电气工程英语 (2).ppt

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1、LOGOUnit twoUnit twoElectric Machinery and Electrical EquipmentPre-reading ActivitiesLECtURE 1 LECtURE 1 LECTURE 1 PRE-READING1.How is electricity generated?Whats the history of electricity?task 1task 1 LECTURE 1 PRE-READINGElectricityistheenergymadeavailablebytheflowofelectricchargethroughaconducto

2、r.Itiscarriedbywiresorproducedbybatteryandisusedtopowermachines.HistoryofElectricityTheearliestformsofelectricityoccurnaturallysuchaslightningorelectricitycausedbymeansoffriction.LECTURE 1 PRE-READINGScientistsconstructedsimplemachinestocreate electricity.Theconnectionbetweenelectricityandmagnetismw

3、asdiscovered.Electricmotorsandgeneratorswereinvented.The generation of electricity becameeconomic.the founders and their major contribution in electricity:Thomas Seebeck(1770-1831):Discoveredthe“SeebeckEffect”.Michael Faraday(1791-1867):Electromagneticinduction.Healsoexplainedhowelectriccurrentworks

4、.James Maxwell(1831-1879):TranslatedFaradaystheoriesintomathematicalexpressions.Thomas Alva Edison(1847-1931):InventedtheelectricbulbNikola Tesla(1856-1943):Devisedthepolyphasealternating-currentsystemsthatformthemodernelectricalpowerindustry.Otto Hahn(1879-1968):Explainedtheprocessofnuclearfissionb

5、ywhichnucleiofatomsofheavyelementscanbreakintosmallernuclei,intheprocessreleasinglargequantitiesofenergy.Albert Einstein(1879-1955):Explainedthatonegramofmasscanbeconvertedintoatorrentialamountofenergy.Electricityisaresultofallthehardworkdonebyabovementionedgreatscientistsandinventors.LECTURE 1 PRE-

6、READINGtask 2task 2Somecommonelectricalmachinesandelectricalequipmentareshowninthefollowingpicturesandtheirnameshavebeengiven.Matchthepictureswiththeircorrespondingnames.transformercontactorswitchelectricgeneratorelectricmotorrelay LECTURE 1 PRE-READING1（）2（）3（）switchcontactorelectricgenerator4（）5（）

7、electricmotor6（）relaytransformer LECTURE 1 PRE-READINGtask 3task 3DISCUSSION-Question1.Whatisthefunctionofanelectricalmachine?Telltheclassthetypesofelectricalmachinesandtheirapplicationsthatyouknow.Types of Electrical MachinesREFERENCE ANSWERS:Transformer:Transformerworksontheprinciplemutualinductio

8、n.Thereisanironcorewhichlinkswindingsoftransformer.Thefluxinthecorelinksbothprimaryandsecondarywindingduetowhichvoltageinducedinthewindings.Transformers are used in various fields like power generation grid,distribution sector,transmission and electric energy consumption.There arevarious types of tr

9、ansformers which are classified based on the differentfactors.REFERENCE ANSWERS:Transformer:For instance,depending on the voltage level there are two types oftransformers,step-uptransformerandstep-downtransformer.Themostimportantapplicationofastep-uptransformerisageneratorstep-up(GSU)transformerused

10、inallgeneratingplants.Thosetransformersusuallyhavelargeturnsratiovalues.Thevoltagevalueproducedinenergygenerationisincreasedandpreparedforthelong-distanceenergytransmission.Thestep-downtransformershaveaveryimportantfunctioninapowersystem.Theylowerthevoltagelevelandadaptittoenergyconsumers.REFERENCE

11、ANSWERS:Generator:Ageneratorisamachinethatconvertsavailablemechanicalenergyintoelectricalenergy.It works on the principle of Faradays Law of ElectromagneticInduction.Based on theoutputobtained,weclassifygeneratorsas:ACGenerators&DCGenerators.TheDCgeneratorcanbeclassifiedintotwomaincategoriesassepara

12、tely excitedandself-excited.Afewapplicationsofthemare:TheseparatelyexcitedtypeDCgeneratorsareusedforpowerandlightingpurposes.TheseriesDCgeneratorisusedinarclampsforlighting,stablecurrentgeneratorandbooster.ComparedwithDCgenerators，wecanconcludethemainadvantagesofACgeneratorsoverDCgenerators:ACgenera

13、torscanbeeasilysteppedupandsteppeddownthroughtransformers.LossesarerelativelylesserthanDCmachineSizeoftheACgeneratorsarerelativelysmallerthanDCgeneratorsREFERENCE ANSWERS:Electric Motor:.Letsgothroughaninstance:Whatdoesthemixerdoforyou?Therotatingbladesmashandmixthingsforyou.Howdoesitwork?Motorsconv

14、ertelectricenergytomechanicalwork.Itworksonelectricity.Electricmotorsareusedinavarietyofapplications.Someofthemarelistedbelow.DrillsWaterPumpsHardDiscDrivesWashingMachinesIndustrialEquipmentThe Primary Classification Of Electric MotorLongevity，efficiency，quietoperationandavailabilityinawiderangeofsi

15、zesandpoweroutputsmakeACmotorsidealformanyapplications such as:vending machines,packaging equipment orapplicationsinstores,hospitalsandrestaurants,etc.DCmotorshaveawiderangeofapplicationsrangingfromelectricshaverstoautomobiles.Tocatertothiswiderangeofapplications,theyareclassifiedintodifferenttypess

16、uchas:SelfExcitedDCMotor,ShuntDCMotor,SeriesDCMotor,etc.LECTURE 1 PRE-READINGDISCUSSION-Question2.How do you define electrical equipment?List some cases of the use of electrical equipment in our daily life.REFERENCE ANSWERS:Broadlyspeaking,electricalequipmentreferstoallkindsofdevicesthatuseelectrici

17、ty,including both industrial electrical equipment and householdappliances.Professionally,it mainly refers to the electrical devices and componentswhichareusedtocontrol,adjust,switch,detectorprotectthecircuitandequipmentbyopening,closing,orchangingtheparametersofthecircuit.There are a variety of elec

18、trical equipment with different structures andfunctions.REFERENCE ANSWERS:For example,according to the voltage level of the circuit,the electricalequipmentcanbeclassifiedintohighvoltageelectricalequipmentandlowvoltageelectricalequipment.According to the principle of operation,the electrical equipmen

19、t can beclassified into manual electrical equipment and automatic electricalequipment.Electricalequipmentisoftenseeninourdailylife.Lightswitchesarethemostcommontypeelectricalequipmentcanbefoundinalmosteveryroomof our house and office.Besides switches,we may also see relays,contactors,fuses,breakersandothertypesofelectricalequipmentinourdailylife.