kmph. Developers say that maglev trains will eventually link cities that
are up to 1,609 km apart. At 500 kmph, you could travel from Paris to Rome in
just over two hours.

 

 

 

Application

·
NASA plans to use magnetic levitation for launching of space vehicles into low
earth orbit.

·
Boeing is pursuing research in Maglev to provide a Hypersonic Ground Test
Facility for the Air Force.

·
The mining industry will also benefit from Maglev.

 

 

 

 

 

DEVELOPMENT OF MAGLEV TRAINS :

 

There are different factors which are used in the development of
maglev trains, these help in movement, stability, guidance etc of a train .

 

PROPULSION:

Some
EMS systems can provide both levitation and propulsion using an on board linear
motor. But some EDS systems are like they can levitate the train using the
magnets on board but cannot propel it forward. As such, vehicles need some
other technology for propulsion. A linear motor (propulsion coils) mounted in
the track is one solution

 

STABILITY:

Any
combination of static magnets cannot be in a stable equilibrium. Therefore a
dynamic magnetic field is required to achieve stabilization. EMS systems rely
on active electronic stabilization which constantly measure the bearing
distance and adjust the electromagnet current accordingly. All EDS systems rely
on changing magnetic fields creating electrical currents, and these can give
passive stability. Because maglev vehicles essentially fly, stabilisation of
pitch, roll and yaw is required by magnetic technology. In addition to
rotation, move forward and backward, sway (sideways motion) or heave (up and
down motions) can be problematic with some technologies.

 

GUIDANCE

Some
systems use Null Current systems (also sometimes called Null Flux systems);
they use a coil which is wound so that it enters two opposing, alternating
fields, so that the average flux in the loop is zero. When the vehicle is in
the straight ahead position, no current flows, but if it moves off-line this
creates a changing flux that generates a field that naturally pushes and pulls
it back into line. This is the guidance system of maglev trains.

 

EVACUATED
TUBES

Some
systems (notably the Swissmetro system) propose the use of maglev train
technology used in evacuated (airless) tubes, which is used to remove air drag.
This has the potential to increase speed and efficiency greatly, as most of the
energy for conventional maglev trains is lost due to aerodynamic drag. One
potential risk for passengers of trains operating in evacuated tubes is that they
could be exposed to the risk of cabin depressurization unless tunnel safety
monitoring systems can repressurize the tube in the event of a train
malfunction or accident.

COMPARISON

 

Comparison I

 

Vehicle Design:

Maglev
is similar to other transport technology, but the implementation varies
considerably according to the application. Choice of vehicle, weight, shape and
length dominate transport system design. There are 3 key issues that affect the
EI of a transport system and are primarily determined by vehicle design.

 

For
high speed travel the dominant energy usage is to overcome aerodynamic drag.
For constant speed travel EI is proportional to drag force per passenger.
Airplanes do much better than it is possible for ground transportation because
of lesser pressure at greater (12,000 m) height.

 

For
low-speed travel the dominant energy loss is due to the need to supply kinetic
energy to change vehicle’s speed and this is lost when brakes are applied.

 

Suspension
and propulsion losses are always significant. Not only is there a direct loss
such as wheel hysteresis and bearing friction but at high speed aerodynamic
loss become more than direct losses. With these facts in mind, consider the
design aspect of the weight, shape and length.

 

Weight:
All transport technology has been moving in the direction of reducing vehicle
weight, and using regenerative braking.

 

Shape:

Shape
is important because it affect aerodynamic loss and noise, both external and
internal. Even low speed vehicle should have modest streamlining and high speed
vehicle need more extreme shapes. Japanese Fastech 360 train designed for
360km/h, Trans rapid TR09 designed for 350-500 km/h. the nose section is very
important for high speed, particularly for vehicles entering existing tunnels.
For HSR the main aerodynamic drag is on the body, wheels and pantograph. Well
designed maglev vehicle have less drag and are quieter than modern high speed
trains, even when going substantially faster.

 

Length:

Vehicle
length is a critical parameter. The frontal area is constrained by the assumed
need to provide height for standing head room and width for at least four
abreast sitting with reasonable comfort. With maglev the frontal can be less
than for conventional trains because the suspension has less frontal area and
there is no pantograph. The minimum length is determined by passenger carrying
ability.

 

Comparison 2:

 

Fuel Efficiency

· Unlike
the previous forms of transportation, Maglev trains run on electricity rather
than fossil fuels. Electricity is a renewable source of energy and can be
created in several different ways including nuclear, hydro and solar plants.
Fossil fuels are non-renewable sources of energy. They must be burnt, releasing
carbon emission in the atmosphere in order to produce energy

·Travelling
at a speed of 300 mph and 150 mph. Maglev trains use 0.4 mega joules and 0.1
mega joules per passenger mile respectively. An automobile travelling at a
speed of 60 mph with 20-mpg fuel efficiency uses 4 mega joules per passenger
per mile. Using these numbers, Maglev trains moving at half this speed attains
efficiency 40 times greater than that of an automobile.

