MAGLEV - Seminar Report by Rohan

A Seminar Report on MAGLEV by ROHAN SHARMA

CONTENTS

SR. NO.

TOPIC

PAGE NO.

1

Introduction

2

2

Historical Background

5

3

Maglev Methods

8

4

Working of Maglev vehicle

9

5

Propulsion Force

9

6

Linear Motor Principle

10

7

Propulsion of Maglev

12

8

Levitating Force

13

9

Lateral Guiding Force

18

10

Braking & Control

19

11

Varying Maglev Speed

20

12

Maglev in INDIA

21

13

Conclusion

22

14

References

23

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A Seminar Report on MAGLEV by ROHAN SHARMA

INTRODUCTION Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended above another object with no support other than magnetic field .The electromagnetic force is used to counteract the effects of the gravitational force. A substance which is diamagnetic repels a magnetic field. Earnshaw's theorem does not apply to diamagnets; they behave in the opposite manner of a typical magnet due to their relative permeability of µr < 1. All materials have diamagnetic properties, but the effect is very weak, and usually

overcome

object's

by

the

paramagnetic

or

ferromagnetic which

act

in

properties, the

opposite

manner. Any material in which the diamagnetic component is strongest will be repelled by a magnet, though this force is not usually very large. Diamagnetic levitation can be used to levitate very light pieces of pyrolytic graphite or bismuth above a moderately strong permanent magnet. As water is predominantly diamagnetic, this technique has been used to

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A Seminar Report on MAGLEV by ROHAN SHARMA

levitate water droplets and even live animals, such as a grasshopper and a frog. The minimum criteria for diamagnetic levitation is

Where: •

χ is the magnetic susceptibility

•

ρ is the density of the material

•

g is the local gravitational acceleration (-9.8 m/s2 on Earth)

•

µ0 is the permeability of free space

•

B is the magnetic field

•

is the rate of change of the magnetic field along the vertical axis.

Assuming ideal conditions along the z-direction of solenoid magnet:

•

Water levitates at

•

Graphite at

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A Seminar Report on MAGLEV by ROHAN SHARMA

A live frog levitating inside a 32 mm diameter vertical bore in a magnetic field of about 16 Tesla at the Nijmegen High Field Magnet Laboratory

Levitating Pyrolytic Carbon Page | 4

A Seminar Report on MAGLEV by ROHAN SHARMA

HISTORICAL HISTORICAL BACKGROUND BACKGROUND Approximately 25 years ago, scientists became interested in developing a train that would combine high-speed with a smooth ride and quiet operation. They developed the "Maglev", or magnetic levitation train. This vehicle rides on a cushion created by the electromagnetic repulsion between a series of on-board magnets and another embedded in the trackway below the train. Thus, this train does not run on wheels. As a result, the ride is very smooth and there is no metal-to-metal contact to generate noise and steel dust. Keeping this kind of Maglev train airborne and in smooth motion requires advanced, extremely accurate feedback circuits and very strict engineering tolerances. The other type of Maglev uses super-conducting coils embedded in the guideway and electromagnets in the train cars to establish the levitation. Two American scientists at Lawrence Livermore National Laboratories have developed a new system called Indutrack which employs the use of passive permanent magnets, just like the ones on your kitchen refrigerator, only larger. In preliminary

tests,

Indutrack

trains

have

higher

lifting

efficiency. Another big advantage of Indutrack is that it does not require the incorporation of superconductive coils in the guideway or in the bottom of the car. These coils require an Page | 5

A Seminar Report on MAGLEV by ROHAN SHARMA

extremely

expensive,

high

maintenance,

ultra-low

temperature helium cooling systems. The new system consists of a series of passive magnets, called Halbach arrays, attached under the vehicle. The guide-way, which replaces the track or conventional subway and railroad trains, has metallic magnetic-inductive coils embedded in its surface. For each pound of the Halbach passive magnets, 50 pounds of vehicle/payload can be lifted. There are two types of Maglev's: ones that use like magnets which repel each other and ones that use opposing magnets that attract with each other. Ones that use repelling magnets' are called Superconducting Maglev's. The magnets allow the train to float. Electromagnetic Maglevs use opposing magnets. Superconducting

Maglevs

use

very

cold

temperature

magnets in order to make electricity without any opposition. The magnets are then put on the bottom of the train. When the train moves, it forms currents from the magnets in the aluminum sheets placed in the guideway. Because of the repelling force, the vehicle rises. Also in the guideway, separate electric currents pass through which push the train forward. Electromagnetic Maglev's go under the guideway. They use opposing magnets that attract with each other. This allows Page | 6

A Seminar Report on MAGLEV by ROHAN SHARMA

the Maglev to pull upward towards the guideway. Like the superconducting Maglev's, separate currents make magnetic fields shift which allows the train to move forward. These Maglev's travel about 3/8's of an inch away from the guideway. In order for the magnets from not hitting the guideway, the lifting current must keep being fixed.

