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
Para

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.
1 motor shown in Fig. 1 is for a washing machine. It is a universal motor,
The
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
2
end becomes a north pole and the other a south pole, depending on which way
the current is flowing around the loop.

1

1


If you put two magnets close together, like poles-for example, two north poles
3
- 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
4
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
5
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
6
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.

2

2


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.)
3

3


A
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.
Component

4

Function

4


1. armature

a. transfer rotation from the motor

2. bearings

b. create an electromagnetic field

3. brushes

c. converts electromagnetic energy to rotation

4. commutator

d. reverses the current to the armature

5. drive shaft

e. support the drive shaft

6. field windings

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.

5

5

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:
consists of
A A is made up of

X
X and Y

is composed of

Y

2 name components:
known as
Carbon blocks

brushes.
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.

6

6


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.

7

7


1

screwed

2

soldered

3

attached

4

wired

5

bonded

6

glued

7

riveted

8

welded

9

brazed

10 nailed

8

8

Unit
Methods
generating
electricity
I
READING
COMPREHENSION
METHODS
OF
ELECTRICITY

6:
for

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 20052006.

AND

GENERATING

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.
9

35

9


40
45

fossil fuels, syngas, biomass, or biogas as
a fuel source.

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.

Task 2

Contextual reference
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 1

Rephrasing
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,

10

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.
10


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.
II

4.
5.
6.
7.
8.
9.
10.

Task 5

Relative clauses 2:
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 nondefining 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.

USE OF LANGUAGE

Task 4

Describing purpose
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.

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 describe the purpose of these
instruments and facilities using of the
structures presented above.
1. A battery charger
2. A megohmmeter
3. A radiator
11

A waveform display equipment
A signal generator

A turbine
A current transformer
A protective relay
A full cell
Pumped-storage hydroelectricity

11


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

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

Equipment

III

A tool or device used for
measuring speed, distance,
temperature, etc. in a vehicle
or on a piece of machinery

INFORMATION TRANSFER

Task 6

Describing component values

Study this table:
Prefix

the things that are needed for
a particular purpose or
activity

Symbol

Multiple
9

Example

Giga

G

10

GHz

Gigahertz

Mega

M

106

MBar

Megabars

3

kilo

k

10

kA

Kiloamps

deci

d

10-1

dB

Decibels

-3

(a)

(b)

(c)

milli

m

10

mV

Millivolts

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

micro

µ

10-6

µs

Microsecs

nano

n

10-9

nF

Nanofarads

pF

picofarads

12

pico

12

p

10

-12


Identify the components in the following circuit and
write out their value in full:

C1
C2
100µF
25V
R4
22kΩ
R1
39kΩ
63V
2.2µF
R2
82kΩ

R3
3.3Ω
10V
470µF
C3
R5
1kΩ
C5
15nF
C4
68nF
R6
1kΩ
R7
100Ω
R8
100Ω
16V
1000µF
C6
16V
100µF
C7
R9
120Ω
1/2W
F
1.25A
RL
L1

2Ω or 4Ω
BC148
BC328
BC148
BD433
BD434
1.4mH
+14V

13

13


IV

Copper has a lower resistance than many
other metals.
7. after, that
Electricity is produced at power plants.
Electricity has to get to the customers.
The customers use the electricity.
8. although
Nuclear power stations have a good
safety record.
There have been some well-known
accidents such as Chernobyl.

GUIDED WRITING

Task 7

Sentence building

Join the following groups of sentences to make the
longer sentences. Use the words printed in italics at
the beginning of each group. You may omit words
and make whatever changes you think are necessary
in the word order and punctuation of the sentences.

1. when
Electricity is generated.
A loop of conducting wire rotates in a
magnetic field.
2. however
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.
Hydrogen is usually only an energy
carrier, and must be formed by some
other power source.
3. as
Co-generation gas turbines (COGT)
offer efficiencies of up to 60%.

9. while
In the 21st century, nations must
optimize use of low-quality fossil fuels

and sustainable-source energy.
Nations must give equal consideration to
resource
depletion,
environment
protection, and the varying economic
considerations affecting all nations.
10. whether
Regardless of the prime mover we can
interface a control system to fit your
specification.
It is a standard application or a custom
designed control system.

They generate power both directly by
combustion of natural gas and also
use residual heat to generate
electricity from steam.

V

4. which
Geothermal power generation is an
environmentally
friendly
power
generation method.
Geothermal power generation produces
only 1/20th of CO2 emissions per a unit
of electricity generated compared with

thermal power generation.
5. before
The connection between magnetism and
electricity was discovered.
Generators used electrostatic principles.
6. because
Copper is used in many wires.
14

READING AND SUMMARIZING

Study this passage carefully and answer the questions
which follow:

FOSSIL FUEL POWER PLANT

14


the entire operation to occur while the cars
are still coupled together. Unloading a train
takes about three hours. Older unloaders
may still use bottom dump rail cars.
Generating stations adjacent to a mine
sometimes haul coal with massive dieselelectric drive trucks with 140 ton capacity.
Trucks this large typically have 8 ft (2.5 m)
diameter tires, too big and heavy to be
licensed for highway use.
For startup or auxiliary purposes, the plant
may use no. 2 or no. 5 fuel oil as well, Fuel

oil may be delivered by tanker truck or train
car. It is stored in vertical cylindrical steel
tanks as large as 90,000 barrels (14,000 m3).
The heavier no. 5 "bunker" fuel must be
steam heated before pumping in cold
climates.
Natural-gas fuelled plants are usually built
adjacent to gas transport pipelines or have
dedicated gas pipelines extended to them.

A fossil fuel power plant (FFPP) (also
known as steam electric power plant in the
US, thermal power plant in Asia, or power
station in the UK) is an energy conversion
center designed on a large scale for
continuous operation. Just as a battery
converts relatively small amounts of
chemical energy into electricity for
temporary or intermittent use, the FFPP
converts the energy stored in fossil fuels
such as coal, oil, or natural gas successively
into thermal energy, mechanical energy, and
finally electric energy for continuous use and
distribution across a wide geographic area.
Each FFPP is a highly complex, customdesigned system. Present construction costs
(as of 2004) run to $1300/kW, or $650
million USD for a 500 MWe unit. Multiple
generating units may be built at a single site
for more efficient use of land, resources, and
labor. The operational descriptions below are

typical for a large plant and will vary from
one plant to the next.
Fuel transport and delivery
Coal may be delivered by transport truck or
railroad cars. A large coal train may be
nearly a mile long, containing 100 cars, each
with 100 tons of coal, for a total load of
10,000 tons. Modern unloaders use rotary
dump devices. The unloader includes a train
positioner arm that moves the entire train to
position a car over a coal hopper. The
dumper clamps an individual car against a
platform, which swivels the car upside down
to dump the coal. Swiveling couplers enable
15

1. How does a fossil fuel power plant
work?
15


2. What does a battery convert into
electricity for temporary or intermittent
use?
3. Can the FFPP can either converts the
energy stored in fossil fuels such as coal,
oil, or natural gas successively orr
elatively small amounts of chemical
energy into thermal energy, mechanical
energy? Why?

4. What are swiveling couplers for?
5. What is stored in vertical cylindrical
steel tanks as large as 90,000 barrels
(14,000 m3)?

16

16