GENERATORS AND ALTERNATORS

Great generators in our power stations, which rotate at a constant speed day and night, summer and winter, are able to generate electric power only because of the electromagnets.

It is calculated that these machines produce more than 99.99 per cent of all the world's electric power.

Although used to operate certain devices requiring small currents for their operation, batteries and cells are unlikely to supply light, heat, and power on our modern large scale. It is dynamo-electric machines that are used for this purpose. These are machines by means of which mechanical power is turned directly into electric power with a loss of only a few per cent.

There are two types of dynamos, namely, the al­ternator and the generator (Fig. 11). The former pro­vides a. c. while the latter supplies d. c, similar to the current from a battery. Both of them must be turned by some outside source of me­chanical power, such as , water power, for example. 'Where cities are far from water power, the mechanical power for the generator mostly comes from burning coal, which operates a steam turbine which turns the generator. Both-generators and alternators consist of the following principal parts: an armature and an electromagnet. The for­mer generally serves as a rotor in d. с generators while it is the magnetic system that serves this purpose in alternators. The latter is usually called a stator for it is in a static condi­tion "In order to get a strong e. m. f., the rotors in large alternators rotate at a speed of thousands of revolutions per minute (г. р. т.). In this connection one could add that the speed of rotation will control the output voltage of the gen­erator in the following manner:

1. The faster the armature is rotated, the more voltage the generator will produce.

2. The slower the rotation, the less the output voltage. Electric power stations which supply electricity over longdistances are at present always equipped with large alter­nators. These supply us with much greater quantities of cur­rent than anything ever supposed by Volta, Oersted and Ampere. In order to produce electricity under the most economical con­ditions, the generators must be as large as possible. In addition to it, they should be kept as fully loaded as possible all the time. As you are likely to remember, the Kuiby­shev and Volgograd stations have 125,000 kil­owatt generators and the Bratsk hydroelec­tric station has twenty 225,000 kilowatt generators.

Russian scientists are known to develop 500,000 kilo­watt generators which are to be installed at the Kras­noyarsk station.

Large installations with turbo-generators of 200,000 to 300,000 kW power are being constructed in different parts of Russia. The eight generators of the Konakovo thermo-electric station not far from Moscow are planned to have 2,400,000 kW of rated capacity.

Our industry is most likely to produce even greater power installations for thermo-electric stations which play such an important part in energy supply of our country..

It goes without saying that the dynamo invented by Fa­raday in 1831 would seem to be a most primitive apparatus compared with the powerful, highly-efficient machines that are in use today. Nevertheless, these generators and alterna­tors work on the same principle as the one invented by the great English scientist. When asked what use his new inven­tion had, Faraday is said to have asked in his turn: "What is the use of a new-born child?" As a matter of fact, the "newborn child" soon became an irreplaceable device we cannot do without.

Fig. 11 shows the principles the construction of an ele­mentary d. с generator is based upon. We see the armature, the electromagnet, the shunt winding, the commutator and the load.

Exercises

1. Learn the following active words:

alternator генератор переменного тока

armature якорь

calculate считать

equip оснащать, оборудовать

operate работать, функционировать

revolutions per minute обороты в минуту

rotate вращаться

shunt шунт, параллельная цепь

thermo-electric station термоэлектростанция

tur­bine турбина

winding обмотка

2. Translate the following sentences:

1.Heat developed in a transmission line or a generator is a needless waste of power. 2. An electric lamp uses the light given off by its filament heated by the current. 3. The experiments made by Oersted attracted Ampere’s attention. 4. Electric power stations supplying power on a large scale are equipped with large alternators.

3.Translate the following sentences and combine the principal and the subordinate clauses with suitable conjunctions:

1. There is a great number of engineering problems the Russian scientists work at. 2. It is quite impossible to name a scientific problem Lomonosov did not turn his attention to. 3.There are many electric appliances we cannot do without. 4.The experiment I told you about will take much time.

4. Answer the following questions:

1. Do you want to translate this article? 2. Do you want me to translate this article? 3. Do you know this scientist? 4. Do you know this scientist to have explained the new phenomenon? 5. Did you hear my report? 6. Did you hear my friend make a report? 7. Did you see my brother? 8. Did you see my brother enter the room?

5. Form adjectives using the suffixes -able, -fut, -less, -ous: