Елохова.Профессиональный английский язык. Учебно-методическое

3.if the electromagnet is lifeless unless the electric current flows through the coil.

4.if the iron core will act as a magnet as long as the current continues to pass along the winding.

5.if the alternator provides a. c.

6.if the generator must be turned by some outside source of mechanical energy.

Exercise 7. Complete the sentences with the words:

commutator, poles, direct, direction, rotates, alternating, circuit, coil, field

A. In the simplest form of generator the conductor is an open (1)____________ of wire rotating between the (2)____________ of a permanent magnet. During a single rotation, one side of the coil passes through the magnetic (3)____________

first in one direction and then in the other, so that the induced current is

(4)____________ current (a. c.), moving first in one direction, then in the other. Each end of the coil is attached to a separate metal slip ring that (5)____________

with the coil. Brushes that rest on the slip rings are attached to the external

(6)____________. Thus the current flows from the coil to the slip rings, then through the brushes to the external circuit. In order to obtain (7)____________

current (d. c.), i.e. current that flows in only one direction, a commutator is used in place of slip rings. The (8)____________ is a single slip ring split into left and right halves that are insulated from each other and are attached to opposite ends of the coil. It allows current to leave the generator through the brushes in only one

(9)____________. This current pulsates, going from no flow to maximum flow and back again to no flow.

Dynamo, magnets, stator, alternator, driven

B. A practical d. c. generator, with many coils and with many segments in the commutator, gives a steadier current. There are also several magnets in a practical generator. In any generator, the whole assembly carrying the coils is called the armature, or rotor, while the stationary parts constitute the (10)____________. Except in the case of the magneto, which uses permanent (11)____________, a. c. and d. c. generators use electromagnets. Field current for the electromagnets is most often d. c. from an external source. The term (12)____________ is often used for the d. c. generator. An a. c. generator is called an (13)____________. To ease various construction problems, alternators have a stationary armature and rotating electromagnets. Most alternators produce a polyphase a. c., a complex type of current that provides a smoother power flow than does simple a. c. By far the greatest amount of electricity for industrial and civilian use comes from large a. c. generators (14)____________ by steam turbines.

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Unit VI. Electric Power Systems

Text 1

Exercise 1. Decide if these sentences are True or False. Read the text:

1.Transmission circuits may be built only underground.

2.There are four possible causes for power flow limitations to a transmission line.

Transmission

The electricity is transported to load locations from a power station to a transmission subsystem. Therefore we may think of the transmission system as providing the medium of transportation for electric energy. The transmission system may be subdivided into the bulk transmission system and the subtransmission system. The functions of the bulk transmission are to interconnect generators, to interconnect various areas of the network, and to transfer electrical energy from the generators to the major load centers.

This portion of the system is called «bulk» because it delivers energy only to so-called bulk loads such as the distribution system of a town, city, or large industrial plant. The function of the sub-transmission system is to interconnect the bulk power system with the distribution system. Transmission circuits may be built either underground or overhead.

Underground cables are used predominantly in urban areas where acquisitions of overhead rights of way are costly or not possible. They are also used for transmission under rivers, lakes and bays. Overhead transmission is used otherwise because, for a given voltage level, overhead conductors are much less expensive than underground cables.

The transmission system is a highly integrated system. It is referred to the substation equipment and transmission lines. The substation equipment contains the transformers, relays, and circuit breakers. Transformers are important static devices which transfer electrical energy from one circuit with another in the transmission subsystem. Transformers are used to step up the voltage on the transmission line to reduce the power loss which is dissipated on the way. A relay is functionally a level-detector; they perform a switching action when the input voltage (or current) meets or exceeds a specific and adjustable value. A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. A change in the status of any one component can significantly affect the operation of the entire system. Without adequate contact protection, the occurrence of undesired electric arcing causes significant degradation of the contacts, which suffer serious damage. There are three possible causes for power flow limitations to a transmission line.

These causes are thermal overload, voltage instability, and rotor angle instability. Thermal overload is caused by excessive current flow in a circuit causing overheating. Voltage instability is said to occur when the power required to

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maintain voltages at or above acceptable levels exceeds the available power. Rotor angle instability is a dynamic problem that may occur following faults, such as short circuit, in the transmission system. It may also occur tens of seconds after a fault due to poorly damped or undamped oscillatory response of the rotor motion. As long as the equal area criterion is maintained, the interconnected system will remain stable. Should the equal area criteria be violated, it becomes necessary to separate the unstable component from the remainder of the system.

Distribution

The distribution system transports the power from the transmission system to the customer. The distribution systems are typically radial because networked systems are more expensive. The equipment associated with the distribution system includes the substation transformers connected to the transmission systems, the distribution lines from the transformers to the customers and the protection and control equipment between the transformer and the customer. The protection equipment includes lightning protectors, circuit breakers, disconnections and fuses. The control equipment includes voltage regulators, capacitors, relays and demand side management equipment.

