Tiếng anh chuyên nghành điện chương 5_6

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Unit 5: Electric Motor Task 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 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 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 motor shown in Fig 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 end becomes a north pole and the other a south pole, depending on which way the current is flowing around the loop 1 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 2 Task 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 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 Match each of these motor components to its function, and then describe its function in a sentence Component Function armature a transfer rotation from the motor bearings b create an electromagnetic field brushes c converts electromagnetic energy to rotation commutator d reverses the current to the armature drive shaft e support the drive shaft field windings f supply current to the armature 1-c; 5-a; 2-e; 4-d; 3-f; 6-b Task Writing Describing components Dismantle this simple dc motor into its components by completing the labeling of the chart below 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: 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 name components: known as Carbon blocks brushes called locate components: The armature is placed between the poles 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 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 screwed soldered attached wired bonded glued riveted welded brazed 10 nailed 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 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 35 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 Contextual reference What the words in italics in these sentences refer to? 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 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 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 Rephrasing Rewrite the following sentences, replacing the words in italics with expressions from the passage which have similar meanings: Small mobile generators are often driven by diesel motors, especially on ships, remote building sites or for emergency standby The world depends mainly on coal and natural gas for power Tidal harnesses use the force of the moon on bodies of water to turn a turbine Pumped-storage hydroelectricity is used to level needs on the power grid Co-generation (combined heat and power) plants integrate the generation of electricity and heat using solar power, 10 Task Checking facts and ideas Decide if these statements are true or false Quote from the passage to support your decisions Steam, water, wind are used as an intermediate energy carrier to drive turbines The world relies only on coal and natural gas for power In hydroelectric power plants, water flows directly through the turbines to power the generators 10 Thermonuclear fusion has been used to generate electricity Power generation by thermonuclear fusion has great potential because it might provide a relatively clean and safe source of electrical power As estimated, the construction of a large experimental reactor will commence in 2005-2006 Co-generation plants achieve efficiencies as high as 80% Heated steam only used to turn turbines 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 10 Task Relative clauses 2: making definitions Study these two sentences: The insulators are deteriorated The insulators are contaminated We can link them in two ways using a relative clause: The insulators WHICH ARE CONTAMINATED are deteriorated The insulators, WHICH ARE CONTAMINATED, are deteriorated Sentence 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 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 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: It is used for measuring voltage It is used to measure voltage We measure voltage with an ammeter 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 A battery charger A megohmmeter 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 a particular job Machine a piece of equipment with moving parts that is designed to 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 Describing component values Study this table: Prefix the things that are needed for a particular purpose or activity Symbol Multiple Example Giga G 10 GHz Gigahertz Mega M 106 MBar Megabars 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 after, that Electricity is produced at power plants Electricity has to get to the customers The customers use the electricity although Nuclear power stations have a good safety record There have been some well-known accidents such as Chernobyl GUIDED WRITING Task 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 when Electricity is generated A loop of conducting wire rotates in a magnetic field 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 as Co-generation gas turbines (COGT) offer efficiencies of up to 60% 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 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 before The connection between magnetism and electricity was discovered Generators used electrostatic principles 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 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 or no 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 "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 How does a fossil fuel power plant work? 15 What does a battery convert into electricity for temporary or intermittent use? 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? What are swiveling couplers for? What is stored in vertical cylindrical steel tanks as large as 90,000 barrels (14,000 m3)? 16 16