 

Comparison 3:

 

Speed and cost:

· When
commuting in a car one’s average arrival time can be hard to calculate due to
traffic and driving conditions. Everyone has been struck in traffic. Unannounced construction, gaper
delays, sometimes nothing at all can create massive delays on the roadway.

 · Car
also requires much maintenance. Automobiles must meet state standards in order
to be legal for the roads and all cars must be insured. This constant
maintenance and legal coverage becomes very costly for any common citizen.

 · Planes
as well experience delays. Prime weather and air traffic condition are
essential in insuring passenger a safe flight. However, when these criteria are
not made, delays occur.

 · In
life, just as in driving, there is no way to predict what will happen in
future. What we can do is to put the odds in our favour is to minimize risk.
That’s where maglev train come into play. Maglev trains have a dedicated
infrastructure solely for the train itself. No other vehicles are compatible
with their magnetic guide ways and so no other vehicles travel on it. This
means no traffic and no collisions. Weather conditions have little to no effect
on maglev trains except under severe conditions. So a train can travel even
when the weather is subpar. In an automobile or conventional locomotive wet
conditions decreases friction between the vehicle and ground. This increases
stopping time and the probability that a vehicle may slip. The magnetic forces
at hand are unaffected by such condition. Since no contact is made between the
maglev train and the railway. Less wear is put on each. This means less
maintenance. Less maintenance creates fewer delays while allowing lower ticket
prices.

 

 

 

 

ADVANTAGES

 

Aircraft are theoretically flexible but commercial air routes are
not. High-speed maglevs are designed to compete on journey times with flights
of 800 kilometres (500 miles) or less. Additionally, while maglevs can serve
several cities in between such routes and be on time in all weather conditions,
airlines cannot come close to such reliability or performance. Because maglev
vehicles are powered by electricity and do not carry fuel, maglev fares are
less susceptible to the heavy price swings created by oil markets. Travelling
via maglev also offers a significant safety margin over air travel since
maglevs are designed not to crash into other maglevs or leave their guideways.
Aircraft fuel is a significant danger during takeoff and landing as there are
chances for accidents. In real-world situations the speed of maglev are less
than aircraft, but maglev still save time due to less number of hurdles it
takes to travel in them as compared to air travel. With air travel, people need
to spend time at airports for check-in, security, boarding, etc. In air travel,
time is also consumed (primarily in busy airports) by the aircraft for taxing,
waiting in queue for take-off and landing, which are negligible in case of
maglev. Because no contact is made between the trains allow for near
frictionless travel. This near frictionless travel has numerous benefits
including higher speeds, less noise, resistance to poor weather conditions, and
decreased maintenance. Maglev trains initially cost more than conventional
means of transportation during construction, but with conventional transport,
friction between tracks and wheels often causes damage over time, which
requires both funds and labour to repair. Maglev trains do not experience this
physical stress, and thus, require only slight further funding once they are
built. They are not entirely frictionless, however. They simply experience no
surface friction, which does help decrease maintenance and power consumption.
Maglev trains do, however, still experience air resistance and slight
electromagnetic drag, but these conditions are present in negligible amounts.
Maglev trains are quieter than conventional transport.

 

Disadvantages:

While the advantages of Maglev Train System may seem quite promising in
themselves, they are not enough to overshadow the biggest problem with the
maglev trains: the high cost incurred on the initial setup. While the fast
conventional trains that have been introduced of late, work fine on tracks
which were meant for slow trains, maglev trains require an all new set up right
from the scratch. As the present railway infrastructure is of no use for
maglevs, it will either have to be replaced with the Maglev System or an
entirely new set up will have to be created?both of which will cost a decent amount
in terms of initial investment. Even though inexpensive as compared to EDS, it
is still expensive compared to other modes. Although Maglevs are pretty quiet, noise caused by air disturbance still
occurs.

 

CONCLUSION

 

 

These trains consume very less energy compared to conventional
trains. They require no large engine kind of stuff as they run using linear
motors. They Move a lot faster than normal trains because they are not affected
by ground friction, they would only have air resistance or drag resistance.
They are incompatible with existing rail lines because they need a separate
track to levitate, unlike the traditional high-speed trains. These technology
needs to be implemented in large countries where transportation time can be
reduced and it is also a safe and efficient way to travel. Initially the cost
is very high but it may decrease in near future. Now
that we know how the technology work, we believe that maglev system can be
research further to be used in advanced application and maglev technologies are
in demand due to it beings environmentally friendly.