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1、SHANDONGＵＮＩＶＥＲＳＩＴＹＯＦＴＥＣＨＮＯＬＯＧＹ毕业设计说明书小型水厂恒压供水控制系统设计学院：电气与电子工程学院专业：自动化学生姓名：李晓粉学号：0812205761指导教师：李素玲2012年6月中文摘要摘要随着社会的飞快发展，城市建设规模的不断扩大，工业化化水平的不断提高，人们生活水平的不断提高，人们对城市供水的质量、数量、稳定性提出了更高的要求。本论文根据小型水厂的工艺特点与要求，设计了一套基于PLC的变频恒压供水控制系统。该系统主要由PLC、变频器、水泵机组、压力变送器、液位变送器等构成。系统有六台
2、水泵电机，一台大功率水泵电机用变频器启动，变频调速运行，另一台大功率水泵电机备用，另外四台电机顺序工频运行。压力变送器检测当前水压信号，送入PLC与设定值比较后进行PID运算，从而控制变频器的输出电压和频率，进而改变水泵电机的转速来改变供水量。当变频器的频率输出升到48Hz时，管网压力还是过低，这时要开启工频泵；当变频器的频率输出降到20Hz时，管网压力还是过高，这时需要停止工频泵。最终保持管网压力稳定在设定值附近。关键词：变频调速,PLC,恒压供水IAbstractAbstractWiththerapiddevelo
3、pmentofthesociety,thescaleofcityconstructionisexpanding,andtheindustrializationlevelincreases,people’sstandardoflivingisrisingconstantly,sopeoplearecontinuouslyimprovingtherequirementstothequalityofwatersupplying,reliabilityofwatersupplysystemandenergysaving.Acc
4、ordingtotherequirementofwatersupply,thispaperdesignsasetofwatersupplysystemoffrequencycontrolofconstantvoltagebasedonPLC..ThesystemconsistsofPLC,frequencyregulator，unitsofpumps,waterleveltransducer,pressuretransducerandsoon.Therearesixpumpsmotorsinthissystem.One
5、ofthebiggestmotorsisstartedwiththefrequencyregulator,theotherbiggestisalternate,anotherarestartedinsequence.PressureregulatordetectsthewaterpressuresignalandthenputsitintothePLCtocomparewiththesetvalue,thenthePIDoperatessoastocontroltheoutputvoltageandfrequencyo
6、ffrequencyregulator,andchangethespeedofthepumpmotortochangethesupplyquantity.Whentheoutputofthefrequencyregulatorisupto48Hz,butthepipepressureistoolow,theindustrialfrequencypumpwillbestartedatthistime;Whentheoutputofthefrequencyregulatorisdownto20Hz,butthepipepr
7、essureistoohigh,theindustrialfrequencypumpwillbestoppedatthistime.Ultimatelythepressureofthepipenetworkremainsconstantaroundthesetting.Keywords:variablefrequencyspeed-regulating,PLC,constant-pressurewatersupplyII目录目录摘要............................................
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