Файл: Учебное пособие по курсу Иностранный язык Казань 2007 удк 804. 37. 022 М90 Мулюков И. М., И. А. Абдуллин Английский язык для технических специальностей Учебное пособие для студентов технических вузов. Казань Казан гос энерг унт, 2007.doc

Exercise 3

Соответствуют ли данные предложения содержанию текста:

1. 
   Electric generators are used to convert mechanical energy into electrical energy.
   
2. 
   Electrical energy is converted into mechanical energy, by electric motors.
   
3. 
   One important mathematical equation underlie the operation of generators and motors?
   
4. 
   The principle of electromagnetic induction was discovered by the Russian scientist Mendeleev in 1831.
   
5. 
   The principle of electromagnetic reaction was first observed by Faraday in 1820.
   
6. 
   If a current is passed through a conductor located in a magnetic field, the field exerts a mechanical force on it.
   
7. 
   The more complicated of all dynamoelectric machines is the disk dynamo developed by Faraday.
   
8. 
   The magnetic field of a permanent magnet is strong enough to operate practically all dynamo machines or motors.
   
9. 
   In large machines, permanent magnets are employed.
   
10. 
    Both motors and generators consist of seven basic units.
    
11. 
    The armature is usually a laminated pig iron rod around which conducting wires are wound in coils.
    

Exercise 4

Используя текст, составьте высказывания с данными словами и выражениями:

To convert energy - by electromagnetic means - mechanical energy - electrical energy – generator – alternator – dynamo – motor - physical principle - electromagnetic induction - magnetic field - conducting loop - electromagnetic reaction – to apply a voltage - permanent magnet – electromagnet - armature - conductor - coil.
Exercise 5

Кратко передайте содержание каждого абзаца.
Exercise 6

Выделите пять основных идей текста.
Exercise 7

Составьте предложения, используя данные выражения:
exciting current (ток возбуждения); charging current (зарядный ток); constant current (ток постоянной величины); earth current (ток заземления); excess current (избыточный ток); field current (ток намагничивания); high-frequency current (ток высокой частоты); induced current (индуцированный ток); peak-to-peak current (удвоенный размах тока);
Exercise 8

Переведите на русский язык следующие предложения:

1. 
   During the early 1830s the English physicist and chemist Michael Faraday discovered a means by which mechanical energy is converted into an electrical energy on a large scale.
   
2. 
   Michael Faraday was engaged in experimental work on magnetism.
   
3. 
   Direct energy-conversion devices have received much attention because of the necessity to develop more efficient ways of transforming available forms of primary energy into electric power.
   
4. 
   Thermoelectric generators are devices that convert heat directly into electricity.
   
5. 
   A basic theory of thermoelectricity was finally formulated during the early 1900s.
   
6. 
   In a solar cell, radiant energy drives electrons across a potential difference at a semiconductor junction.
   
7. 
   Thie process, called electromagnetic induction, provides the working principle for electric generators.
   
8. 
   Electric motors, which convert electrical energy to mechanical energy, run virtually every kind of machine that uses electricity.
   
9. 
   The battery, invented by the Italian physicist Alessandro Volta about 1800, changes chemical energy directly into an electric current.
   

Exercise 9

Переведите на английский язык:

1. 
   Электрические двигатели используются для преобразования электрической энергии в механическую энергию.
   
2. 
   Электрические генераторы используются для преобразования механической энергии в электрическую энергию.
   
3. 
   Принцип электромагнитной индукции, открытый британским ученым Майклом Фарадеем, лежит в основе работы генераторов и двигателей.
   
4. 
   Принцип электромагнитной реакции был открыт французским ученым Ампером в 1820 году.
   
5. 
   При прохождении электрического тока через проводник, расположенный в магнитном поле, поле оказывает механическую силу на проводник.
   
6. 
   Электродвигатель, установленный на этом станке, изготовлен на заводе «Электросила» в 1960 году.
   
7. 
   Магнитное поле постоянного магнита недостаточно для использования в мощных двигателях.
   
8. 
   Для мощных двигателей и машин используются электромагниты.
   
9. 
   Двигатели и генераторы состоят из двух основных элементов: электромагнита и якоря
   

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Exercise 10

Текст на самостоятельный перевод:
Electric generators and motors

Other important energy-conversion devices emerged during the 19th century. During the early 1830s the English physicist and chemist Michael Faraday discovered a means by which to convert mechanical energy into electricity on a large scale. While engaged in experimental work on magnetism, Faraday found that moving a permanent magnet into and out of a coil of wire induced an electric current in the wire. This process, called electromagnetic induction, provided the working principle for electric generators.

