干擾源類型及對控制板系統的干擾

1. 來自空間的輻射干擾

空(kong)間的(de)輻(fu)射(she)(she)電(dian)磁場(chang)主要來自電(dian)力網(wang)絡、雷電(dian)、無線電(dian)廣(guang)播、電(dian)視、雷達、高頻感(gan)應加熱設備，其分布極為復雜。若控制板系統置于所射(she)(she)頻場(chang)內(nei)。就(jiu)會受到(dao)輻(fu)射(she)(she)干擾(rao)，其影響主要通過(guo)兩條(tiao)路(lu)徑(jing):一(yi)是對控制板通信網(wang)絡的(de)輻(fu)射(she)(she)，由通信線路(lu)的(de)感(gan)應引人(ren)干擾(rao);二是直接對控制板內(nei)部(bu)的(de)輻(fu)射(she)(she)，由電(dian)路(lu)感(gan)應產生干擾(rao)。

2. 來自系統外引線的干擾

a. 來自電源的干擾

控(kong)制板系統的正常供電(dian)(dian)電(dian)(dian)源均由(you)電(dian)(dian)網供電(dian)(dian)。由(you)于電(dian)(dian)網覆蓋范圍(wei)廣，它(ta)將受(shou)到所(suo)有空間電(dian)(dian)磁干擾而在線(xian)路(lu)上感(gan)應出電(dian)(dian)壓和電(dian)(dian)流(liu)。尤其(qi)是電(dian)(dian)網內(nei)部的變化，開關操作(zuo)浪(lang)涌、大型電(dian)(dian)力設備起停、電(dian)(dian)網短路(lu)暫態沖擊等(deng)，都(dou)通過輸電(dian)(dian)線(xian)路(lu)傳到電(dian)(dian)源。控(kong)制板電(dian)(dian)源通常采(cai)用隔(ge)離(li)電(dian)(dian)源，但其(qi)機(ji)構及制造工藝(yi)因素使其(qi)隔(ge)離(li)性并不理想。

b. 來自信號線引入的干擾

控制板(ban)系(xi)(xi)統連接(jie)的(de)各類(lei)(lei)信(xin)(xin)號(hao)(hao)傳輸線，除了傳輸有效的(de)各類(lei)(lei)信(xin)(xin)息之外，總會有外部(bu)干(gan)(gan)擾(rao)信(xin)(xin)號(hao)(hao)侵(qin)入。此干(gan)(gan)擾(rao)主要(yao)有兩種(zhong)途徑(jing):一是通(tong)過(guo)變送器供電(dian)電(dian)源或共用(yong)信(xin)(xin)號(hao)(hao)儀表的(de)供電(dian)電(dian)源串入的(de)電(dian)網(wang)干(gan)(gan)擾(rao);二是信(xin)(xin)號(hao)(hao)線受空間電(dian)磁輻射感應(ying)的(de)干(gan)(gan)擾(rao)，即(ji)信(xin)(xin)號(hao)(hao)線上的(de)外部(bu)感應(ying)干(gan)(gan)擾(rao)，這是很(hen)嚴重的(de)。由信(xin)(xin)號(hao)(hao)引(yin)(yin)(yin)(yin)入干(gan)(gan)擾(rao)會引(yin)(yin)(yin)(yin)起(qi)vo信(xin)(xin)號(hao)(hao)工作(zuo)異常和測量精(jing)度的(de)降低，嚴重時將引(yin)(yin)(yin)(yin)起(qi)元器件(jian)損傷。對于隔離性能差的(de)系(xi)(xi)統，還將導致信(xin)(xin)號(hao)(hao)間互相(xiang)干(gan)(gan)擾(rao)，引(yin)(yin)(yin)(yin)起(qi)共地系(xi)(xi)統總線回流，造成(cheng)邏輯數(shu)據變化(hua)、誤動和死(si)機。

