Tiếng anh chuyên nghành điện chương 5_6

Unit 5 Electric motor, Unit 5 Electric motor, Unit 6 Methods for generating electricity, Unit 6 Methods for generating electricity, tiếng anh chuyên ngành điện, tài liệu tiếng anh chuyên nghành, bài tâp tiếng anh chuyên nghành, tiếng anh chuyên nghành, bài giảng tiếng anh chuyên nghành, Tiếng anh chuyên nghành điện chương 5_6

Unit 5: Electric Motor

Task 1

Working in your group, list as many items as you can in the home which use electric motors Which room has the most items?

Reading Skimming

Now you study scanning -locating specific information quickly Another useful strategy

is reading a text quickly to gel a general idea of the kind of information it contains You can then decide which parts of the text are worth reading in more detail later,

depending on your reading purpose This strategy is called skimming.

Task 2

Skim this text and identify the paragraphs which contain information on each of these

topics The first one has been done for you

a What electric motors are used for paragraph 1

b The commutator

c Why the armature turns

d Electromagnets

e Effect of putting magnets together

f The armature

In an electric motor an electric current and magnetic field produce a turning movement This can drive all sorts of machines, from wrist-watches to trains The motor shown in Fig 1 is for a washing machine It is a universal motor, which can run on direct current or alternating current

An electric current running through a wire produces a magnetic field around the wire If an electric current flows around a loop of wire with a bar of iron through it, the iron becomes magnetized It is called an electromagnet; one end becomes a north pole and the other a south pole, depending on which way the current is flowing around the loop

Para

1

2

If you put two magnets close together, like poles-for example, two north poles

- repel each other, and unlike poles attract each other

In a simple electric motor, like the one shown in Fig 2, a piece of iron with loops of wire round it, called an armature, is placed between the north and south poles of a stationary magnet, known as the field magnet When electricity flows around the armature wire, the iron becomes an electromagnet

The attraction and repulsion between the poles of this armature magnet and the poles of the field magnet make the armature turn As a result, its north pole is close to the south pole of the field magnet Then the current is reversed

so the north pole of the armature magnet becomes the south pole Once again, the attraction and repulsion between it and the field magnet make it turn The armature continues turning as long as the direction of the current, and therefore its magnetic poles, keeps being reversed

To reverse the direction of the current, the ends of the armature wire are connected to different halves of a split ring called a commutator Current flows to and from the commutator through small carbon blocks called brushes As the armature turns, first one half of the commutator comes into contact with the brush delivering the current, and then the other, so the direction of the current keeps being reversed

3

4

5

6

Task 3

Match each of these diagrams with the correct description A, B, C, or D One of the

descriptions does not match any of the diagrams (The diagrams are in the correct

sequence, but the descriptions are not.)

The armature turns a quarter of a turn Then electric contact is broken because of the gap in the commutator, but the armature keeps turning because there is nothing

to stop it

B

When current flows, the armature becomes an electromagnet Its north pole is attracted by the south pole and repelled by the north pole of the field magnet C

When a universal motor is run on direct current, the magnetic poles in the

armature change while those of the field magnet remain constant

D

When the commutator comes back into contact with the brushes, current flows through the armature in the opposite direction Its poles are reversed and the turn continues

Language study Describing function

Try to answer this question:

What does an electric motor do?

When we answer a question like this, we describe the function of something We can describe the function of an electric motor in this way:

An electric motor converts electrical energy to mechanical energy.

We can emphasize the function like this:

The function of an electric motor is to convert electrical energy to mechanical energy.

Task 4

Match each of these motor components to its function, and then describe its function in a sentence

1 armature

2 bearings

3 brushes

4 commutator

5 drive shaft

6 field windings

a transfer rotation from the motor

b create an electromagnetic field

c converts electromagnetic energy to rotation

d reverses the current to the armature

e support the drive shaft

f supply current to the armature

1-c; 5-a; 2-e; 4-d; 3-f; 6-b

Task 5

Writing Describing components

Dismantle this simple dc motor into its components by completing the labeling of the chart below

Now study this description of the motor.

A simple dc motor consists of a field magnet and an armature The armature is placed

between the poles of the magnet The armature is made up of a loop of wire and a split

ring known as a commutator The loop is connected to the commutator Current is

supplied to the motor through carbon blocks called brushes.