During the late 1860s Zénobe-Théophile Gramme, a French engineer and inventor, built a continuous-current generator. Dubbed the Gramme dynamo, this device contributed much to the general acceptance of electric power. By the early 1870s Gramme had developed several other dynamos, one of which was reversible and could be used as an electric motor. Electric motors, which convert electrical energy to mechanical energy, run virtually every kind of machine that uses electricity.

All of Gramme's machines were direct-current (DC) devices. It was not until 1888 that Nikola Tesla, a Serbian-American inventor, introduced the prototype of the present-day alternating-current (AC) motor.

Direct energy-conversion devices

Most of these energy converters, sometimes called static energy-conversion devices, use electrons as their “working fluid” in place of the vapour or gas employed by such dynamic heat engines as the external-combustion and internal-combustion engines mentioned above. In recent years, direct energy-conversion devices have received much attention because of the necessity to develop more efficient ways of transforming available forms of primary energy into electric power. Four such devices—the electric battery, the fuel cell, the thermoelectric generator (or at least its working principle), and the solar cell—had their origins in the early 1800s.

The battery, invented by the Italian physicist Alessandro Volta about 1800, changes chemical energy directly into an electric current. A device of this type has two electrodes, each of which is made of a different chemical. As chemical reactions occur, electrons are released on the negative electrode and made to flow through an external circuit to thepositive electrode. The process continues until the circuit is interrupted or one of the reactants is exhausted. The forerunners of the modern dry cell and the lead-acid storage battery appeared during the second half of the 19th century.

The fuel cell, another electrochemical producer of electricity, was developed by William Robert Grove, a British physicist, in 1839. In a fuel cell, continuous operation is achieved by feeding fuel (e.g., hydrogen) and an oxidizer (oxygen) to the cell and removing the reaction products.

Thermoelectric generators are devices that convert heat directly into electricity. Electric current is generated when electrons are driven by thermal energy across a potential difference at the junction of two conductors made of dissimilar materials. This effect was discovered by Thomas Johann Seebeck, a German physicist, in 1821. Seebeck observed that a compass needle near a circuit made of different conducting materials was deflected when one of the junctions was heated. He investigated various materials that produce electric energy with an efficiency of3 percent. This efficiency was comparable to that of the steam engines of the day. Yet, the significance of the discovery of the thermoelectric effect went unrecognized as a means of producing electricity because of Seebeck's misinterpretation of the phenomenon as a magnetic effect caused by a difference in temperature. A basic theory of thermoelectricity was finally formulated during the early 1900s, though no functional generators were developed until much later.

In a solar cell, radiant energy drives electrons across a potential difference at a semiconductor junction in which the concentrations of impurities are different on the two sides of the junction. What is often considered the first genuine solar cell was built in the late 1800s by Charles Fritts, who used junctions formed by coating selenium (a semiconductor) with an extremely thin layer of gold (see Exploiting renewable energy sources below).

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Text B

Direct-Current (DC) Generators

If an armature revolves between two stationary field poles, the current in the armature moves in one direction during half of each revolution and in the other direction during the other half. To produce a steady flow of unidirectional, or direct, current from such a device, it is necessary to provide a means of reversing the current flow outside the generator once during each revolution. In older machines this reversal is accomplished by means of a commutator, a split metal ring mounted on the shaft of the armature. The two halves of the ring are insulated from each other and serve as the terminals of the armature coil. Fixed brushes of metal or carbon are held against the commutator as it revolves, connecting the coil electrically to external wires. As the armature turns, each brush is in contact alternately with the halves of the commutator, changing position at the moment when the current in the armature coil reverses its direction. Thus there is a flow of unidirectional current in the outside circuit to which the generator is connected. DC generators are usually operated at fairly low voltages to avoid the sparking between brushes and commutator that occurs at high voltage. The highest potential commonly developed by such generators is 1500 V. In some newer machines this reversal is accomplished using power electronic devices, for example, diode rectifiers.

Modern DC generators use drum armatures that usually consist of a large number of windings set in longitudinal slits in the armature core and connected to appropriate segments of a multiple commutator. In an armature having only one loop of wire, the current produced will rise and fall depending on the part of the magnetic field through which the loop is movingA commutator of many segments used with a drum armature always connects the external circuit to one loop of wire moving through the high-intensity area of the field, and as a result the current delivered by the armature windings is virtually constant. Fields of modern generators are usually equipped with four or more electromagnetic poles to increase the size and strength of the magnetic field. Sometimes smaller interpoles are added to compensate for distortions in the magnetic flux of the field caused by the magnetic effect of the armature. DC generators are commonly classified according to the method used to provide field current for energizing the field magnets. A series-wound generator has its field in series with the armature, and a shunt-wound generator has the field connected in parallel with the armature. Compound-wound generators have part of their fields in series and part in parallel. Both shunt-wound and compound-wound generators have the advantage of delivering comparatively constant voltage under varying electrical loads. The series-wound generator is used principally to supply a constant current at variable voltage. A magneto is a small DC generator with a permanent-magnet field.

