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

空間(jian)的輻(fu)射(she)電磁場主要來(lai)自電力網(wang)絡、雷電、無線電廣播(bo)、電視(shi)、雷達(da)、高頻(pin)感應(ying)加熱設備，其分布極為復雜。若控(kong)制(zhi)板系統置(zhi)于所射(she)頻(pin)場內。就會受(shou)到輻(fu)射(she)干(gan)擾，其影響主要通(tong)過(guo)兩條路(lu)徑:一是對(dui)控(kong)制(zhi)板通(tong)信(xin)網(wang)絡的輻(fu)射(she)，由(you)(you)通(tong)信(xin)線路(lu)的感應(ying)引(yin)人干(gan)擾;二是直(zhi)接對(dui)控(kong)制(zhi)板內部的輻(fu)射(she)，由(you)(you)電路(lu)感應(ying)產生(sheng)干(gan)擾。

2. 來自系統外引線的干擾

a. 來自電源的干擾

控制板系統的(de)正常供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源均由電(dian)(dian)(dian)網(wang)供(gong)電(dian)(dian)(dian)。由于電(dian)(dian)(dian)網(wang)覆(fu)蓋范圍(wei)廣，它將受(shou)到所有空間(jian)電(dian)(dian)(dian)磁干擾(rao)而在線路(lu)上(shang)感應出電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流。尤其(qi)是電(dian)(dian)(dian)網(wang)內部的(de)變化(hua)，開(kai)關操作浪涌、大型電(dian)(dian)(dian)力設備起停、電(dian)(dian)(dian)網(wang)短(duan)路(lu)暫態沖(chong)擊等，都通(tong)過(guo)輸電(dian)(dian)(dian)線路(lu)傳到電(dian)(dian)(dian)源。控制板電(dian)(dian)(dian)源通(tong)常采用隔(ge)離電(dian)(dian)(dian)源，但其(qi)機構及制造工藝因素使其(qi)隔(ge)離性并不理想。

b. 來自信號線引入的干擾

控制板(ban)系(xi)統(tong)連接的(de)(de)各類信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)傳輸(shu)線，除了傳輸(shu)有(you)效(xiao)的(de)(de)各類信(xin)(xin)(xin)(xin)(xin)息之(zhi)外，總(zong)會有(you)外部干擾(rao)(rao)(rao)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)侵入。此干擾(rao)(rao)(rao)主要(yao)有(you)兩種(zhong)途徑:一是通過(guo)變(bian)送器(qi)供(gong)電(dian)電(dian)源(yuan)或共用信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)儀表的(de)(de)供(gong)電(dian)電(dian)源(yuan)串入的(de)(de)電(dian)網干擾(rao)(rao)(rao);二是信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)線受空間電(dian)磁(ci)輻(fu)射感應(ying)(ying)的(de)(de)干擾(rao)(rao)(rao)，即信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)線上的(de)(de)外部感應(ying)(ying)干擾(rao)(rao)(rao)，這是很嚴重的(de)(de)。由信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)引入干擾(rao)(rao)(rao)會引起(qi)vo信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)工作異常和測量(liang)精度的(de)(de)降(jiang)低(di)，嚴重時將引起(qi)元器(qi)件(jian)損(sun)傷。對(dui)于隔離(li)性能差的(de)(de)系(xi)統(tong)，還將導致(zhi)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)間互相(xiang)干擾(rao)(rao)(rao)，引起(qi)共地系(xi)統(tong)總(zong)線回流，造成(cheng)邏輯數據變(bian)化、誤動和死機。

