Учебные задания по английскому языку для студентов 2 курса направления бакалавриата «Электроэнергетика и электротехника» 4 семестр

UNIT THREE

MISCELLANEOUS MACHINES

READING

1.Scan the first paragraph of the text and say what machines are used for current conversion.

2.Scan the rest of the article and enumerate the devices used for torque transmission and for amplification.

3.Read the text and answer the questions.

a.Why is it often necessary to use special machines?

b.How do motor generators operate?

c.What is the function of a rotary converter?

d.What are the components of a selsyn?

e.What type of connection is used in selsyn armatures?

f.What are the major applications of selsyns?

g.What is the principle of operation of amplifiers?

For special applications several combined types of dynamoelectric machines are employed. It is frequently desirable to change from direct to alternating current or vice versa, or to change the voltage of a DC supply, or the frequency or phase of an AC supply. One means of accomplishing such changes is to use a motor operating from the available type of electric supply to drive a generator delivering the current and voltage wanted. Motor generators, consisting of an appropriate motor mechanically coupled to an appropriate generator, can accomplish most of the indicated conversions. A rotary converter is a machine for converting alternating to

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direct current, using separate windings on a common rotating armature. The AC supply voltage is applied to the armature through slip rings, and the DC voltage is led out of the machine through a separate commutator. A dynamotor, which is usually used to convert low-voltage direct current to high-voltage direct current, is a similar machine that has separate armature windings.

Pairs of machines known as synchros, selsyns, or autosyns are used to transmit torque or mechanical movement from one place to another by electrical means. They consist of pairs of motors with stationary fields and armatures wound with three sets of coils similar to those of a three-phase alternator. In use, the armatures of selsyns are connected electrically in parallel to each other but not to any external source. The field coils are connected in parallel to an external AC source. When the armatures of both selsyns are in the same position relative to the magnetic fields of their respective machines, the currents induced in the armature coils will be equal and will cancel each other out. When one of the armatures is moved, however, an imbalance is created that will cause a current to be induced in the other armature. The magnetic reaction to this current will move the second armature until it is in the same relative position as the first. Selsyns are widely used for remote-control and remote-indicating instruments where it is inconvenient or impossible to make a mechanical connection.

DC machines known as amplidynes or rotortrols, which have several field windings, may be used as power amplifiers. A small change in the power supplied to one field winding produces a much larger corresponding change in the power output of the machine. These electrodynamic amplifiers are frequently employed in servomechanism and other control systems.

VOCABULARY PRACTICE

1.Explain the words and word combinations in bold in the text.

2.Find English equivalents to the following words and word combinations.

a.уравновешивать;

b.двигатель-генератор;

c.следящая система;

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d.запускать (генератор);

e.дистанционное управление;

f.постоянное поле;

g.наоборот;

h.одноякорный преобразователь.

3. Complete each sentence (a-g) with one of the endings (1-7).

a.An amplifier is a device that responds…

b.Amplifiers of various types are widely used…

c.Amplifying action can be provided…

d.Most electronic systems, however, now employ…

e.Such an integrated circuit consists of…

f.An electronic amplifier can be designed…

g.If the output is altered in shape…

1.…in such electronic equipment as radio and television receivers, highfidelity audio equipment, and computers.

2.…after passing through the amplifier, amplitude distortion exists.

3.…many thousands of transistors and related devices on a single tiny silicon

chip.

4.…solid-state microcircuits as amplifiers.

5.…to a small input signal and delivers a larger out signal.

6.…to produce a magnified output signal identical in every respect to the input

signal.

7.…by electromechanical devices (transformers and generators) and vacuum

tubes.

4.Write out the passage using one of the adjectives from the list.

A single amplifier is usually (1)___________to raise the output to the

(2)________level. In such cases the output of the first amplifier is fed into a second, whose output is fed to a third, and so on, until the output level is (3)__________. The

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result is cascade, or multistage amplification. Long-distance telephone, radio, television, (4)________control and (5)__________instruments, radar, and

(6)_________other devices all depend on this (7)________process of amplification. The (8)________amplification of a multistage amplifier is the product of the gains of the (9)__________stages.

