Stability:
A paper on
Earnshaw's theorem proved conclusively
MAGNETIC LEVITATION
that it is not possible to stably levitate using static,
macroscopic,
"classical"
electromagnetic fields. The forces acting on an
object
in
any
combination
of
gravitational, electrostatic, and magneto
PAPER PRESENTED BY:
static fields will make the object's position M.HIMA PRATYUSHA EEE IV YEAR DHRUVA INSTITUTE OF ENGINNERING & TECHNOLOGY
unstable. However, several possibilities exist to make levitation viable, by violating the assumptions of the theorem — for example, the use of electronic stabilization or
Abstract:
diamagnetic materials.
The use of natural resources in our day to
Methods:
day life is increasing
which leads to
There are several methods to obtain
shortage of these resources in the
magnetic levitation. The primary ones used
generation,mainly in transportation we are
in
wasting a lot of crude oils and other
electromagnetic
resources which leads to global earthing. So
electrodynamics suspension (EDS), and
in this paper we’re discussing
Inductrack.
magnetic
levitation
and
the
es
maglev
trains
are
servo-stabilized
suspension
(EMS),
in
transportation .
Introduction: Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended above another object with no other than magnetic fields. The
Mechanical constraint:
electromagnetic force is used to counteract
If two magnets are mechanically constrained
the effects of the gravitational force.
along a single vertical axis (a piece of string,
for example), and arranged to repel each
opposite manner. Any material in which the
other strongly, this will act to levitate one of
diamagnetic component is strongest will be
the magnets above the other. This is not
repelled by a magnet, though this force is
considered true levitation, however, because
not
there is still a mechanical . A popular
levitation can be used to levitate very light
toy based on this principle is the Revolution,
pieces of pyrolytic graphite or bismuth
invented by Gary Ritts, and produced
above a moderately strong permanent
commercially by Carlisle Co. (U.S. Patent
magnet.
5,182,533 ),
diamagnetic, this technique has been used to
which
constrains
repelling
magnets against a piece of glass.
usually
As
very
large.
water
is
Diamagnetic
predominantly
levitate water droplets and even live animals, such as a grasshopper and a frog; however, the magnetic fields required for this are very high, typically in the range of 16 teslas, and therefore create significant A live frog
problems if ferromagnetic materials are nearby. The minimum criteria for diamagnetic levitation is
levitates inside a 32 mm diameter vertical bore of a Bitter solenoid in a magnetic field
,
of about 16 teslas at the Nijmegen High
where:
Field Magnet Laboratory.
● χ is the magnetic susceptibility
A substance which is diamagnetic repels a
●Ï• is the density of the material
magnetic field. Earnshaw's theorem does not
●g is the local gravitational acceleration
apply to diamagnets; they behave in the
(9.8 m/s2 on Earth)
opposite manner of a typical magnet due to
●μ0 is the permeability of free space
their relative permeability of μr < 1. All
●B is the magnetic field
materials have diamagnetic properties, but the effect is very weak, and usually
●
overcome by the object's paramagnetic or
field along the vertical axis
ferromagnetic properties, which act in the
is the rate of change of the magnetic
Assuming ideal conditions along the z-
suspension
direction of solenoid magnet:
electromagnets mounted at the ends of a pair
●Water
levitates
at
(EMS),
uses
conventional
of structures under the train; the structures wrap around and under each side of the guideway. The magnets are attracted up
●Graphite
levitates
at
towards laminated iron rails in the guideway and lift the train. However, this system is inherently unstable; the distance between the electromagnets and the guideway, which is about 10 mm (3/8 in), must be continuously
Diamagnetically-stabilized levitation
monitored and adjusted by computer to
A permagnet can be stably suspended by
prevent the train from hitting the guideway.
various configurations of strong permanent magnets and strong diamagnets. When using
The second design, called electrodynamic
superconducting magnets, the levitation of a
suspension (EDS), uses the opposing force
permanent magnet can even be stabilized by
between magnets on the vehicle and
the small diamagnetism of water in human
electrically conductive strips or coils in the
fingers.
guideway to levitate the train This approach is inherently stable, and does
Magnetic Levitation Train
not
Magnetic Levitation Train or Maglev Train,
adjustment; there is also a relatively large
a high-speed ground vehicle levitated above
clearance between the guideway and the
a track called a guideway and propelled by
vehicle, typically 100 to 150 mm (4 to 6 in).
magnetic fields. Magnetic levitation train
However, an EDS maglev system uses
technology can be used for urban travel at
superconducting magnets, which are more
relatively low speeds (less than 100 km/h, or
expensive than conventional electromagnets
60 mph).
and require a refrigeration system in the
How Maglev Trains Work
train
Two different approaches to magnetic
temperatures (see Superconductivity). Both
levitation
been
EMS and EDS systems use a magnetic wave
developed. The first, called electromagnetic
travelling along the guideway to propel the
train
systems
have
require
to
continued
keep
them
monitoring
cooled
to
and
low
maglev train while it is suspended above the track.
