Magnetic levitation train
A MAGLEV (magnetic levitation) train does not run along a track in the
normal way. Instead, magnetic fields lift it above the track, so that the train
'floats' along.
Because they have no wheels, axles, suspension, dampers, or brakes,
Maglev vehicles are light and compact. They are also pollution-free, as no
fuel is burned within the train, and cheap to maintain.
The Maglev system at Birmingham Airport carries passengers from the
terminal to the railway station and the National Exhibition Centre. The cars
are made of lightweight fibreglass, carried on an aluminium chassis. All the
electrical equipment which powers the cars is situated under the floors or the
seats. Each car can take 32 passengers and their luggage, up to a weight of
8 tonnes. The trains travel at a maximum speed of 42km/h.
A concrete guideway above the ground supports a T-shaped track for the
two-car Maglev trains. The train is lifted from the track by magnetic attraction.
This is the force by which two opposite magnetic poles attract each other (just
as two of the same poles 20 repel each other). Powerful electromagnets at
each corner of the train exert a pulling force which lifts the train upwards so
that it floats 15 mm above the track.
As people get on and off, the weight of the train varies. It may drop closer to
the track than the required 15mm, or rise further from it. To keep it at an
even distance from the track, the force is varied by a microprocessor.
Each train is driven by an electric motor called a linear induction motor.
Electromagnetic windings, or coils, on the train generate a magnetic field in
which the magnetic poles shift along the train. The field induces electric
current in the track, which in turn generates its own magnetic field. The two fields in the track and the train interact so that the shifting field pulls the floating train along the track.
Exercise 4. Make a list of the advantages of the Maglev train. You may use
the text to help you.
Exercise 5. Now list the disadvantages. You may use the text to help you.
Exercise 6. Look through the text once again and try to find things which can be used with the attribute “magnetic”. Make up your own sentences with
these words and find the ones in the text.
Exercise 7. Dealing with unfamiliar words.
Answer this question using the extract from the text below.
Why are Maglev trains so light?
Because they have no wheels, axles, suspension, dampers, or brakes,
Maglev vehicles are light and compact.
In your answer, you may have used the word damper. Do you know what
it means? Do you need to know its exact meaning.?
We can ignore unfamiliar words which do not help with our reading purpose. Some words we cannot ignore, but often an approximate rather than exact meaning of a word is all that is required. Sometimes we can work out the approximate meaning of a word from its context. For example, we can say that dampers are probably:
1 heavy (not light)
2 large (not compact)
3 part of the undercarriage (same set as wheels, axles, suspension, and
brakes)
Try to work out (to guess) the meaning of any of the words printed in
bold in this text whose meaning you do not know. Check your answers with
a dictionary.
When first introduced, linear motors were seen as a major technological
breakthrough. However, disappointingly few practical applications have
been found for this new development. An earlier innovation, the Wankel
engine, was radically different from conventional engines, having a rotary
piston and no valves. Wankel engines were adopted by the Mazda car
company. However, Wankel engines are now rarely used because of
problems with fuel consumption and maintenance. The Wankel story
illustrates the risks involved in developing any new product - success can
mean a market lead over competitors but failure means that expensive
development costs must be written off with no result. Sadly, technological
superiority does not guarantee success. Betamax video tapes, technically
better than their rivals, gave way to VHS because of better marketing.
Exercise 8. Language study Prediction
Study this diagram. What will be the result of this action?
Action Result
Two magnets are held together with opposite poles facing.
When an action is always followed by the same result, we can link them
like this:
If/When two magnets are held together with opposite poles facing, they
attract each other.
or
If/When two magnets are held together with opposite poles facing, they
will attract each other.
When an action is always followed by the same result, the statement
becomes a general principle or law. Using the law, we can predict what
will happen in particular cases.
Exercise 9. Predict the result of the action illustrated here.
Action Result
Two magnets are held together with like poles facing.
Now write the principle illustrated.
If two magnets —————————————.————
Exercise 10. Predict the results of each of these actions. Then link
each action and result in a sentence.
