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Кабiнет 45

Англiйська мова
 
Поточний час: 28 трав 2020, 05:31

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Автор Повідомлення
 Заголовок повідомлення: Самостійне вивчення № 54
ПовідомленняДодано: 06 бер 2017, 19:52 
Адміністратор

Зареєстрований: 17 черв 2014, 17:23
Повідомлення: 652
Самостійне вивчення № 54

Тема: Електричний привід. Поряд слів у розповідному реченні.

(Торic. Electric drive. Word order in declarative sentences. )


Мета: Ознайомити студентів з новою лексикою, тренувати їх у читанні, виконанні письмового завдання з граматики.

Тривалість 45 хвилин


Література:

основна:

1. Інтернет - ресурси


додаткова:


1. Верба Л.Г. Граматика сучасної англійської мови .- К:, 2002 с




Методичні рекомендації:

1. Прочитайте та перекладіть текст “Electric drive ”

2. Підберіть англійські еквіваленти до українських слів.

3. Підберіть до термінів їх визначення.

4. Вставте в речення необхідну лексику.

5. Напишіть початкову форму від даних слів.

6. Виконайте вправи на вживання порядка слів у розповідному реченні.



1. Read and translate the text “Electric drive”

Зображення Listen to the record https://vk.com/club129211035 (Unit 54)

What is Electrical Drive?

Whenever the term electric motor or electrical generator is used, we tend to think that the speed of rotation of these machines is totally controlled only by the applied voltage and frequency of the source current. But the speed of rotation of an electrical machine can be controlled precisely also by implementing the concept of drive.

The main advantage of this concept is- the motion control is easily optimized with the help of drive. In very simple words, the systems which control the motion of the electrical machines are known as electrical drives. A typical drive system is assembled with an electric motor (may be several) and a sophisticated control system that controls the rotation of the motor shaft.

Nowаdays, this control can be done easily with the help of software. So, the controlling becomes more and more accurate and this concept of drive also provides the ease of use. This drive system is widely used in large number of industrial and domestic applications like factories, transportation systems, textile mills, fans, pumps, motors, robots etc. Drives are employed as prime movers for diesel or petrol engines, gas or steam turbines, hydraulic motors and electric motors.

Now coming to the history of electrical drives, this was first designed in Russia in the year 1838 by B.S. Jacobi, when he tested a DC electric motor supplied from a storage battery and propelled a boat.

Today almost everywhere the application of electric drives is seen. The very basic block diagram an electric drives is shown below. The load in the figure represents various types of equipments which consist of electric motor, like fans, pumps, washing machines etc.

Зображення


Зображення
Classification of Electrical Drives or Types of Electrical Drives


The classification of electrical drives can be done depending upon the various components of the drive system. Now according to the design, the drives can be classified into three types such as single-motor drive, group motor drive and multi motor drive. The single motor types are the very basic type of drive which is mainly used in simple metal working, household appliances etc.

Group electric drives are used in modern industries because of various complexities. Multi motor drives are used in heavy industries or where multiple motoring units are required such as railway transport. If we divide from another point of view, these drives are of two types:

1. Reversible types drives

2. Non reversible types drives.

This depends mainly on the capability of the drive system to alter the direction of the flux generated.


Зображення Parts of Electrical Drives

The diagram which shows the basic circuit design and components of a drive, also shows that, drives have some fixed parts such as, load, motor, power modulator, control unit and source. These equipments are termed as parts of drive system. Now, loads can be of various types i.e. they can have specific requirements and multiple conditions, which are discussed later, first of all we will discuss about the other four parts of electrical drives i.e. motor, power modulator, source and control unit.

Electric motors are of various types. The DC motors can be divided in four types – shunt wound DC motor, series wound DC motor, compound wound dc motor and permanent magnet DC motor. AC motors are of two types – induction motors and synchronous motors. Now synchronous motors are of two types – round field and permanent magnet. Induction motors are also of two types – squirrel cage and wound motor. Besides all of these, stepper motors and switched reluctance motors are also considered as the parts of drive system.

