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

空間的(de)輻射電(dian)磁(ci)場主(zhu)要(yao)來自電(dian)力網絡、雷(lei)電(dian)、無線電(dian)廣(guang)播、電(dian)視、雷(lei)達、高頻(pin)感應加熱設備，其(qi)分布極為復(fu)雜。若(ruo)控制板系統置于所射頻(pin)場內(nei)。就會受到輻射干(gan)擾(rao)，其(qi)影響主(zhu)要(yao)通(tong)過兩(liang)條路徑:一是(shi)對(dui)(dui)控制板通(tong)信(xin)網絡的(de)輻射，由通(tong)信(xin)線路的(de)感應引人干(gan)擾(rao);二是(shi)直(zhi)接(jie)對(dui)(dui)控制板內(nei)部的(de)輻射，由電(dian)路感應產生干(gan)擾(rao)。

2. 來自系統外引線的干擾

a. 來自電源的干擾

控制板系(xi)統的(de)正常(chang)供電(dian)(dian)(dian)電(dian)(dian)(dian)源(yuan)均由(you)電(dian)(dian)(dian)網(wang)供電(dian)(dian)(dian)。由(you)于電(dian)(dian)(dian)網(wang)覆蓋(gai)范圍廣，它將受到所有空間電(dian)(dian)(dian)磁干(gan)擾而在線路(lu)上感應出(chu)電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流。尤其(qi)是電(dian)(dian)(dian)網(wang)內部(bu)的(de)變化，開關操作浪涌、大型(xing)電(dian)(dian)(dian)力設備起停(ting)、電(dian)(dian)(dian)網(wang)短路(lu)暫態沖擊等，都通(tong)過輸電(dian)(dian)(dian)線路(lu)傳到電(dian)(dian)(dian)源(yuan)。控制板電(dian)(dian)(dian)源(yuan)通(tong)常(chang)采用隔離(li)電(dian)(dian)(dian)源(yuan)，但其(qi)機構及(ji)制造工藝因(yin)素使其(qi)隔離(li)性并不理想。

b. 來自信號線引入的干擾

控制板系(xi)統(tong)(tong)連接的(de)(de)(de)各類信(xin)(xin)(xin)號傳(chuan)輸線(xian)(xian)，除了傳(chuan)輸有(you)效的(de)(de)(de)各類信(xin)(xin)(xin)息之外，總(zong)會有(you)外部干擾信(xin)(xin)(xin)號侵入。此干擾主(zhu)要有(you)兩種途徑:一是(shi)通過變送器(qi)供(gong)電(dian)(dian)電(dian)(dian)源(yuan)或共(gong)用(yong)信(xin)(xin)(xin)號儀表的(de)(de)(de)供(gong)電(dian)(dian)電(dian)(dian)源(yuan)串入的(de)(de)(de)電(dian)(dian)網干擾;二(er)是(shi)信(xin)(xin)(xin)號線(xian)(xian)受空間電(dian)(dian)磁輻射感應(ying)的(de)(de)(de)干擾，即(ji)信(xin)(xin)(xin)號線(xian)(xian)上的(de)(de)(de)外部感應(ying)干擾，這是(shi)很嚴重的(de)(de)(de)。由信(xin)(xin)(xin)號引入干擾會引起vo信(xin)(xin)(xin)號工(gong)作(zuo)異(yi)常和測量精度(du)的(de)(de)(de)降低，嚴重時將(jiang)引起元(yuan)器(qi)件(jian)損傷。對于隔離(li)性能(neng)差的(de)(de)(de)系(xi)統(tong)(tong)，還(huan)將(jiang)導致信(xin)(xin)(xin)號間互相干擾，引起共(gong)地系(xi)統(tong)(tong)總(zong)線(xian)(xian)回流，造成邏輯數據變化(hua)、誤動和死機(ji)。

