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唐山学院毕业设计设计题目：基于PLC的变频中央空调温度控制系统设计系别：智能与信息工程学院班级：姓名：指导教师：田丽欣2016年6月1日基于PLC的变频中央空调温度控制系统设计摘要为了保证环境温度和湿度的舒适，大多酒店、大型商场、工厂车间、写字楼甚至学校等都装有中央空调系统，方便管理以及节约能源。但传统的中央空调能源利用率还是相对较低，普遍存在30%左右的无效能耗。传统的中央空调能源消耗大，而效率相对低下，无论负荷的大小，电机已及系统都是在全负荷的状态下工作的，当用户不需要这么大的负荷时，就造成了资源的浪费。中央空调系统由空调主机，冷却水泵、冷却塔，冷冻水泵、风机、盘管系统等组成。冷冻水是流过空调主机后，经过空调主机制冷降温，通过冷冻泵输送到各个房间中，然后通过盘管系统，和室内的空气进行热交换，最后再流回空调主机，形成循环。而冷却水系统则主要是给空调主机降温，在冷却泵的作用下，冷却水流经空调主机，把空调主机的热量带走，再在冷却塔处经由却塔风机进行散热，最后再流回空调主机，形成循环。冷冻水、冻却水作为热量的载体，不断地把室内的热量带到室外。本论文所研究的中央空调系统可在PLC的控制下，利用PT-100温度变送器采集室内温度，通过EM235模拟量输入输出模块将采集到的温度度数转化为模拟量，进行PID计算，转化后输送给变频器，变频器再带动电机做出相应的加减速转动，使室内温度发生变化，从而形成闭环控制，实现最优控制，低能源高效率，保证居住、工作环境的温度和湿度的同时，最大空间的节约能源，提高能源利用率。关键词：中央空调温度控制PLCEM235变频器PID控制DesignofVariablefrequencycentralairconditioningtemperaturecontrolsystembasedonPLCAbstractInordertoensurethecomfortofthetemperatureandhumidityenvironment,manyhotels,largeshoppingmalls,factories,officebuildings,andevenschoolshavebeeninstalledcentralair-conditioningsystem,tofacilitatethemanagementandenergyconservation.Butthetraditionalcentralairconditioningenergyutilizationisstillrelativelylow,thereareabout30%oftheinvalidenergyconsumption.Thetraditionalcentralair-conditioningenergyconsumption,andefficiencyisrelativelylow,regardlessofthesizeoftheload,motorandsystemareworkingunderthestateoffullload,whenusersdonotneedsuchabigload,causingthewasteofresources.Thecentralairconditioningsystembytheairconditioninghost,coolingwaterpump,coolingtower,chilledwaterpump,fancoilsystem,etc.Chilledwateristhroughtheairconditioninghost,afteracoolairconditioningrefrigerationhost,throughthefrozenpumpintotherooms,andthenthroughthecoilsystem,andindoorairheatexchange,andthenflowbacktotheairconditioninghost,formacircle.Coolingandcoolingwatersystemaremainlyforairconditioninghost,undertheeffectofcoolingpump,coolingwaterflowingthroughtheairconditioninghost,andtakeawaythequantityofheatofairconditioninghost,throughthetowerfanforcoolingincoolingtowerplaceagain,andthenflowbacktotheairconditioninghost,formacircle.Chilledwater,frozenwaterasheatcarrier,constantlybroughttheindoorquantityofheattooutdoor.ThispaperstudiedthecentralairconditioningsystemisunderthecontrolofPLC,usingthePT-100temperaturetransmittercollectionandindoortemperature,byEM235analoginput/outputmodulecollectedtemperaturereadingscanbeconvertedtoanalog,thePIDcalculation,conveyingtheconvertedtofrequencyconverter,frequencyconvertertodrivethemotormakesthecorrespondingrotationalaccelerationanddeceleration,makeindoortemperaturechanges,thusformingaclosedloopcontrol,realizetheoptimalcontrol,lowenergyefficiency,guaranteethelivingandworkingenvironmentoftemperatureandhumidityatthesametime,thebiggestspacetosaveenergy,improveenergyefficiency.Keywords:Controlofcentralairconditioningtemperature;PLC;EM235;Frequencychanger;PIDcontrol;目录1引言..........................................................................................................................11.1课题研究的意义...........................................................................................11.2中央空调控制系统研究现状.......................................................................11.3设计的任务和要求.......................................................................................22中央空调系统的构成及工作原理..........................................................................32.1中央空调系统的工作原理...........................................................................32.2中央空调系统的构成...................................................................................32.2.1冷冻水循环系统................................................................................32.2.2冷却水循环系统................................................................................32.2.3空调主机............................................................................................42.2.4风机盘管系统....................................................................................43中央空调系统控制原理..........................................................................................53.1传统控制方式介绍.......................................................................................53.2中央空调的变频调速原理...........................................................................53.3电机的软启动...............................................................................................73.3.1电机普通启动电流............................................................................73.3.2软启动设备介绍................................................................................73.3.3软启动的应用....................................................................................73.3.4软启动的优点....................................................................................83.3.5软启动器与变频器的区别................................................................83.4中央空调的电机频率的PID控制...............................................................93.4.1PID控制原理......................................................................................93.4.2PID参数整定的常规方法及手段....................................................103.4.3温度控制回路.........................................