電動執行器由電動執行機構和調節機構兩部分組成,它根據自動化儀表輸入的4mA~20mA信號,轉換為力或力矩以推動各類調節閥或其他執行機構,從而達到自動控制完成壓力、溫度、流量的檢測,在調節過程中進行實時故障診斷,必要時進行調整和校準。本文講述了電動執行機構調節工作原理及智能調節閥的功能特點,總(zong)結(jie)現代化工業生產過程安全、優質運行的電動(dong)調節規律。
一、電動執行器的組成和工作原理
電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)執行(xing)器(qi)由電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)執行(xing)機(ji)(ji)構(gou)(gou)和調節(jie)機(ji)(ji)構(gou)(gou)兩部(bu)分組(zu)(zu)成,其中將(jiang)調節(jie)控制信號轉換成為力(li)(li)或力(li)(li)矩的部(bu)分叫做電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)執行(xing)機(ji)(ji)構(gou)(gou),各種調節(jie)閥統稱為調節(jie)機(ji)(ji)構(gou)(gou)。電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)執行(xing)機(ji)(ji)構(gou)(gou)是使(shi)用調電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)機(ji)(ji)或推動(dong)(dong)(dong)(dong)(dong)器(qi)電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)元件轉換為力(li)(li)或力(li)(li)矩以推動(dong)(dong)(dong)(dong)(dong)各類調節(jie)閥開關。電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)執行(xing)器(qi)主要由伺(si)服放大器(qi)DFC、電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)操作器(qi)DFD、位(wei)置發送器(qi)WF,伺(si)服電(dian)(dian)動(dong)(dong)(dong)(dong)(dong)機(ji)(ji)SM、減速(su)器(qi)J等組(zu)(zu)成。
電動執行器的工作過程是:來自PLC調節信號輸出送到伺服放大器DFC,與位置傳感器WF發送的反饋信號相比較,經微處理器運算后將其差值經電路放大后去控制伺服電動機正轉或反轉,經過減速器減速后驅動輸出軸產生直線移動或角旋轉。輸出結果再次經位置傳感器定位發出位置指示和4mA~20mA的反饋信號送到伺服放大器的輸入端。微處理器再次比較反饋信號和儀表調節信號,若反饋信號和輸入信號相等時,控制電動執行機構停止使閥門穩定在儀表輸出的位置上,電動執行器也可以通過電動操作器進行手動操作。一般是通過現場調節儀表旋鈕,輸出位置控制信號控制電動機正轉或反轉驅動執行機構調節閥門開(kai)度等。伺服電動(dong)機是執行機構的(de)(de)動(dong)力(li)部分,它具有啟(qi)(qi)動(dong)轉(zhuan)矩大和(he)啟(qi)(qi)動(dong)電流較小的(de)(de)特(te)點,位置傳(chuan)感器是根據差動(dong)變送器的(de)(de)工(gong)作原理,利用(yong)輸(shu)出軸的(de)(de)位移改變鐵芯在(zai)差動(dong)線圈中的(de)(de)位置,以產生(sheng)反饋信號和(he)位置信號。
二、手動操作器
手操(cao)(cao)器(qi)主要用(yong)(yong)(yong)在啟動(dong)或(huo)電(dian)動(dong)執行(xing)器(qi)系(xi)統中實(shi)現手動(dong)操(cao)(cao)作,它與調(diao)節器(qi)配(pei)合(he),完成從自動(dong)到(dao)手動(dong)或(huo)手動(dong)到(dao)自動(dong)的無(wu)干擾切(qie)換,也可以在控(kong)制系(xi)統出故障時或(huo)系(xi)統投(tou)運時用(yong)(yong)(yong)它進行(xing)手動(dong)遙控(kong)。與氣動(dong)執行(xing)器(qi)配(pei)合(he)使用(yong)(yong)(yong)的叫(jiao)Q型操(cao)(cao)作器(qi),與電(dian)動(dong)執行(xing)器(qi)配(pei)合(he)使用(yong)(yong)(yong)的叫(jiao)D型操(cao)(cao)作器(qi)。
