2832

U N I T 4

Ex. 1. Copy and memorize the following terms.

Glossary

ferromagnetic – ферромагнитный mutual induction – взаимная индукция primary coil – первичная обмотка secondary coil – вторичная обмотка step down – понижать напряжение

to step up – повышать напряжение turn – виток

Ex. 2. Copy the following words and memorize their meanings:

9flux – поток

9permeability – проницаемость

9thumbnail – маленький, крошечный (размером с ноготь)

9to couple – соединять

9to dissipate – рассеивать

Ex.3. Translate the following sentences from English into Russian

1. The left hand can also be used to demonstrate the magnetic flux surrounding a wire carrying a current. 2. Permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. 3. Russian engineer Pavel Yablochkov invented a lighting system based on a set of induction coils where the primary coils were connected to a source of alternating current and the secondary coils could be connected to several "electric candles" (arc lamps) of his own design. 4. Transformers are used to step down the high overhead line voltages. 5. A substation that has a step-up transformer increases the voltage while decreasing the current, while a step-down transformer decreases the voltage while increasing the current for domestic and commercial distribution. 6. The turn is one round in a coil of rope or other material. 7. One loop of wire is usually referred to as a turn, and a coil consists of one or more turns. 8. Mutual inductance occurs when the change in current in one inductor induces a voltage in another nearby inductor. 9. In order to concentrate the magnetic field generated by a wire, it is commonly wound into a coil, where many turns of wire sit side by side. 10. Gas is lighter than air and leakages dissipate in the atmosphere.

Ex.4. Translate the following sentences from English into Russian paying attention to the Nominative Absolute Construction.

1.The reflected signal having been received, the distance to the object was counted.

2.An electric arc is a discharge accompanied by a temperature of over 3,000°C, produced when an electric current flows through a gap between two electrodes, the current being carried by the vapour of the electrode. 3. Other factors being constant, the current is known to be directly proportional to conductivity. 4. The area is constant, being equal to the cross-sectional area of the transformer core, whereas the magnetic field varies with time according to the excitation of the primary. 5. In this case, the magnetic circuits are connected together, the core thus containing a three-phase flow of flux. 6. The secondaries of the transformers will have two phases 90 degrees apart in time, a balanced two-phase load being evenly balanced over the three supply phases. 7. However, high voltages also have disadvantages, the main one being the increased insulation required, and generally increased difficulty in their safe handling. 8. Three

41

separate coils in the generator stator are physically offset by an angle of 120° to each other, three current waveforms being produced, they are equal in magnitude and 120° out of phase to each other. 9. The frequency of the electrical system varies by country; most electric power is generated at either 50 or 60 Hz.

Ex.4. Practice the reading of the following word combinations. You are to copy them and memorize their meaning

To transfer electrical energy, inductively coupled conductors, magnetic field within a coil of wire, to induce a voltage, magnetic flux, wrapped around a core, magnetic permeability, ratio of the number of turns, ferromagnetic core, air-core transformer, national power grids, to dissipate electrical energy, to enable economic transmission of power.

Ex.5. Match the words in column A with their definitions in column B.

	A		B
1.	mutual induction	a)	the output side of a transformer using electromagnetic
			induction
2.	primary coil	b)	the total magnetic field passing through a surface
3.	secondary coil	c)	a transformer with the lack of a core
4.	magnetic flux	d)	the input side of a using transformer electromagnetic
			induction
5.	air-core transformer	e)	a measurement device designed to provide a current in its
			secondary coil proportional to the current flowing in its
			primary
6.	current transformer	f)	the production of an electromotive force in a circuit by a
			change in the current in an adjacent circuit that is linked
			to the first by the flux lines of a magnetic field
7.	voltage transformer	g)	a transformer, often with symmetrical windings, which is
			used to decouple two circuits
8.	isolation transformer	h)	an instrument transformer, used for metering and
			protection in high-voltage circuits

Read the text and translate it using a dictionary if necessary.

T R A N S F O R M E R S

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors – the transformer's coils. The transformer is based on two principles: firstly, that an electric current can produce a magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil. Current passing through the primary coil creates a magnetic field. The primary and secondary coils are wrapped around a core of very high magnetic permeability, such as iron, so that most of the magnetic flux passes through both primary and secondary coils.

