最近給一石料廠維修一臺傳送帶電動機線路,發現了一款小型的斷相保護器。由于(yu)以前沒見過,感覺很好奇(qi),便(bian)進行了拆(chai)卸。拆(chai)卸后(hou),見元器件少,電(dian)路(lu)簡單,便(bian)繪制出了接線圖(tu),共同行參考。
它的(de)動作原理是(shi):當運行中(zhong)的(de)電(dian)(dian)(dian)動機有斷相時,電(dian)(dian)(dian)動機的(de)中(zhong)性點(dian)不是(shi)零電(dian)(dian)(dian)位,與地形(xing)成電(dian)(dian)(dian)位差,此電(dian)(dian)(dian)壓(ya)經整(zheng)流穩壓(ya),使繼電(dian)(dian)(dian)器J得(de)電(dian)(dian)(dian)吸合,常閉點(dian)斷開,接觸器C線圈供電(dian)(dian)(dian)被切斷,C斷電(dian)(dian)(dian)釋放,從而(er)保護電(dian)(dian)(dian)動機不因缺(que)相而(er)燒(shao)毀。
斷相保護器概念簡介
三(san)相電(dian)動機(ji)“斷相保(bao)護”的研究
隨著工農業生產(chan)的(de)(de)(de)發展,三(san)(san)相(xiang)(xiang)電(dian)(dian)動(dong)機(ji)得到了(le)廣泛的(de)(de)(de)應用,在(zai)生產(chan)機(ji)械的(de)(de)(de)電(dian)(dian)氣控(kong)制(zhi)線路中,采取了(le)對電(dian)(dian)動(dong)機(ji)的(de)(de)(de)各種保護措施。由于(yu)過流保護、短路保護、欠(qian)壓(ya)保護、過載保護及零壓(ya)保護很容易(yi)實現控(kong)制(zhi),但在(zai)很多(duo)斷相(xiang)(xiang)情況(kuang)下,三(san)(san)相(xiang)(xiang)電(dian)(dian)動(dong)機(ji)低(di)速運轉,定子電(dian)(dian)流很大,很容易(yi)造成電(dian)(dian)動(dong)機(ji)的(de)(de)(de)燒毀,經(jing)濟損失嚴重。因(yin)此,對三(san)(san)相(xiang)(xiang)電(dian)(dian)動(dong)機(ji)“斷相(xiang)(xiang)保護”的(de)(de)(de)研究也(ye)越(yue)來越(yue)受關注(zhu)。
從電(dian)(dian)流(liu)(liu)方(fang)面看,目前(qian)常(chang)用(yong)的三相(xiang)(xiang)(xiang)電(dian)(dian)動(dong)機(ji)(ji)斷(duan)(duan)相(xiang)(xiang)(xiang)保(bao)(bao)護(hu)(hu)器,用(yong)戶使(shi)用(yong)時(shi)大多數(shu)不(bu)(bu)(bu)會配比(bi)、計(ji)算與調試,很(hen)不(bu)(bu)(bu)方(fang)便,而且(qie)斷(duan)(duan)相(xiang)(xiang)(xiang)后(hou)沒有記憶功能,不(bu)(bu)(bu)能與閘(zha)刀配合使(shi)用(yong),使(shi)用(yong)范圍(wei)受到限制;從接線方(fang)面看,對(dui)(dui)Y型(xing)聯接的電(dian)(dian)動(dong)機(ji)(ji),當(dang)某(mou)相(xiang)(xiang)(xiang)斷(duan)(duan)相(xiang)(xiang)(xiang)則(ze)該(gai)相(xiang)(xiang)(xiang)無(wu)電(dian)(dian)流(liu)(liu),而另兩(liang)相(xiang)(xiang)(xiang)中有某(mou)相(xiang)(xiang)(xiang)電(dian)(dian)流(liu)(liu)比(bi)額(e)定電(dian)(dian)流(liu)(liu)高時(shi),則(ze)將使(shi)該(gai)相(xiang)(xiang)(xiang)保(bao)(bao)護(hu)(hu)器切(qie)斷(duan)(duan)電(dian)(dian)源,使(shi)電(dian)(dian)動(dong)機(ji)(ji)停止運行,從而實現斷(duan)(duan)相(xiang)(xiang)(xiang)保(bao)(bao)護(hu)(hu)。