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單詞復(fù)習(xí)：Diesel/gasolineenginessynchronous/asynchronousangularvelocitystripslider-crank/campneumatic上一課回憶1第1頁(yè)Lesson12MachineToolMotor

機(jī)床電機(jī)

重點(diǎn)詞匯：primemover原動(dòng)機(jī)magneticpole/magneticfield

instantaneously2第2頁(yè)P(yáng)aragraph1ElectricMotorsaretheprimemoverformostmachinetoolfunctions.Theyaremadeinavarietyoftypestoservethreegeneralmachinetoolneeds:spindlepower,slidedrives,andauxiliarypower.Mostofthemuse3-phaseACpowersuppliedat380V.電動(dòng)機(jī)是大多數(shù)機(jī)床原動(dòng)機(jī)。3第3頁(yè)P(yáng)aragraph2:

TheBasic

Allelectricmotorsusetheprinciplethatlikemagneticpolesrepelandunlikepolesattract.Currentthroughacoilorpermanentmagnetscreatesmagneticfields.所有電機(jī)都遵循磁極同極相斥，異極相吸原理。電流通過(guò)線圈或永久磁鐵時(shí)產(chǎn)生磁場(chǎng)。4第4頁(yè)Motorsdelivertorquebyshiftingthemagneticfieldswithinthemotor,sotherotorisconstantlydrawnaround.5第5頁(yè)P(yáng)aragraph3:

Initially,allmotorsuseddirectcurrent(DC).Thiscurrentcreatesmagneticfieldsinthestatorandrotor,thenmechanicallyenergizingandde-energizingstatorcoilscauseamovingfieldthatdrawstherotoraround.6第6頁(yè)Withalternatingcurrent(AC)motors,thecurrentitselfswitchesinpolarityfrompositivetonegative.SendingACtothestatorcoilscreatesfieldsthatdrawrotoraround.交流電機(jī)中，電流會(huì)自動(dòng)從正極變到負(fù)極。將交流電供應(yīng)定子線圈就會(huì)產(chǎn)生磁場(chǎng)使轉(zhuǎn)子旋轉(zhuǎn)起來(lái)。7第7頁(yè)P(yáng)aragraph4:

Formostmachinetoolapplications,versionsoftheACasynchronousmotorareusedforspindledrives,whileslidedrivesaregenerallysynchronous.8第8頁(yè)P(yáng)aragraph5ALittleHistory

Thedesignproblemthroughtheyearswithmachinetoolsandmotorshasbeenhowtogethightorqueatavarietyofspeeds.Initially,mechanicaltransmissionsconsistingofgears,belts,andgear/beltcombinationsgavespeedchangingcapability.Upto36speedranges（速率范圍）werecommonatonetime.9第9頁(yè)Butallthisextrahardwareiscostlyandneedsmaintaince.Inthelastdecade,asspeedrequirementshaverisentheinaccuracycausedbyvibration,whichwasnotaproblematlowerspeed,madethecomplexmechanicaltransmissionunacceptableforsomeapplications.10第10頁(yè)Machinetoolbuildersstillusemechanicaltransmissionformanyapplicationsbutbecauseofmoreversatilemotorspeedcontrol,three-speedtransmissionsaremorecommon.在許多應(yīng)用中，機(jī)床制造商仍然在使用機(jī)械傳動(dòng)，由于有許多多用途電機(jī)能夠調(diào)速，因此，以主軸、滑塊、從屬裝置三種速度運(yùn)行傳動(dòng)仍在廣泛應(yīng)用。11第11頁(yè)Fortoday’soperation,consideraspindlespeedfor3600rpmaslowwithhighspeedgenerally10,000rpmandgreater.Somespindles,suchassmall-diametergrindingquills（磨床主軸）,operateat200,000rpm.在如今，人們會(huì)以為轉(zhuǎn)速3600轉(zhuǎn)/分鐘是低速，高速一般為10000轉(zhuǎn)/分，甚至更高。Paragraph612第12頁(yè)Atthesametime,motordesignandcontroltechnologyhaveprogresseddramatically.Nowthankstocomputertechnology,it’spossibletoquicklymodifymotorspeedandtorque.同步，電機(jī)設(shè)計(jì)和控制技術(shù)也取得了巨大進(jìn)步。目前，要感激計(jì)算機(jī)技術(shù)，使迅速調(diào)整電機(jī)速度和轉(zhuǎn)矩成為也許。13第13頁(yè)P(yáng)aragraph7SpindleMotors

Aspindleisamotor-drivenshaftthatbothpositionsandtransmitspowertoatoolorholdsaworkpiece.Spindlemotors,themajormotorsonamachinetool,drivethespindleshafts.14第14頁(yè)TheACasynchronousinductionspindlemotorisalsocalledasquirellcagemotor.Alternatingcurrent-fluctuatingfrompositivetonegativeinasinewave-issenttothreestatorwindingscausingarotatingmagneticfield.異步交流感應(yīng)主軸電機(jī)也叫鼠籠式電機(jī)。按正弦波從正到付波動(dòng)交變電流傳到定子繞組，產(chǎn)生了旋轉(zhuǎn)磁場(chǎng)。Paragraph815第15頁(yè)Atthesametime,currentinducedintotherotorsetsupanotherfield.Forcessetupbythesetwofieldscauserotorrotation.Tostop,acontrolreversescurrentflow.同步，轉(zhuǎn)子中感應(yīng)電流也生成了另一種磁場(chǎng)。這兩種磁場(chǎng)形成力使轉(zhuǎn)子旋轉(zhuǎn)?？刂齐娏鞣聪蛄鲃?dòng)可實(shí)現(xiàn)停車(chē)。16第16頁(yè)P(yáng)aragraph9Lowercostmotorsofthistypecontrolspeedbyvaryingfrequency.Larger,andmoreprecisemotors,usevectorcontrol

thatrequiresamicroprocessorwithamathalgorithmtocontrolcurrentaccurately,boththecurrentmagnetizingthecoilandthecurrentproducingtorque.Themotorcanthereforehavemaximumtorqueatanyspeed.17第17頁(yè)P(yáng)aragraph10