A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a voltage in the secondary winding. This effect is called mutual induction.

42

If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP).

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP.

In the vast majority of transformers, the coils are wound around a ferromagnetic core, aircore transformers being a notable exception.

Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of national power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household voltage. Transformers are essential for high voltage power transmission, which makes long distance transmission economically practical.

A major application of transformers is to increase voltage before transmitting electrical energy over long distances through wires. Wires have resistance and so dissipate electrical energy at a rate proportional to the square of the current through the wire. By transforming electrical power to a high-voltage (and therefore low-current) form for transmission and back again afterward, transformers enable economic transmission of power over long distances.

Ex.5. Complete the sentences using the correct variant. Sometimes more than one variant are possible.

1.A transformer is used ….

b)to transfer energy.

c)to change the voltage value in a circuit.

2.Electric power is transferred at a high voltage and reduced to any value ….

a)due to resistors.

b)due to capacitors.

c)due to transformers.

3.A transformer consists of ….

a)cores only.

b)a core and the primary and the secondary windings.

c)the primary and the secondary windings.

4.The function of the primary is ….

a)to prevent the change of voltage.

b)to supply energy.

c)to receive energy.

5.The function of the secondary winding is ….

a)to receive energy.

b)to supply energy.

c)to transfer energy.

6.A step-up transformer is used ….

a)to decrease the secondary voltage.

b)to increase the secondary voltage.

43

7.A step-down transformer is used ….

a)to decrease the secondary voltage.

b)to increase the secondary voltage.

8.In a step-up transformer the number of turns ….

a)of the secondary winding is greater than the number of turns of the primary.

b)of the primary winding is greater than the number of turns of the secondary.

9.A major application of transformers is ….

a)to increase voltage before transmitting electrical energy over long distances.

b)to decrease voltage before transmitting electrical energy over long distances.

Ex.6. Consult the text and complete the sentences according to the model: Model: Iron core transformers have a core. →

Iron core transformers have a core w h i l e air-core transformers do not have a core.

1.The secondary winding of a transformer is connected to the load.

2.The primary winding of a transformer receives energy.

3.A step-down transformer decreases the primary voltage.

4.In a step-up transformer the number of turns of the secondary winding is greater than the number of turns of the primary.

Ex.7. Fill in the blanks with the words given in the box. Translate the sentences.

kilohertz	conducting	between	solid
transformers	voltages	turns	coils

The (1)… material used for the windings depends upon the application, but in all cases the individual (2)… must be electrically insulated from each other to ensure that the current travels throughout every turn. For small power and signal transformers, in which currents are low and the potential difference (3)… adjacent turns is small, the (4)… are often wound from enameled magnet wire, such as Formvar wire. Larger power transformers operating at high

(5)… may be wound with copper rectangular strip conductors insulated by oil-impregnated paper and blocks of pressboard.

High-frequency transformers operating in the tens to hundreds of (6)… often have windings made of braided Litz wire to minimize the skin-effect and proximity effect losses. Large power (7)… use multiple-stranded conductors as well, since even at low power frequencies non-uniform distribution of current would otherwise exist in high-current windings.

U N I T 5

Ex. 1. Copy and memorize the following terms.

Glossary

cable – кабель clearance – зазор

full-wave rectifier – двухполупериодный выпрямитель half-wave rectifier – однополупериодный выпрямитель overhead transmission line – воздушная линия передачи power outage – отключение электроэнергии

power plant – электростанция

44

power transmission network – сеть электропередач shielding – экранирование

strand – жила кабеля substation – подстанция

Ex.2. Copy the following words and memorize the meanings.

9adverse – неблагоприятный

9alloy – сплав; сплавлять металлы

9consecutive - последовательный

9delivery – доставка

9distant – отдалённый

9flutter – вибрация; вибрировать

9obstacle – препятствие

9oscillatory – колебательный

9to be subject to smth. – быть подверженным чему-л.

9to encroach – вторгаться, посягать

9to imply – подразумевать

9to observe – соблюдать

9to reinforce – усиливать

9сonsumer – потребитель

Ex.2. Translate the following sentences from English into Russian.

1.Democracy implies a respect for individual liberties. 2. Gold and iron alloy with ease.