Components of maglev train: The magnetic field created in this wire-andbattery experiment is the simple idea behind
Above is an image of the guide way for
a maglev train rail system. There are three
the Yamanashi maglev test line in Japan.
Below is an illustration that shows how the guide way works.
components to this system:
A large electrical power source
Metal coils lining a guide way or track
Large guidance magnets attached to the underside of the train. 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 fuel, the magnetic field created by the electrified coils in the guide way walls and the track combine to propel the train.
The magnetized coil running along the track, called a guide way, 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 guide way. Once the train is levitated, power is supplied to the coils within the guide way walls to create a unique system of magnetic fields that pull and push the train along the guide way. The electric current supplied to the coils in the guide way 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
that the Transrapid maglev train can reach
to pull the vehicle forward, while the
300
magnetic field behind the train adds more
Japanese
forward thrust.
competing version of maglev trains that use
Maglev trains float on a cushion of air,
an electrodynamics suspension (EDS)
eliminating friction. This lack of friction and
system, which is based on the repelling force
the trains' aerodynamic designs allow these
of magnets.
trains
ground
The key difference between Japanese and
transportation speeds of more than 310 mph
German maglev trains is that the Japanese
(500 kph), or twice as fast as Amtrak's
trains use super-cooled, superconducting
fastest commuter train. In comparison, a
electromagnets. This kind of electromagnet
Boeing-777 commercial aero plane used for
can conduct electricity even after the power
long-range flights can reach a top speed of
supply has been shut off. In the EMS
about 562 mph (905 kph). Developers say
system, which uses standard electromagnets,
that maglev trains will eventually link cities
the coils only conduct electricity when a
that are up to 1,000 miles (1,609 km) apart.
power supply is present. By chilling the
At 310 mph, you could travel from Paris to
coils at frigid temperatures, Japan's system
Rome in just over two hours.
saves energy.
Developing technology:
Another difference between the systems is
In , engineers have developed an
that the Japanese trains levitate nearly 4
electromagnetic suspension (EMS) system,
inches (10 cm) above the guide way. One
called Transrapid. In this system, the
potential drawback in using the EDS system
bottom of the train wraps around a steel
is that maglev trains must roll on rubber tires
guide way. Electromagnets attached to the
until they reach a liftoff speed of about 62
train's undercarriage are directed up toward
mph (100 kph). Japanese engineers say the
the guide way, which levitates the train
wheels are an advantage if a power failure
about 1/3 of an inch (1 cm) above the guide
caused a shutdown of the system. 's
way and keeps the train levitated even when
Transrapid train is equipped with an
it's not moving. Other guidance magnets
emergency battery power supply.
to
reach
unprecedented
mph
with
engineers
people are
onboard.
developing
embedded in the train's body keep it stable during travel. has demonstrated
Advantages over conventional trains:
a
Maglev
of
maglev test track is under construction in
advantages over conventional trains that use
Yamanashi Prefecture, about 100 km (60
steel wheels on steel rails. Because magnetic
mi) west of Tokyo. When tests on the latest
levitation trains do not touch the guideway,
maglev vehicle have been completed, the
maglev systems overcome the principal
test track is planned to be extended to Tokyo
limitation of wheeled trains—the high cost
and Osaka. This new commercial line will
of maintaining precise alignment of the
relieve enger demand on the Shinkansen
tracks to avoid excessive vibration and rail
high-speed
deterioration at high speeds. Maglevs can
operates at peak speeds of 240 km/h (149
provide sustained speeds greater than 500
mph). In China in December 2002 a
km/h (300 mph), limited only by the cost of
German-built maglev line between the
power to overcome wind resistance. The fact
financial district of Shanghai and the city’s
that maglevs do not touch the guideway also
airport was opened. The journey time for the
has other advantages: faster acceleration and
30 km (19 mi) journey is eight minutes.
braking;
systems
offer
greater
a
climbing
number
railway,
which
currently
capability;
enhanced operation in heavy rain, snow, and
Conclusion:
ice; and reduced noise. Maglev systems are
In spite of using natural resources ,if we use
also energy-efficient on routes of several
the property of magnetic
hundred kilometres' length, they use about
transportation ,we are going to save the
half as much energy per enger as a
future generation from pollution and it’s
typical commercial aircraft. Like other
harmful effects.
electrical transport systems, they also reduce the use of oil, and pollute the air less than aircraft, diesel locomotives, and cars (see Air Pollution). Current
plans
for
high-speed
maglev
systems include a 283-km (175-mi) route from Berlin to Hamburg, which has been approved
by
the
German
parliament;
commercial operations are scheduled to begin by 2005. In Japan, a 43-km (27-mi)
levitation in