III. Выберите и вставьте нужное слово в данные предложения.
1. The field coil consists of a ... turns of heavy wire (many, few). 2. If the load increases the motor ... (stops, slows down). 3. The series motor runs very ... with light loads (rapidly, slowly). 4. For this reason series motors are seldom used when a constant operating ... is needed (current, speed). 5. The ... developed by any d.c. motor depends on the armature current and the field strength (load, torque). 6. When the motor speed is ... the back-e.m.f. is of course, low and the armature current is high (low, zero).
IV. Определите, от каких имен прилагательных образованы следующие наречия. Переведите эти пары слов на русский язык :
rapidly, dangerously, frequently, furiously, highly, slowly, heavily.
V. От полученных в упражнении IV имен прилагательных образуйте степени сравнения. Переведите все формы на русский язык.
Образец. 1. warm – warmer, (the) warmest;
2. interesting – more interesting – (the) most interesting.
VI. Выразите согласие или несогласие с данными утверждениями (парная работа).
1. The series motor runs very slowly with light loads. 2. If the load is completely removed, the motor will speed dangerously and fly apart. 3. Series motor must always be run under no-load conditions. 4. Series motors are variable-speed motors. 5. Thus the series motor has a low starting torque. 6. If there is an opposing torque on starting, the motor will accelerate furiously.
VII. Переведите слова второго собеседника в диалоге.
1. Would you tell me how does the series motor run with different loads?
2. Он работает очень медленно при больших нагрузках и очень быстро при малых.
1. What will happen (произойдет) if the load completely removed?
2. Он будет опасно набирать скорость и разлетится на части.
1. So, can series motor be run under no-load conditions?
2. Нет, двигатели с последовательным возбуждением никогда не должны работать в условиях без нагрузки.
1. And what can you say about the speed of the series motors?
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2. Их скорость значительно изменяется, когда меняется нагрузка.
VIII. Расскажите о вращающем моменте двигателя с последовательным возбуждением, употребив данные слова и словосочетания:
the torque, developed by any d.c. motor, armature current, field strength, very high, motor speed, low or zero, because of its high starting torque, never, unloaded, depends on, is, is starting, must be started.
Text 4
Compound Motors
A compound motor is a combination of series and shunt motor. The field consists of two separate sets of coils. One set, whose coils are wound with many turns of fine wire, is connected across the armature as a shunt field. The other set, whose coils are wound few turns of heavy wire, is connected in series with the armature as a series field.
The characteristics of the compound motor combine the features of the series and shunt motors. Cumulatively-compound motors, whose series and shunt fields are connected to aid each other, are the most common. In a cumulatively-compound motor, an increase in load decreases the speed and greatly increases the developed torque. The starting torque is also large.
Thus the cumulative compound motor is fairly constant-speed motor, with excellent pulling power on heavy loads, and good starting torque.
In a differentially-compound motor the series field opposes the shunt field, and the total field is weakened when the load increases. This allows the speed to increase with increased load, up to a safe operating point. The starting torque is very low, and the differentially-compound motor is rarely used.
Words and Word Combinations
| compound motor | двигатель со смешанным возбуждением |
| combination n | соединение, сочетание |
| combine v | сочетать |
| characteristics n | характеристика |
| feature n | характерная черта, особенность |
| increase n | увеличение |
| fairly adv | довольно |
| pulling power | тянущая сила |
| weaken v | ослаблять |
| safe a | безопасный |
| operating point | рабочая точка |
| rarely adv | редко |
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E x e r c i s e s
I. Прочитайте и переведите следующие слова и словосочетания :
compound, combination, wound, characteristics, features, cumulatively, large, excellent, pulling power, differentially, weaken (weakened), safe, rarely, fairly, oppose – opposes.
II. Найдите в тексте эквиваленты следующих слов и словосочетаний :
виток, тонкая проволока, несколько витков толстой проволоки, двигатель с постоянной скоростью, очень низкий.
III. Вставьте нужное слово.
1. A compound motor is a ... of series and shunt motor (combination, assembly). 2. The field consists of ... separate sets of coils (many, two). 3. In a cumulatively-compound motor, an increase in load ... the speed (increases, decreases). 4. In a differentially-compound motor ... increases with increased load (torque, speed). 5. The differentially-compound motor is ... used (rarely, often).
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