Exercise 2. Answer the questions:

1. What does the transmission system do?

2. Give the definition for the world «bulk».

3.What are the forms of transmission circuits?

4.How does the system of transformers function?

5.Describe the distribution system of electric power.

6.What are the components of the protection and control equipment?

Text 2

Transformers

The transformer is a device for changing the electric current from one voltage to another. As a matter of fact, it is used for increasing or decreasing voltage. A simple transformer is a kind of induction coil. It is well known that in its usual form it has no moving parts. On the whole, it requires very little maintenance provided it is not misused and is not damaged by lightning.

We may say that the principal parts of a transformer are two windings, that is coils, and an iron core. They call the coil which is supplied with current the «primary winding», or just «primary», for short. The winding from which they take the current is referred to as the «secondary winding» or «secondary», for short. It is not new to you that the former is connected to the source of supply, the latter being connected to the load.

When the number of turns of wire on the secondary is the same as the number on the primary, the secondary voltage is the same as the primary, and we get what is called a «one-to-one» transformer. In case, however, the number of turns on the

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secondary winding is greater than those on the primary, the output voltage is larger than the input voltage and the transformer is called a step-up transformer. On the other hand, the secondary turns being fewer in number than the primary, the transformer is known as a step-down transformer.

The transformer operates equally well to increase the voltage and to reduce it. By the way, the above process needs a negligible quantity of power. It is important to point out that the device under consideration will not work on d. c. but it is rather often employed in direct-current circuits.

Transformers are used in stepping up the voltages for distribution or transmission over long distances and then in stepping these voltages down. For example, three large step-up transformers which are used to increase the potential to 275,000 volts for transmission over long-distance transmission lines. At the consumers end of the line, in some distant locality three step-down transformers are made use of to reduce hat valued (i.e., 275,000 volts) to 2,300 volts. Local transformers, in their turn, are expected to decrease the 2,300 volts to lower voltages, suitable for use with small-motors and lamps. One could have some other transformers in the systems that reduce the voltage even further. All radio sets and all television sets are known to use two or more kinds of transformers. These are familiar examples showing that electronic equipment cannot do without transformers. The facts you have been given above illustrate the wide use of transformers and their great importance.

Vocabulary:

maintenance – техническое обслуживание, эксплуатация to misuse – злоупотребление

distribution – распределение, распространение figure – изображение

consumer – потребитель

to reduce – уменьшать, сокращать locality – местность

suitable – подходящий, годный familiar – известный equipment – оборудование

Exercise 1. Answer the questions:

1.What is a transformer?

2.What is a transformer used for?

3.Are there any moving parts in a transformer?

4.Can a transformer be damaged by lightning?

5.What are the principal parts of a transformer?

6.How many windings are there in a transformer?

7.What winding is connected to a load?

8.What is the purpose of a step-up transformer?

9.What is known as a step-down transformer?

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10.Does a transformer work on d. c.?

11.What circuits is the transformer used in?

12.What purpose are step-down transformers used for?

13.Is your radio set equipped with a transformer?

14.Can we do without transformer?

15.Are transformers used both in industry and in our homes?

Exercise 2. Find the following equivalents in the text:

для изменения напряжения; для повышения (понижения) напряжения; индукция катушки; называется вторичной обмоткой; подсоединен к источнику тока; количество витков проволоки; незначительная мощность; рассматриваемое устройство; применяется в цепях постоянного тока; передача на большие расстояния; линии передач; удобный для использования; отдаленная местность; известные примеры; электронное оборудование

Exercise 3. Find the Russian equivalents to the following word combinations:

number of; as a matter of fact; on the basis of; for this reason; it goes without saying; at last; on the whole; to step up; to increase current; to offer resistance; electrical engineering; to step down

наконец; повышать (напряжение); оказывать сопротивление; понижать (напряжение); ряд; увеличить ток; на основе чего-либо; по этой причине; в целом; электротехника; на самом деле; само собой разумеется

Exercise 4. Arrange the following words in the pairs of synonyms:

a)amount; big; matter; application; at present; tube; research; to step down; appliance; minute; arrow

b)investigation; device; needle; quantity; substance; to lower; small; large; new; use; pipe

Exercise 5. Arrange the following words in the pairs of antonyms:

a)left; increase; beginning; d. c.; above; step-up; at rest; high; short; more

b)end; low; long; step-down; in motion; less; decrease; below; a. c.; right

Exercise 6. Find the wrong statements and correct them:

1.The transformer is a device used to increase or decrease the electrical current.

2.The principal parts of a transformer are a coil and an iron core.

3.The coil is called the secondary winding.

4.When the number of turns of wire on the secondary is the same as the number on the primary, the primary voltage is the same as the secondary.