3.The company has made a profit for seven consecutive years. 4. Climate change may have adverse impacts on human health. 5. Unlike pure metals, most alloys do not have a single melting point, but a melting range in which the material is a mixture of solid and liquid phases.

6.The restaurant pays cash on delivery for fish, which the local fishermen like. 7. Consumers have a right to know what they are buying. 8. Fear of change is an obstacle to progress. 9. In the 1920s Edwin Hubble observed that distant galaxies look redder than nearby ones. 10. If something thin or light flutters, it moves up and down or from side to side with a lot of quick, light movements. 11. The oscillatory universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a big bang and ending with a big crunch. 12. Imposing speed restrictions is easy, but forcing motorists to observe them is trickier. 13. The sea has been encroaching on the land for years.

14.Underground power cables are less subject to damage from severe weather conditions. 15. The windows were of reinforced glass.

Ex.3. Fill in the blanks with the words given in the box. Translate the sentences.

full-wave rectifier	cable	clearance	overhead power lines	substations
power plants	grid	power outage	transmission networks	half-wave rectifier

1. A … converts either the positive or negative half of the AC wave, while the other half is blocked. 2. Since most of the insulation is provided by air, … are generally the lowest-cost method of transmission for large quantities of electric energy. 3. There was less than a foot's … between the ship's sides and the wharf. 4. A … is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. 5. Electricity in a remote location might be provided by a simple distribution … linking a central generator to homes. 6. A …

45

converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. 7. Transmission lines, when interconnected with each other, become high voltage …. 8. At the center of nearly all … is a generator, a rotating machine that converts mechanical energy into electrical energy by creating relative motion between a magnetic field and a conductor. 9. Electric power transmission or "high voltage electric transmission" is the bulk transfer of electrical energy, from generating power plants to … located near to population centers. .10. … are particularly critical at sites where the environment and public safety are at risk.

Read the text and translate it using a dictionary if necessary.

E L E C T R I C P O W E R T R A N S M I S S I O N

(1)Electric power transmission is a process in the delivery of electricity to consumers. A power transmission network typically connects power plants to multiple substations near a populated area. Electric power transmission allows distant energy sources (such as hydroelectric power plants) to be connected to consumers in population centers. Usually transmission lines use three phase alternating current. Single phase AC current is sometimes used in a railway electrification system. High-voltage direct current systems are used for long distance transmission, or some undersea cables, or for connecting two different AC networks.

(2)Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in transmission. A power transmission network is called a grid.

(3)Overhead conductors are not covered by insulation. The conductor material is nearly always an aluminium alloy, made into several strands and possibly reinforced with steel strands. Copper was sometimes used for overhead transmission but aluminium is lower in weight for equivalent performance, and much lower in cost.

(4)Since overhead transmission lines are uninsulated, design of these lines requires minimum clearances to be observed to maintain safety. Adverse weather conditions of high wind and low temperatures can lead to power outages: wind speeds can permit conductors to encroach operating clearances, resulting in a flashover and loss of supply. Oscillatory motion of the physical line can be termed gallop or flutter depending on the frequency and amplitude of oscillation.

(5)Electric power can also be transmitted by underground power cables instead of overhead power lines. They can assist the transmission of power across densely populated urban areas or areas where land is unavailable or there are rivers and other natural obstacles.

(6)Some advantages of underground power cables are those:

•Less subject to damage from severe weather conditions (mainly lightning, wind and freezing)

•All electric currents generate EMF, but the shielding provided by the earth surrounding underground cables restricts their range and power. Underground cables pose no hazard to low flying aircraft or to wildlife, and are significantly safer as they pose no shock hazard (except to the unwary digger).

(7)Voltage multipliers, as the name implies, are circuits designed to multiply the input voltage. The input voltage may be doubled (voltage doubler), tripled (voltage tripler), quadrupled (voltage quadrupler), etc. Voltage multipliers are also power converters. An AC input is converted to a higher DC output. These circuits allow high voltages to be obtained using a much lower voltage AC source.

46

(8)Typically, voltage multipliers are composed of half-wave rectifiers, capacitors, and diodes. For example, a voltage tripler consists of three half-wave rectifiers, three capacitors, and three diodes. Full-wave rectifiers may be used in a different configuration to achieve even higher voltages. Also, both parallel and series configurations are available. For parallel multipliers, a higher voltage rating is required at each consecutive multiplication stage, but less capacitance is required. The voltage capability of the capacitor limits the maximum output voltage.

