2. Complete the sentences with words given in previous exercise and translate them into Russian.

1. The two basic parts of a synchronous machine are _____ and the armature.

2. The rotor may be constructed with salient poles, or be cylindrical, i.e., round with no _____.

3. The water-wheel-driven hydroelectric gen­erators are commonly of the vertical type with _____ salient-pole rotors.

4. The stator core consists of punching of _____ .

5. The stator core has _____ double layer lap winding.

6. The end-winding must be securely braced against movement _____ of short-circuit electromagnetic forces.

7. Amortisseur windings serve several useful functions such as the starting of synchronous motors as induction motors, damping rotor oscillations, _____ under certain short-circuit conditions.

8. A _____ or a permanent-magnet type _____ may be employed to acti­vate the exciter.

9._____, using hydrogen or water as coolant, are employed both for the stator and rotor of large turbogenerators.

3. Give adequate Russian equivalents of the italicized words.

Involve - общий элемент смысла: включение в деятельность, движение или объем. Частотные русские эквиваленты: to involve - включать в себя; влечь за собой, вызывать; вовлекать; запутывать, осложнять и т.д.; to be involved - быть включенным, вовлеченным, участвующим, сложным и т.д.

1. The first industrial revolution involved the replacement of human and animal muscle power by power of machines. 2. A technical project often starts as a simple practical activity involving only a few scientists or engineers. 3. This institute is involved in a research project on laser techniques. 4. The activities involved in various space programs have created a revolution in scientific research.

Matter - общий элемент смысла: нечто материальное, ощутимое, существенное; то, что имеет значение. Частотные русские эквиваленты: matter - материя, вещество; материал (статьи, книги и т.п.), сущность, предмет; дело, вопрос и т.д.; to matter - иметь значение.

A.I. Chemistry deals with changes in the composition of matter, physics is concerned with changes in the location or size of matter. 2. Animal and human organisms fight off infections and other invasions by foreign matter. 3. The subject matter of the lecture was the influence of the climate on the development of a nation. 4. This collection of stones provides an interesting reading matter. 5. It is no easy matter to describe this phenomenon in detail. 6. His taking part in the discussion made the matters worse. 1. The answer to

this question, however, will hardly matter under present conditions.

B. Make up English-Russian pairs of the word groups equivalent in meaning.

As a matter of fact; in a matter of seconds; it does not matter; it is a matter of common experience; it is a matter of common knowledge.

За какие-нибудь секунды; каждый знает из опыта; не имеет значения (неважно); общеизвестно; фактически.

4. Read and translate the text.

CONSTRUCTIONAL FEATURES OF SYNCHRONOUS MACHINES.

The two basic parts of a synchronous machine are the magnetic field structure, carrying a dc-excited winding, and the armature, often having a three-phase winding in which the ac emf is generated. The use of a rotating dc-field system is almost universal, because it permits the ac windings to be placed on the stator, where they are more conveniently braced against electromagnetic forces and insulated for high voltage. Thus, almost all modern synchronous machines have stationary armatures and rotating field structures.

The rotor may be constructed with salient poles, or be cylindrical, i.e., round with no polar projections. The prime-mover speed has a profound influ­ence on the constructional form, and in all large units the limiting feature is the centrifugal force on the rotor. Steam- or gas-turbine-driven machines, known as turbogenerators (turbo-alternators or turbine-generators), are run at high speed, and usually have two- or four-pole round (cylindrical) rotors of solid forged steel, with a diameter limited to about 1.2 m and an axial length of several maters. Generators driven by water power, known as hydroelectric (hydro or water wheel) gener­ators, are built for a wide range of comparatively low turbine speeds, and are axially short, but have large diameters to accommodate many salient poles on their rotors. Diesel-electric generators are also low-speed machines with sa­lient poles rotors. The construction of synchronous machines may vary from one to another in several aspects. While the water-wheel-driven hydroelectric gen­erators are commonly of the vertical type with vertically mounted salient-pole rotors, most of the others, including turbine-generators, are of the horizontal type. The constructional details also depend greatly on the type of cooling methods employed. The rotor-end windings or overhangs must be properly secured by the use of end-bells or retaining rings. The feasibility of using superconducting winding on the rotor is being investigated for large turbogenerator.

The stator of a synchronous machine is essentially similar to that of a polyphase induction machine. The stator core consists of punching (often built up of segmented sectors) of high quality laminations having slot-embedded double layer lap winding. Almost all synchronous generators are three-phase wye-connected machines with a 60° phase spread. The end-winding must be securely braced against movement under the impact of short-circuit electromagnetic forces.

Many salient-pole synchronous machines are commonly equipped with damper (amortisseur) windings, which consist usually of a set of copper or brass bars set in pole-lace slots and connected together at the ends of the machine. Amortisseur windings have some effect on stability, and serve several useful functions such as the starting of synchronous motors as induction motors, damping rotor oscillations, reducing over voltages under certain short-circuit conditions, and aiding in synchronizing the machine. The cylindrical rotor of a turbine-generator may be considered as equivalent to an amortisseur of infinitely many circuits.

The dc winding on the rotating field structure may be connected to an external dc source through slip rings and brushes. The dc excitation may be pro­vided by a self-excited dc generator, known as the exciter, mounted on the same shaft as the rotor of the synchronous machine. In slow-speed machines with large ratings, such as hydro generators, the exciter may not be self-excited; rather, a self-excited or a permanent-magnet type pilot exciter may be employed to acti­vate the exciter. Because of the maintenance problems associated with direct-coupled dc generators beyond a certain rating, an alternative form of excitation is provided sometimes by silicon diodes and thyristors. The two types of solid-state excitation systems are (a) static systems having stationary diodes or thy­ristors that supply the excitation current to the rotor through brushes and slip rings, and (h) brushless system having shaft-mounted rectifiers rotating with the rotor, thereby eliminating the need for brushes and slip rings.

The severe electric and magnetic loadings in a synchronous machine produce heat that must be properly dissipated. The manner in which the active parts of a machine are cooled determines its overall physical size and structure. The cooling problem is particularly serious in large turboaltemators, where econ­omy, mechanical requirements, transportation limitations, and erection and as­sembly problems demand compactness, especially for the rotor forging. Direct-conductor-cooling methods, using hydrogen or water as coolant, are employed both for the stator and rotor of large turbogenerators. Such innovative cooling techniques have made it possible to achieve two-pole turbogenerator ratings of 2,000 MVA in a single unit.