5.The transformer is known as a step-down transformer if the secondary turns being fewer in number than the primary.

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6.The output voltage is smaller than the input voltage if the number of turns on the primary winding is greater than those on the secondary.

7.The transformer acts differently to increase the voltage and to reduce it.

Exercise 7. Translate into English:

1.Трансформатор используется для повышения или понижения напряжения.

2.Трансформатор одинаково хорошо понижает и повышает напряжение.

3.Обмотка, генерирующая ток, называется вторичной.

4.Трансформатор подсоединен к источнику тока.

5.Трансформатор не может работать от постоянного тока.

Exercise 8. What is:

1.step-up transformer;

2.step-down transformer;

3.«one-to-one» transformer

Exercise 9. Compare:

1.A solenoid and an electromagnet.

2.A direct current and an alternating current.

3.A step-up transformer and a step-down transformer.

4.A stator and a rotor.

5.A primary winding and a secondary winding.

Text 3

Types of Transformers

There are different types of transformers. By the purpose they are classified into step-up transformers and step-down transformers. In a step-up transformer the output voltage is larger than the input voltage, because the number of turns on the secondary winding is greater than that of the primary. In a step-down transformer the output voltage is less than input voltage as the number of turns on the secondary is fewer than that on the primary.

By the construction transformers are classified into core-type and shell-type transformers. In the core-type transformers the primary and the secondary coils surround the core. In the shell type transformers the iron core surrounds the coils. Electrically they are equivalent. The difference is in the mechanical construction.

By the methods of cooling transformers are classified into air-cooled, oilcooled and water-cooled transformers.

By the number of phases transformers are divided into single-phase and polyphase transformers.

Instrument transformers are of two types, current and potential.

A current transformer is an instrument transformer used for the transformation of a current at a high voltage into proportionate current at a low voltage. Current transformers are used in conjunction with a.c. meters or instruments where the

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current to be measured must be of low value. They are also used where highvoltage current has to be metered. A voltage transformer, which is also called a potential transformer, may be defined as an instrument transformer for the transformation of voltage from one value to another. This transformer is usually of a step-down type because it is used when a meter is installed for use on a highvoltage system.

Transformers operate equally well to increase the voltage and to reduce it. The above process needs a negligible quantity of power. Transformers are widely used in our everyday life. All radio sets and all television sets are known to use two or more kinds of transformers. These are familiar examples showing that electronic equipment cannot do without transformers.

Exercise 1. Answer the questions:

1.What voltage is larger in a step-up transformer and why?

2.What voltage is less in a step-down transformer and why?

3.What is the construction of a core-type transformer?

4.What is the construction of a shell-type transformer?

5.What are the two types of instrument transformers?

6.What are current transformers used for?

7.What are potential transformers used for?

Exercise 2. Find the following equivalents in the text:

повышающий/ понижающий трансформатор; выходящее/ входящее напряжение; число витков; механическое устройство; монофазные/ полифазные трансформаторы; высокое / низкое напряжение; незначительное количество.

Exercise 3. Find the Russian equivalents to the following word combinations

Core-type/ shell-type transformers; air-cooled/ oil-cooled/ water-cooled transformers; current / potential transformers; in conjunction with smith; to reduce; electronic equipment.

Exercise 4. Complete the sentences:

1.By the purpose transformers are … .

2.By the construction transformers are … .

3.By the methods of cooling transformers are … .

4.By the number of phases transformers are … .

5.Transformers operate equally well… .

6.Process of voltage changing needs… .

7.Familiar examples of transformer applications are … .

Exercise 5. Discuss the following:

1.Types of transformers.

2.Use of transformers in everyday life.

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Unit VII. Types of Electric Power Plants

Text 1

Electric Power Plants

Electric power is generated at electric power plants. The main unit of an electric power plant comprises a prime mover and the generator which it rotates.

In order to actuate the prime mover energy is required. Many different sources of energy are in use nowadays. To these sources belongs heat obtained by burning fuels, pressure due to the flow of air (wind), solar heat, etc.

According to the kind of energy used by the prime mover, power plants are divided into groups. Thermal, hydraulic (water-power) and wind plants form these groups. According to the kind of prime mover, electric power plants are classed as:

a)Steam turbine plants, where steam turbines serve as prime movers. The main generating units at steam turbine plants are the turbo generators. Steam turbine plants belong to the modern, high-capacity class of power plants.

b)Steam engine plants, in which the prime mover is a piston-type steam

engine.

Nowadays no large generating plants of industrial importance are constructed with such prime movers. They are used only for local power supply.

c)Diesel-engine plants in them diesel internal combustion engines are installed. These plants are also of small capacity, they are employed for local power supply.

d)Hydroelectric power plants employ water turbines as prime movers. Therefore they are called hydro turbine plants. Their main generating unit is the hydro generator.

