Faults of Motors and Ways of Their Repair.

Motors may have different faults. A faulty motor does not start, or, when it is started, it operates at an excessive speed.

Its brushes may spark and its windings and the commutator may be overheated and burnt. Besides, a motor may produce an abnormal noise, etc. All these and other faults should be detected and repaired.

 

Vocabulary

To achieve- достигать

To belong- принадлежать, относиться

To feed- снабжать, питать

To determine- определять

To relate- относиться (к),быть связанным (с)

Predominant- преобладающий

Graph- кривая, график

National economy- народное хозяйство

To repair- ремонтировать

Brush- щетка

Gap- зазор, люфт

Spark- искра

Speed- скорость

Noise- шум

Slow- медленный

Excessive- избыточный

Check- проверка

To adjust- регулировать, подгонять

 

2.Выполните упражнения:

1)Распределите данные ниже слова на три группы:

Action (действие) process (процесс) doer (исполниетль)

utilizer, protect, distribution, utilize, protection, distributor, consumption, consume, utilization, consumer

2) Ответьте на вопросы:

1. What enterprises are called electric power consumers?

2. When do their operating characteristics vary?

3. What consumers belong to the four different groups?

4. What conditions does the load graph determine?

5. What type of system is called a power system?

6. What processes interconnect the components of a power system?

7. In what way is an economical utilization of power installations achieved?

3) Подберите русские эквиваленты к данным словосочетаниям:

a. load graph________________________________

lighting load______________________________

power load_______________________________

b. power utilizing devices______________________

parallelly operating plants____________________

enterprises utilizing power___________________

4) Поставьте предложения в отрицательную форму:

Water- turbine works are called hydro turbines.

Load graph determines the operating load conditions.

Interconnected operation of power plants will achieve economical concumption of electric power.

Сделайте краткий пересказ текста по-английски.

3.Control text. Переведите текст и составьте 3-4 вопроса по основному содержанию текста:

Electric Motors

Motors are used for converting different forms of energy into mechanical energy.

The main part of a motor is a coil or armature. The armature is placed between the poles of a powerful magnet. When a motor is put into operation current starts flowing through the coil (armature) and the armature starts rotating.

Electric motors are used practically in every branch of industry, transport, and agriculture. Naturally, they are produced in many different designs. They are used in industrial plants, and operate under different conditions.

Each motor is supplied with a nameplate which bears machine ratings: output power, voltage, the rated current, the starting current, the power factor, the efficiency, and the rated torque.

These motor ratings should be taken into consideration since they are necessary for the users. On them depends the length of motors' service life, which is normally equal to about 10 years, provided that the operating conditions are normal. Naturally, under abnormal conditions the service life becomes much shorter: motors operate poorly and may have different faults.

Energy Resources of Today

People are energy-rich today. Solar energy is considered to be a potentially limitless source of clean energy. The waters of the world contain potential fuel -in the form of a special isotope of hydrogen -deuterium. It is sufficient to power fusion reactors for thousands of years.

 

Unit II

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Substations

A substation is designed to receive energy from a power system, convert it and distribute it to the feeders. Thus a substation serves as a distribution centre. Substations feed (supply) various consumers provided that their basic load characteristics are similar. Therefore the energy is distributed without transformation of the voltage supplied.

Common substations comprise isolators, switchgear buses, oil circuit breakers, fuses, power and instrument transformers and reactors.

Substations are classed into step up and step down ones. The step up substations includes transformers that increase the voltage. Connected to the busbars of the substation are the power transmission lines of power plants of the system.

Transformer substations are classed into indoor and outdoor; both types are used for feeding industrial enterprises. Compared to other types of substations, transformer substations have certain advantages. They have flexible construction and easy and reliable operation. In case of a fault in the left-hand sections, the main circuit breaker opens while the normally open sections circuit breaker closes and puts the voltage of the sections to normal. Power from a substation is delivered to distribution centres.