而△型(xing)聯接中情況就不(bu)(bu)(bu)一樣,在保(bao)(bao)護(hu)(hu)器保(bao)(bao)護(hu)(hu)的情況下(xia)仍將電(dian)(dian)動(dong)機(ji)(ji)燒毀(hui),達(da)不(bu)(bu)(bu)到斷(duan)(duan)相(xiang)(xiang)(xiang)保(bao)(bao)護(hu)(hu)的目的。所以,對(dui)(dui)Y型(xing)聯接的電(dian)(dian)動(dong)機(ji)(ji)采用(yong)電(dian)(dian)流(liu)(liu)型(xing)、熱效(xiao)應型(xing)作(zuo)斷(duan)(duan)相(xiang)(xiang)(xiang)保(bao)(bao)護(hu)(hu),對(dui)(dui)△型(xing)聯接的電(dian)(dian)動(dong)機(ji)(ji)斷(duan)(duan)相(xiang)(xiang)(xiang)保(bao)(bao)護(hu)(hu)采用(yong)電(dian)(dian)壓型(xing)作(zuo)斷(duan)(duan)相(xiang)(xiang)(xiang)保(bao)(bao)護(hu)(hu)。
電(dian)壓(ya)型(xing)電(dian)動(dong)機斷相(xiang)保護器,在(zai)Y型(xing)、△型(xing)聯接的電(dian)動(dong)機中都能(neng)起斷相(xiang)保護作用(yong),克服了(le)熱效應(ying)型(xing)、電(dian)流型(xing)在(zai)電(dian)動(dong)機斷相(xiang)保護中的局限性,而且(qie)具有低(di)電(dian)壓(ya)、過電(dian)壓(ya)保護功能(neng),適用(yong)于三相(xiang)四(si)線380V供(gong)電(dian)條件下的各(ge)種電(dian)動(dong)機。
運行因素
在(zai)三(san)相(xiang)(xiang)電(dian)(dian)動機(ji)的(de)使(shi)用過(guo)程中(zhong),經常出現其因缺相(xiang)(xiang)運(yun)行而燒毀(hui)的(de)情況,根據研(yan)究,以下幾個方面(mian)的(de)因素(su)只要存在(zai)一條(tiao),就可導致電(dian)(dian)動機(ji)的(de)斷相(xiang)(xiang)運(yun)行。
(1)某(mou)相熔體燒斷。
(2)控制電動(dong)機(ji)的閘刀開關(guan)如果不(bu)及時檢(jian)修(xiu),質量較差,再加上長時間(jian)使用,也會(hui)發(fa)生(sheng)斷相故(gu)障。
(3)當用電(dian)量集中時,在變壓器低壓出口的保險片和配電(dian)室內(nei)供(gong)電(dian)總閘刀(dao)熔(rong)斷器容易熔(rong)斷。
(4)電動(dong)機中某相(xiang)繞組內部接頭斷線(xian)或(huo)者是導線(xian)接頭接觸不良都(dou)會造成(cheng)斷相(xiang)運行(xing)。
(5)操作頻率(lv)過(guo)高或者負(fu)載較大時,造成電動機短路,從(cong)而燒(shao)斷熱元件。
(6)當電(dian)動機超(chao)負載(zai)運行(xing)、故障運行(xing)、供電(dian)線路電(dian)壓(ya)不(bu)(bu)穩定或者交流接(jie)觸器容量選擇不(bu)(bu)當時,會造成(cheng)主觸頭接(jie)觸不(bu)(bu)良,導致斷相運行(xing)。
斷相保護原理