c. 來自接地系統混亂時的干擾

接(jie)地(di)(di)(di)(di)是(shi)提高電(dian)子設備電(dian)磁(ci)兼容性的(de)(de)(de)(de)有(you)效手段(duan)之(zhi)(zhi)一。正確地(di)(di)(di)(di)接(jie)地(di)(di)(di)(di)，既能抑制電(dian)磁(ci)干(gan)擾(rao)(rao)的(de)(de)(de)(de)影響，又能抑制設備向外發出(chu)干(gan)擾(rao)(rao);而(er)錯誤(wu)的(de)(de)(de)(de)接(jie)地(di)(di)(di)(di)，反而(er)會引入(ru)嚴重的(de)(de)(de)(de)干(gan)擾(rao)(rao)信號(hao)，使控(kong)(kong)(kong)制板(ban)系(xi)統將(jiang)無法正常(chang)(chang)工作(zuo)。接(jie)地(di)(di)(di)(di)系(xi)統混亂對(dui)控(kong)(kong)(kong)制板(ban)系(xi)統的(de)(de)(de)(de)干(gan)擾(rao)(rao)主要是(shi)各個接(jie)地(di)(di)(di)(di)點(dian)電(dian)位(wei)分布不(bu)均，不(bu)同接(jie)地(di)(di)(di)(di)點(dian)間(jian)存在(zai)(zai)地(di)(di)(di)(di)電(dian)位(wei)差(cha)，引起(qi)地(di)(di)(di)(di)環路(lu)電(dian)流，影響系(xi)統正常(chang)(chang)工作(zuo)。例如電(dian)纜(lan)(lan)屏(ping)蔽(bi)層(ceng)必須一點(dian)接(jie)地(di)(di)(di)(di)，如果電(dian)纜(lan)(lan)屏(ping)蔽(bi)層(ceng)兩端(duan)都接(jie)地(di)(di)(di)(di)，就存在(zai)(zai)地(di)(di)(di)(di)電(dian)位(wei)差(cha)，這時(shi)就有(you)電(dian)流流過屏(ping)蔽(bi)層(ceng)，當(dang)發生(sheng)異常(chang)(chang)狀態如雷擊時(shi)，地(di)(di)(di)(di)線(xian)電(dian)流將(jiang)更大(da)。此(ci)外，屏(ping)蔽(bi)層(ceng)、接(jie)地(di)(di)(di)(di)線(xian)和地(di)(di)(di)(di)之(zhi)(zhi)間(jian)有(you)可能構成閉(bi)合環路(lu)，在(zai)(zai)變化磁(ci)場的(de)(de)(de)(de)作(zuo)用(yong)下(xia)(xia)，屏(ping)蔽(bi)層(ceng)內又會出(chu)現感應電(dian)流，通(tong)過屏(ping)蔽(bi)層(ceng)與(yu)芯線(xian)之(zhi)(zhi)間(jian)的(de)(de)(de)(de)禍合，干(gan)擾(rao)(rao)信號(hao)形成回路(lu)。模擬(ni)地(di)(di)(di)(di)電(dian)位(wei)的(de)(de)(de)(de)分布將(jiang)導致測(ce)量(liang)精(jing)度下(xia)(xia)降，引起(qi)對(dui)信號(hao)測(ce)控(kong)(kong)(kong)的(de)(de)(de)(de)嚴重失真和誤(wu)動作(zuo)。控(kong)(kong)(kong)制板(ban)工作(zuo)的(de)(de)(de)(de)邏輯電(dian)壓干(gan)擾(rao)(rao)容限較低(di)，邏輯地(di)(di)(di)(di)電(dian)位(wei)的(de)(de)(de)(de)分布干(gan)擾(rao)(rao)容易(yi)影響控(kong)(kong)(kong)制板(ban)的(de)(de)(de)(de)邏輯運算和數據存貯，造成數據混亂、程序跑(pao)飛或死(si)機。

控制板抗干擾設計的一般方法

抑制電磁干擾(rao)的基本原則(ze)是(shi)抑制干擾(rao)源、切斷或衰減電磁干擾(rao)的傳播途徑、提高裝置和(he)系統的抗干擾(rao)能(neng)力。

