Tiếng anh chuyên nghành điện chương 7

Unit 7 Type of Generator, Unit 7 Type of Generator,Unit 7 Type of Generator, tiếng anh chuyên ngành điện, tài liệu tiếng anh chuyên nghành, bài giảng tiếng anh chuyên nghành, tiếng anh chuyên nghành, bài tâp tiếng anh chuyên nghành, Tiếng anh chuyên nghành điện chương 7

Unit 7: Type of Generator

I READING AND COMPREHENSION

TYPES OF GENERATORS

Steam Units: Steam-electric (thermal) generating units are typically the large base load plants Steam produced in a boiler turns a turbine to drive an electric generator (Figure 3a) Fossil fuels (coal, petroleum and petroleum products, natural gas or other gaseous fuels) and other combustible fuels, such as biomass and waste products, are burned in a boiler to produce the steam Nuclear plants use nuclear fission as the heat source to make steam Geothermal or solar thermal energy also produce steam The thermal efficiency of fossil-fueled steam-electric plants is about 33 to 35 percent The waste heat is emitted from the plant either directly into the atmosphere, through a cooling tower, or sent to a lake for cooling A water pump brings the residual water from the condenser back to the boiler

Gas Units: Gas turbines and combustion engines use the hot gas from burning fossil

fuels, rather than steam, to turn a turbine that drives the generator These plants can be brought up quickly, and so are used as peaking plants The number of gas turbines is growing as technological advances in gas turbine design and declining gas prices have made the gas turbine competitive with the large steam-electric plants However, thermal efficiency is slightly less than that of the large steam-electric plants (Figure 3b) The gas wastes are disposed of through an exhaust stack

Figure 3a Schematic of generic thermal generator

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Combined-Cycle Units: Combined cycle plants first use gas turbines to generate

power and then use the waste heat in a steam-electric generator to produce more electricity Thus, combined-cycle plants make more efficient use of the heat energy in fossil fuels New technology is improving the thermal efficiency of combined-cycle plants, with some reports of 50 to 60 percent thermal efficiency (Figure 3c)

Cogenerating Units: Cogenerators, also known as combined heat and power

generators, are facilities that utilize heat for electricity generation and for another form

of useful thermal energy (steam or hot water), for manufacturing processes or central heating There are two types of cogeneration systems: bottom-cycling and top-cycling

In a bottom-cycling configuration, a manufacturing process uses high temperature steam first and a waste-heat recovery boiler recaptures the unused energy and uses it to drive a steam turbine generator to produce electricity In one of two top-cycling configurations, a boiler produces steam to drive a turbine-generator to produce electricity, and steam leaving the turbine is used in thermal applications such as space heating or food preparation In another top-cycling configuration, a combustion turbine or diesel engine burns fuel to spin a shaft connected to a generator to produce electricity, and the waste heat from the burning fuel is recaptured in a waste-heat recovery boiler for use in direct heating or producing steam for thermal applications (Figure 3d)

Figure 3b Schematic of gas turbine

Figure 3c Schematic of combined cycle

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Other Units: The kinetic energy in moving water and wind is used to turn turbines

at hydroelectric plants and wind facilities to produce electricity Other types of energy conversion include photovoltaic (solar) panels that convert light energy directly to electrical energy, and fuel cells that convert chemical energy directly to electrical energy

Task 1 Rephrasing

Rewrite the following sentences, replacing the words in italics with expressions

from the passage which have similar meanings:

1 Steam produced in a boiler spins a turbine to drive an electric generator.

2 Fossil fuels (coal, petroleum and petroleum products, natural gas or other

gaseous fuels) and other flammable fuels, such as biomass and waste products,

are burned in a boiler to produce the steam

3 The waste heat is discharged from the plant either directly into the atmosphere,

through a cooling tower, or sent to a lake for cooling

4 The gas wastes are disposed of through an chimney.

5 The number of gas turbines is growing as technological progress in gas turbine

design and declining gas prices have made the gas turbine competitive with the large steam-electric plants

Task 2 Contextual reference

What do the pronouns in italics in these sentences refer to?