c. 來自接地系統混亂時的干擾

接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)是提(ti)高電(dian)(dian)(dian)(dian)子設備電(dian)(dian)(dian)(dian)磁兼(jian)容性(xing)的(de)(de)(de)(de)有(you)效(xiao)手段之(zhi)(zhi)(zhi)一(yi)。正(zheng)確地(di)(di)(di)(di)(di)(di)(di)(di)接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)，既能抑制(zhi)電(dian)(dian)(dian)(dian)磁干(gan)擾的(de)(de)(de)(de)影(ying)(ying)響(xiang)，又(you)能抑制(zhi)設備向外發出干(gan)擾;而錯誤(wu)的(de)(de)(de)(de)接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)，反而會引(yin)入嚴重(zhong)的(de)(de)(de)(de)干(gan)擾信號(hao)，使(shi)控(kong)(kong)(kong)制(zhi)板系(xi)統(tong)(tong)(tong)將無法正(zheng)常(chang)工作。接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)系(xi)統(tong)(tong)(tong)混(hun)亂(luan)對控(kong)(kong)(kong)制(zhi)板系(xi)統(tong)(tong)(tong)的(de)(de)(de)(de)干(gan)擾主要是各(ge)個接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)點(dian)(dian)電(dian)(dian)(dian)(dian)位(wei)分布不均(jun)，不同接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)點(dian)(dian)間存在(zai)(zai)地(di)(di)(di)(di)(di)(di)(di)(di)電(dian)(dian)(dian)(dian)位(wei)差(cha)，引(yin)起地(di)(di)(di)(di)(di)(di)(di)(di)環路電(dian)(dian)(dian)(dian)流(liu)，影(ying)(ying)響(xiang)系(xi)統(tong)(tong)(tong)正(zheng)常(chang)工作。例如(ru)電(dian)(dian)(dian)(dian)纜屏(ping)蔽(bi)(bi)層(ceng)必(bi)須一(yi)點(dian)(dian)接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)，如(ru)果電(dian)(dian)(dian)(dian)纜屏(ping)蔽(bi)(bi)層(ceng)兩端都接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)，就存在(zai)(zai)地(di)(di)(di)(di)(di)(di)(di)(di)電(dian)(dian)(dian)(dian)位(wei)差(cha)，這時(shi)就有(you)電(dian)(dian)(dian)(dian)流(liu)流(liu)過(guo)屏(ping)蔽(bi)(bi)層(ceng)，當發生(sheng)異常(chang)狀態如(ru)雷擊時(shi)，地(di)(di)(di)(di)(di)(di)(di)(di)線(xian)(xian)電(dian)(dian)(dian)(dian)流(liu)將更大。此(ci)外，屏(ping)蔽(bi)(bi)層(ceng)、接(jie)(jie)地(di)(di)(di)(di)(di)(di)(di)(di)線(xian)(xian)和(he)地(di)(di)(di)(di)(di)(di)(di)(di)之(zhi)(zhi)(zhi)間有(you)可能構成閉合(he)環路，在(zai)(zai)變化磁場的(de)(de)(de)(de)作用下，屏(ping)蔽(bi)(bi)層(ceng)內又(you)會出現(xian)感(gan)應(ying)電(dian)(dian)(dian)(dian)流(liu)，通過(guo)屏(ping)蔽(bi)(bi)層(ceng)與芯(xin)線(xian)(xian)之(zhi)(zhi)(zhi)間的(de)(de)(de)(de)禍合(he)，干(gan)擾信號(hao)形(xing)成回路。模(mo)擬地(di)(di)(di)(di)(di)(di)(di)(di)電(dian)(dian)(dian)(dian)位(wei)的(de)(de)(de)(de)分布將導(dao)致測量精度下降，引(yin)起對信號(hao)測控(kong)(kong)(kong)的(de)(de)(de)(de)嚴重(zhong)失(shi)真(zhen)和(he)誤(wu)動作。控(kong)(kong)(kong)制(zhi)板工作的(de)(de)(de)(de)邏(luo)輯電(dian)(dian)(dian)(dian)壓干(gan)擾容限較(jiao)低，邏(luo)輯地(di)(di)(di)(di)(di)(di)(di)(di)電(dian)(dian)(dian)(dian)位(wei)的(de)(de)(de)(de)分布干(gan)擾容易(yi)影(ying)(ying)響(xiang)控(kong)(kong)(kong)制(zhi)板的(de)(de)(de)(de)邏(luo)輯運算(suan)和(he)數據存貯，造成數據混(hun)亂(luan)、程序(xu)跑飛或死機。