c. 來自接地系統混亂時的干擾

接(jie)地(di)(di)(di)是提高電(dian)(dian)子(zi)設備(bei)電(dian)(dian)磁兼容(rong)(rong)性(xing)的(de)(de)有效手段之一。正(zheng)確地(di)(di)(di)接(jie)地(di)(di)(di)，既能(neng)(neng)抑(yi)制電(dian)(dian)磁干(gan)擾(rao)的(de)(de)影(ying)(ying)響，又能(neng)(neng)抑(yi)制設備(bei)向外發出(chu)干(gan)擾(rao);而(er)錯誤的(de)(de)接(jie)地(di)(di)(di)，反而(er)會引入嚴重(zhong)的(de)(de)干(gan)擾(rao)信(xin)(xin)號(hao)，使控(kong)制板(ban)(ban)系統(tong)將無法正(zheng)常工作(zuo)。接(jie)地(di)(di)(di)系統(tong)混(hun)亂對(dui)控(kong)制板(ban)(ban)系統(tong)的(de)(de)干(gan)擾(rao)主要是各(ge)個(ge)接(jie)地(di)(di)(di)點電(dian)(dian)位分布(bu)(bu)不(bu)(bu)均(jun)，不(bu)(bu)同接(jie)地(di)(di)(di)點間(jian)(jian)存(cun)(cun)在地(di)(di)(di)電(dian)(dian)位差，引起(qi)地(di)(di)(di)環路(lu)電(dian)(dian)流，影(ying)(ying)響系統(tong)正(zheng)常工作(zuo)。例(li)如(ru)電(dian)(dian)纜(lan)(lan)屏(ping)(ping)蔽(bi)層(ceng)(ceng)必須一點接(jie)地(di)(di)(di)，如(ru)果電(dian)(dian)纜(lan)(lan)屏(ping)(ping)蔽(bi)層(ceng)(ceng)兩(liang)端都接(jie)地(di)(di)(di)，就(jiu)存(cun)(cun)在地(di)(di)(di)電(dian)(dian)位差，這時就(jiu)有電(dian)(dian)流流過屏(ping)(ping)蔽(bi)層(ceng)(ceng)，當發生異常狀態(tai)如(ru)雷擊(ji)時，地(di)(di)(di)線電(dian)(dian)流將更大。此外，屏(ping)(ping)蔽(bi)層(ceng)(ceng)、接(jie)地(di)(di)(di)線和地(di)(di)(di)之間(jian)(jian)有可能(neng)(neng)構成(cheng)閉合(he)環路(lu)，在變(bian)化磁場的(de)(de)作(zuo)用下，屏(ping)(ping)蔽(bi)層(ceng)(ceng)內又會出(chu)現(xian)感應(ying)電(dian)(dian)流，通過屏(ping)(ping)蔽(bi)層(ceng)(ceng)與芯線之間(jian)(jian)的(de)(de)禍合(he)，干(gan)擾(rao)信(xin)(xin)號(hao)形成(cheng)回路(lu)。模擬地(di)(di)(di)電(dian)(dian)位的(de)(de)分布(bu)(bu)將導致測量(liang)精度下降，引起(qi)對(dui)信(xin)(xin)號(hao)測控(kong)的(de)(de)嚴重(zhong)失真(zhen)和誤動(dong)作(zuo)。控(kong)制板(ban)(ban)工作(zuo)的(de)(de)邏(luo)輯電(dian)(dian)壓干(gan)擾(rao)容(rong)(rong)限(xian)較(jiao)低，邏(luo)輯地(di)(di)(di)電(dian)(dian)位的(de)(de)分布(bu)(bu)干(gan)擾(rao)容(rong)(rong)易(yi)影(ying)(ying)響控(kong)制板(ban)(ban)的(de)(de)邏(luo)輯運算和數據存(cun)(cun)貯，造成(cheng)數據混(hun)亂、程序跑飛或(huo)死(si)機。

控制板抗干擾設計的一般方法

抑(yi)制(zhi)(zhi)電(dian)磁干擾(rao)(rao)的(de)(de)基本原則(ze)是(shi)抑(yi)制(zhi)(zhi)干擾(rao)(rao)源、切斷或衰(shuai)減電(dian)磁干擾(rao)(rao)的(de)(de)傳播(bo)途徑、提高裝置(zhi)和系統的(de)(de)抗干擾(rao)(rao)能力。

1. 設備選型

在(zai)選擇(ze)設(she)備時(shi)，首先要(yao)選擇(ze)有(you)較高(gao)抗(kang)干(gan)擾能(neng)(neng)力的(de)產(chan)(chan)品(pin)，其(qi)次還應了解生產(chan)(chan)廠(chang)給(gei)出(chu)的(de)抗(kang)干(gan)擾指標，如(ru)(ru)耐(nai)壓能(neng)(neng)力、共模(mo)抑制(zhi)比(bi)(bi)，對(dui)最大(da)電場強度和最高(gao)頻率范(fan)圍設(she)置。另外(wai)考察其(qi)在(zai)類似工作(zuo)中的(de)應用實績(ji)。如(ru)(ru)果(guo)選擇(ze)國外(wai)進口產(chan)(chan)品(pin)要(yao)注意(yi):我國是采用220v高(gao)內(nei)(nei)阻(zu)電網(wang)制(zhi)式，比(bi)(bi)如(ru)(ru)日(ri)本是110v低(di)內(nei)(nei)阻(zu)電網(wang)。由(you)于我國電網(wang)內(nei)(nei)阻(zu)大(da)，零(ling)點(dian)電位(wei)漂(piao)移(yi)大(da)，地電位(wei)變(bian)化大(da)，工業(ye)企業(ye)現場的(de)電磁(ci)干(gan)擾至(zhi)少要(yao)比(bi)(bi)日(ri)本高(gao)4倍以上(shang)，對(dui)系(xi)統抗(kang)干(gan)擾性(xing)能(neng)(neng)要(yao)求更高(gao)，在(zai)國外(wai)能(neng)(neng)正常工作(zuo)的(de)控制(zhi)板產(chan)(chan)品(pin)在(zai)國內(nei)(nei)工業(ye)就(jiu)(jiu)不一定(ding)能(neng)(neng)可靠運行，這(zhe)就(jiu)(jiu)要(yao)求在(zai)采用國外(wai)產(chan)(chan)品(pin)時(shi)，按我國的(de)標準((GB/T13926)合理(li)選擇(ze)。

