Magnetic Levitation Abstract o1o2x

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