控制板抗干擾設計的一般方法

抑(yi)制電磁干擾(rao)的(de)基本(ben)原則是抑(yi)制干擾(rao)源、切(qie)斷或衰減電磁干擾(rao)的(de)傳播途徑、提高裝置和系(xi)統的(de)抗干擾(rao)能(neng)力(li)。

1. 設備選型

在(zai)選擇(ze)(ze)設備時，首先要(yao)(yao)選擇(ze)(ze)有較高(gao)抗(kang)(kang)干(gan)擾(rao)能力的(de)(de)產(chan)(chan)品，其(qi)次還應(ying)了解生(sheng)產(chan)(chan)廠給出的(de)(de)抗(kang)(kang)干(gan)擾(rao)指標，如(ru)(ru)耐壓能力、共模抑制比，對(dui)最大電(dian)(dian)場強(qiang)度和最高(gao)頻率范圍設置。另外考(kao)察其(qi)在(zai)類(lei)似工(gong)(gong)作中的(de)(de)應(ying)用實績(ji)。如(ru)(ru)果選擇(ze)(ze)國(guo)(guo)(guo)外進口產(chan)(chan)品要(yao)(yao)注意:我國(guo)(guo)(guo)是采用220v高(gao)內(nei)阻電(dian)(dian)網(wang)制式，比如(ru)(ru)日本是110v低內(nei)阻電(dian)(dian)網(wang)。由于我國(guo)(guo)(guo)電(dian)(dian)網(wang)內(nei)阻大，零點電(dian)(dian)位(wei)漂移大，地電(dian)(dian)位(wei)變化(hua)大，工(gong)(gong)業(ye)企(qi)業(ye)現場的(de)(de)電(dian)(dian)磁(ci)干(gan)擾(rao)至(zhi)少要(yao)(yao)比日本高(gao)4倍以上，對(dui)系統抗(kang)(kang)干(gan)擾(rao)性能要(yao)(yao)求更高(gao)，在(zai)國(guo)(guo)(guo)外能正常工(gong)(gong)作的(de)(de)控制板產(chan)(chan)品在(zai)國(guo)(guo)(guo)內(nei)工(gong)(gong)業(ye)就不一定能可靠運行，這就要(yao)(yao)求在(zai)采用國(guo)(guo)(guo)外產(chan)(chan)品時，按我國(guo)(guo)(guo)的(de)(de)標準((GB/T13926)合(he)理選擇(ze)(ze)。

2. 設計施工中的抗干擾設計

為保證系統(tong)在(zai)(zai)工業電(dian)磁(ci)(ci)環境中免受(shou)或減少內(nei)外電(dian)磁(ci)(ci)干擾(rao)，必須綜合(he)抗干擾(rao)設計(ji)，在(zai)(zai)設計(ji)階段采取措施。綜合(he)抗干擾(rao)設計(ji)主要內(nei)容包括:對控(kong)制板(ban)'系統(tong)及外引(yin)線進(jin)行屏蔽以防空(kong)間輻射(she)電(dian)磁(ci)(ci)干擾(rao);對外引(yin)線進(jin)行隔離、濾波(bo)，特別是動力電(dian)纜，應該與信號(hao)線分層布置(zhi)，以防通過外引(yin)線引(yin)入傳導電(dian)磁(ci)(ci)干擾(rao);正確設計(ji)接地點(dian)和接地裝置(zhi)，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)(xi)統(tong)(tong)中，電(dian)(dian)(dian)源占有十分重要的(de)(de)(de)地位。電(dian)(dian)(dian)網干擾串入控(kong)制(zhi)板系(xi)(xi)統(tong)(tong)主要通過控(kong)制(zhi)板系(xi)(xi)統(tong)(tong)的(de)(de)(de)供(gong)(gong)(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源、變送(song)器(qi)供(gong)(gong)(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源和(he)與控(kong)制(zhi)板系(xi)(xi)統(tong)(tong)具(ju)有直接(jie)(jie)電(dian)(dian)(dian)氣(qi)(qi)連(lian)接(jie)(jie)的(de)(de)(de)儀表供(gong)(gong)(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源等藕合進入的(de)(de)(de)。對(dui)于控(kong)制(zhi)板系(xi)(xi)統(tong)(tong)供(gong)(gong)(gong)電(dian)(dian)(dian)的(de)(de)(de)電(dian)(dian)(dian)源，一般(ban)都采用隔離性能(neng)較好電(dian)(dian)(dian)源;而(er)對(dui)于變送(song)器(qi)供(gong)(gong)(gong)電(dian)(dian)(dian)的(de)(de)(de)電(dian)(dian)(dian)源和(he)控(kong)制(zhi)板系(xi)(xi)統(tong)(tong)有直接(jie)(jie)電(dian)(dian)(dian)氣(qi)(qi)連(lian)接(jie)(jie)的(de)(de)(de)儀表的(de)(de)(de)供(gong)(gong)(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源，選擇分布電(dian)(dian)(dian)容小、抑(yi)制(zhi)性強(qiang)的(de)(de)(de)配電(dian)(dian)(dian)器(qi)，抑(yi)制(zhi)電(dian)(dian)(dian)網引入的(de)(de)(de)干擾。