電(dian)(dian)動機斷相保護裝置的(de)電(dian)(dian)路(lu)(lu)共有(you)六個外(wai)(wai)接(jie)端(duan)子,其中N是(shi)接(jie)電(dian)(dian)源的(de)零(ling)線,A、B、C是(shi)接(jie)主電(dian)(dian)路(lu)(lu)對應(ying)的(de)A相B相和C相,IN和OUT兩個接(jie)線端(duan)與控制回路(lu)(lu)電(dian)(dian)源串接(jie)。每(mei)個外(wai)(wai)接(jie)端(duan)子的(de)內部(bu)都是(shi)固有(you)部(bu)件,必須一(yi)(yi)(yi)一(yi)(yi)(yi)對應(ying),同時,柱(zhu)與柱(zhu)之間的(de)距離(li)應(ying)盡可能地大(da),這樣可以防止并聯接(jie)線柱(zhu)之間短(duan)路(lu)(lu)。因此,這些固有(you)部(bu)件一(yi)(yi)(yi)定要謹慎接(jie)好,接(jie)錯時還(huan)有(you)可能燒(shao)壞保護裝置。
斷相保護方法
電動機(ji)斷(duan)(duan)相(xiang)保(bao)(bao)護(hu)的(de)方法有:采(cai)用(yong)電壓(ya)繼(ji)(ji)電器、采(cai)用(yong)斷(duan)(duan)絲(si)電壓(ya)保(bao)(bao)護(hu)、采(cai)用(yong)帶斷(duan)(duan)相(xiang)保(bao)(bao)護(hu)的(de)熱繼(ji)(ji)電器、采(cai)用(yong)專門為(wei)斷(duan)(duan)相(xiang)運(yun)行而(er)設計的(de)斷(duan)(duan)相(xiang)保(bao)(bao)護(hu)繼(ji)(ji)電器、采(cai)用(yong)欠(qian)電流繼(ji)(ji)電器等。
斷相保護的目的
在(zai)三(san)相(xiang)電(dian)(dian)動(dong)機的(de)(de)運行中,只(zhi)要有以下情況之一(yi)(yi)(yi),如接(jie)(jie)觸器(qi)觸點燒損(sun)等造成(cheng)(cheng)一(yi)(yi)(yi)相(xiang)接(jie)(jie)觸不良(liang),安裝維護等原因造成(cheng)(cheng)一(yi)(yi)(yi)相(xiang)斷(duan)(duan)線或(huo)者三(san)相(xiang)電(dian)(dian)源的(de)(de)熔(rong)斷(duan)(duan)器(qi)一(yi)(yi)(yi)相(xiang)熔(rong)斷(duan)(duan),都會造成(cheng)(cheng)三(san)相(xiang)電(dian)(dian)動(dong)機斷(duan)(duan)相(xiang)運行。如果(guo)發現(xian)不及(ji)(ji)時,還會造成(cheng)(cheng)電(dian)(dian)動(dong)機的(de)(de)燒毀以及(ji)(ji)設備的(de)(de)損(sun)壞,從(cong)而影(ying)響連續(xu)的(de)(de)生產,造成(cheng)(cheng)一(yi)(yi)(yi)定的(de)(de)損(sun)失。
為了保障電(dian)動(dong)機(ji)的(de)(de)安全(quan)運行,一般(ban)重要電(dian)動(dong)機(ji)都裝有各種斷相保護裝置(zhi),以防(fang)在發生缺相時(shi)造成(cheng)電(dian)動(dong)機(ji)的(de)(de)燒毀(hui),盡可能減少不必要的(de)(de)損(sun)失。
基本原理
當(dang)今的(de)電動機缺相保護電路線路復(fu)雜,元(yuan)件較多,工作可靠性不高(gao),大部(bu)分采用電子(zi)式保護裝(zhuang)置,或者由于工作失(shi)常,造成電動機不能合(he)閘(zha)或保護拒(ju)動,影響生產的(de)順利進(jin)行。
本(ben)文介紹的保護裝置(zhi)不僅具有(you)元件(jian)少,原理簡單,基(ji)本(ben)不需維護、工作可靠等多方(fang)面的特點,而(er)且(qie)通過盡可能(neng)適當(dang)的配置(zhi)元件(jian),還可起(qi)到無功補償的作用(yong)。