Hydroelectric Power Plants

Hydroelectric power plants are built on rivers. Large-capacity hydroelectric power plants are commonly located at considerable distances from the consumers of electric power.

The production process at these plants is rather simple: the water flows into the hydroturbine runner, acts upon-the runner blades and rotates the runner and the turbine shaft.

The generator shaft is connected to the turbine runner shaft. The difference in the water level influences the power capacity of a plant, i. e. the magnitude of the water head and daily inflow of water fluctuates considerably according to the season.

The production process is different at power plants of different constructions and of different kinds. In atomic power plants, for example, it is not so simple as in hydroelectric plants.

 

Vocabulary

auxiliary- вспомогательный, добавочный

breaker- выключатель, прерыватель

busbar- собирательная шина

feeder- фидер

flexible- гибкий

to comprise- включать в себя

to distribute- распределять

as... to- что касается

as well as- так же, как и

blade- лопасть

level- уровень

magnitude- величина

head- (зд.) верх, верхушка

plant-станция, завод

runner- ротор

shaft- привад, вал

to rotate- вращать(ся)

to influence- влиять

to fluctuate- колебаться

 

2. Выполните упражнения:

1) Завершите предложения, используя правильный вариант, переведите:

1. A substation serves a) to consume energy.

b) to distribute energy.

c) to convert energy.

 

2. A substation feeds consumers a) with various load characteristics.

b) with similar load characteristics.

3. The lines of power plants are a) to the busbars connected b) to the switchgear.

 

4. A substation comprises a) the main elements.

b) the main and auxiliary elements.

 

5. Flexible construction is a) an advantage.

b) a disadvantage.

2) Ответьте на вопросы:

1. What does a substation serve for?

2. What type of consumers does a substation feed?

3. What parts are the power transmission lines connected to?

4. What components does a substation comprise?

5. What types are substations classed into?

6. What are advantages of a transformer substation?

7. On what sites are hydroelectric power plants built?

8. Are large-capacity plants located far from consumers of power?

9. Is the production process at the plants simple or is it complex?

10. What influences the power capacity of a plant?

11. According to what factors does the daily inflow of water fluctuate?

12. Does the production process at the plant depend on its construction?

13. Do you know that a thermal power plant seldom has an efficiency more

than 40%?

3) Поставьте вопрос к предложению начиная с вопросительного слова, стоящего в скобках:

1) Hydroelectric power plants are built on rivers. (Where)

2) Large- capacity power plants at a short distance from consumers of power. (What)

3) The power capacity of a plant is influenced by the difference in the water level. (What by)

4) The daily inflow of water fluctuates according to the season. (How)

5) The production process depends upon the construction of the plant. (How)

 

Control text.

Переведите текст и найдите ответы на следующие вопросы

HV Power Transmission

A high-capacity hydrogenerator produces an a.c. current at 22,000 V. The current with the potential difference of 220,000 V is produced by means of the transformers at a step-up station and then transmitted over the power lines.

The current potential difference is lowered to medium 6,600 V at the main step-down substation at the end of the line. From here the power is transmitted to the next substations. Transformers stepping the voltage down from 6,600 V are installed at those substations.

Due to voltage conversion, alternating current is used widely in in­dustry. Direct current for battery charging for trams, trolleybuses and electric locomotives is changed from alternating current by means of rectifiers.

Superconductivity

In the electric generating field, as well as in the electric-transmission and storage-technology areas, considerable attention is focused on the use of superconductivity conductors. Cooling an electric conductor to temperatures close to absolute zero (-273°C) results in the conductors' losing their resistance to electric current. Accordingly, their ohmic losses also drop greatly. Current densities of tens of millions amperes per sq cm can be tolerated in such conductors.

Cryogenic technology being now mastered, one can foresee the pos­sibility of supercooling not only generators but also underground transmission lines and storage coils.

 

1. Where is the current potential difference lowered?

2. Where is the main step-down substation installed?

3. Conductors can never lose their resistance to the flow of electric current?

4. Generators and underground transmission lines can be supercooled?

 

Unit III