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Кабiнет 45

Англiйська мова
Поточний час: 22 січ 2022, 19:54

Часовий пояс: UTC + 2 години

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Автор Повідомлення
 Заголовок повідомлення: Заняття 7 (7 семестр)
ПовідомленняДодано: 10 лист 2019, 16:33 

Зареєстрований: 17 черв 2014, 17:23
Повідомлення: 657
Заняття 7 (7 семестр)

Тема:Апаратура керування та захисту електроприводів: кнопкові пости, рубильники, контролери, запобіжники, автоматичні вимикачі, електромагнітні пускачі, контактори, теплове реле. Порядок слів у спонукальних та окличних реченнях.
Торic :Button switches, knife-switches, safety devices. Word order in exclamatory sentences.

1. Read and translate the text “Knife switch”

Listen to the record (Unit 55)

A knife switch is a type of switch used to control the flow of electricity in a circuit. It is composed of a hinge which allows a metal lever, or knife, to be lifted from or inserted into a slot or jaw. The hinge and jaw are both fixed to an insulated base, and the knife has an insulated handle to grip at one end. Current flows through the switch when the knife is pushed into the jaw. Knife switches can take several forms, including single throw, in which the "knife" engages with only a single slot, and double throw, in which the knife hinge is placed between two slots and can engage with either one. Also, multiple knives may be attached to a single handle and can be used to activate more than one circuit simultaneously.


1917 motor switch, with extra contacts

Though used commonly in the past, knife switches are now rare, finding use largely in science experiments where the position of the switch may be plainly seen in demonstration. The knife switch is extremely simple in construction and use, but its exposed metal parts present a great risk of electric shock, and the switch is subject to arcing when opened at higher voltages, which poses a further risk of shock or burns to the operator and can cause fires or explosions under certain conditions.

Open knife switches were supplanted by safety switches with current carrying contacts inside a metal enclosure which can only be opened by switching off the power. In modern applications, automatic switches (such as contactors or relays), and manual switches such as circuit breakers are used. These devices use a snap action mechanism which opens the switch contacts rapidly, and feature an arc chute where the arc caused by opening the switch is quenched. These devices also prevent injury due to accidental contact, as all of the current carrying metal parts of the switch are hidden within or surrounded by insulating guards.


Open knife switch


Dual pole, dual throw knife switch in one of its two closed positions

2. Find in the column B English equivalents to Ukrainian words.

1. metal enclosure / a. вимикачі

2. knife switch / b. іскрогаснa камера

3. science experiment / c. для запобігання травм

4. circuit breakers / d. механізм миттєвої дії

5. electric shock / e. вибухи

6. to prevent injury / f. ручні перемикачі

7. snap action mechanism / g. металевий важіль

8. arc chute / h. металевий корпус

9. knife hinge / i. ізолюючі огорожі

10. explosions / j. ніж шарнира

11. manual switches / k. рубильник

12. insulating guards / l. ураження електричним струмом

13. metal lever / m. науковий експеримент

3. Write these words into the table according parts of speech.

manual, circuit, explosion, accidental, commonly, safety, switch, rapidly, metal, subject, experiment, jaw, extremely, simple, position, application, arc.

Noun - torque

adjective - great

adverb - absolutely

4. Choose the right words.

Knife switch

1. Knife (switch /switches) consist of a flat metal blade, hinged at one end, with an insulating handle for operation, and a fixed contact.

2. When the switch is closed, current flows through the hinged pivot and blade and through the (fixing/fixed) contact.

3. Such switches (is/are) usually not enclosed.

4. The knife and contacts are typically formed of copper, steel, or brass, depending (on/in) the application.

5. Fixed contacts may be backed up with a (spring/summer).

6. Several parallel blades (can/could) be operated at the same time by one handle.

7. The parts may be mounted on an (insulating/semiconducting) base with terminals for wiring, or may be directly bolted to an insulated switch board in a large assembly.

8. Since the electrical contacts are exposed, the switch is used only where people cannot accidentally come in contact with the switch or where the voltage is so low as to not present a (hazard/gift).

9. Knife switches are made in (many/much) sizes from miniature switches to large devices used to carry thousands of amperes.

10. In electrical transmission and distribution, gang-operated switches are used in circuits up to the (high/highest) voltages.

11. The (advantages/disadvantages) of the knife switch are the slow opening speed and the proximity of the operator to exposed live parts.

12. Metal-enclosed (safe/safety) disconnect switches are used for isolation of circuits in industrial power distribution.

13. Sometimes spring-loaded auxiliary blades are (fit/fitted) which momentarily carry the full current during opening, then quickly part to rapidly extinguish the arc.

5. Read the information about push button switches and put 10 questions to the text.

Push switch

A push button is a momentary or non-latching switch which causes a temporary change in the state of an electrical circuit only while the switch is physically actuated. An automatic mechanism (i.e. a spring) returns the switch to its default position immediately afterwards, restoring the initial circuit condition. There are two types:

• A push to make switch allows electricity to flow between its two contacts when held in. When the button is released, the circuit is broken. This type of switch is also known as a Normally Open (NO) Switch. (Examples: doorbell, computer case power switch, calculator buttons, individual keys on a keyboard)


Push-to-make switch electronic symbol

• A push to break switch does the opposite, i.e. when the button is not pressed, electricity can flow, but when it is pressed the circuit is broken. This type of switch is also known as a Normally Closed (NC) Switch. (Examples: Fridge Light Switch, Alarm Switches in Fail-Safe circuits)


Push-to-break switch electronic symbol

Many Push switches are designed to function as both push to make and push to break switches. For these switches, the wiring of the switch determines whether the switch functions as a push to make or as a push to break switch.


Commercially Available Push Switch - Wired up as a Push to Break Switch


Commercially Available Push Switch - Wired up as a Push to Make Switch

6. Do grammar exercises. Mind word order in exclamatory sentences.

6.1. Translate exclamatory sentences into Ukrainian.


What a/an …! What …!

What a pleasant face! What fresh air!

What a deep lake! What deep snow!

What an easy text! What high hills!

What an interesting film! What dangerous snakes!

What a warm day! What nice scenery!

What a strong wind! What cold water!

What a beautiful river! What nasty weather!

What a lovely hedge! What deep knowledge!

What an old university! What short hear!

What dangerous pirates!

What long roads!

What exciting stories!

What tasty potatoes!

What attractive face!

6.2. Translate exclamatory sentences into English.

1. Яка суха погода!

2. Які найважливіші новини!

3. Який гіркий апельсин!

4. Якась хвилююча думка!

5. Які красиві довге волосся!

6. Які свіжі овочі!

7. Який великий картопля!

8. Яка солодка морква!

9. Який незвичайний пейзаж!

10. Який вологий клімат!

6.3. Translate exclamatory sentences into Ukrainian

What ….! How…..!

1. What a brave officer he is. How brave the officer is!

2. What a peaceful country it is! How peaceful the country is!

3. What an expensive present was it! How expensive the present was!

4. What an exciting trip it has been! How exciting the trip it has been!

5. What clean water it was! How clean the water it was!

6. What fresh air it is! How fresh the air is!

7. What polite girls they are! How polite the girls are!

8. What great adventures they will be! How great the adventures will be!

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