Essay: Magnetic Levitation

Magnetic Levitation is a technique or method by which an object is levitated or
suspended and propelled using MAGNETISM. Basically the Magnetic Forces
(Attraction or Repulsion) are used to eliminate the acceleration due to Gravity, Air
resistance and any other friction or resistance to the movement of the object.
LIFT AND STABILITY
The two major necessities are to provide a sufficient Lifting Force to act against
gravity and to provide Stability such that the system or object doesn’t slide, slip or
vibrate when the force is removed .As the object is suspended in air it does not
touch the guide way or magnet hence reducing the wear and tear caused due to
friction. This Lift and Stability is provided to the vehicle by Magnetism, either
attraction, repulsion or both are employed to levitate the vehicle above the
guideway or track. The simultaneous presence of both attraction and
repulsion propels the vehicle forward. If the guideway also possesses
superconducting electromagnetic properties then the vehicle can be
levitated even after power supply has been cut off , as the superconducting
electromagnets conduct current even when the power supply is cut off.
Hence for providing stability both static and dynamic we need a
feedback system which automatically detects the position and movement of
the vehicle and provides necessary corrections if the vehicle comes closer
or goes away from the track. The methods of levitation are discussed in
the next section.
[1] Mechanical Constraint (Pseudo Levitation):-
Mechanical Constraint basically means either using the attractive
or repulsive force for effective levitation of the vehicle. If we
are using repulsion then we align the two magnets vertically such
that they have a strong force of repulsion then this will levitate
one magnet above the other.
[2] Servo Mechanisms:-
As we know that magnetic attraction from a fixed magnetic field
Increases with decrease in the distance and decreases with increase
In distance. This is unstable and may lead to vibrations and jerks during
the travel therefore a feedback system is required to check the position,
velocity of the vehicle. This feedback system is required to adjust one or
two electromagnets every time it senses any abruptness and adjusts
the position of the vehicle to the stable one.
[3] Induced Currents:-
If a time varying magnetic field is applied on a conductor then a
reverse current is set up in the conductor which opposes the
magnetic field .This is the phenomenon caused according to the
LENZ’s LAW.
Hence these systems are auto stabilizing but sometimes external
damping is also required which can be incorporated by feedback system.
[4] Diamagnetically Stabilized Levitation:-
If a conductor is levitated above an electromagnet with Alternating
Current flowing through the electromagnet, because of this any normal
conductor behaves as a diamagnetic material. The conductor behaves so
because of the eddy currents produced in the conductor. The fields due
the eddy currents opposes the field due to the electromagnet and hence
repels the conductor away from the electromagnet. This is an ideal
method for levitation and providing propulsion.
MAGLEV vehicles designed till date are based on two principles or techniques of levitation which include:-
Electromagnetic Suspension is based on the attraction forces between
the magnetic materials. As we know that like poles repel and opposite
poles attract , the same principle is used in EMS . Here the system is
oriented in ‘C’ shaped manner , where the Electromagnets are attached
to the train on the lower half of ‘C’ , and the upper half is
attached to the vehicle. The Electromagnets are aligned towards the rail
from below. Hence the rail comes between the ‘C’ shaped cavity and as
Magnetic attraction varies inversely with the cube of distance so even a
little change in distance between the magnets produces largely varying
forces.
Electrodynamic Suspension is based on attraction as well as repulsion.
Even repulsion alone is enough to levitate the vehicle on the track. Here
both the train and the guideway exert magnetic forces on each other and
hence the train is suspended by repulsion and propelled by attraction.
These types of systems have an advantage over EMS systems that no
feedback control is required here as they are dynamically stable because
of the attractive and repulsive forces.
The main area of study of my Term Paper starts from here:-
The main requirement for power in a MAGLEV system is to propel the
vehicle, and that takes place by producing magnetic fields which
requires a lot of Energy. Most of the energy is consumed for overcoming
air drag and rest is required for air conditioning ,lighting, etc. Energy
may be replenished by Regenerative Braking which even stabilizes
the train and converts its kinetic energy into some other form thus
slowing it down and storing the energy for later use.
Power consumption at low speeds of the MAGLEV vehicle is high
because for less velocity, force used to accelerate the vehicle is
significant. Hence for short distances power consumption is high
and Non ‘ Economical. According to the basic principle of energy,
the power used to overcome air resistance increases with the cube
of velocity and therefore it is significantly dominating at high
speeds. Also the requirement of energy per unit distance increases
by the square of velocity while the time decreases linearly.
MAGLEV vehicle may be of any type but its energy consumption
can be decreased and efficiency can be increased by two
very well-known methods, Regenerative Braking and Evacuated
tubes . Regenerative braking increases the energy efficiency of the
train and allows the Kinetic Energy of the train to be used in some
other task . The brakes convert the Kinetic Energy into other forms
,thus it can be used for air conditioning , lighting etc. This reduces
the load on external Energy sources and saves Energy. Evacuated
Tubes help in reducing Air Drag by reducing atmospheric pressure
and thus less energy is required to accelerate the vehicle. This
reduces Energy consumption.
‘ High SPEED of the MAGLEV vehicle than the normal
transportation in use.
‘ Less expensive cost of maintenance as wear and tear due to friction
is absent.
‘ Energy efficient vehicles and burn no fuel.
‘ No environment or noise pollution , even silent than traffic.
‘ Designed in a way that chances of derailment and accidents are
reduced.
‘ They can be made more wider than normal trains and hence
provide with more space in the interiors and make the travel more comfortable.
‘ Can operate on higher ascending turfs than normal railroads
consuming 30% less energy.
‘ Completely new infrastructure is required as MAGLEV trains
cannot operate on existing normal tracks.
‘ Such new tracks are much more expensive than normal ones and
require huge capital investment.
‘ Rare Earth metals are required for MAGLEV trains which are very
expensive.
‘ Separate powerhouses are required to meet the Energy demands
for running the MAGLEV systems.
The major scope of working on MAGLEV in future is to make it more
efficient, faster and cheaper means of transport. The efficiency part can
be enhanced if less power is consumed in overcoming air drag and this
will also result in increasing the speed of presently existing MAGLEV
vehicles. This concept has been actualized by a Chinese scientist who
has successfully demonstrated the use of vacuum tubes in lowering the
atmospheric pressure by approx. 10 %, which results in very less Air
Drag and hence lets the vehicle approach higher velocities. More
Enhancement in this technology can result in developing efficient and
Speedier travel options.