So, there are various types of electric motors, and they are used according to their specifications and uses. When the electrical drives were not so popular, induction and synchronous motors were usually implemented only where fixed or constant speed was the only requirement. For variable speed drive applications, DC motors were used. But as we know that, induction motors of same rating as a DC motors have various advantages like they have lighter weight, lower cost, lower volume and there is less restriction on maximum voltage, speed and power ratings. For these reasons, the induction motors are rapidly replaced the DC motors.

Moreover induction motors are mechanically stronger and require less maintenance. When synchronous motors are considered, wound field and permanent magnet synchronous motors have higher full load efficiency and power factor than induction motors, but the size and cost of synchronous motors are higher than induction motors for the same rating.

Brushless DC motors are similar to permanent magnet synchronous motors. They are used for servo applications and nowadays used as an efficient alternative to DC servo motors because they don’t have the disadvantages like commendation problem. Beside of these, stepper motors are used for position control and switched reluctance motors are used for speed control.

Power Modulators - are the devices which alter the nature or frequency as well as changes the intensity of power to control electrical drives.

Roughly, power modulators can be classified into three types:

Зображення Converters,
ЗображенняVariable impedance circuits,
ЗображенняSwitching circuits.


As the name suggests, converters are used to convert currents from one type to other type. Depending on the type of function, converters can be divided into 5 types:

ЗображенняAC to DC converters
ЗображенняAC regulators
ЗображенняChoppers or DC - DC converters
ЗображенняInverters
ЗображенняCycloconverters


AC to DC converters are used to obtain fixed DC supply from the AC supply of fixed voltage. The very basic diagram of AC to DC converters is like.

Зображення

ac to dc converter


AC Regulators are used to obtain the regulated AC voltage, mainly auto transformers or tap changer transformers are used in this regulators.

Зображення

ac to ac converter

Choppers or DC - DC converters are used to get a variable DC voltage. Power transistors, IGBT's, GPO's, power MOSFET's are mainly used for this purpose.

Зображення

dc to dc converter

Inverters are used to get AC from DC; the operation is just opposite to that of AC to dc converters. PWM semiconductors are used to invert the current.

Зображення

dc to dc converter

Cycloconverters are used to convert the fixed frequency and fixed voltage AC into variable frequency and variable voltage AC. Thyristors are used in these converters to control the firing signals.

Зображення

ac to ac converter

Variable Impedance circuits are used to controlling speed by varying the resistance or impedance of the circuit. But these controlling methods are used in low cost DC and ac drives. There can be two or more steps which can be controlled manually or automatically with the help of contactors. To limit the starting current inductors are used in AC motors.

Switching circuits in motors and electrical drives are used for running the motor smoothly and they also protect the machine during faults. These circuits are used for changing the quadrant of operations during the running condition of a motor. And these circuits are implemented to operate the motor and drives according to predetermined sequence, to provide interlocking, to disconnect the motor from the main circuit during any abnormal condition or faults.

Sources may be of 1 phase and 3 phases. 50 Hz AC supply is the most common type of electricity supplied in many countries, both for domestic and commercial purpose. Synchronous motors which are fed 50 Hz supply have maximum speed up to 3000 rpm, and for getting higher speeds higher frequency supply is needed. Motors of low and medium powers are fed from 400 V supply, and higher ratings like 3.3 kv, 6.6 kv, 11 kv etc are provided also.

Зображення Control Unit

Choice of control unit depends upon the type of power modulator that is used. These are of many types, like when semiconductor converters are used, and then the control unit consists of firing circuits, which employ linear devices and microprocessors.

Зображення
Advantages of Electrical Drives


Electrical drives are readily used these days for controlling purpose but this is not the only the advantage of electrical drives. There are several other advantages:

These drives are available in wide range torque, speed and power.

The control characteristics of these drives are flexible. According to load requirements these can be shaped to steady state and dynamic characteristics. As well as speed control, electric breaking, gearing, starting many things can be accomplished.

Зображення They are adaptable to any type of operating conditions, no matter how much vigorous or rough it is.

ЗображенняThey can operate in all the four quadrants of speed torque plane, which is not applicable for other prime movers.