Words and expressions

armature - якорь

commutator - коллектор, коммутатор.

переключатель

terminal - зажим, клемма, наконечник

rectifiers - выпрямитель

winding - обмотка

loop - виток, контур

distortion - искажение

flux - поток

compound-wound generator - генератор со смешанным

возбуждением

shunt-wound generator - генератор с параллельным

возбуждением

series-wound generator - последовательно соединенный

генератор

magneto - магнитоэлектрическая машина

Exercise 1

Ответьте на следующие вопросы:

1. 
   How does current move during the revolution of an armature between two stationary field poles?
   
2. 
   What is necessary to produce a steady flow of or direct current?
   
3. 
   What is held against the commutator as it revolves?
   
4. 
   What happens as the armature turns?
   
5. 
   Is there a flow of unidirectional current in the outside circuit to which the generator is connected?
   
6. 
   Why DC generators are usually operated at low voltages?
   
7. 
   What is highest potential developed by DC generators?
   
8. 
   What kind of armatures are used in modern DC generators?
   
9. 
   Why are the fields of modern generators equipped with four or more electromagnetic poles?
   
10. 
    What devices are added to compensate for distortions in the magnetic flux of the field caused by the magnetic effect of the armature?
    
11. 
    How generators are commonly classified?
    
12. 
    What are the advantages of compound-wound and shunt-wound generators?
    
13. 
    What is the main application of series-wound generator?
    

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Exercise 2

Заполните пропуски недостающими по смыслу словами, используя текст:

1. 
   If an … revolves between two stationary field poles, the current in the armature moves in one … during half of each revolution and in the … direction during the other half.
   
2. 
   Fixed brushes of metal or carbon are held against the … as it revolves.
   
3. 
   DC generators are usually operated at … voltages.
   
4. 
   The highest potential commonly developed by … generators is 1500 V.
   
5. 
   Modern DC generators use drum … that usually consist of a large number of windings.
   
6. 
   In an armature having only one loop of wire, the current produced will … and … depending on the part of the magnetic field through which the loop is moving.
   
7. 
   Fields of modern generators are usually equipped with … or more electromagnetic poles.
   
8. 
   DC generators are classified according to the method used to provide … for energizing the field magnets.
   
9. 
   A shunt-wound generator has the field connected in … with the armature.
   
10. 
    Compound-wound generators have part of their … in series and part in parallel.
    
11. 
    Compound-wound generators have the advantage of delivering comparatively constant … under varying electrical loads.
    

Exercise 3

Соответствуют ли данные предложения содержанию текста:

1. 
   AC generators are usually operated at fairly low voltages to avoid the sparking between brushes and commutator.
   
2. 
   The highest potential commonly developed by DC generators is 1500 V.
   
3. 
   Modern DC generators use drum armatures that usually consist of a large number of windings.
   
4. 
   DC generators are rarely classified according to the method used to provide field current for energizing the field magnets.
   
5. 
   A series-wound generator has its field in parallel with the armature.
   
6. 
   A shunt-wound generator has the field connected in series with the armature.
   
7. 
   Compound-wound generators have part of their fields in series and part in parallel.
   
8. 
   Shunt-wound and compound-wound generators have the disadvantage of delivering variable voltage under constant electrical loads.
   
9. 
   A magneto is a small AC generator with a permanent-magnet field.
   

Exercise 4

Используя текст, составьте высказывания с данными словами и выражениями:
Revolution of an armature – steady flow of current - to reverse the current – to be mounted on – to be insulated from each other - to serve as – to be held against – to be in contact alternately with – to reverse direction - to be operated at – to consist of – to be set in – to be delivered by – to be equipped with – to be added to compensate - to increase the size and strength – to be caused by - to be classified according to – to have the advantage of - to be used principally to.
Exercise 5

Кратко передайте содержание каждого абзаца.
Exercise 6

Выделите пять основных идей текста.
Exercise 7

Составьте предложения, используя данные выражения:

• 
  armature (якорь); drum armature (барабанный якорь); disc-type armature (дисковый якорь); meter armature (якорь счетчика); ring armature (кольцевой якорь); shuttle armature (якорь Н-образного сечения); smooth-core (гладкий якорь, без пазов)); spider armature (якорная звезда).
  
• 
  commutator (переключатель); battery commutator (полюсной переключатель); electronic commutator (электронный переключатель); flat-spot commutator (коллектор с местной выработкой); plug commutator (штепсельный переключатель); shrink-ring commutator (коллектор с бандажами); split-ring commutator (коллектор из двух полуколец).
  