To write a description, you need to use language to:

1 dismantle a piece of equipment into its main parts These expressions

will help:

A A is made up of X and Y

2 name components:

known as

called

3 locate components:

The armature is placed between the poles.

4 connect components:

The loop is connected to the commutator.

Task 6:

Complete the text with the help of the diagram on the next page Use the following words:

are made up

is placed

is composed

consists

A transformer ……….of two coils, a primary and a secondary The coils are wound

on a former which is mounted on a core The coils……….of a number of loops of wire The core……….of thin pieces of soft iron U- and T-shaped pieces are used The former……….on the leg of the T

Now label the diagram opposite using the completed text

Word study

Study these expressions for describing how components are connected to each other

A is bolted to B = A is connected to B with bolts

A is welded to B = A is connected to B by welding

A is fixed to B = no specific method given

Explain each of these methods of connection

1 screwed

2 soldered

3 attached

4 wired

5 bonded

6 glued

7 riveted

8 welded

9 brazed

10 nailed

Unit 6:

Methods for

generating

electricity

COMPREHENSION

METHODS OF GENERATING

ELECTRICITY

Methods for transforming other power

into electrical power

5 10 15 20 25 30

Rotating turbines attached to electrical

generators produce most commercially

available electricity Turbines may be driven

by using steam, water, wind or other fluids

as an intermediate energy carrier The most

common usage is by steam in fossil fuel

power plants or nuclear power plants, and by

water in hydroelectric dams Small mobile

generators are often driven by diesel

engines, especially on ships, remote building

sites or for emergency standby

Fuel cells produce electricity using a variety

of chemicals and are seen by some people to

be the most likely source of power in the

long term, especially if hydrogen can be

used as the feedstock However, hydrogen is

usually only an energy carrier, and must be

formed by some other power source

Primary energy sources used in electrical power generation

The world relies mainly

on coal and natural gas for power The high capital requirements of nuclear power and the fear of its dangers have prevented the ordering

of new nuclear power plants in North America since the 1970s

Steam turbines can be powered using steam produced from geothermal sources, solar energy, or nuclear reactors, which use the energy created by the fission of radioactive plutonium or uranium

to generate heat

Nuclear power plants often use a primary and secondary steam circuit

to add an additional layer of protection between the location of the nuclear fuel and the generator room

Hydroelectric power plants use water flowing directly through the turbines to power the generators Tidal harnesses use the force of the moon on bodies of water to spin

a turbine Wind turbines use wind to turn turbines that are hooked up to a generator Pumped-storage hydroelectricity is used to level demands on the power grid

Power generation by thermonuclear fusion has been suggested as a possible way of generating electricity; currently a number of technical obstacles and environmental concerns stand in the way, but if realized fusion might provide a relatively clean and safe source of electrical power The construction of a large experimental reactor (ITER) is expected to commence in 2005-2006

40 45

Improving efficiency

Co-generation (combined heat and power)

plants combine the generation of electricity

and heat using solar power, fossil fuels,

syngas, biomass, or biogas as a fuel source

These plants can achieve efficiencies as high

as 80%, but many of these plants being built

today only expect to achieve stated

maximum 55% efficiency Heated steam

turns a turbine, and then excess heat is

distributed for space heating in buildings,

industrial processes or green house heating

Whole communities can benefit from heat

distributed through a district heating scheme

The ability to achieve tri-generation using

fossil fuels or solar energy to generate heat,

electricity and evaporative cooling exists

These combined power plants have the best

energy conversion ratio after hydroelectric

plants Small photovoltaic arrays, windmills

and bicycles hooked up to a turbine can all

be used to generate mobile electricity

Rewrite the following sentences,

replacing the words in italics with

expressions from the passage which have

similar meanings:

1 Small mobile generators are often driven

by diesel motors, especially on ships,

remote building sites or for emergency

standby

2 The world depends mainly on coal and

natural gas for power

3 Tidal harnesses use the force of the

moon on bodies of water to turn a

turbine

4 Pumped-storage hydroelectricity is

used to level needs on the power grid

5 Co-generation (combined heat and

power) plants integrate the generation of

electricity and heat using solar power,

fossil fuels, syngas, biomass, or biogas as

a fuel source

What do the words in italics in these

sentences refer to?