ЗображенняThey do not pollute the environment.

ЗображенняThey do not need refueling or preheating, they can be started instantly and can be loaded immediately.

ЗображенняThey are powered by electrical energy which is atmosphere friendly and cheap source of power.


Because of the above mentioned advantages of electrical drives, they are getting more and more popular and are used in a wider range of applications.



2. Read the text once again and find in the text English equivalents for the following Ukrainian phrases.

дешеве джерело живлення, не потрібна дозаправка, гнучкий, захистити машину під час несправності, повний опір, напівпровідники.


3.Match the words and their definitions given below.

Зображення Term Definition

ЗображенняA

1. electrical drives
2. synchronous motors
3.sources
4. variable impedance circuits
5. cycloconverters
6. induction motors
7. multi motor drives
8. brushless DC motors
9. inverters
10. power modulators


ЗображенняB.

a) may be of 1 phase and 3 phases.
b) are used to controlling speed by varying the resistance or impedance of the circuit.
c) are mechanically stronger and require less maintenance
d) are used in heavy industries or where multiple motoring units are required such as railway transport
e) are the devices which alter the nature or frequency as well as changes the intensity of power to control electrical drives
f) are used to get AC from DC
g) The systems which control the motion of the electrical machines are known as...
h) are of two types – round field and permanent magnet
i) are used to convert the fixed frequency and fixed voltage AC into variable frequency and variable voltage AC.
j) are used for servo applications



4. Complete the text using the missing words.


mechanical /mechanism / storage battery / use

1.A …which transmits motion from one shaft to another and controls the velocity ratio of the shafts by electrical means.
2. Electric Drive is a set of devices to convert electric energy into… energy and to regulate the converted energy flux according to a specific law.
3.The first electric drive was devised in Russia in 1838, when B. S. Jakobi tested a DC electric motor supplied from a…and used it to drive a screw propeller on a boat.
4.The widespread industrial… of electric drives stems from the discovery of the rotating magnetic field and the construction of a three- phase induction motor by M. O. Dolivo-Dobrovol’skii.


5. Give the initial form of the following words.

used, operating, conditions, higher, countries, fixed, mainly, totally, applied, more, lighter, abnormal.


6. Do grammar exercises. Mind word order in the simple declarative sentences.


Зображення

Зображення

6.1. Decide whether the word order is right or wrong.Correct the wrong sentences:

Зображення


1. Mary speaks very well English.
2. When I heard the news, I phoned him immediately.
3. Ann drives every day her car to work.
4. You should go to the dentist every six months.
5. I think I’ll go early to bed tonight.
6. How many people do you know who go on Sundays to church?
7. We both were astonished when we heard the news.

8. I usually am very tired when I get home from work.
9. I soon found the keys I had lost.
10. I am going on Monday to Paris.
11. Stepper motors are used for position control and switched reluctance motors are used for speed control.


6.2. Put the parts of a sentence in the correct order:


1. some interesting books/we found/in the library.
2. quietly/the door/I closed.
3. his name/after a few minutes/I remembered.
4. again/please don’t ask/that question.
5. a letter to her parents/Ann writes/every week.
6. at the top of the page/your name/please write.
7. to London/ for a few days next week/I’m going.
8. opposite the park/a new hotel/they are building.
9. he won/easily/the game.
10. children/very much/I like.

6.3. Arrange the words in the sentences using the correct word order:

1. Ukraine, a state, is, sovereign.
2. Has, a system, democratic, political, it.
3. A referendum, in Ukraine, 1991, took place, on December 1.
4. Very, is, of Ukraine, geographical, with countries, the development, of its relations, to, favourable, the position, of Europe.
5. Textile, there are, in enterprises, many, Ukraine.
6. The main branches, what, of industry, are, in Ukraine?
7. Presently, the largest, of, branch, the machine-building, is, industry.
8. Today’s, to satisfy, the consumers’ wants, industries, are unable.
9.Branches,of,agricultural,are,main,there,Ukraine,two,production,in.
10. Farms, Ukraine, are, owned, and, controlled, most, in, the government, by.


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