1. 設備選型

在(zai)選(xuan)(xuan)擇設(she)備時(shi)，首先要(yao)選(xuan)(xuan)擇有較高(gao)抗(kang)(kang)干(gan)擾(rao)能力的(de)產品(pin)，其次還應(ying)了解生產廠給出的(de)抗(kang)(kang)干(gan)擾(rao)指標，如耐(nai)壓(ya)能力、共模抑制比，對(dui)最(zui)大電(dian)場(chang)強度和最(zui)高(gao)頻率范圍設(she)置。另外考察其在(zai)類似工(gong)作(zuo)中的(de)應(ying)用(yong)實績。如果(guo)選(xuan)(xuan)擇國(guo)外進口產品(pin)要(yao)注意(yi):我國(guo)是采用(yong)220v高(gao)內阻電(dian)網(wang)制式(shi)，比如日本是110v低內阻電(dian)網(wang)。由于我國(guo)電(dian)網(wang)內阻大，零點電(dian)位(wei)漂移大，地電(dian)位(wei)變化大，工(gong)業企業現場(chang)的(de)電(dian)磁干(gan)擾(rao)至少要(yao)比日本高(gao)4倍以上，對(dui)系(xi)統(tong)抗(kang)(kang)干(gan)擾(rao)性能要(yao)求更高(gao)，在(zai)國(guo)外能正(zheng)常(chang)工(gong)作(zuo)的(de)控制板產品(pin)在(zai)國(guo)內工(gong)業就不一定能可靠運行，這就要(yao)求在(zai)采用(yong)國(guo)外產品(pin)時(shi)，按我國(guo)的(de)標準((GB/T13926)合理選(xuan)(xuan)擇。

2. 設計施工中的抗干擾設計

為保(bao)證(zheng)系統(tong)在(zai)工業(ye)電(dian)(dian)磁(ci)環境中免(mian)受或減(jian)少(shao)內外電(dian)(dian)磁(ci)干(gan)擾，必須(xu)綜合抗干(gan)擾設(she)(she)計，在(zai)設(she)(she)計階(jie)段采(cai)取(qu)措施。綜合抗干(gan)擾設(she)(she)計主要(yao)內容包括:對(dui)控制板(ban)'系統(tong)及外引(yin)線進(jin)行(xing)屏蔽以防空間輻射電(dian)(dian)磁(ci)干(gan)擾;對(dui)外引(yin)線進(jin)行(xing)隔(ge)離、濾波，特別是動(dong)力電(dian)(dian)纜，應該與信號線分(fen)層布置，以防通過外引(yin)線引(yin)入(ru)傳導(dao)電(dian)(dian)磁(ci)干(gan)擾;正確設(she)(she)計接(jie)(jie)地(di)點和接(jie)(jie)地(di)裝置，完善(shan)接(jie)(jie)地(di)系統(tong)。

主要抗干擾措施

1. 采用性能優良的電源

在(zai)控(kong)制(zhi)(zhi)(zhi)板(ban)(ban)系(xi)統(tong)(tong)中，電(dian)(dian)(dian)(dian)(dian)源(yuan)占有(you)十分(fen)重要(yao)的地位。電(dian)(dian)(dian)(dian)(dian)網(wang)干(gan)擾串入控(kong)制(zhi)(zhi)(zhi)板(ban)(ban)系(xi)統(tong)(tong)主要(yao)通(tong)過控(kong)制(zhi)(zhi)(zhi)板(ban)(ban)系(xi)統(tong)(tong)的供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)、變送(song)器供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)和(he)(he)與控(kong)制(zhi)(zhi)(zhi)板(ban)(ban)系(xi)統(tong)(tong)具有(you)直接電(dian)(dian)(dian)(dian)(dian)氣(qi)(qi)連接的儀表(biao)供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)等藕合進入的。對(dui)于控(kong)制(zhi)(zhi)(zhi)板(ban)(ban)系(xi)統(tong)(tong)供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)(dian)源(yuan)，一(yi)般都(dou)采用(yong)隔離性能(neng)較好電(dian)(dian)(dian)(dian)(dian)源(yuan);而對(dui)于變送(song)器供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)(dian)源(yuan)和(he)(he)控(kong)制(zhi)(zhi)(zhi)板(ban)(ban)系(xi)統(tong)(tong)有(you)直接電(dian)(dian)(dian)(dian)(dian)氣(qi)(qi)連接的儀表(biao)的供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)，選擇分(fen)布電(dian)(dian)(dian)(dian)(dian)容小、抑制(zhi)(zhi)(zhi)性強的配(pei)電(dian)(dian)(dian)(dian)(dian)器，抑制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)網(wang)引入的干(gan)擾。