1 The high capital requirements of nuclear

power and the fear of its dangers have

prevented the ordering of new nuclear power plants in North America since the 1970s (line 15)

(a) The high capital requirement’s (b) Nuclear power’s

(c) New nuclear power plant’s

2 Steam turbines can be powered using steam produced from geothermal sources,

solar energy, or nuclear reactors, which

use the energy created by the fission of radioactive plutonium or uranium to generate heat (line 19)

(a) Steam turbines (b) Geothermal sources (c) Nuclear reactors

3 Wind turbines use wind to turn turbines

that are hooked up to a generator (line

27) (a) Steam turbines (b) Wind turbines (c) Turbines

Task 3 Checking facts and ideas

Decide if these statements are true or false Quote from the passage to support your decisions

1 Steam, water, wind are used as an intermediate energy carrier to drive turbines

2 The world relies only on coal and natural gas for power

3 In hydroelectric power plants, water flows directly through the turbines to power the generators

4 Thermonuclear fusion has been used to

generate electricity

5 Power generation by thermonuclear

fusion has great potential because it

might provide a relatively clean and safe

source of electrical power

6 As estimated, the construction of a large

experimental reactor will commence in

2005-2006

7 Co-generation plants achieve

efficiencies as high as 80%

8 Heated steam only used to turn turbines

9 Tri-generation power plants have the

best energy conversion ratio after

hydroelectric plants

10 Small photovoltaic arrays, windmills

and bicycles can all be used to generate

mobile electricity

When we answer the question What is X

for?, we describe the purpose of X.

EXAMPLE

What is a voltmeter for?

We can use the following ways to describe

the purpose of a voltmeter:

1 It is used for measuring voltage

2 It is used to measure voltage

3 We measure voltage with an ammeter

4 We measure current using an ammeter

Now describe the purpose of these

instruments and facilities using of the

structures presented above

1 A battery charger

2 A megohmmeter

3 A radiator

4 A waveform display equipment

5 A signal generator

6 A turbine

7 A current transformer

8 A protective relay

9 A full cell

10 Pumped-storage hydroelectricity

making definitions

Study these two sentences:

1 The insulators are deteriorated

2 The insulators are contaminated

We can link them in two ways using a relative clause:

1 The insulators WHICH ARE CONTAMINATED are deteriorated

2 The insulators, WHICH ARE CONTAMINATED, are deteriorated Sentence 1 means that only the contaminated insulators are deteriorated Other insulators such as silicon coated insulators are not

deteriorated The relative clause is a defining one It defines the type of insulators which are contaminated It carries essential information.

Sentence 2 means that all the insulators are deteriorated and all the insulators are

contaminated The relative clause is a non-defining one It adds some extra information to the sentence but it is not essential We can remove it from the

sentence and the sentence still makes good

sense It is separated from the rest of the sentence by commas.

One use of defining relative clauses is to make definitions Study this diagram:

(a) An electric motor (c) converts electrical energy into

mechanical energy (b) a machine

is which

Now make ten definitions using the information in

the following table You must decide on the correct

combinations of (a), (b), and (c).

Apparatus the tools or other pieces of

equipment that are needed for a particular activity or task

Device an object or a piece of

equipment that has been designed to do a particular job

Machine a piece of equipment with

moving parts that is designed

to do a particular job

Instrument A tool or device used for

measuring speed, distance, temperature, etc in a vehicle

or on a piece of machinery

Equipment the things that are needed for

a particular purpose or activity

Porcelain

A radiator

A transducer

A circuit

breaker

Thermo tracer

A transformer

A generator

A miliammeter

A governor

Copper

an instrument

a device

an equipment

a machine

an apparatus

a material

controls the rotational speed of turbines

converts mechanical energy into electrical energy changes the magnitude of

an ac voltage

measures small currents

dismisses heat from equipment does not readily release electrons provide an easy path for an electric current converts changes

in the physical variable into electrical signals protects power system from excessive

currents measures temperature using infrared rays

III INFORMATION TRANSFER

Task 6 Describing component values

Study this table:

Prefix Symbol Multiple Example Giga G 10 9 GHz Gigahertz Mega M 10 6 MBar Megabars kilo k 10 3 kA Kiloamps deci d 10 -1 dB Decibels milli m 10 -3 mV Millivolts micro µ 10 -6 µ s Microsecs nano n 10 -9 nF Nanofarads pico p 10 -12 pF picofarads