該保護裝置(zhi)的(de)原理(li)是(shi):三(san)相(xiang)(xiang)(xiang)星形接線的(de)中性(xing)點(dian),三(san)相(xiang)(xiang)(xiang)負載平(ping)衡時電(dian)(dian)(dian)位基本是(shi)低電(dian)(dian)(dian)位,當(dang)三(san)相(xiang)(xiang)(xiang)電(dian)(dian)(dian)源(yuan)缺(que)相(xiang)(xiang)(xiang)時,中性(xing)點(dian)電(dian)(dian)(dian)位會(hui)升高(gao)到(dao)相(xiang)(xiang)(xiang)電(dian)(dian)(dian)壓。根據此特點(dian)監測電(dian)(dian)(dian)源(yuan)的(de)供電(dian)(dian)(dian)情況,可以起(qi)到(dao)缺(que)相(xiang)(xiang)(xiang)保護作用。
接線說明
接(jie)線時,三(san)個電(dian)(dian)容器(qi)接(jie)成星形,電(dian)(dian)容器(qi)端子(zi)分別接(jie)A、B、C三(san)相(xiang)(xiang)(xiang)電(dian)(dian)源,中性(xing)(xing)點(dian)接(jie)電(dian)(dian)壓(ya)繼(ji)電(dian)(dian)器(qi)的(de)線圈(quan),線圈(quan)另一端接(jie)地(di)。電(dian)(dian)壓(ya)繼(ji)電(dian)(dian)器(qi)的(de)常(chang)閉(bi)接(jie)點(dian)應串接(jie)于交(jiao)流(liu)(liu)接(jie)觸(chu)器(qi)的(de)控制回(hui)路(lu)中。當A、B、C任一相(xiang)(xiang)(xiang)斷開(kai)時,中性(xing)(xing)點(dian)電(dian)(dian)位升(sheng)高為(wei)相(xiang)(xiang)(xiang)電(dian)(dian)壓(ya),電(dian)(dian)壓(ya)繼(ji)電(dian)(dian)器(qi)動作(zuo),使交(jiao)流(liu)(liu)接(jie)觸(chu)器(qi)的(de)控制回(hui)路(lu)斷開(kai),切除電(dian)(dian)動機(ji)電(dian)(dian)源,實(shi)現了斷相(xiang)(xiang)(xiang)保護。
對于低電(dian)(dian)壓電(dian)(dian)動(dong)機來講,主要(yao)是耐壓水平足夠(gou)就可以(yi),電(dian)(dian)容(rong)器容(rong)量不需太大。在選擇電(dian)(dian)容(rong)器容(rong)量時,可以(yi)結合(he)電(dian)(dian)動(dong)機的(de)功率選擇合(he)適的(de)電(dian)(dian)容(rong)值。
對于(yu)高壓電動(dong)機,其保(bao)(bao)護(hu)裝置(zhi)相對完(wan)善。這種保(bao)(bao)護(hu)裝置(zhi)適用于(yu)各(ge)類三相感應(ying)式電動(dong)機,接線簡單,基本(ben)不占用空間,容易實現。
分類
從(cong)保護原理上(shang)看,可分為(wei)兩類(lei):一(yi)、基(ji)于電(dian)(dian)壓(ya)的(de)斷相(xiang)(xiang)(xiang)(xiang)(xiang)保護。原理是(shi)通過(guo)檢測電(dian)(dian)源(yuan)電(dian)(dian)壓(ya)來發(fa)現是(shi)否(fou)存在缺(que)(que)相(xiang)(xiang)(xiang)(xiang)(xiang)。一(yi)般這類(lei)產品往往兼(jian)有相(xiang)(xiang)(xiang)(xiang)(xiang)序(xu)保護功能(neng),稱為(wei)“電(dian)(dian)壓(ya)相(xiang)(xiang)(xiang)(xiang)(xiang)序(xu)繼電(dian)(dian)器”。