• 
  terminal ( зажим, клемма, вывод); battery terminal (полюс батареи); connecting terminal (зажим, клемма); earth terminal (заземляющий зажим); outlet terminal (трансформаторный ввод); pole terminal (полюсный наконечник); spade (наконечник для многожильного кабеля).
  
• 
  rectifier (выпрямитель); arc rectifier (дуговой выпрямитель); biphase rectifier (двухфазный выпрямитель); crystal rectifier (кристаллический выпрямитель ); dry rectifier (металлический выпрямитель); electrolytic rectifier (электролитический выпрямитель); electron rectifier (кенотронный выпрямитель); heavy-duty rectifier ( мощный кенотрон); mechanical rectifier (механический выпрямитель); mercury-arc rectifier (ртутный выпрямитель); pulsed rectifier (импульсный выпрямитель); valve rectifier (кенотронный выпрямитель, кенотрон).
  
• 
  winding (обмотка); armature winding (обмотка якоря); auxiliary winding (вспомогательная обмотка ); closed-coil winding (замкнутая обмотка); drum winding (барабанная обмотка); primary winding (первичная обмотка); starting winding (пусковая обмотка); exciting winding (обмотка возбуждения).
  
• 
  distortion (искажение); distortion of field (смещение поля); amplitude distortion (амплитудное искажение); frequency distortion (частотное искажение); phase distortion (фазовое искажение).
  

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Exercise 8

Переведите на русский язык следующие предложения:

1. 
   Thermoelectric generators are devices that convert heat directly into electricity.
   
2. 
   Electric current is generated when electrons are driven by thermal energy across a potential difference at the junction of two conductors made of dissimilar materials.
   
3. 
   A direct-current (DC) generator is a rotating machine that supplies an electrical output with unidirectional voltage and current.
   
4. 
   Voltage is induced in coils by the rate of change of the magnetic field through the coils as the machine rotates.
   
5. 
   The field is produced by direct current in field coils or by permanent magnets on the stator.
   
6. 
   In practical machines, the rotor contains many coils symmetrically arranged in slots around the periphery and all connected in series.
   
7. 
   The voltage magnitude is proportional to the rotor speed and the magnetic flux.
   
8. 
   Control of output voltage is normally provided by control of the direct current in the field.
   
9. 
   For convenience in design, direct-current generators are usually constructed with four to eight field poles.
   
10. 
    The number of stationary brushes bearing on the rotating commutator is usually equal to the number of poles but may be only two in some designs.
    
11. 
    Direct-current generators were widely used prior to the availability of economical rectifier systems supplied by alternators.
    
12. 
    In some applications, the direct-current generator retains an advantage over the alternator-rectifier in that it can operate as a motor as well, reversing the direction of power flow.
    

Exercise 9

Переведите на английский язык:

1. 
   В генераторах постоянного тока якорь вращается между двумя постоянными полевыми полюсами.
   
2. 
   Для обеспечения устойчивого потока однонаправленного тока от генератора постоянного тока, необходимо обеспечить изменение направления тока единожды в течение каждого вращения якоря.
   
3. 
   В старых генераторах постоянного тока, движение в обратном направлении достигалось при помощи коммутатора.
   
4. 
   Изолированные друг от друга полукольца служат терминалами катушки якоря.
   
5. 
   Металлические щетки, установленные перед коммутатором соединяют катушку с внешними проводами.
   
6. 
   Во время вращения якоря, каждая щетка поочередно контачит с половинами коммутатора.
   
7. 
   Генераторы постоянного тока обычно используются для выработки низкого напряжения.
   
8. 
   Напряжение, вырабатываемое генераторами постоянного тока, не превышает уровня 1500 вольт.
   
9. 
   Величина и сила магнитного поля напрямую виляет на мощность генератора.
   

Exercise 10

Текст на самостоятельный перевод:

DC Motors

In general, DC motors are similar to DC generators in construction. They may, in fact, be described as generators “run backwards.” When current is passed through the armature of a DC motor, a torque is generated by magnetic reaction, and the armature revolves. The action of the commutator and the connections of the field coils of motors are precisely the same as those used for generators. The revolution of the armature induces a voltage in the armature windings. This induced voltage is opposite in direction to the outside voltage applied to the armature, and hence is called back voltage or counter electromotive force (emf). As the motor rotates more rapidly, the back voltage rises until it is almost equal to the applied voltage. The current is then small, and the speed of the motor will remain constant as long as the motor is not under load and is performing no mechanical work except that required to turn the armature. Under load the armature turns more slowly, reducing the back voltage and permitting a larger current to flow in the armature. The motor is thus able to receive more electric power from the source supplying it and to do more mechanical work.

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