Кущ Т.Ю., Воловник М.С. Основы английского языка для судовых электриков (1998)

B:...

A: I’ve got it now. One point I’d like still to clear up. I’ve found out that compound motors are a compromise between series & shunt motors. Will you tell me what it means?

B:...

A: Thanks a lot. You were of great help to me. Now I have clear & complete comprehension of motors.

B:...

41. /5 мин./ Прочтите следующие тексты и укажите номера предложений, которые дополняют тему “Типы двигателей постоянного тока”.

А 1. The magnetic system of DC machines comprises two ;poles. 2. These poles are stationary ki space. 3. They create a magnetic flux of constant magnitude. 4. Between these poles an armature is inserted. 5: To rectify the current in the external circuit, the machine is furnished with a special device called the commutator.

В 1. There are three types of dc motors: the series motors, the shunt motors, &' the compound motors. 2. These types are alike externally. 3. They differ in construction of the field coils.4. They differ in the connection between the fjjfcjd & the armature.

C 1. The dc shunt motor contains a field composed of many turns of wire. 2. Its field is connected in parallel with the armature.

3. The motor has constant-speed characteristic. 4. It is used on applications that require constant speed.

42. /40 мин./ Прочтите следующий текст, стараясь понять его содержание. Напишите по несколько вопросов к каждому абзацу. Будьте готовы обсудить основные моменты текста, используя эти вопросы.

Main Structural Elements of DC Machines

The dc machine consists of two main parts: the stationary part, designed mainly for producing the magnetic flux, & the rotating part. These parts are separated fron each other by the air gap. The stationary part of a d-c machine comprises: a/ the main poles; b/ the commutating poles; с/ the frame.

A. The main pole. It consists, of laminated core. At the end directed towards the armature, the pole core.widens into pole shoe. Mounted onto the core is field coil. The coil is wound on frame. For better cooling the field may be subdivided along thp height into two or more parts with ventilation channels between them. The poles are bolted to yoke with the help of special bolts.

B. The commutating pole. It is similar to the. main pole. The commutating poles are arranged strictly midway between the main ' poles & are bolted to the yoke. Commutating poles are usually made of solid steel, but for machines operating on abruptly varying load they are made of sheet steel.

C. The frame is the name given to the stationary part of the machine to which ате fixed the main & commutating poles & by means, of which the machine is bolted to its bedplate. The ring-shaped portion is called the yoke. The frame of modern machine is made of cast iron or steel. The rotating part is called the armature. The armature is a cylindrical body, rotating in the space between the magnetic poles & comprising: d/ a slotted armature core; e/ a winding inserted in the armature slot; f/ the commutator & g/ the brush gear.

D. The armature core is assembled of steel sheet laminations.

To reduce eddy current losses the sheets are insulated with a thin layer of varnish. The armature core is pressed from both sides by clamping device either specially fixed onto the shaft or tightened by bolts. To improve the cooling of machines they have a special ventilator fan mounted on the shaft.

E. Armature winding. All modern dc machines employ the drum-wound armature. The winding is laid entirely on the outside of the armature core periphery.-The winding is built up in sections wound on special moulds & then laid in the armature core slots.

F. The commutator. The ends of all armature coils are joined to the commutator. A simple, cylindrical commutator it is. It consists of a number of small wedge-shaped segments of copper, which • when assembled together form a cylinder. The copper bars are separated from each other by sheet mica & are insulated from their supporting ring§ by means of mica cones & gaskets.

G7 Brush gear. To collect the' current of a rotating commutator or to lead the current to it a brush-gear is used which consists of: a) brushes, b) brush-holders, c) brush studs or brush-holder arms, d/ brush-rocker, e/ the current-collecting busbars. The brushes employed in modern machines are solely composition’of carbon & graphite or carbon & copper, the latter used for low-voltage commutator DC machines. The brush is inserted into the brush-holder where a spring presses it against the commutator. The brush-holder is mounted on

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a stud w;hich maintains the brush in a definite position in relation to the commutator. The current from the brush is led to the stud by means of a special flexible lead. Each brush stud usually carries two or more brushes working in. parallel. All brushes of the same polarity are interconnected by busbars to the machine terminals.

Ключи.

6 - cfgjlmpqrs

7 - dfghjprsuwxa’c’d’

9 - 1, 5

11- 1 bdhiklnqrwx, 2 acgjmsuyz

12- acdf

16 - 1. Результаты были очень благоприятны, особенно результаты Джоунса. 2.Эта реакция аналогична той /реакции/, которую мы наблюдали. ^.Двигатели смешанного возбуждения развивают более высокий пусковой вращающий момент по сравнению с пусковым моментом двигателей параллельного возбуждения. 4.На скорость и молекулярные веса влияет понижение температуры, причем скорость уменьшается, а молекулярные веса увеличиваются. 5.Мы нашли новые пути синтеза,т.к. старые /пути синтеза/ были неудовлетворительными.

18-1. Чем больше размеры и выходная мощность машины, тем большая необходимость выполнения условий симметрии якорной обмотки. 2. На земле столько воды, сколько было всегда: ни больше, ни меньше. 3. В наш век загрязнения /среды/ одним из наиболее обнадеживающих исследований является работа, которая выполняется по очистке сточных вод. 4. Чем больше нагрузка, тем меньше скорость.

41 - А5; В2,3; С 1,4.

Section 2

Тема: “Асинхронные двигатели” Грамматический материал: Предлоги.

Basic Topical Text Induction Squirrel-Cage Motors

1. A great majority of the motors usgd aboard ships are designed to operate on ac. There are some advantages in the use of ac motors besides the wide availability

2. There are two most common types - the induction & synchronous motors. In induction motors the rotor currents are supplied by electromagnetic induction. The stator windings contain one or more out-of-time-phase currents, which produce corresponding mmf. These mmfs currents establish a rotating magnetic field across

the air gap. This magnetic field rotates continuously at constant speed regardless of the load on the motor. The stator winding corresponds to the armature winding of a dc motor or to the primary winding of a transformer. The rotor is not connected electrically to the power supply. The induction motor derives its name from the fact that mutual induction takes place between the stator & the rotor under operating conditions. The magnetic revolving field produced by the stator cuts across the rotor conductors inducing the voltage in the conductors. This induced emf voltage causes rotor current to flow. Hence, motor torque is developed by the interaction of the rotor current & the magnetic field.