(9) Voltage multipliers have many applications. For example, voltage multipliers can be found in everyday items like televisions and photocopiers. Even more applications can be found in the laboratory, such as cathode ray tubes, oscilloscopes, and photomultiplier tubes.

Ex. 4. Match the halves of the sentence together.

	A			B
1.	A power transmission network typically	a)	to reduce the energy lost in transmission.
	connects power plants …
2.	High-voltage direct current systems …	b) underground		power	cables instead	of
			overhead power lines.
3.	Electricity is transmitted at high	c)	circuits designed to multiply the input
	voltages …		voltage.
4.	Aluminium is lower in weight for	d)	half-wave rectifiers, capacitors, and
	equivalent performance …		diodes.
5.	Electric power can also be transmitted by …	e)	to multiple substations
6.	Oscillatory motion of the physical line	f)	restricts their range and power.
	can be termed gallop or flutter …
7.	Voltage multipliers are …	g) depending		on the	frequency	and
			amplitude of oscillation.
8.	Voltage multipliers are composed of …	h)	are used for long distance transmission
9.	The shielding provided by the earth	i)	and much lower in cost.
	surrounding underground cables …

Ex. 5. Go back to the text and using the paragraph reference find words which are similar to:

¾customer, grid, joins, permits, remote (paragraph 1);

¾decrease, power (paragraph 2);

¾almost, wires, a number of, operation (paragraph 3);

¾because, unfavourable, power cut, intrude (paragraph 4);

¾aid, barriers (paragraph 5);

¾danger (paragraph 6);

¾increase, receive (paragraph 7);

¾usually, constitute, reach (paragraph 8).

Ex.3. Translate the following sentences from Russian into English.

1.Различают воздушные и кабельные линии электропередачи

2.Воздушная линия электропередачи – устройство, предназначенное для передачи или распределения электрической энергии по проводам, находящимся на открытом воздухе и прикреплённым к опорам или другим сооружениям.

47

3.Кабельная линия электропередачи – это линия для передачи электроэнергии, состоящая из одного или нескольких параллельных кабелей.

4.Кабельные линии делятся на подземные и подводные

5.Потери электроэнергии в проводах зависят от силы тока, поэтому при передаче её на дальние расстояния, напряжение многократно повышают с помощью трансформатора, что при передаче той же мощности позволяет значительно снизить потери.

6.Система электроснабжения – это совокупность источников и систем преобразования, передачи и распределения электрической энергии.

7.Опоры предназначены для сооружений линий электропередач напряжением 35 кВ и выше при температуре наружного воздуха до –65 °C и являются одним из главных конструктивных элементов линий электропередач.

8.Умножитель напряжения – это электрическая цепь, которая преобразует переменный электрический ток низкого напряжения в постоянный электрический ток более высокого напряжения, используя конденсаторов и диодов в сети.

C H A P T E R T H R E E E L E C T R I F I E D R A I L

U N I T 1

Ex. 1. Copy and memorize the following terms.

Glossary

Earth potential – потенциал Земли electric traction – электрическая тяга

overhead current collector –воздушный токоприёмник, return circuit – цепь обратного тока

pantograph – токоприёмник

shoe – скользящий контакт, скользун third rail – контактный рельс

Ex. 2. Copy the following words and memorize their meanings:

9barely – просто, только

9diaper – детская пелёнка

9former – предшествующий

9resemblance – сходство

9via – посредством

	Ex. 3. Match the phrases in column A with their definitions in column B.
	A		B
1.	Earth potential	a)	a device that collects electric current from overhead
			lines
2.	electric traction	b)	a single-wire transmission line for supplying single-
			phase electrical power from an electrical grid to
			remote areas at low cost
3.	overhead current collector	c)	used to collect the current on the train
4.	return circuit	d)	a method of providing electric power to a railway
			48

			train, through a continuous rigid conductor placed
			alongside or between the rails of a railway track
5.	pantograph	e)	is zero-voltage
6.	shoe	f)	used for trolleybuses, trams, electric locomotives to
			lead electrical power from overhead lines to the
			electrical equipment of the vehicles
7.	third rail	g)	electric motive power provided for such movement,
			especially on a railway

Ex. 4. Many words in English can be both nouns, adjectives and verbs. Fill in the blanks using the correct forms of the words in brackets. You may have to change verb tenses or make plurals. Translate the sentences.

