外文翻譯--恒壓供水.doc

Constantpressurewater-supplyWiththeprogressdevelopmentofsocialeconomicandtheconstructscaleofcitycontinuouslyenlarge,increasingofpopulationandstandardoflivingofpeoplecontinuouslyimproved,moreandmoredemandingtoquantity,qualityandstabilityofwatersupplybringforwardincity.Theautomaticdegreeofwaterworksintownismuchlowerthanthecorrespondenceincity.Especiallyinsomeoldwaterworks,theequipmentofautomaticcontrolsystemisdroppedbehind.Thecontrolofunitismainlydependedonmanualoperatingofwatches.Theprocessofcontrolisverycomplicatedandthatmanualcontrolcantmeetthechangeofpressureinthepipesandthewaterlevelofthepurepond.Italsocantacttheproperfeedbackintime.Forthesakeofwatersupply,theelectromotorunitusuallyworksinthestateofovercharge.Notonlyefficiencyofelectromotorislowandelectricityconsumingisbigger,butalsothepressureofpipesisoverloadinlongterm.Onthebasisofanalyzingstatusinquoofthewaterworksinourcountry,thispaperdesignsasuitofconstantpressurewatersupplyautomaticcontrolsystembyusingvariablefrequencyspeed-regulatingtechnologybasedonPLC.ThesystemismadeupofPLC,transducer,unitsofpumpsandelectromotors,pressuresensor,industrialcontrolcomputerandconsole.Thesystemisusedatransducertomakefourelectromotorsstarting,runningandtiming.Thetwohigh-powerelectromotors(220Kw)andlow-powerelectromotors(160Kw)ispartlycirculated.ToconnectcontrolcomputerwithPLCandrealizesupervisal,arealtimesupervisalcontrolsoftwareofwatersupplysystemisdeveloped.Thesoftwarehasthefunctionofdataconnection,communication,statecontroloffacilitiesanddatamanagement.Totuneupthefrequencyofpowersupplybythetransducerinthesystem,thisadjustingmakethespeedofelectromotorandperformancecurveofpumpchange.Atlast,itmakethestatusofapumpalter.Throughanalyzingthefigureofenergywastingofpump,thequalityinpipesisdirectproportionofthespeedofpumpifthespeedofpumpisreduced.Thepowerofelectromotorfellthecubeofthespeedofpump.Sotheenergywastingofconstantpressurewatersupplybasedonvariablefrequencyspeedregulatingtechnologyisenvidentlessthanthetraditionalmodeisusedthrottletosupplywater.ThroughusingSTEP7MicroWinprogramsoftwareofSIMENSCompanyinGermaninthecontrolsystem,aPIDcontrollerofpressurecontrolwithinPLCisdesigned.Thecontrollercancomparethemeasurevalueandthevalueinadvanceofpressure.Throughreal-timecontrollingtheoutputvoltageandfrequencyoftransducer,theoutputqualityofpumpischangedalongwiththechangingofpumpsspeed.Itmakesthepressureofpipeself-regulatingandsteadyinthescheduledvalue.Therearesomedrawbackssuchasconversioncurrentisgreat,easytoburnthefuseandswitchifoffinvariablefrequencytoworkingfrequencyofhigh-powerelectromotor.Intheformerresearching,theconversionofvariablefrequencytoworkingfrequencyisonlyemphasizedthespeediness.Theconversionisusuallyfailedbecausethekeyisnotthespeedinessofconversion.Throughanalyzingandresearchingtheproblemofvariablefrequencytoworkingfrequencyofhigh-powerelectromotorintheory,thekeyofconversionispointedoutinthepaper.Onthebasisofanalyzingequivalentcircuitdiagramandvector-diagramofinduction-motor,thephaseofworkingfrequencypowerwhetherornotconsistentwiththeoutputphaseofvariablefrequencypoweratthemomentofconversionisthekeytodecidewhethertheconversionissuccessfully.Withtheapplicationofphasedetectorinindustrialexperimentonthespot,whenthephaseofworkingfrequencypowersupplyisconsistentwiththeoutputphaseofvariablefrequencypowersupply,PLCsendsouttheinstructiontoswitchofftheoutputoftransducer.Theelectromotorisconnectedwiththeindustrialfrequencyvoltageafteritwasdisconnectedfromtheoutputoftransducer.Theconversiontimeislessthanhalfhundredms.Theswitchoffcurrentofvariablefrequencytoworkingfrequencyisaroundoneandhalftimesofratingcurrentofelectromotorwhenthemeasuresismade.Itissucceedtosolvetheproblemofvariablefrequencytoworkingfrequencyandrealizingthesmoothconversionofhigh-powerelectromotor.Itreducedtheimpactonpowersupplyandequipments,too.Theoperationandexperimentdemonstratesthatthesystemmaketheworkofwatersupplyautomatedinsomedegree.Itisgoodforenergysavingandimprovingthemanagementofwaterworks.Itsalsofacilitytomountandmaintain,reliabletooperating,andprecisetosuperviseandcontrol.Thesupervisorycontrolsoftwarehasabundantfunctions,kindinterfaceandconveniencetousing.恒壓供水隨著社會(huì)經(jīng)濟(jì)的飛速發(fā)展，城市建設(shè)規(guī)模的不斷擴(kuò)大，人口的增多以及人們生活水平的不斷提高，對(duì)城市供水的數(shù)量、質(zhì)量、穩(wěn)定性提出了越來(lái)越高的要求。我國(guó)中小城市水廠尤其是老水廠自動(dòng)控制系統(tǒng)配置相對(duì)落后，機(jī)組的控制主要依賴值班人員的手工操作?？刂七^(guò)程繁瑣，而且手動(dòng)控制無(wú)法對(duì)供水管網(wǎng)的壓力和水位變化及時(shí)作出恰當(dāng)?shù)姆磻?yīng)。為了保證供水，機(jī)組通常處于超壓狀態(tài)運(yùn)行，不但效率低、耗電量大，而且城市管網(wǎng)長(zhǎng)期處于超壓運(yùn)行狀態(tài)，曝?fù)p也十分嚴(yán)重。本論文結(jié)合我國(guó)中小城市供水廠的現(xiàn)狀，設(shè)計(jì)了一套基于PLC的變頻調(diào)速恒壓自動(dòng)控制供水系統(tǒng)。變頻調(diào)速恒壓供水自動(dòng)控制系統(tǒng)由可編程控制器、變頻器、水泵電機(jī)組、壓力傳感器、工控機(jī)以及控制柜等構(gòu)成。系統(tǒng)采用一臺(tái)變頻器拖動(dòng)4臺(tái)電動(dòng)機(jī)的起動(dòng)、運(yùn)行與調(diào)速，其中兩臺(tái)大機(jī)(220Kw)和兩臺(tái)小機(jī)(160Kw)分別采用循環(huán)使用的方式運(yùn)行。通過(guò)工控機(jī)和PLC連接，開發(fā)出了用于工控機(jī)的集數(shù)據(jù)采集和通信、設(shè)備狀態(tài)控制和數(shù)據(jù)管理的監(jiān)測(cè)程序，實(shí)現(xiàn)了監(jiān)測(cè)控制。在變頻調(diào)速恒壓供水系統(tǒng)中，單臺(tái)水泵工況的調(diào)節(jié)是通過(guò)變頻器來(lái)改變電源的頻率f來(lái)改變電機(jī)的轉(zhuǎn)速n，從而改變水泵性能曲線得以實(shí)現(xiàn)的。分析水泵工況的能耗比較圖，可以看出利用變頻調(diào)速實(shí)現(xiàn)恒壓供水，當(dāng)轉(zhuǎn)速降低時(shí)，流量與轉(zhuǎn)速成正比，功率以轉(zhuǎn)速的三次方下降，與傳統(tǒng)供水方式中用閥門節(jié)流方式相比，在一定程度上可以減少能量損耗，能夠明顯節(jié)能。控制系統(tǒng)中采用了德國(guó)SIMENS公司的STEP7MicroWin編程軟件，設(shè)計(jì)了一個(gè)用于供水系統(tǒng)壓力控制的PID控制器，PID控制器內(nèi)置在PLC中。該控制器對(duì)壓力給定值與測(cè)量值的偏差進(jìn)行處理，實(shí)時(shí)控制變頻器的輸出電壓和頻率，進(jìn)而改變水泵電動(dòng)機(jī)的轉(zhuǎn)速來(lái)改變水泵出水口流量，實(shí)現(xiàn)管網(wǎng)壓力的自動(dòng)調(diào)節(jié)，使管網(wǎng)壓力穩(wěn)定在設(shè)定值附近。大功率電機(jī)變頻轉(zhuǎn)工頻時(shí)存在轉(zhuǎn)換電流大，容易燒毀熔斷保險(xiǎn)或跳閘的情況。在以前的研究中，變頻轉(zhuǎn)工頻時(shí)只是強(qiáng)調(diào)轉(zhuǎn)換過(guò)程要求在瞬間完成，并沒有指出問(wèn)題的關(guān)鍵所在，因此轉(zhuǎn)換并不成功。本論文針對(duì)大功率電機(jī)變頻轉(zhuǎn)工頻轉(zhuǎn)換存在的問(wèn)題在理論上作深入細(xì)致的研究，根據(jù)感應(yīng)電動(dòng)機(jī)的等效電路和相量圖分析，指出大功率電機(jī)變頻轉(zhuǎn)工頻能否成功，關(guān)鍵在于變頻轉(zhuǎn)工頻瞬時(shí)，工頻電源和變頻輸出電源是否相位一致。在現(xiàn)場(chǎng)工業(yè)試驗(yàn)引入鑒頻鑒