2. 電纜選擇和敷設

為了(le)減少動力電(dian)纜輻射電(dian)磁干擾，不(bu)(bu)同(tong)類型的信(xin)(xin)號(hao)(hao)分(fen)別(bie)由不(bu)(bu)同(tong)電(dian)纜傳(chuan)輸，信(xin)(xin)號(hao)(hao)電(dian)纜應按傳(chuan)輸信(xin)(xin)號(hao)(hao)種類分(fen)層(ceng)敷(fu)(fu)設，嚴禁用(yong)同(tong)一電(dian)纜的不(bu)(bu)同(tong)導線同(tong)時傳(chuan)送動力電(dian)源和信(xin)(xin)號(hao)(hao)，避免信(xin)(xin)號(hao)(hao)線與(yu)動力電(dian)纜靠近(jin)平行敷(fu)(fu)設.以減少電(dian)磁干擾。

3. 硬件濾波及軟件抗干擾措施

信(xin)號在(zai)接入(ru)計算機前(qian)，在(zai)信(xin)號線與地間并聯(lian)電容，以減少共模干擾。由于(yu)電磁干擾的(de)復雜性，要根本消除干擾影響(xiang)是不可能的(de)，困此(ci)在(zai)控(kong)制板系統的(de)軟(ruan)件(jian)設計和組態時，還應在(zai)軟(ruan)件(jian)方面(mian)進(jin)行(xing)抗(kang)干擾處理，進(jin)一步提高(gao)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)(de)目(mu)的(de)(de)(de)通(tong)常有兩個，其(qi)一為(wei)了安(an)全，其(qi)二(er)是為(wei)了抑制(zhi)干擾(rao)。完(wan)善的(de)(de)(de)接(jie)(jie)(jie)地(di)(di)(di)(di)系(xi)(xi)統(tong)(tong)是控(kong)制(zhi)板(ban)系(xi)(xi)統(tong)(tong)抗電磁干擾(rao)的(de)(de)(de)重(zhong)要措施之(zhi)一。系(xi)(xi)統(tong)(tong)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)式(shi)(shi)有:浮地(di)(di)(di)(di)方(fang)式(shi)(shi)、直接(jie)(jie)(jie)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)式(shi)(shi)和(he)(he)電容接(jie)(jie)(jie)地(di)(di)(di)(di)三種方(fang)式(shi)(shi)。對(dui)控(kong)制(zhi)板(ban)系(xi)(xi)統(tong)(tong)而言，它屬高速低電平控(kong)制(zhi)裝置，應采(cai)用直接(jie)(jie)(jie)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)式(shi)(shi)。由于(yu)信號(hao)電纜分布(bu)電容和(he)(he)輸(shu)入裝置濾波(bo)等(deng)的(de)(de)(de)影響，裝置之(zhi)間(jian)的(de)(de)(de)信號(hao)交換頻(pin)率一般(ban)都低于(yu)l MHz，所以控(kong)制(zhi)板(ban)系(xi)(xi)統(tong)(tong)接(jie)(jie)(jie)地(di)(di)(di)(di)線(xian)采(cai)用一點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)和(he)(he)串聯(lian)一點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)式(shi)(shi)。集中布(bu)置的(de)(de)(de)控(kong)制(zhi)板(ban)系(xi)(xi)統(tong)(tong)適于(yu)并聯(lian)一點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)式(shi)(shi)，各裝置的(de)(de)(de)柜體中心接(jie)(jie)(jie)地(di)(di)(di)(di)點(dian)以單獨的(de)(de)(de)接(jie)(jie)(jie)地(di)(di)(di)(di)線(xian)引向接(jie)(jie)(jie)地(di)(di)(di)(di)極。如果(guo)裝置間(jian)距較大(da)，應采(cai)用串聯(lian)一點(dian)接(jie)(jie)(jie)地(di)(di)(di)(di)方(fang)式(shi)(shi)。