5. Fill in the correct preposition.

Servomechanisms automatically compare the controlled output ___ a mechanism ___ the controlling input. The difference ___ the settings or positions ___

the output and the input is called the error signal, which regulates the output ___ a desired value. Servomechanisms may be mechanical, electrical, hydraulic, or optical. The process ___ sending the error signal back ___ comparison ___ the input is called feedback, and the whole process ___ the input, output, error signal, and feedback is called a closed loop.

An example ___ a servomechanism is the automatic control system ___ which a thermostat ___ a house controls the heat output ___ the heating furnace. Other examples include automatic pilots used ___ ships, aircraft, and space vehicles, ___

which the direction ___ motion ___ the vehicle is controlled ___ a compass setting. Unmanned spacecraft are automatically turned to point their cameras, radio antennas, and solar panels ___ the desired directions ___ servomechanisms. The input ___ that case is the sensing ___ the direction ___ the sun and stars, and the output is the control ___ small jets that turn and orient the spacecraft.

SPEAKING

Make a presentation on a particular type of alternator.

WRITING

Write an advertisement introducing various types of AC motors. MODULE IIII

ASSESSMENT

Translate from English into Russian.

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HIGH-SPEED SYNCHRONOUS GENERATORS

Generators driven by high-speed turbines are almost always constructed with horizontal shafts. The rotor diameter is usually limited to a maximum of about one metre because of the high centrifugal forces produced. The length of the rotor may be several metres. The rotor shaft and the field structure are made of a solid alloy steel forging in which slots are machined to accept the field coils. These coils are insulated typically with mica and glass laminate. The coils are held in place by nonmagnetic wedges in the tops of the slots.

The stator provides a path for the continuously varying magnetic flux. The stator core is therefore constructed of thin sheets, or laminations, of magnetic steel. The steel, being an electrical conductor, would tend to short-circuit the voltage induced in it if it were solid. Lamination breaks up the path along the length of the stator and keeps the power losses in the stator steel at an acceptable value. Slots are punched around the inside periphery of the laminations to accommodate the stator coils. In large generators, each stator coil normally contains only one turn.

High-speed generators are enclosed within a closed cylindrical stator housing that extends between the bearings at the two ends. They are cooled by hydrogen gas circulating within the housing and also frequently through ducts within the stator conductors. Very large generators are cooled by circulating water through the stator and rotor conductors.

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MODULE IV

UNIT ONE

ELECTRIC LIGHTING

READING

1. Read the text and complete statements 1-6 with the best ending A, B or C.

1) Electric lighting…

A. produces electricity.

B.is made possible by various lamps.

C.means a great number of devices.

2) A properly heated conductor…

A. produces light.

B. saves energy.

C. can be perfect.

3) Within glass bulbs must be either an inert gas or…

A. natural gas.

B. hydrogen.

C. vacuum.

4) In filaments, the light to heat ratio and the temperature are…

A. directly proportional.

B. inversely proportional.

C. constant.

5) The inert atmosphere in incandescent lamps increases their…

A. light energy.

B. evaporation.

C. durability.

6) Fused-quartz glass tubes have…

A. large dimensions.

B. limited applications.

C. reinforced walls.

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Electric lighting is illumination by means of any of a number of devices that convert electrical energy into light. The types of electric lighting devices most commonly used are the incandescent lamp, the fluorescent lamp, and the various types of arc and electric-discharge vapor lamps.

If an electric current is passed through any conductor other than a perfect one, a certain amount of energy is expended that appears as heat in the conductor. Inasmuch as any heated body will give off a certain amount of light at temperatures above 525° C (977° F), a conductor heated above that temperature by an electric current will act as a light source. The incandescent lamp consists of a filament of a material with a high melting point sealed inside a glass bulb from which the air has been evacuated, or which is filled with an inert gas. Filaments with high melting points must be used because the proportion of light energy to heat energy radiated by the filament rises as the temperature increases, and the most efficient light source is obtained at the highest filament temperature. Carbon filaments were employed in the first practical incandescent lamps, but modern lamps are universally made with filaments of fine tungsten wire, which has a melting point of 3410° C (6170° F). The filament must be enclosed in either a vacuum or an inert atmosphere, otherwise the heated filament would react chemically with the surrounding atmosphere. Using an inert gas instead of a vacuum in incandescent lamps has the advantage of slowing evaporation of the filament, thus prolonging the life of the lamp. Most modern incandescent lamps are filled with a mixture of argon or krypton and a small amount of nitrogen.