優(you)點(dian)是(shi)使用(yong)簡單,一(yi)臺“電(dian)(dian)壓(ya)相(xiang)(xiang)(xiang)(xiang)(xiang)序(xu)繼電(dian)(dian)器”能(neng)保護多臺電(dian)(dian)動(dong)(dong)機(ji)(ji),缺(que)(que)點(dian)是(shi)只能(neng)對電(dian)(dian)源(yuan)缺(que)(que)相(xiang)(xiang)(xiang)(xiang)(xiang)進行(xing)保護,對于交(jiao)流接觸器觸點(dian)接觸不(bu)良等造成(cheng)的(de)電(dian)(dian)動(dong)(dong)機(ji)(ji)缺(que)(que)相(xiang)(xiang)(xiang)(xiang)(xiang)不(bu)起保護作用(yong)。另外(wai),對于動(dong)(dong)態缺(que)(que)相(xiang)(xiang)(xiang)(xiang)(xiang)(即電(dian)(dian)動(dong)(dong)機(ji)(ji)運(yun)轉后再發(fa)生的(de)缺(que)(que)相(xiang)(xiang)(xiang)(xiang)(xiang)),因電(dian)(dian)動(dong)(dong)機(ji)(ji)的(de)發(fa)電(dian)(dian)作用(yong),失電(dian)(dian)的(de)那一(yi)相(xiang)(xiang)(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)并不(bu)為(wei)零,而通常(chang)只比正常(chang)的(de)相(xiang)(xiang)(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)略低,這類(lei)產品的(de)誤(wu)判率較(jiao)高。
二、基于電流的斷相保護
通常(chang)是(shi)(shi)(shi)用電(dian)(dian)流(liu)(liu)互感器(qi)檢測電(dian)(dian)動(dong)機(ji)三相(xiang)(xiang)電(dian)(dian)流(liu)(liu),不(bu)(bu)(bu)論是(shi)(shi)(shi)電(dian)(dian)源故障還是(shi)(shi)(shi)交流(liu)(liu)接觸器(qi)觸點接觸不(bu)(bu)(bu)良,都能保(bao)(bao)護(hu)(hu)。這類(lei)產(chan)品通常(chang)叫做“電(dian)(dian)動(dong)機(ji)綜(zong)合保(bao)(bao)護(hu)(hu)器(qi)”,集(ji)過載保(bao)(bao)護(hu)(hu)、缺相(xiang)(xiang)保(bao)(bao)護(hu)(hu),三相(xiang)(xiang)不(bu)(bu)(bu)平衡保(bao)(bao)護(hu)(hu)等(deng)功(gong)能于一(yi)身。這類(lei)產(chan)品又分電(dian)(dian)子式和(he)智能型兩大類(lei),電(dian)(dian)子式的(de)功(gong)能較(jiao)簡單,價格便宜,目前市(shi)面上的(de)產(chan)品性能和(he)質(zhi)量良莠不(bu)(bu)(bu)齊,從幾(ji)十元到一(yi)兩百元一(yi)個不(bu)(bu)(bu)等(deng),基本選擇原則還是(shi)(shi)(shi)一(yi)分價錢(qian)一(yi)分貨。智能型功(gong)能完(wan)(wan)善但價格較(jiao)貴,最明(ming)顯(xian)的(de)特征是(shi)(shi)(shi)智能型一(yi)般都可以顯(xian)示電(dian)(dian)流(liu)(liu)。目前市(shi)面上有一(yi)種叫“維繼”的(de)產(chan)品,性能和(he)價格都比較(jiao)適(shi)中(zhong),對(dui)電(dian)(dian)機(ji)斷相(xiang)(xiang)的(de)保(bao)(bao)護(hu)(hu)比較(jiao)完(wan)(wan)善。電(dian)(dian)動(dong)機(ji)燒毀有60%是(shi)(shi)(shi)因為缺相(xiang)(xiang)引(yin)起(qi)的(de),所以電(dian)(dian)動(dong)機(ji)的(de)斷相(xiang)(xiang)保(bao)(bao)護(hu)(hu)非常(chang)重要。
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