The main parts of the Maglev: Guide way and guide rails - keep the train to on track Landing wheels; levitation coils - run along the base of the guide way (used in superconducting maglevs) Emergency landing wheel; superconducting magnets and propulsion coils - run along the base of guide way (used in electromagnetic maglev's), and a linear induction motor moves and brakes the vehicle on the track. Page | 7

A Seminar Report on MAGLEV by ROHAN SHARMA

MAGLEV METHODS •

Repulsion between like poles of permanent magnets or electromagnets.

•

Repulsion between a magnet and a metallic conductor induced by relative motion.

•

Repulsion

between

a

metallic

conductor

and

an

AC

electromagnet. •

Repulsion between a magnetic field and a diamagnetic substance.

•

Repulsion between a magnet and a superconductor.

•

Attraction between unlike poles of permanent magnets or electromagnets.

•

Attraction between the open core of an electromagnetic solenoid and a piece of iron or a magnet.

•

Attraction between a permanent magnet or electromagnet and a piece of iron.

•

Attraction between an electromagnet and a piece of iron or a magnet, with sensors and active control of the current to the electromagnet used to maintain some distance between them.

•

Repulsion between an electromagnet and a magnet, with sensors

and

active

control

of

the

current

to

the

electromagnet used to maintain some distance between them.

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A Seminar Report on MAGLEV by ROHAN SHARMA

WORKING OF OF MAGLEV VEHICLE Basically the construction depends on 3 different working forces.
PROPULSION FORCE
LEVITATING FORCE
LATERAL GUIDING FORCE

1. PROPULSION FORCE This is a horizontal force which causes the movement of train. It requires 3 parameters. •

Large electric power supply

•

Metal coil lining, a guide way or track.

•

Large magnet attached under the vehicle.

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A Seminar Report on MAGLEV by ROHAN SHARMA

PRINCIPLE OF LINEAR MOTOR Its principle is similar to induction motor having linear stator and flat rotor. The 3-phase supply applied to the stator produces a constant speed magnetic wave, which further produces a repulsive force.

A linear motor or linear induction motor is essentially a multi-phase alternating current (AC) electric motor that has had its stator "unrolled" so that instead of producing a torque (rotation) it produces a linear force along its length. The most common mode of operation is as a Lorentz-type actuator, in which the applied force is linearly proportional to the current and the magnetic field (F = qv × B). Many designs have been put forward for linear motors, falling into two major categories, low-acceleration and highPage | 10

A Seminar Report on MAGLEV by ROHAN SHARMA

acceleration linear motors. Low-acceleration linear motors are suitable for maglev trains and other ground-based transportation applications. High-acceleration linear motors are normally quite short, and are designed to accelerate an object up to a very high speed and then release the object, like roller coasters. They are usually used for studies of hypervelocity collisions, as weapons, or as mass drivers for spacecraft propulsion. The high-acceleration motors are usually of the linear induction design (LIM) with an active three-phase winding on one side of the air-gap and a passive conductor plate on the other side. The lowacceleration, high speed and high power motors are usually of the linear synchronous design (LSM), with an active winding on one side of the air-gap and an array of alternatepole magnets on the other side. These magnets can be permanent magnets or energized magnets. The Transrapid Shanghai motor is an LSM.

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A Seminar Report on MAGLEV by ROHAN SHARMA

Maglev vehicles are propelled primarily by one of the following three options: 1.A linear synchronous motor (LSM) in which coils in the guideway are excited by a three phase winding to produce a traveling wave at the speed desired; Trans Rapid in Germany employs such a system.

2. A Linear Induction Motor (LIM) in which an electromagnet underneath the vehicle induces current in an aluminum sheet on the guideway.

3. A reluctance motor is employed in which active coils on the vehicle are pulsed at the proper time to realize thrust.

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A Seminar Report on MAGLEV by ROHAN SHARMA

2. LEVITATING FORCE The levitating force is the upward thrust which lifts the vehicle in the air. There are 3 types of levitating systems 1. EDS system 2. EMS system 3. INDUCTRACK system

Levitating force is produced due to the eddy current in the conducting ladder by the electromagnetic interaction. At low speed the force due to induced poles cancel each other. At high speed a repulsive force is taken place as the magnet is shifted over a particular pole.

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A Seminar Report on MAGLEV by ROHAN SHARMA

I.

EDS SYSTEM:

In EDS both the rail and the train exert a magnetic field, and the train is levitated by the repulsive force between these magnetic fields. 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.

Onboard magnets and large margin between rail and train enable highest recorded train speeds (581 km/h).This system

is

inherently

stable.

Magnetic

shielding

for

suppression of strong magnetic fields and wheels for travel at low speed are required. It can’t produce the propulsion force. So, LIM system is required. Page | 14

A Seminar Report on MAGLEV by ROHAN SHARMA

II. EMS SYSTEM: Maglev concepts using electro -magnetic suspension employ attractive forces. Magnetic fields inside and outside the vehicle are insignificant; proven, commercially available technology that can attain very high speeds (500 km/h); no wheels or secondary propulsion system needed.

