1. Ответьте на вопросы

1. What was the invention of Faraday in 1831?

2. What is the fault of battery?

3. What is the working principle of dynamo-electric machines?

4. How many types of dynamos are there? Define them

5. What is needed to produce electricity for generator and alternator?

6. What is needed to generate electricity? Define them

7. How many types of alternators are there? Define them

8. Where was installed the biggest generator ever?

9. Where did soviet scientists construct more powerful generator?

10. What is electromagnet?

2. Найдите синонимы

Powerful, appearance, efficient, powerful, constant, fact, definite, outside, stationary, seldom, strong, certain, rarely, light, mighty, daylight, efficacious, reality.

Найдите антонимы

Powerful, efficient, fact, outside, stationary, seldom, strong, today, certain, light, strengthens, inefficient, fiction, inside, mobile, often, weak, tomorrow, uncertain, dark.

3. Переведите следующие слова и выражения на английский язык

1. Аппарат. 2. Изобретение. 3. Токи. 4. Аккумуляторы. 5. Тепло. 6. Мощность. 7. Электродинамические машины. 8. Энергия.

4. Переведите следующие слова и выражения на русский язык

1. Electrical energy. 

2. Electric power. 

3. Generator. 

4. Alternator. 5. Armature.  6. Electromagnetic voltage. 7. Engine.

Transmission of three-phase power

The three windings discussed above can be made to supply three individual circuits, when all six ends must be used. It is possible, however, to link the three circuits electrically with the result that the number of conductors necessary for the transmission of the power is reduced.

In the first instance it is possible to affect an economy by using a common return, this being permissible since it does not disturb the electrical arrangement. This implies that the three rear ends of the turns, A', B', and С' must all be joined, together with the three rear ends of the three resistances used as loads. This arrangement is illustrated in Fig. 7 which shows the three generator windings connected together at one end, the other ends being connected to three conductors for the purpose of transmitting the power. The return conductor carries the vector sum of these three currents back to the common junction of the three generator windings.

If the three e. m. f. s are all equal and the three load resistances are also all equal, the three currents will also be all equal and will have a phase difference of 120° from one another. In these circumstances the system is said to be balanced.

Three-Wire Transmission. In a balanced three-phase system the three currents are equal and can be represented by the graphs shown in Fig. 6, substituting current for e. m. f. The resultant current in the fourth (return) conductor is, at any instant, the algebraic sum of the three line currents and, on examination of the graphs, it is found that this algebraic sum is zero at every instant. The fourth (return) conductor thus carries no current and it can be omitted. The connections now take the form shown in Fig. 8, three conductors only being employed.

Each conductor now acts in turn as the return for the other two. This can be checked from Fig. 6, where it is seen that the reverse current in one phase is always equal to the forward current in the other two.

Three-Phase Four-Wire System. This is a system of connections which permitsthe employment of a three-phase load and three single-phase loads simultaneously, as shown in Fig. 9. It re-introduces the fourth conductor to act as a common return for the three singlephase loads, this conductor being called the neutral. The other three conductors are called the line conductors. The system is earthed as before, byconnecting the neutral conductor to an earthed plate or other earthing connection.

Colour Scheme. For purposes of standardization it is now the general practice tomark each particular phase by a distinctive colour. The three phases are coloured red, white (or yellow), and blue, respectively, while the neutral conductor is coloured green.