2. 設計施工中的抗干擾設計

為保證(zheng)系統(tong)在工業電(dian)(dian)磁(ci)環境(jing)中免(mian)受或減少內外電(dian)(dian)磁(ci)干擾(rao)(rao)，必須綜(zong)合抗干擾(rao)(rao)設計，在設計階段采取措施。綜(zong)合抗干擾(rao)(rao)設計主要內容包括:對控制板'系統(tong)及外引線(xian)進行屏(ping)蔽以(yi)防(fang)空(kong)間輻射電(dian)(dian)磁(ci)干擾(rao)(rao);對外引線(xian)進行隔(ge)離、濾波，特別是動力電(dian)(dian)纜(lan)，應該與信號線(xian)分(fen)層(ceng)布置，以(yi)防(fang)通過(guo)外引線(xian)引入傳導電(dian)(dian)磁(ci)干擾(rao)(rao);正確設計接地點和接地裝置，完善接地系統(tong)。

主要抗干擾措施

1. 采用性能優良的電源

在控(kong)制(zhi)板系(xi)統(tong)(tong)中，電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)占(zhan)有十(shi)分重要的(de)(de)地位。電(dian)(dian)(dian)(dian)(dian)(dian)網干(gan)擾(rao)串入控(kong)制(zhi)板系(xi)統(tong)(tong)主要通過控(kong)制(zhi)板系(xi)統(tong)(tong)的(de)(de)供電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)、變送(song)器(qi)供電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)和與控(kong)制(zhi)板系(xi)統(tong)(tong)具有直接電(dian)(dian)(dian)(dian)(dian)(dian)氣連接的(de)(de)儀表供電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)等藕合(he)進入的(de)(de)。對于(yu)控(kong)制(zhi)板系(xi)統(tong)(tong)供電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，一般都采用隔離性能(neng)較好電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan);而對于(yu)變送(song)器(qi)供電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)和控(kong)制(zhi)板系(xi)統(tong)(tong)有直接電(dian)(dian)(dian)(dian)(dian)(dian)氣連接的(de)(de)儀表的(de)(de)供電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，選擇分布(bu)電(dian)(dian)(dian)(dian)(dian)(dian)容小、抑(yi)制(zhi)性強的(de)(de)配電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)，抑(yi)制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)網引入的(de)(de)干(gan)擾(rao)。

2. 電纜選擇和敷設

為了(le)減少動(dong)力(li)電(dian)纜(lan)輻射(she)電(dian)磁(ci)干(gan)擾，不同(tong)(tong)類型的(de)信(xin)(xin)號(hao)分別由不同(tong)(tong)電(dian)纜(lan)傳(chuan)輸(shu)，信(xin)(xin)號(hao)電(dian)纜(lan)應按傳(chuan)輸(shu)信(xin)(xin)號(hao)種類分層敷設(she)，嚴禁用同(tong)(tong)一電(dian)纜(lan)的(de)不同(tong)(tong)導線同(tong)(tong)時傳(chuan)送動(dong)力(li)電(dian)源和信(xin)(xin)號(hao)，避免信(xin)(xin)號(hao)線與動(dong)力(li)電(dian)纜(lan)靠近平行敷設(she).以(yi)減少電(dian)磁(ci)干(gan)擾。

3. 硬件濾波及軟件抗干擾措施

信號在接(jie)入計(ji)算機前，在信號線與地間并聯電容，以(yi)減少共模干(gan)擾。由于電磁干(gan)擾的復雜性，要根本消除干(gan)擾影響是不可能的，困此在控(kong)制板系(xi)統(tong)的軟件(jian)(jian)設計(ji)和組(zu)態時，還應在軟件(jian)(jian)方面進(jin)行抗干(gan)擾處理，進(jin)一步(bu)提高系(xi)統(tong)的可靠性。