Modern wind-electric power plants utilize various turbines; these plants as well as the small capacity hydroelectric power plants are widely used in agriculture.

Vocabulary:

power plant – электростанция

to comprise – охватывать, заключать в себе prime – главный, основной

mover – двигатель, движитель to rotate – вращать(ся)

to actuate – побуждать

to obtain – достигать, приобретать, применять, получать fuel – топливо

pressure – давление, (эл) напряжение, (тех) прессование thermal – тепловой, термальный

steam turbine plant – электростанция с паровой турбиной hydraulic – гидравлический

capacity – (тех) мощность

piston-type steam engine – (тех) паровой двигатель поршневого типа diesel engine plants – электростанции с дизельным двигателем

diesel internal combustion engines – дизельный двигатель внутреннего сгорания

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to install – устанавливать; (тех) проводить to employ – применять, использовать

to utilize – использовать, утилизировать

Exercise 1. Answer the questions:

1.What plants generate electric power?

2.What kinds of energy do prime movers employ?

3.What sources of energy are in use nowadays?

4.What power plants do you know?

5.How are plants with different kinds of prime movers called?

6.What are the main generating units at steam turbine plants?

7.In what plants are combustion engines employed?

8.What are diesel-engine plants?

9.How are plants employing water turbines called?

10.Where are wind-electric power plants widely used?

Exercise 2. Complete the sentences with the prepositions:

because of, in addition to, according to, in spite of, due to, by means of, as to

1. Things fall under their own weight with an acceleration … gravity. 2. … the modern theory electrons can revolve only in definite orbits around the nucleus. 3.

… its usefulness a direct current system has one great disadvantage. 4. Any moving body will continue to move … its inertia. 5. … instruments measuring current and voltage there are devices for measuring energy. 6. The energy of falling water is transformed into electric energy … hydraulic turbines. 7. … metals they differ greatly in the ease with which electrons can be made to move from atom to atom. 8.

The problem was whether the element can be arranged … that law. 9. … magnet effects, dynamos are able to convert mechanical energy into electrical energy with a loss of only a few per cent.

Text 2

Thermal Power Station

A modern thermal power-station is known to consist of four principal components, namely, coal handling and storage, boiler house, turbine house, switchgear.

Besides the principal components mentioned above there are many additional parts of the plant. The most important of them is the turbo generator in which the current is actually generated.

A steam turbine requires boilers to provide steam. Boilers need a coalhandling plant on the one hand and an ash-disposal plant on the other. Large fans are quite necessary to provide air for the furnaces. Water for the boilers requires feed pumps. Steam must be condensed after it has passed through the turbines, and this requires large quantities of cooling water. The flue gases carry dust which must be removed by cleaning the gases before they go into the open air.

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A modern thermal power-station is equipped with one or more turbine generator units which convert heat energy into electric energy. The steam to drive the turbine which, in its turn, turns the rotor or revolving part of the generator is generated in boilers heated by furnaces in which one of three fuels may be used– coal, oil and natural gas. Coal continues to be the most important and the most economical of these fuels.

It is necessary to point out that the power machine building industry has started to manufacture even greater capacity installations for thermal powerstations.

Thermal power-stations are considered to be the basis of Russian power industry. More than 80% of the country’s total power output comes from the above stations.

It is necessary to say that separate power-stations in our country are integrated Into power systems. Integration of power systems is a higher stage in scientific and technical development of power engineering. The Integrated Power System in the central part of Russia is one of the largest in the world.

Vocabulary:

thermal power-stations – тепловая электростанция, ТЭЦ coal handling – угольная эстакада

storage – хранилище boiler house – котельная

turbine house – турбинный (машинный) зал (электростанции или ГЭС) switchgear – аппаратура распределительных устройств

coal-handling plant – «завод топливоподачи» ash-disposal plant – «золоудалительный завод» flue gases – топочные (дымовые) газы

Exercise 1. Find the English equivalents in the text:

блоки генераторов; ротор; вращающаяся деталь; мощные установки; выходная мощность; объединение в одно целое энергетических систем

Exercise 2. Translate into Russian:

to consist of four principal components; turbo generator; turbine requires boilers; furnaces; fans; pumps; to be condensed after; cooling water; dust; equipped with; to convert heat energy into electrical energy

Exercise 3. Complete the sentences with the words from Exercises 1 and 2:

1. The heated or vaporized fluid exits the … for use in various processes or heating applications. 2. The oil shale burnt at Narva produces roughly 46% ash, so the stations produce about 4, 5 million tons of ash per year; the … system involves washing it away with water. 3. … is commonly used for cooling internal combustion engines in automobiles and large electrical generators. 4. … produce air flows with high volume and low pressure, as opposed to compressors which

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