Read and translate the text.
Fuses
Fuses are widely used nowadays as protection devices. They are utilized in various circuits, electrical equipment and installations. Fuses serve to protect them against overcurrents and short-circuits.
There are different types of fuses in use nowadays. Of them, quartzsand fuses serve for voltages up to 500 volts; fuses of this kind are produced with current ratings of 15 to 60 amp and of 100 to 350 amp. Fuses are commonly used in low-voltage industrial installations rated up to 1,000 V.
Fuse protection is based on a very simple principle: in case of a short-circuit or overcurrent, when the maximum value of current has been exceeded, the fusible link of a fuse is heated to its melting point.
This opens the circuit and disconnects the circuit from the power source. In case of a fault, one should replace the faulty fusible element by a new one. Fuses are used both in direct current (d.c.) and alternating current (a.c.) circuits.
3. Complete the sentences using the correct variant:
b) for both a.c. and d.c.
3. In case of a fault
a) the whole fuse should be replaced.
b) the faulty link should be replaced.
4. Fuse protection is based on
a) a simple principle.
b) a complex principle.
1. Both solid and gaseous insulators are highly in use.
2. In case a fuse gets faulty it should be replaced by a new one.
in modem installations.
5. Answer the questions. Use them in a talk with your groupmate:
1. What does a fuse serve for?
2. For what type of current are fuses used?
3. What should be done in case of a faulty fuse?
4. What principle is fuse protection based on?
Практическое занятие 20. Компоненты электрических цепей
Lesson 20. Components of Electric Circuits
1. Read and learn the words:
Read and translate the text.
Components of Electric Circuits
The main components of any circuit are devices that produce and utilize electric energy. They are: 1. power sources, 2. utilizing loads, 3. connecting conductors.
The most common power sources are electric generators and primary cells. Electric generators convert chemical energy into electric energy. Loads include electric heaters, electric motors, incandescent lamps, etc.
Motors convert electric energy into mechanical, incandescent lamps and heaters convert electric energy into light and heat. Utilizing devices or loads convert electric energy into thermal, mechanical or chemical energy.
Electric power is delivered from power sources to loads by electric wires. According to their material, wires can be aluminium, copper, steel, etc.
Besides, electric circuits use different types of switches, protection devices (relays and fuses), and meters (ammeters, voltmeters, wattmeters, etc.).
3. Complete the sentences using the correct variant:
1. The main components of electric circuits are
b) power sources, load and wires.
2. Power sources are used
a) to produce electric energy.
b) to deliver it to the loads.
3. Electric conductors are used
a) to connect the circuit elements.
b) to deliver electric power
4. Protection devices are utilized
a) in some circuits.
5. A switch is utilized
a) in some circuits.
4. Answer these questions:
1. What are the main components of an electric circuit?
2. What is the function of an electric source?
3. What is the function of a load?
4. What is the function of wire conductors?
5. What other devices are utilized in a circuit?
5. Say a few words about your electrical engineering laboratory.
Say what power sources and what loads are utilized there. Have a talk with your groupmate about their types and their operation.
Практическое занятие 21. Электрические линии и их эффективность
Lesson 21. Electric Lines and Their Efficiency
1. Read and learn the words:
Read and translate the text.
Перевод текста electric lines and their efficiency
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Electric Lines and Their Efficiency
Wires are used to deliver electric power and to interconnect differed components of electrical installations. Conductors used for electr|
Answer these questions:
1. Why is aluminium widely used nowadays?
2. Is its cost very low or comparatively low?
length of transmission lines
.’eanaj площадь, область
шина [‘entapraiz] предприятие
длина линий передачи
район городской застройки
2. Put down the Russian for:
interdependent city areas
interacting underground lines_____________________________
interconnected overhead lines_________________________________
transmitting power lines
transmission and distribution lines _______________
A power system is an interconnection of electric power stations by high voltage power transmission lines. Nowadays the electricity is transmitted over long distances and the length of transmitting power lines varies from area to area.
A wire system is termed a power line in case it has no parallel branches and a power network in case it has parallel branches.
According to their functions, power lines and networks are subdivided into transmission and distribution lines.
Transmission lines serve to deliver power from a station to distribution centres. Distribution lines deliver power from distribution centres to the loads.
Lines are also classed into: 1) overhead; 2) indoor; 3) cable (underground).
Overhead lines include line conductors, insulators, and supports. The conductors are connected to the insulators, and these are connected to the supports. The greater the resistance, the higher are the heating losses in the conducting wires. In order to reduce the losses, a step-down transformer can be used.
Indoor lines include conductors, cords, and buses. The conductor may include one wire or a combination of wires not insulated from one another. They deliver electric current to the consumers.
As to underground lines, they are used in city areas. Accordingly, they are used in cities and towns, and in the areas of industrial enterprises.
3* Complete these sentences using the correct variant.
1. Electric power is transmitted a) by electric lines.
b) by power networks.
2. Lines are divided into
3. An overhead line includes
4. The insulators are connected
5. Conductors consist of
6. Underground lines are used
a) overhead and underground.
b) overhead, indoor and underground.
a) conductors and supports.
b) conductors, insulators and supports.
b) in areas of enterprises.
c) in agricultural areas.
| danger | I’demdja] | опасность |
| strength | [strerj9] | сила |
| earth | [з:0] | заземление, земля |
| ground | земля, почва | |
| dead | [ded] | выключенный |
| dangerous | I’deir^ras] | опасный |
| strong | сильный, яркий (о свете) | |
| to save | спасать | |
| to disappear | исчезать | |
| to appear | появляться | |
| live | llaiv] | под напряжением |
| 4ГУ | сухой | |
| wet | сырой, мокрый |
4. Complete the sentences using while or as to. Follow the model on page
1. The system is termed a power linein case it has no parallel branches
5. Answer these questions:
1. By what means is electric power system transmitted?
2. Which system has no parallel branches?
3. Into what groups are all the transmitting lines classed?
4. What components does an overhead line have?
5. What elements do conductors consist of?
6. In what areas are overhead (underground) lines used?
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