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.恒壓供水隨著社會經(jīng)濟的飛速發(fā)展，城市建設規(guī)模的不斷擴大，人口的增多以及人們生活水平的不斷提高，對城市供水的數(shù)量、質(zhì)量、穩(wěn)定性提出了越來越高的要求。我國中小城市水廠尤其是老水廠自動控制系統(tǒng)配置相對落后，機組的控制主要依賴值班人員的手工操作?？刂七^程繁瑣，而且手動控制無法對供水管網(wǎng)的壓力和水位變化及時作出恰當?shù)姆磻?。為了保證供水，機組通常處于超壓狀態(tài)運行，不但效率低、耗電量大，而且城市管網(wǎng)長期處于超壓運行狀態(tài)，曝損也十分嚴重。本論文結(jié)合我國中小城市供水廠的現(xiàn)狀，設計了一套基于PLC的變頻調(diào)速恒壓自動控制供水系統(tǒng)。變頻調(diào)速恒壓供水自動控制系統(tǒng)由可編程控制器、變頻器、水泵電機組、壓力傳感器、工控機以及控制柜等構(gòu)成。系統(tǒng)采用一臺變頻器拖動4臺電動機的起動、運行與調(diào)速，其中兩臺大機(220Kw)和兩臺小機(160Kw)分別采用循環(huán)使用的方式運行。通過工控機和PLC連接，開發(fā)出了用于工控機的集數(shù)據(jù)采集和通信、設備狀態(tài)控制和數(shù)據(jù)管理的監(jiān)測程序，實現(xiàn)了監(jiān)測控制。在變頻調(diào)速恒壓供水系統(tǒng)中，單臺水泵工況的調(diào)節(jié)是通過變頻器來改變電源的頻率f來改變電機的轉(zhuǎn)速n，從而改變水泵性能曲線得以實現(xiàn)的。分析水泵工況的能耗比較圖，可以看出利用變頻調(diào)速實現(xiàn)恒壓供水，當轉(zhuǎn)速降低時，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?？刂葡到y(tǒng)中采用了德國SIMENS公司的STEP7MicroWin編程軟件，設計了一個用于供水系統(tǒng)壓力控制的PID控制器，PID控制器內(nèi)置在PLC中。該控制器對壓力給定值與測量值的偏差進行處理，實時控制變頻器的輸出電壓和頻率，進而改變水泵電動機的轉(zhuǎn)速來改變水泵出水口流量，實現(xiàn)管網(wǎng)壓力的自動調(diào)節(jié)，使管網(wǎng)壓力穩(wěn)定在設定值附近。大功率電機變頻轉(zhuǎn)工頻時存在轉(zhuǎn)換電流大，容易燒毀熔斷保險或跳閘的情況。在以前的研究中，變頻轉(zhuǎn)工頻時只是強調(diào)轉(zhuǎn)換過程要求在瞬間完成，并沒有指出問題的關(guān)鍵所在，因此轉(zhuǎn)換并不成功。本論文針對大功率電機變頻轉(zhuǎn)工頻轉(zhuǎn)換存在的問題在理論上作深入細致的研究，根據(jù)感應電動機的等效電路和相量圖分析，指出大功率電機變頻轉(zhuǎn)工頻能否成功，關(guān)鍵在于變頻轉(zhuǎn)工頻瞬時，工頻電源和變頻輸出電源是否相位一致。在現(xiàn)場工業(yè)試驗引入鑒頻鑒