Radical changes in incandescent lamp design have resulted from substituting compact fused-quartz glass tubes for glass bulbs. These new, stronger-walled bulbs have made tungsten-halogen lamps, a variation of the incandescent lamp, possible. Tungsten-halogen lamps use the regenerative cycle of halogens to return evaporated tungsten particles to the filament, thus extending the life of the bulb. The high temperatures required to take advantage of halogen’s regenerative cycle made this idea impossible until the walls of the bulb could be made stronger by the introduction of quartz. These bulbs are filled with a mixture of argon and halogen (usually bromine) gases along with a small amount of nitrogen.

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VOCABULARY PRACTICE

1. Find English equivalents to the words and word combinations in bold.

a.испарение;

b.дуговая лампа;

c.извлекать пользу, выгоду;

d.лампа накаливания;

e.температура плавления;

f.паросветная лампа;

g.нить накала;

h.вольфрамово-галоидная лампа;

i.азот;

j.лампа дневного света.

2. Replace the words underlined in each sentence with a particular verb

a.A lot of energy is used to illuminate this spacious room.

b.The rotor core is surrounded with cylindrical conductors.

c.If we use this machine, we can get a powerful energy source.

d.Some additional devices will make the equipment life longer.

e.Heat the liquid until it has changed into steam.

f.With this material, the lamp will send out more light.

g.In case of emergency, all people must be removed to a safe place.

h.The organs are kept in airproof plastic bags.

i.The smoke occupied the room.

j.The pipeline should be enlarged.

3. Put each verb in brackets into a suitable form.

Electric arc is a type of continuous electric discharge, (1)_______(give) intense light and heat, (2)______(form) between two electrodes in a gas at low pressure or in

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open air. (3)______(start) an arc, the ends of two pencil-like electrodes, usually made of carbon, (4)______(bring) into contact and a large current (about 10 amp)

(5)______(pass) through them. This current (6)______(cause) intense heating at the point of contact, and if the electrodes then (7)_______(separate), a flamelike arc

(8)______(form) between them. The discharge (9)_______(carry) largely by electrons (10)______(travel) from the negative to the positive electrode, but also in part by positive ions (11)______(travel) in the opposite direction. The impact of the ions (12)_______(produce) great heat in the electrodes, but the positive electrode is hotter, because the electrons (13)______(impinge) on it have greater total energy.

Arcs (14)___(use) as a high-intensity light source. Arc lights have the advantage of (15)_____(be) concentrated sources of light, because some 85 percent of the light intensity (16)_____(come) from a small area of the tip of the positive carbon electrode. Mercury-vapor lamps and sodium-vapor lamps are (17)______(enclose) arc lamps in which the arc (18)_______(maintain) in an atmosphere of mercury or sodium vapor at (19)______(reduce) pressure.

4. Write out the passage using one of the words from the list.

Bright neon lights (1)_______throughout the night in big cities all over the world. Neon lamps are used for art, (2)________, and even airplane (3)_______. They are made by (4)_______air from glass (5)_______, then (6)_______them with neon gas. When the light is “on,” an electric current (7)______through the gas between two electrodes (8)______ within the tube. The neon (9)______a luminous band between the two electrodes.

5. Complete the text with words formed from the words in capitals.

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UNIT TWO

TYPES OF LAMPS

READING

Read the following text. Some phrases have been left out of the text. Choose from phrases A-I below to complete the gaps. There is one phrase you will not need.

Electric-discharge lamps depend on the ionization and the resulting electric discharge in vapors or gases at low pressures (1)________________. Representative examples of these types of devices are the mercury-vapor arc lamp, which gives an intense blue-green light and is used for photographic and roadway illumination, and the neon lamp, (2)_________________. In newer electric-discharge lamps, other metals are added to mercury and phosphor on the enclosing bulbs to improve color and efficacy. Glasslike, translucent ceramic tubes have led to high-pressure sodium vapor lamps of unprecedented lighting power.

The fluorescent lamp is another type of electric-discharge device used for general-purpose illumination. It is a low-pressure mercury vapor lamp contained in a glass tube, (3)__________________. The radiation in the arc of the vapor lamp causes the phosphor to become fluorescent. Much of the radiation from the arc is invisible ultraviolet light, but this radiation is changed to visible light if it excites the phosphor. Fluorescent lamps have several important advantages. By choosing the proper type of phosphor, the light from such lamps can be made to approximate the

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