Action Result
1 A steel bar is subjected to tensile forces. The bar ——————
———— ————
2 We apply an effort at E. The block _____________
3 The switch is closed. __________________
6
V
6
V 3 W
4 The switch is pressed. ______________________
150mA
240
V,
240V 750 W
5 We move the effort by one meter. The load__________________
6 We move the effort by 50 centimeters. ______________
The circuit is broken. ________________
8. 120 V ac is applied across the primary. _____________________
10:1
We apply an impact load to a brittle body. ___________________
10. We apply 24 V ac to the transformer primary. ______________
1:2
Exercise 11. Explanations
Study this diagram. It shows how a Maglev train is supported without physical
contact with the track. Can you explain how this works?
The explanation consists of a series of at least six steps. The first step is:
1 Current flows through the magnet coil.
The last step is:
6 The train is lifted.
Can you think of any of the steps in between?
Explanations consist of a series of steps. Some steps in an explanation have
cause and effect links; others have time links. Here are some of the steps
which explain how the train is lifted. What kinds of links are there between the
stages?
1 Current flows through the magnet coil.
2 The current creates a magnetic field round the poles.
3 The field induces a current in the track.
4 The track becomes magnetized.
5 The two magnets attract each other.
6 The train is lifted.
You can show cause and effect links in these ways:
1+2 Current flows through the magnet coil, creating a magnetic
field round the corners.
3+4 The field induces a current in the track; therefore the track becomes
magnetized.
5+6 The two magnets attract each other, (thereby) lifting the train.
Thereby can be omitted from the last example.
Exercise 12. Study these diagrams. They explain how the propulsion system
operates.
The train is propelled by a linear-induction motor mounted under the vehicle.
The current creates a linear travelling field which constantly reacts with the
aluminium secondary track, causing relative motion. To stop the train the
current is moved.
Try to complete the blanks in this set of steps which form an explanation of
the propulsion system.
1 Current ______ through the motor coils.
2 The current creates _______ fields in .he motor.
3 The fields -_______ currents in the track.
4 The track becomes_______.
5 The current through the linear motor _____.
6 The magnetic _______ in the motors shift.
7 There is ______ and repulsion between the new motor fields and the
track fields.
8 The motor pulls the train along the ______ to line up the fields.
9 The ______through the coils changes and the process is repeated.
Exercise 13. Define the function of infinitives in the following sentences,
translate them into Ukrainian.
1. The driving cars of the experimental British train were to be fitted with 4
gas-turbine engines.
2. To put this train into service will be possible only after a series of special tests. 3. High-speed traffic requires the permanent way to be excellently laid and carefully maintained.
4. To increase the speed of trains is a complicated problem.
5. The linear electric motor to be used on the Japanese railways will greatly increase the speed of trains.
6. The new instruments to be introduced on the substations will increase the reliability of the electric machines and the auxiliary apparatus.
7. It should be noted that speed control devices are used to provide definite speeds under certain conditions.
8. An electric locomotive contains electrical control equipment needed to control the electrical energy supplied to the motors.
9. Passenger and freight traffic is supposed to increase.
Exercise 14. Choose the form of infinitives in the following sentences with the help of the table given below.
The Infinitive
|
Active
|
Passive
|
Indefinite
|
to take |
to be taken |
Perfect |
to have taken |
to have been taken |
Continuous |
to be taking |
|
Perfect Continuous |
to have been taking |
|
1. She was believed (to feel) unwell for some time.
2. He seems (to read) a lot. He seems (to read) now. He seems (to read)
since morning. He seems (to read) all the books in the library.
3. I want (to take) you to the concert. I want (to take) to the concert by my
father.
4. I am glad (to do) all the work yesterday.
5. She seems (to work) at this problem ever since she came here.
6. I am sorry (to break) your pen.
7. He began writing books not because he wanted (to earn) a living: he
wanted (to read) and not (to forget).
8. He seems (to know) French very well: he is said (to spend) his youth in
Paris.
9. The woman pretended (to read) and not (to hear) the bell.
10. They seemed (to quarrel): I could hear angry voices from behind the door.
18
11. Perhaps it would upset her (to tell) the truth of the matter.
12. Her ring was believed (to lose) until she happened (to find) during the
general cleaning. It turned out (to drop) between the sofa and the wall.