1 Gas turbines and combustion engines use the hot gas from burning fossil fuels,

rather than steam, to turn a turbine that drives the generator (line 12)

(a) Gas turbines and combustion engines

(b) The hot gas

(c) Steam

(d) A turbine

Figure 3d Cogeneration Schematic

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2 However, thermal efficiency is slightly less than that of the large steam-electric

plants (line 16)

(a) Gas turbine design

(b) The gas turbine

(c) The large steam-electric plants

(d) Thermal efficiency

3 In a bottom-cycling configuration, a manufacturing process uses high temperature steam first and a waste-heat recovery boiler recaptures the unused energy and uses

it to drive a steam turbine generator to produce electricity (line 28)

(a) High temperature steam

(b) A waste-heat recovery boiler

(c) The unused energy

(d) A manufacturing process

4 Other types of energy conversion include photovoltaic (solar) panels that convert light energy directly to electrical energy, and fuel cells that convert chemical

energy directly to electrical energy (line 39, 40)

(a) Other types of energy conversion; fuel cells

(b) Photovoltaic panels; fuel cells

(c) Energy conversion; electrical energy

(d) Photovoltaic panels; light energy

Task 3 Checking facts and ideas

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

1 Combined cycle plants first use gas turbines to generate power and then use the waste heat in a steam-electric generator to produce more electricity

2 Coal, petroleum and petroleum products, natural gas are combustible fuels

3 Biomass and waste products are combustible fuels

4 The thermal efficiency of fossil-fueled steam-electric plants is not over 50 percent

5 Cogenerators only utilize heat for electricity generation

6 In a top-cycling configuration, the waste heat from the burning fuel is recaptured

in a waste-heat recovery boiler for producing electricity

7 The moving water provides kinetic energy for generating electricity

8 Combined-cycle units could be reached 50 to 60 percent thermal efficiency

9 The waste heat is emitted from the plant directly into the atmosphere

10 Gas turbines mainly use the steam from burning fossil fuels to drive generators

II USE OF LANGUAGE

Task 4 Describing function

To describe the function of X (an apparatus, a device, equipment and so on), we

answer the question What does X do?

EXAMPLE

What does a switch do? It changes the condition of a circuit

We can emphasize function by using this pattern:

The function of X is to do sth

The function of a switch is to change the condition of a circuit

Now identify the following components and explain the function of each component with the help of this list

1 A boiler

2 A nuclear plant

3 A gas turbine

4 An electric generator

5 A cooling tower

6 A water pump

7 A condenser

8 An exhaust stack

9 Photovoltaic panels

10 Fuel cells

(a) converts chemical energy directly to electrical energy

(b) turns a turbine to drive an electric generator

(c) converts light energy directly to electrical energy

(d) uses nuclear fission to make steam

(e) disposes the gas wastes

(f) generates steam

(g) brings the residual water from the condenser back to the boiler

(h) emits the heat wastes from the plant directly into the atmosphere

(i) extracts energy from a flow of combustion gas

(j) converts mechanical energy into electrical energy

Task 5 Describing position and connection

When describing the position of a component or how it is connected in a circuit, phrases of this pattern are used:

Be + participle + preposition

Attached to

Applied to

Connected across

Connected between

Connected to

Located within

Mounted on

Mounted under

Wired to

Wound round

EXAMPLES

1 The bulbs are connected across the battery

2 Microwave radar antenna is mounted under helicopter.

Microwave Radar antenna Helicopter

10 GHz Radar antenna

van

1 10 GHz Radar antenna (1)…… van during non-contact experiment at Skagit River

2 When a number of solar cells (2)…… each other and mounted in a support frame,

it is referred to as a module

3 Wires (3)……… a steel core

4 Air preheater (4)… the boiler

5 Turbine (5)… the generator

6 Pulverizer (6)… stoker and boiler

7 Turbine and generator (7)… powerhouse

wires

steel core

III INFORMATION TRANSFER

Task 6 Reading generator rating plates

The capacity of a synchronous generator is equal to the product of the voltage per

phase, the current per phase, and the number of phases It is normally stated in

megavolt-amperes (MVA) for large generators or kilovolt-amperes (kVA) for small generators Both the voltage and the current are the effective, or rms, values (equal

to the peak value divided by 2)

The voltage rating of the generator is normally stated as the operating voltage

between two of its three terminals—i.e., the phase-to-phase voltage For a winding

connected in delta, this is equal to the phase-winding voltage For a winding connected

in wye, it is equal to 3 times the phase-winding voltage

The capacity rating of the machine differs from its shaft power because of two factors