Q型操(cao)(cao)作(zuo)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)工(gong)作(zuo)過程(cheng)是:當(dang)操(cao)(cao)作(zuo)器(qi)(qi)(qi)(qi)處(chu)于自(zi)動(dong)(dong)(dong)狀態時(shi),來(lai)(lai)自(zi)調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)輸(shu)出(chu)(chu)電(dian)(dian)(dian)流(liu)(liu)通過負載(zai)(zai)(zai)R,并(bing)由操(cao)(cao)作(zuo)器(qi)(qi)(qi)(qi)中一個(ge)電(dian)(dian)(dian)流(liu)(liu)顯示(shi)其大小(xiao),其中負載(zai)(zai)(zai)R可(ke)以是電(dian)(dian)(dian)氣(qi)轉換(huan)器(qi)(qi)(qi)(qi),也(ye)可(ke)以是電(dian)(dian)(dian)氣(qi)閥門定(ding)位器(qi)(qi)(qi)(qi)或電(dian)(dian)(dian)動(dong)(dong)(dong)執行器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)輸(shu)入阻(zu)抗,在復雜(za)控制系統中也(ye)可(ke)以是串級控制系統中的(de)(de)(de)(de)(de)(de)副(fu)調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)輸(shu)入阻(zu)抗。當(dang)操(cao)(cao)作(zuo)器(qi)(qi)(qi)(qi)處(chu)于手(shou)動(dong)(dong)(dong)狀態時(shi),來(lai)(lai)自(zi)調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)流(liu)(liu)不流(liu)(liu)過負載(zai)(zai)(zai)R,而由操(cao)(cao)作(zuo)器(qi)(qi)(qi)(qi)中的(de)(de)(de)(de)(de)(de)可(ke)調(diao)(diao)(diao)(diao)恒流(liu)(liu)源向負載(zai)(zai)(zai)提供手(shou)動(dong)(dong)(dong)操(cao)(cao)作(zuo)電(dian)(dian)(dian)流(liu)(liu),其大小(xiao)可(ke)由手(shou)操(cao)(cao)電(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)調(diao)(diao)(diao)(diao)節(jie),并(bing)通過另(ling)一個(ge)電(dian)(dian)(dian)流(liu)(liu)表顯示(shi)。與此(ci)同時(shi),通過調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)背(bei)面(mian)的(de)(de)(de)(de)(de)(de)跟(gen)(gen)蹤電(dian)(dian)(dian)壓(ya)輸(shu)出(chu)(chu)的(de)(de)(de)(de)(de)(de)接線(xian)端(duan)(duan)子向調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)中積(ji)分(fen)電(dian)(dian)(dian)容(rong)兩端(duan)(duan)提供直流(liu)(liu)跟(gen)(gen)蹤電(dian)(dian)(dian)壓(ya),大小(xiao)與手(shou)動(dong)(dong)(dong)操(cao)(cao)作(zuo)電(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)(de)大小(xiao)相對(dui)應,當(dang)調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)中的(de)(de)(de)(de)(de)(de)積(ji)分(fen)電(dian)(dian)(dian)容(rong)兩端(duan)(duan)收到(dao)跟(gen)(gen)蹤電(dian)(dian)(dian)壓(ya)后,調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)輸(shu)出(chu)(chu)電(dian)(dian)(dian)流(liu)(liu)就(jiu)隨(sui)跟(gen)(gen)蹤電(dian)(dian)(dian)壓(ya)做出(chu)(chu)相應改變。從(cong)自(zi)動(dong)(dong)(dong)到(dao)手(shou)動(dong)(dong)(dong),要先調(diao)(diao)(diao)(diao)節(jie)手(shou)操(cao)(cao)作(zuo)器(qi)(qi)(qi)(qi),使其輸(shu)出(chu)(chu)電(dian)(dian)(dian)流(liu)(liu)與調(diao)(diao)(diao)(diao)節(jie)器(qi)(qi)(qi)(qi)輸(shu)出(chu)(chu)電(dian)(dian)(dian)流(liu)(liu)相等,即能進行切換(huan)。
三、智能電動執行器
智能電動(dong)執(zhi)行器控制(zhi)電源(yuan)有單相(xiang)(xiang)和三(san)相(xiang)(xiang)兩(liang)類,三(san)相(xiang)(xiang)智能電動(dong)執(zhi)行器主體(ti)和單相(xiang)(xiang)智能電動(dong)執(zhi)行器的(de)(de)主體(ti)相(xiang)(xiang)同,以單相(xiang)(xiang)智能電動(dong)執(zhi)行器的(de)(de)工作過程分析(xi)智能電動(dong)執(zhi)行器的(de)(de)工作原理。
工作(zuo)過(guo)程(cheng)是PLC或(huo)變送(song)器(qi)的(de)(de)(de)4mA~20mA信(xin)(xin)號(hao)(hao)傳給(gei)智能(neng)伺(si)服(fu)(fu)放大器(qi),經(jing)伺(si)服(fu)(fu)微(wei)處(chu)(chu)理(li)(li)器(qi)掃(sao)描監測該(gai)輸入信(xin)(xin)號(hao)(hao)和(he)位置反饋信(xin)(xin)號(hao)(hao),定(ding)時(shi)比(bi)較(jiao)。微(wei)處(chu)(chu)理(li)(li)器(qi)比(bi)較(jiao)這兩個(ge)信(xin)(xin)號(hao)(hao),若(ruo)信(xin)(xin)號(hao)(hao)不相等,正負差值(zhi)超過(guo)平衡位置值(zhi),即(ji)發出控制信(xin)(xin)號(hao)(hao)調(diao)整智能(neng)伺(si)服(fu)(fu)放大器(qi)中(zhong)的(de)(de)(de)功率晶(jing)閘管的(de)(de)(de)導(dao)(dao)通(tong)(tong)角,使晶(jing)閘管導(dao)(dao)通(tong)(tong)驅動伺(si)服(fu)(fu)電動機轉動,調(diao)節(jie)閥(fa)(fa)門開(kai)度;同(tong)時(shi)伺(si)服(fu)(fu)微(wei)處(chu)(chu)理(li)(li)器(qi)將調(diao)節(jie)閥(fa)(fa)位置信(xin)(xin)號(hao)(hao)轉換成(cheng)相應(ying)的(de)(de)(de)脈沖量發往操(cao)作(zuo)器(qi),顯示(shi)閥(fa)(fa)門的(de)(de)(de)開(kai)度百分數(shu)(shu)。當接受變送(song)器(qi)信(xin)(xin)號(hao)(hao)進入PI調(diao)節(jie)工作(zuo)方式時(shi),微(wei)處(chu)(chu)理(li)(li)器(qi)將變送(song)器(qi)信(xin)(xin)號(hao)(hao)與給(gei)定(ding)值(zhi)進行比(bi)較(jiao),并(bing)按(an)預(yu)先設置好的(de)(de)(de)參數(shu)(shu)PI進行計算并(bing)發出控制信(xin)(xin)號(hao)(hao)調(diao)節(jie)閥(fa)(fa)門開(kai)度,直到(dao)兩個(ge)信(xin)(xin)號(hao)(hao)平衡。
![](//img.duoso.com.cn/HtmlEditor/2014/11/20141103104206543.png)
圖1 單相智(zhi)能電動執行機構框圖
四、智能調節閥
智能調節閥由控制器、傳感器、信(xin)號變換器、I/O及通信(xin)接口、執行機構、調節閥組成,具有(you)以下特點(dian):
1.具有智能(neng)(neng)控制(zhi)(zhi)功能(neng)(neng)。可按給(gei)定(ding)值自動進行PID調節,控制(zhi)(zhi)流(liu)量(liang)、壓力(li)、壓差和溫度等(deng)過程(cheng)變量(liang),還可支持串(chuan)級控制(zhi)(zhi)方(fang)式等(deng)。
2.具有(you)保持功能。無(wu)論電(dian)源、機械部件、控(kong)制信號等(deng)出(chu)現故障(zhang)都會(hui)自動采取(qu)保護措施,以保證(zheng)本身及生產過程(cheng)安全(quan)可靠(kao)。
3.具有通信功能(neng)。與上位機控制(zhi)系統(tong)連(lian)接,操作人(ren)員可在遠方(fang)對其進行(xing)檢測、整(zheng)定、修(xiu)改(gai)參(can)數等。
4.具有診(zhen)斷(duan)功能。智能調(diao)節閥的(de)閥體和執(zhi)行機構上(shang)裝有傳(chuan)感器(qi)專門用于故障診(zhen)斷(duan),發現問題立即執(zhi)行預(yu)先(xian)設定的(de)程序,自動采取措施并(bing)報警(jing),實現安(an)全運行。
5.一體化(hua)結構(gou)。智能調節(jie)閥把(ba)閥體、控制電路、傳(chuan)感器、執行機構(gou)全部裝在一個(ge)現場儀器中。
五、結語
電動執(zhi)行機(ji)(ji)構(gou)(gou)與調節機(ji)(ji)構(gou)(gou)的(de)鏈接有多種方式,一般(ban)是將兩者(zhe)固定安裝(zhuang)在一起(qi),構(gou)(gou)成(cheng)一個完整(zheng)執(zhi)行器(qi),也有用(yong)機(ji)(ji)械連桿(gan)把(ba)兩者(zhe)就地連接起(qi)來。隨著電子(zi)技術的(de)迅速(su)發展(zhan),微(wei)處(chu)理器(qi)被引入到儀表中,出現了智(zhi)能(neng)式執(zhi)行器(qi),把(ba)常規儀表的(de)檢測、控制(zhi)、調節等功(gong)能(neng)有機(ji)(ji)組合在一起(qi),具備了多種功(gong)能(neng)并被廣泛應用(yong)于生(sheng)產(chan)和生(sheng)活中。