Vectorcontrolalsoprovidesbothpositionandcurrentfeedbackinrealtime.Currentfeedbackgivesagoodindicationofwhatthespindleanditstoolaredoing(spinninginairorcuttingmetal).Thisinformationalsodetermineshowmuchtimeagiventoolhasbeenused,whichisimportantforautomatictoolmanagement.矢量控制也能夠提供定位控制和實(shí)時(shí)電流反饋。電流反饋能夠顯示主軸和刀具正在做什么（空轉(zhuǎn)或切削金屬）。這些信息也可測(cè)定刀具工作了多長(zhǎng)時(shí)間，這對(duì)自動(dòng)管理刀具非常主要。18第18頁(yè)Insometoolchangers（換刀裝置）,spindlepositioncontrolisimportantfortoolholder（刀架）orientation.It’snecessarytoknowwherethetoolisforautomatictoolchangerstofunctionproperly.在某些換刀裝置中，主軸定位控制對(duì)刀架定位非常主要。自動(dòng)換刀裝置必須確定刀具位置才能正確工作。19第19頁(yè)AnothermotordesignnowgainingacceptanceasaspindledriveistheDCblushlessmotor（無(wú)刷電機(jī)）withpermanentmagnetrotor.Thismotorhashightorqueatlowerspeed,whichisimportantwhenusinglargertools.另一種正取得人們認(rèn)可主軸驅(qū)動(dòng)機(jī)構(gòu)是配有永磁轉(zhuǎn)子直流無(wú)刷電機(jī)。這種電機(jī)低速時(shí)扭矩大，對(duì)使用大型刀具非常有用。Paragraph11

20第20頁(yè)Directcurrentbrushlessmotorsdon’tdevelopasmuchheatascomparableACmotors,butarelarger,morecostly,andhavespeedlimitations.直流無(wú)刷電機(jī)同交流電機(jī)比不會(huì)散發(fā)大量熱量，但體積更大，價(jià)格昂貴，尚有速度限制。21第21頁(yè)P(yáng)aragraph12FeedMotors

Positioningmotorsdrivetheballscrewsthatmovetheslidescarryingspindlesorworktables.Withpositioningmotors,thekeyfeaturesareacceleration,deceleration,smoothness,andaccuracysotheslideorspindlegetstowhereit’sneededquickly.位置控制電機(jī)驅(qū)動(dòng)滾珠絲杠，使拖板帶著主軸和工作臺(tái)一起移動(dòng)。該電機(jī)主要特性是良好加速性、減速性、光滑度和精確性，這樣拖板或主軸才能迅速達(dá)到指定位置。22第22頁(yè)Aswithspindlemotors,positioningmotorswereinitiallyDCbrushtype.ThenACinductionbecamepopular,followedbyhydraulicdrives.Hydraulicshavegoodaccelerationandpower-to-weightratiobecauseoflowmass.像主軸電機(jī)同樣，位置控制電機(jī)開(kāi)始也是用直流電刷。然后交流感應(yīng)電機(jī)開(kāi)始流行，隨后是液壓傳動(dòng)。由于質(zhì)量輕，液壓傳動(dòng)有著良好加速性和功率重量比。23第23頁(yè)Althoughstillusedinsomehighrepeatabilityapplications,theyweregenerallydisplacedbyACservosthatofferlongerlife,higherefficiency,andlessheatgeneration.盡管在某些高反復(fù)性應(yīng)用中仍在使用，液壓傳動(dòng)基本被壽命長(zhǎng)、效率高和發(fā)熱量小交流伺服電機(jī)所取代。24第24頁(yè)P(yáng)aragraph13

Today’smostpopularpositioningmotoriscommonlyknownsimplyasanACservo.Ithaspermanentmagnetsintherotorandcoilsinthestatorthatareactivedtocreatearotatingmagneticfield.25第25頁(yè)Itsmainadvantagesaresmallvolume,hightorque,andlittleheating.Permanentmagnetmotorsareeasiertocontrolbecauseofthemoredefinedrelationbetweencurrentinwindingsandtorqueproduced.26第26頁(yè)P(yáng)ositioncontrolisthekeyfeatureinfeedmotoroperation.Itisimportanttoknowthataccuratepositioningdependsonfeedback,oraclosed-loopsystem.Accuracydependsonhowwellthesystemwasmadeandifanythinginterferedwithsystemmotion.Paragraph14AccuratePositioning

27第27頁(yè)Withfeedbackorclosedloop,themotorobeysthecommand,buthasasensorthatsendsbackthesignal,“Here’swhereIam.”Ifit’snottherightplace,thecontrolwarnstheoperatororsendsacorrectivesignal.Thisconversationbetweenthemotorandcontroltakesplacealmostinstantaneously.Paragraph15

28第28頁(yè)Motorstellwheretheyarewithencoders（編碼器）andresolvers（分解器）.Anencoderisadeviceattachedtothemotorshaft.Itgeneratesadigitalsignalthatnoteshowmanyturnsorp