III. Заполните пропуски, выбрав нужный вариант.
1. The ... of the induction motor and the synchronous motor are different. 2. No insulation is required between the ... and the ... . 3. The rotating magnetic field generated in the ... induces an e.m.f. in the rotor. 4. A ... ... ... is made up of heavy copper bars connected together at either end. 5. If a winding contains coils placed in the rotor slots the rotor is called a ... ... .
(core, stator, wound rotor, bars, rotor, squirrel-cage winding)
IV. Выберите из правого столбика слова или словосочетания, чтобы закончить предложения.
| 1. The induction motor is the most commonly used ... ... | field strength |
| 2. The induction motor rotor is a ... ... | stator winding |
| 3. The air gap between the rotor and stator is kept very small to obtain maximum ... ... | magnetic field |
| 4. The current in the rotor circuit caused by the induced e.m.f. sets up a ... ... | laminated cylinder |
| 5. A rotating magnetic field is generated when a.c. is applied to the ... ... | a.c. motor |
V. Найдите многокомпонентные определительные словосочетания в приведенных ниже предложениях. Переведите их на русский язык.
1. The rotor is a self-contained unit. 2. A "squirrel-cage winding" is made up of heavy copper bars. 3. The rotor gets as close to the moving stator field as its weight and its load will allow. 4. The rotating magnetic field generated in the stator induces an e.m.f. in the rotor. 5. The induction motor is commonly used because of its robust construction and low manufacturing cost.
VI. Заполните пропуски предлогами in, between, to, by, up, from.
1. The induction motor derives its name ... the fact that a.c. currents are induced ... the rotor circuit. 2. A "squirrel-cage winding" is made ... of a heavy metal ring. 3. No insulation is required ... the core and the bars. 4. The current in the rotor circuit is caused ... this induced e.m.f. 5. If a.c. is applied ... the stator windings, a rotating magnetic field is generated. 6. The rotor moves ... the same direction as the stator field.
VII. Определите функцию выделенных слов. Переведите предложения на русский язык .
Образец: сonnecting – причастие I, определение; used – причастие II, определение; is connected – причастие II, часть простого глагольного сказуемого.
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1. The induction motor is a laminated cylinder with slots in its surface. 2. No insulation is required between the core and the bars because of the very low voltage generated in the rotor bars. 3. The rotating field cuts the bars of the rotor. 4. An induced current tries to oppose the changing field. 5. The force excerted on the rotor by the reaction between the rotor and the stator fields will set about trying to cancel out the continuous motion of the stator field.
VIII. Выразите свое согласие или несогласие с данными утверждениями, используя следующие фразы: You are quite right; I agree with you; I’m afraid you are not right; You are wrong (парная работа).
1. The induction motor is not commonly used. 2. The stator construction of the induction motion and of the synchronous motor is different. 3. The air gap between the rotor and the stator is kept very small to obtain maximum field strength. 4. Since the stator field is rotating continuously, the rotor cannot line up with it, but must always follow along behind it. 5. The rotor and the stator move in different directions and never line up with each other.
IX. Дайте характеристику aсинхронного двигателя, пользуясь набором слов и словосочетаний:
simplicity, robust construction, source of voltage, laminated cylinder, winding, slots, core, bars, "wound rotor", to induce, current, rotor circuit, to set up, to induce a current, conductors of the rotor, to line up.
Text 6
Two-phase Induction Motors
Induction motors are designed for three-phase, two-phase, or single-phase operation. But in every case the a.c. applied to the stator must generate a rotating field which will pull the rotor with it.
You have already seen how three-phase a.c. applied to a three-phase symmetrically distributed winding will generate a rotating magnetic field. A two-phase induction motor has its stator made up of two windings placed at right angles to each other around the stator.
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If the voltages applied to phase A-AI and B-BI are 90 degrees out of phase, the currents which will flow in the phases will be displaced by 90 degrees. Since the magnetic fields generated in the coils will be in phase with their respective currents, the magnetic fields will also be 90 degrees out of phase with each other. These two out-phase magnetic fields, whose coil axes are at right angles to each other, will add together at every instant during their cycle to produce a resultant field which will rotate one revolution for each cycle of a.c.
From 180 degrees to 360 degrees the resultant magnetic field rotates through another half-cycle and completes a revolution.
Thus, by placing two windings at right angles to each other, and by exciting three windings with voltages 90 degrees out of phase, a rotating magnetic field can be created.
Words and Word Combination
| pull v | тянуть, тащить |
| distribute v | распределять |
| angle n | угол |
| displace v | перемещаться |
| out of phase | не совпадающий по фазе, не в фазе |
| add together | складывать |
| resultant a | результирующий |
| thus adv | так, таким образом |
| complete v | заканчивать, завершать |
| revolution n | оборот |
E x e r c i s e s
I. Прочитайте слова и назовите те, которые сходны с русскими по звучанию:
to design, to pull, symmetrically, to distribute, angle, axe, cycle, resultant, revolution, to complete, to excite, to create, already, phase.
II. Найдите в тексте эквиваленты следующих слов и словосочетаний :
генерировать поле, двухфазный асинхронный двигатель, прямой угол, расположиться под прямым углом, не совпадающий по фазе, перемещаться на 90 градусов, складывать(ся), результирующее поле, круговое вращение, завершить оборот, создать поле.
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