2. 電纜選擇和敷設

為(wei)了減少(shao)動(dong)力(li)(li)電(dian)(dian)纜(lan)(lan)輻射電(dian)(dian)磁干(gan)擾(rao)，不(bu)(bu)同類型(xing)的信(xin)號(hao)分別由不(bu)(bu)同電(dian)(dian)纜(lan)(lan)傳(chuan)輸(shu)，信(xin)號(hao)電(dian)(dian)纜(lan)(lan)應(ying)按(an)傳(chuan)輸(shu)信(xin)號(hao)種類分層敷設(she)，嚴(yan)禁用同一(yi)電(dian)(dian)纜(lan)(lan)的不(bu)(bu)同導線(xian)同時傳(chuan)送動(dong)力(li)(li)電(dian)(dian)源和信(xin)號(hao)，避(bi)免信(xin)號(hao)線(xian)與(yu)動(dong)力(li)(li)電(dian)(dian)纜(lan)(lan)靠(kao)近平(ping)行敷設(she).以減少(shao)電(dian)(dian)磁干(gan)擾(rao)。

3. 硬件濾波及軟件抗干擾措施

信號在接入計算(suan)機前，在信號線(xian)與地間并聯電容，以(yi)減少共模干(gan)(gan)擾(rao)。由于電磁干(gan)(gan)擾(rao)的(de)復雜性，要(yao)根本消除干(gan)(gan)擾(rao)影響是不可能(neng)的(de)，困此在控制板系統的(de)軟(ruan)件設計和組態(tai)時，還應在軟(ruan)件方面進行抗干(gan)(gan)擾(rao)處理，進一(yi)步提高系統的(de)可靠性。

4. 選擇正確接地點系統

接(jie)(jie)(jie)地(di)(di)(di)(di)的(de)(de)目的(de)(de)通常(chang)有兩(liang)個，其一(yi)(yi)(yi)為了安全，其二是為了抑制(zhi)(zhi)干(gan)擾。完善的(de)(de)接(jie)(jie)(jie)地(di)(di)(di)(di)系統(tong)(tong)(tong)是控(kong)(kong)制(zhi)(zhi)板(ban)系統(tong)(tong)(tong)抗電磁干(gan)擾的(de)(de)重要措施之一(yi)(yi)(yi)。系統(tong)(tong)(tong)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)(fang)式有:浮地(di)(di)(di)(di)方(fang)(fang)式、直接(jie)(jie)(jie)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)(fang)式和電容接(jie)(jie)(jie)地(di)(di)(di)(di)三種(zhong)方(fang)(fang)式。對控(kong)(kong)制(zhi)(zhi)板(ban)系統(tong)(tong)(tong)而言，它屬高(gao)速低(di)電平控(kong)(kong)制(zhi)(zhi)裝(zhuang)(zhuang)置(zhi)(zhi)，應(ying)采用(yong)直接(jie)(jie)(jie)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)(fang)式。由于(yu)(yu)信(xin)號(hao)(hao)電纜分(fen)布電容和輸入裝(zhuang)(zhuang)置(zhi)(zhi)濾波(bo)等的(de)(de)影響，裝(zhuang)(zhuang)置(zhi)(zhi)之間(jian)的(de)(de)信(xin)號(hao)(hao)交(jiao)換頻率一(yi)(yi)(yi)般都(dou)低(di)于(yu)(yu)l MHz，所(suo)以控(kong)(kong)制(zhi)(zhi)板(ban)系統(tong)(tong)(tong)接(jie)(jie)(jie)地(di)(di)(di)(di)線采用(yong)一(yi)(yi)(yi)點接(jie)(jie)(jie)地(di)(di)(di)(di)和串聯一(yi)(yi)(yi)點接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)(fang)式。集中布置(zhi)(zhi)的(de)(de)控(kong)(kong)制(zhi)(zhi)板(ban)系統(tong)(tong)(tong)適于(yu)(yu)并(bing)聯一(yi)(yi)(yi)點接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)(fang)式，各裝(zhuang)(zhuang)置(zhi)(zhi)的(de)(de)柜體(ti)中心接(jie)(jie)(jie)地(di)(di)(di)(di)點以單獨的(de)(de)接(jie)(jie)(jie)地(di)(di)(di)(di)線引向接(jie)(jie)(jie)地(di)(di)(di)(di)極。如果(guo)裝(zhuang)(zhuang)置(zhi)(zhi)間(jian)距(ju)較大，應(ying)采用(yong)串聯一(yi)(yi)(yi)點接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)(fang)式。