5. 控制板輸入、輸出信號回路采用光電隔離

利用(yong)光電禍(huo)合(he)器的(de)開關特性實(shi)現(xian)輸(shu)人和(he)輸(shu)出(chu)信號的(de)完全隔(ge)離(li)，已(yi)成(cheng)為抑制(zhi)干(gan)擾的(de)有效措施之一。光電輻合(he)器把(ba)各種模擬(ni)負載(zai)和(he)數字信息(xi)源(yuan)隔(ge)離(li)開來，也就(jiu)是(shi)把(ba)“模擬(ni)的(de)”和(he)“數字的(de)”斷開。光電藕合(he)器能實(shi)現(xian)良好隔(ge)離(li)的(de)原因有三個。

a. 由于光電(dian)(dian)(dian)棍合(he)器輸(shu)入(ru)電(dian)(dian)(dian)阻(zu)(zu)抗很(hen)小(xiao)而干擾(rao)源的(de)內(nei)阻(zu)(zu)則很(hen)大，因(yin)此分壓到光電(dian)(dian)(dian)藕合(he)器輸(shu)入(ru)端的(de)干擾(rao)信號較小(xiao)，輸(shu)入(ru)回路(lu)與輸(shu)出回路(lu)之間分布電(dian)(dian)(dian)容(rong)極小(xiao)，而且絕緣電(dian)(dian)(dian)阻(zu)(zu)較高(gao)，因(yin)此回路(lu)一(yi)邊的(de)干擾(rao)很(hen)難通過光電(dian)(dian)(dian)藕合(he)的(de)回饋送到另一(yi)邊;

b. 光電藕(ou)合(he)器在密封條件(jian)下實現輸(shu)(shu)入(ru)回路(lu)與輸(shu)(shu)出(chu)回路(lu)的光禍(huo)合(he)，不會受外界光的影響;

c. 無論(lun)是模擬還(huan)是數字信(xin)(xin)號，在(zai)輸(shu)(shu)入、輸(shu)(shu)出(chu)通(tong)道(dao)上都采用(yong)(yong)光電(dian)(dian)禍合(he)電(dian)(dian)路，用(yong)(yong)光線來藕(ou)合(he)信(xin)(xin)號，使輸(shu)(shu)人、輸(shu)(shu)出(chu)沒有(you)電(dian)(dian)的(de)直(zhi)接聯系(xi)，可以有(you)效地防止漏電(dian)(dian)、短(duan)路、打火、感應(ying)引起的(de)過電(dian)(dian)壓串(chuan)入控制板(ban)(ban)系(xi)統。因(yin)此在(zai)控制板(ban)(ban)系(xi)統現場uo信(xin)(xin)號經光電(dian)(dian)藕(ou)合(he)器隔離(li)，與控制板(ban)(ban)系(xi)統本體分開，切(qie)斷了(le)干(gan)擾噪聲的(de)通(tong)道(dao)，解決了(le)輸(shu)(shu)入、輸(shu)(shu)出(chu)回(hui)路的(de)抗干(gan)擾問題，使系(xi)統調(diao)試(shi)方便，運行(xing)可靠。

結束語

工程實踐表明(ming)，采用以(yi)上杭干(gan)(gan)擾(rao)設(she)計(ji)和措施可以(yi)取得很好的效果。但是(shi)控(kong)制板(ban)系(xi)統中的干(gan)(gan)擾(rao)是(shi)一個十分(fen)復雜的問題(ti)，還需(xu)在實踐中不(bu)斷摸索(suo)，綜合(he)考(kao)慮各(ge)方面的因素(su)，進一步(bu)完善優化抗干(gan)(gan)擾(rao)設(she)計(ji)方法，合(he)理有效地抑制干(gan)(gan)擾(rao)。