The separation between the vehicle and the guideway must be constantly monitored and corrected by computer systems to

avoid

collision

due

to

the

unstable

nature

electromagnetic attraction.

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of

A Seminar Report on MAGLEV by ROHAN SHARMA

III.

INDUCTRACK SYSTEM:

The inductrack guide way would contain two rows of tightly packed levitation coils, which would act as the rails. Each of these “rails” would be lined by two Halbach arrays carried underneath the maglev vehicle: one positioned directly above the “rail” and one along the inner side of the “rail”. The Halbach arrays above the coils would provide levitation while the Halbach arrays on the sides would provide lateral guidance that keeps the train in a fixed position on the track.

The track is actually an array of electrically-shorted circuits containing insulated wire. In one design, these circuits are aligned like rungs in a ladder. As the train moves, a magnetic field repels the magnets, causing the train to levitate.

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A Seminar Report on MAGLEV by ROHAN SHARMA

There are two inductrack designs, Inductrack I and II. Inductrack I is designed for high speeds, while inductrack II is suited for slow speeds. Inductrack trains could levitate higher with greater stability. As long as it’s moving a few miles per hour, an inductrack train will levitate nearly an inch above the track. A greater gap above the track means that the train would not require complex sensingsystems to maintain stability. Permanent magnets had not been used before because scientists thought that they would not create enough levitating force. The inductrack design bypasses this problem by arranging the magnets in a Halbach array. The magnets are configured so that the intensity of the magnetic field concentrates above the array instead of below it which generates higher magnetic field. The inductrack II design incorporates two Halbach arrays to generate a stronger magnetic field at lower speeds. Dr. Richard post at the Livermore National Laboratory in California came up with this concept in response to safety and cost concerns. The prototype tests caught the attention of NASA, which awarded a contract to Dr.post and his team to explore the possibility of using the inductrack system to launch satellites into orbit.

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A Seminar Report on MAGLEV by ROHAN SHARMA

3. LATERAL GUIDING FORCE Guidance or steering refers to the sideward forces that are required to make

the

vehicle

follow

the

guideway. The necessary forces are supplied

in

an

exactly

analogous

fashion to the suspension forces, either attractive or repulsive. The same magnets on board the vehicle, which

supply

lift,

can

be

used

concurrently for guidance or separate guidance magnets can be used. It requires the following arrangements: • Guideway levitating coil • Moving magnet

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A Seminar Report on MAGLEV by ROHAN SHARMA

BRAKING & CONTROL OF MAGLEV TRAINS GENERALY TWO TYPES OF BREAKING ARE USED • AERODYNOMIC BREAKING • ELECTOMAGNETIC BREAKING

Yamanashi Superconducting Magnet

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A Seminar Report on MAGLEV by ROHAN SHARMA

Varying Maglev Speed The Maglev’s speed can vary from standstill to full operating speed by simply adjusting the frequency of the alternating current. To bring the train to a full stop, the direction of the travelling field is reversed. Even during braking, there isn't any mechanical contact between the stator and the rotor.

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A Seminar Report on MAGLEV by ROHAN SHARMA

MAGLEV in INDIA

Mumbai – Delhi: A maglev line project was presented to India's railways minister Lalu Prasad Yadav by an American company. If approved, this line would serve between the cities of Mumbai and Delhi, the Prime Minister Manmohan Singh said that if the line project is successful the Indian government would build lines between other cities and also between

Mumbai

centre

and

Chattrapati

Shivaji

International Airport. Maharashtra has also approved feasibility study for Maglev train between Mumbai, which is commercial capital of India and state govt capital and Nagpur, which is second capital of the state and about 1000 km away. It plans to connect developed area of Mumbai and Pune with Nagpur via underdeveloped hinterland via Ahmednagar, Beed, Latur, Nanded and Yavatmal. Page | 21

A Seminar Report on MAGLEV by ROHAN SHARMA

CONCLUSION It’s no longer science fiction, maglev trains are the new way of transportation in the near future, just some obstacles are in the way, but with some researches nothing is impossible. With no engine, no wheels, no pollution, new source of energy, floating on air, the concept has token tens of years to develop, just recently it’s true capacities has been realized. Competing planes with speed, boats with efficiency, traditional trains with safety, and cars with comfort, it seems like it isn't a fair fight....

Advantages 1.

Quicker and efficient transport

2.

No noise

3.

Comfortable, smooth ride due to very little friction

4.

Safe and cost-effective

5.

Less consumption of natural resources

6.

Environment-friendly as no gas is emitted

Disadvantage 1.

Highly Expensive

2.

Complex control system

3.

No overlap or junction can done

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A Seminar Report on MAGLEV by ROHAN SHARMA

REFERENCES • Principles of Electrical Machines • www.wikipedia.org • www.howstuffworks.com • www.google.co.in

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