5. 控制板輸入、輸出信號回路采用光電隔離

利(li)用(yong)光(guang)電(dian)禍合器(qi)的(de)(de)開(kai)關特性(xing)實現(xian)輸人和(he)(he)輸出信號的(de)(de)完全隔(ge)離，已成為抑制干擾的(de)(de)有效措施(shi)之一。光(guang)電(dian)輻合器(qi)把(ba)各種模擬負(fu)載和(he)(he)數字(zi)信息(xi)源隔(ge)離開(kai)來，也就是把(ba)“模擬的(de)(de)”和(he)(he)“數字(zi)的(de)(de)”斷開(kai)。光(guang)電(dian)藕合器(qi)能實現(xian)良好隔(ge)離的(de)(de)原(yuan)因有三個。

a. 由于光電(dian)(dian)(dian)棍合(he)器輸入電(dian)(dian)(dian)阻(zu)抗很(hen)小而干(gan)擾源的(de)內阻(zu)則(ze)很(hen)大(da)，因此(ci)分壓到(dao)光電(dian)(dian)(dian)藕合(he)器輸入端(duan)的(de)干(gan)擾信號(hao)較(jiao)小，輸入回路(lu)與輸出回路(lu)之間分布電(dian)(dian)(dian)容極(ji)小，而且絕(jue)緣電(dian)(dian)(dian)阻(zu)較(jiao)高，因此(ci)回路(lu)一(yi)邊(bian)的(de)干(gan)擾很(hen)難通過(guo)光電(dian)(dian)(dian)藕合(he)的(de)回饋(kui)送到(dao)另一(yi)邊(bian);

b. 光(guang)電藕合器在密封條件下實現(xian)輸入回(hui)路與輸出回(hui)路的光(guang)禍合，不(bu)會受外(wai)界光(guang)的影(ying)響;

c. 無論(lun)是(shi)模擬還是(shi)數字(zi)信(xin)(xin)號，在輸(shu)(shu)入、輸(shu)(shu)出通道上都(dou)采(cai)用光電禍合(he)電路，用光線來藕合(he)信(xin)(xin)號，使(shi)輸(shu)(shu)人(ren)、輸(shu)(shu)出沒有電的直接聯系(xi)(xi)(xi)，可以(yi)有效地防止(zhi)漏電、短路、打火、感應引起的過(guo)電壓(ya)串入控(kong)(kong)制(zhi)板系(xi)(xi)(xi)統(tong)(tong)。因此在控(kong)(kong)制(zhi)板系(xi)(xi)(xi)統(tong)(tong)現場(chang)uo信(xin)(xin)號經(jing)光電藕合(he)器隔離，與控(kong)(kong)制(zhi)板系(xi)(xi)(xi)統(tong)(tong)本體分開，切斷了干(gan)擾噪聲(sheng)的通道，解(jie)決了輸(shu)(shu)入、輸(shu)(shu)出回路的抗干(gan)擾問(wen)題，使(shi)系(xi)(xi)(xi)統(tong)(tong)調試方便，運行(xing)可靠。

結束語

工程實踐表明(ming)，采用以上杭干(gan)擾(rao)設計和措(cuo)施可以取得(de)很好(hao)的(de)效果。但(dan)是控制板系(xi)統中(zhong)的(de)干(gan)擾(rao)是一個十(shi)分復雜的(de)問(wen)題，還需在實踐中(zhong)不斷摸索，綜合考慮各方面的(de)因素，進一步(bu)完善優化抗干(gan)擾(rao)設計方法(fa)，合理(li)有效地(di)抑制干(gan)擾(rao)。