—namely, the power factor and the efficiency The power factor is the ratio of the

real power delivered to the electrical load divided by the total voltage–current product

for all phases The efficiency is the ratio of the electrical power output to the

mechanical power input The difference between the two power values is the power

loss consisting of losses in the magnetic iron due to the changing flux, losses in the resistance of the stator and rotor conductors, and losses from the winding and bearing friction In large synchronous generators, these losses are generally less than 5 percent

of the capacity rating These losses must be removed from the generator by a cooling system to maintain the temperature within the limit imposed by the insulation of the windings

SYNCHRONOUS GENERATOR DATA

Unit Number: Total number of units with listed specifications on site: _ Manufacturer: Type: Date of manufacture: _ Serial Number (each): Phases: Single Three R.P.M.: Frequency (Hz): _

Rated Output (for one unit): _Kilowatt _Kilovolt-Ampere Rated Power Factor (%): Rated Voltage (Volts): _Rated Amperes: Field Volts: Field Amps: Motoring power (kW):

Neutral Grounding Resistor (if applicable): _ t

I2

Additional information:

IV 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 while

In any generator, the whole assembly carrying the coils is called the armature, or rotor

The stationary parts constitute the stator

2 but

There are advantages and disadvantages to all types of generators

Consumer generators most often run on either gasoline, diesel, or propane

3 that

A direct-current (DC) generator is a rotating machine

A rotating machine supplies an electrical output with unidirectional voltage and current

4 if

An induction machine can operate as a generator

The induction machine is connected to an electric supply network operating at a substantially constant voltage and frequency

5 when

Generators offer a level of safety and security

A power supply is unstable

6 because

These three factors energy, environment, and economy are interdependent Advances in one must be compatible with the others

V READING AND SUMMARIZING

Study this passage carefully and answer the questions which follow:

STRUCTURE AND PRINCIPLE OF ENGINES

We have used thermal engines widely since they invented in the 17th century There are many kinds of the engine, and they are used in our life In this session, the structure, the principle and the characteristics of the thermal engines and the power source are presented

• 1769: J Watt invented a reciprocating steam engine with a condenser

• 1816: R Stirling invented a hot air engine (Stirling engine) which utilizes a reheat energy

• 1839: J Ericsson developed several hot air engines (Ericsson engine) in these days

• 1876: N Otto developed a spark ignition engine (gasoline engine)

• 1883: C Laval developed a steam turbine

• 1892: R Diesel invented the principle of a compression ignition engine (Diesel engine)

• 1930: F Whittle invented a gas turbine for an airplane

• 1944: A practical rocket engine is developed in Germany

• 1952: F Bacon invented a fundamental fuel cell

Reciprocating Steam Engine

The reciprocating steam

engine is the first engine

which was reached practical

use This engine obtains a

mechanical power using static

pressure of the steam After

the Industrial Revolution, it

had been used as the power

sources for industries and

transportations while a long time But it is replaced by internal combustion engines, and not used nowadays

Generally, the steam engine consists of a boiler, a heater, a piston, a cylinder, condenser and a water pump as shown in a right figure An intake and an exhaust valve are located on the top of the cylinder

Stirling Engine

The Stirling engine consists of two

pistons as shown in a right figure It is

a closed cycle external combustion

engine which uses the working gas

repeatedly without any valve A

memorable characteristic of this engine

is that a regenerator is adopted in order

to obtain a high efficiency In those

days invented the engine, this had been

called 'Hot air engine' together with an

Ericsson engine described bellow

After many developments, the Stirling

engines in the present come to get a

high power and a high efficiency by using high pressure helium or hydrogen as the working gas But this engine has not reached practical use yet, because it has several problems such as a heavy weight and a high production cost

Ericsson Engine

J Ericsson developed several engines by

reforming the Stirling engine (called the

hot air engine in these days) One of them

is called the Ericsson engine nowadays It

is an opened cycle external combustion

engine with two valves at a supply cylinder

and power cylinder as shown in a right

figure Also, most of the engines invented

by J Erickson were used the regenerator

Gasoline Engine

Nowadays, the gasoline engine (spark ignition

engine) is used widely as the power source of

automobiles As the principle of this engine, a

mixture gas of the fuel and the air is compressed in

the cylinder at the first And the gas explodes by use

of an ignition plug, and generates the output power

As good characteristics of the engine, it can be

realized a smaller and light weight engine, and has a

possibility of the high engine speed and high power

Also, the maintenance of the engine is very simple