1.I will do everything in my … to help you. This boat is … with the latest improved model of our engine. (power)

2.I wanted a more athletic and muscular… . The church was …of brick. (build)

3.No major …were made to the book. Susan has changed a lot since I last saw her. (change)

4.In its … state, the car is worth £1,000. Strong … can be very dangerous for swimmers. (current)

5.We followed the tyre … across a muddy field. Police have been … the four criminals all over Central America. (track)

6.Flying is one of the … forms of travel. Fire resistant record protection … consist of self-contained devices that incorporate insulated bodies, doors, drawers or lids. (safe)

7.What size … do you take? The car was …with radial tyres. (shoe)

8.The plants grow in every … and size. People’s political beliefs are …, by what they see in the papers. (shape)

9.He has a lot ….of in the media. Give the names of two people who can be … in an emergency. (contact)

10.He is a wise and kind man, and comes of a good…. His headaches … from vision problems. (stem)

11.Be sure to make …of all the documents. Jeremy had copied from the girl next to him. (copy)

12.The …revolves around the Sun. Make sure that the machine is properly…. (earh/Earth)

Read the text and translate it using a dictionary if necessary.

E L E C T R I C T R A C T I O N

(1)There is a wide variety of electric traction systems around the world, which have been built according to the type of railway, its location and the technology available at the time of the installation. Many installations seen today were first built up to 100 years ago, some when electric traction was barely out its diapers, so to speak, and this has had a great influence on what is seen today.

(2)In the last 20 years there has been a gigantic acceleration in railway traction development. This has run in parallel with the development of power electronics and microprocessors. What have been the accepted norms for the industry for, sometimes, 80 years,

49

have suddenly been thrown out and replaced by fundamental changes in design, manufacture and operation. Many of these developments are highly technical and complex.

(3)Because these changes have been so rapid, there are still plenty of examples of the original technology around and in regular use.

(4)To begin with, the electric railway needs a power supply that the trains can access at all times. It must be safe, economical and user friendly. It can use either DC (direct current) or AC (alternating current), the former being, for many years, simpler for railway traction purposes, the latter being better over long distances and cheaper to install but, until recently, more complicated to control at train level.

(5)Transmission of power is always along the track by means of an overhead wire or at ground level, using an extra, third rail laid close to the running rails. AC systems always use overhead wires, DC can use either an overhead wire or a third rail; both are common.

(6)The third rail system uses a "shoe" to collect the current on the train, perhaps because it was first called a "slipper" by the pioneers of the industry (it slipped along the rail) but it was not very pretty to look at, so perhaps someone thought shoe was a better description. Whatever the origin, shoe has stuck to this day.

(7)Both overhead systems require at least one collector attached to the train so it can always be in contact with the power. Overhead current collectors use a "pantograph", so called because that was the shape of most of them until about 30 years ago. A pantograph is a device that collects electric current from overhead lines for electric trains or trams. The term stems from the resemblance to pantograph devices for copying writing and drawings. The return circuit is via the running rails back to the substation. The running rails are at earth potential and are connected to the substation.

Ex. 5. Search the text for the English equivalents of the following Russian phrases:

в зачаточном состоянии, построены в соответствии с, большое ускорение, принятые нормы, множество примеров, удобный для пользователя, наземный уровень, расположенный близко к рельсам, электроснабжение, термин происходит.

Ex. 6. Go back to the text, guess the meaning of the following phrases and translate them into Russian:

electric traction systems, the time of the installation, railway traction development, run in parallel, highly technical and complex, railway traction purposes, the latter being better, overhead wires.

Ex.7. Match the halves of the sentences together.

	A		B
1.	Electric traction systems have been	a)	cheaper to install but, until recently, more
	built...		complicated to control at train level.
2.	The electric railway needs ...	b)	by means of an overhead wire or a third rail.
3.	Direct current has been...	c)	to collect the current on the train.
4.	Alternating current has been ...	d)	according to the type of railway, its location
			and the technology available.
5.	Transmission of power is always	e)	for many years, simpler for railway traction
	along the track ...		purposes
6.	DC systems can use ...	f)	earth potential and are connected to the
			substation.
			50