4. 選擇正確接地點系統

接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)的(de)(de)(de)目的(de)(de)(de)通常有(you)兩個(ge)，其一(yi)為了(le)安全，其二(er)是為了(le)抑制(zhi)干(gan)擾。完(wan)善的(de)(de)(de)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)系(xi)統(tong)是控(kong)制(zhi)板(ban)系(xi)統(tong)抗電(dian)磁干(gan)擾的(de)(de)(de)重要措施(shi)之一(yi)。系(xi)統(tong)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)方式有(you):浮地(di)(di)(di)(di)(di)(di)(di)(di)方式、直(zhi)接(jie)(jie)(jie)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)方式和電(dian)容接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)三種方式。對(dui)控(kong)制(zhi)板(ban)系(xi)統(tong)而(er)言，它屬高速低電(dian)平控(kong)制(zhi)裝置，應采(cai)用直(zhi)接(jie)(jie)(jie)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)方式。由(you)于信號電(dian)纜分布電(dian)容和輸入裝置濾波等的(de)(de)(de)影響(xiang)，裝置之間的(de)(de)(de)信號交換(huan)頻率(lv)一(yi)般都低于l MHz，所以控(kong)制(zhi)板(ban)系(xi)統(tong)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)線采(cai)用一(yi)點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)和串(chuan)聯(lian)一(yi)點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)方式。集(ji)中布置的(de)(de)(de)控(kong)制(zhi)板(ban)系(xi)統(tong)適于并聯(lian)一(yi)點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)方式，各裝置的(de)(de)(de)柜(ju)體中心接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)點(dian)以單獨(du)的(de)(de)(de)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)線引向接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)極。如果裝置間距較(jiao)大，應采(cai)用串(chuan)聯(lian)一(yi)點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)方式。

5. 控制板輸入、輸出信號回路采用光電隔離

利用光電(dian)禍合(he)器(qi)的開(kai)關特性(xing)實現輸人和(he)輸出(chu)信號的完全隔(ge)離，已成為抑(yi)制干擾的有效(xiao)措施(shi)之一。光電(dian)輻合(he)器(qi)把(ba)各種模擬(ni)負載和(he)數字(zi)信息源隔(ge)離開(kai)來，也就(jiu)是把(ba)“模擬(ni)的”和(he)“數字(zi)的”斷開(kai)。光電(dian)藕合(he)器(qi)能(neng)實現良(liang)好隔(ge)離的原因有三(san)個。

a. 由于(yu)光電(dian)棍合(he)器(qi)輸(shu)入電(dian)阻抗很(hen)小而干(gan)擾(rao)源的內阻則很(hen)大，因此分壓到(dao)光電(dian)藕合(he)器(qi)輸(shu)入端(duan)的干(gan)擾(rao)信號較小，輸(shu)入回(hui)路(lu)與輸(shu)出回(hui)路(lu)之間分布(bu)電(dian)容極小，而且絕緣電(dian)阻較高，因此回(hui)路(lu)一邊的干(gan)擾(rao)很(hen)難通過光電(dian)藕合(he)的回(hui)饋送(song)到(dao)另一邊;

b. 光電藕合器在密封條件下實現輸(shu)入回路(lu)與輸(shu)出(chu)回路(lu)的(de)光禍合，不(bu)會受外界光的(de)影響;

c. 無論是(shi)模擬還是(shi)數(shu)字信(xin)號，在輸(shu)(shu)(shu)入(ru)(ru)、輸(shu)(shu)(shu)出(chu)通道上都(dou)采用(yong)光(guang)電(dian)(dian)禍合(he)電(dian)(dian)路，用(yong)光(guang)線(xian)來(lai)藕合(he)信(xin)號，使(shi)輸(shu)(shu)(shu)人(ren)、輸(shu)(shu)(shu)出(chu)沒有電(dian)(dian)的(de)直(zhi)接聯系，可以(yi)有效地防止漏(lou)電(dian)(dian)、短(duan)路、打火、感(gan)應(ying)引起的(de)過電(dian)(dian)壓串(chuan)入(ru)(ru)控制板系統(tong)。因此在控制板系統(tong)現場uo信(xin)號經光(guang)電(dian)(dian)藕合(he)器隔(ge)離，與控制板系統(tong)本體分開(kai)，切(qie)斷了(le)干(gan)擾噪聲的(de)通道，解決了(le)輸(shu)(shu)(shu)入(ru)(ru)、輸(shu)(shu)(shu)出(chu)回路的(de)抗干(gan)擾問題，使(shi)系統(tong)調試方便，運行可靠(kao)。

結束語

工程實(shi)踐表明，采用(yong)以上杭干擾(rao)(rao)設計(ji)和措施可以取(qu)得很好的效(xiao)果(guo)。但是(shi)控(kong)制(zhi)板系統中的干擾(rao)(rao)是(shi)一(yi)個十分復雜的問題，還需在實(shi)踐中不(bu)斷(duan)摸索(suo)，綜(zong)合考慮各方面的因素(su)，進一(yi)步完善優化(hua)抗干擾(rao)(rao)設計(ji)方法，合理(li)有效(xiao)地(di)抑(yi)制(zhi)干擾(rao)(rao)。