觸點動作時產生(sheng)的(de)火花(hua)要怎么(me)消除？
由于電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)繼(ji)電(dian)(dian)(dian)(dian)(dian)器觸(chu)點(dian)的跳動或者(zhe)開閉的一瞬間均(jun)會引起(qi)(qi)感(gan)性負載的變化，產生氣體放(fang)電(dian)(dian)(dian)(dian)(dian)現象(xiang)，但電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)繼(ji)電(dian)(dian)(dian)(dian)(dian)器觸(chu)點(dian)通斷的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)較小，觸(chu)點(dian)間不會出(chu)現電(dian)(dian)(dian)(dian)(dian)弧，但會出(chu)現“火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)(dian)”，這是由于觸(chu)點(dian)電(dian)(dian)(dian)(dian)(dian)路(lu)中存(cun)在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)感(gan)，則在(zai)(zai)斷開時(shi)(shi)電(dian)(dian)(dian)(dian)(dian)感(gan)上會出(chu)現過(guo)電(dian)(dian)(dian)(dian)(dian)壓，它與電(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)壓一起(qi)(qi)加(jia)在(zai)(zai)觸(chu)點(dian)間隙(xi)上，使剛分開一點(dian)距離的觸(chu)點(dian)間隙(xi)擊穿而放(fang)電(dian)(dian)(dian)(dian)(dian)。由于能(neng)量(liang)所限(xian)，只會產生火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)(dian)，觸(chu)點(dian)間存(cun)在(zai)(zai)的電(dian)(dian)(dian)(dian)(dian)容與電(dian)(dian)(dian)(dian)(dian)感(gan)中能(neng)量(liang)的交(jiao)替轉(zhuan)換，使火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)隱時(shi)(shi)現，而成為(wei)一種高(gao)頻信號(hao)，通過(guo)高(gao)頻輻射、導線傳遞及(ji)分布電(dian)(dian)(dian)(dian)(dian)容等途徑而串擾(rao)到(dao)相關電(dian)(dian)(dian)(dian)(dian)路(lu)中，造成干擾(rao)信號(hao)。再者(zhe)火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)(dian)對觸(chu)點(dian)也會造成損傷，而會降低觸(chu)點(dian)的使用壽命，電(dian)(dian)(dian)(dian)(dian)火(huo)花(hua)會燒蝕觸(chu)點(dian)表面(mian)，使其表面(mian)不平造成接(jie)觸(chu)不良的故障。
RC消火花電路
因此必須設法消(xiao)(xiao)除電(dian)火(huo)花，實(shi)用的(de)(de)消(xiao)(xiao)火(huo)花電(dian)路(lu)(lu)是(shi)RC消(xiao)(xiao)火(huo)花電(dian)路(lu)(lu)，如圖(tu)所示。圖(tu)中虛線框(kuang)內是(shi)一(yi)(yi)種(zhong)半RC吸(xi)收(shou)電(dian)路(lu)(lu)，RC消(xiao)(xiao)火(huo)花電(dian)路(lu)(lu)基本作用原理是(shi)，把R和C相(xiang)串(chuan)聯后(hou)再并聯在(zai)電(dian)流繼電(dian)器(qi)觸(chu)(chu)點的(de)(de)兩端。使(shi)電(dian)感(gan)中的(de)(de)能量不通過(guo)觸(chu)(chu)點而(er)通過(guo)RC；它只吸(xi)收(shou)觸(chu)(chu)點斷(duan)開時(shi)產生的(de)(de)自感(gan)電(dian)勢(shi)。在(zai)電(dian)流繼電(dian)器(qi)觸(chu)(chu)點接通瞬間，由于RC被短(duan)路(lu)(lu)，所以沒有(you)吸(xi)收(shou)作用，圖(tu)中虛線框(kuang)外(wai)是(shi)一(yi)(yi)種(zhong)全吸(xi)收(shou)電(dian)路(lu)(lu)，在(zai)觸(chu)(chu)點斷(duan)開時(shi)自感(gan)電(dian)勢(shi)經過(guo)二(er)(er)極管V在(zai)負載rL上(shang)消(xiao)(xiao)耗(hao)掉。在(zai)實(shi)際應用中選(xuan)(xuan)擇(ze)以上(shang)電(dian)路(lu)(lu)中的(de)(de)一(yi)(yi)種(zhong)就行了。但(dan)要(yao)注(zhu)意的(de)(de)是(shi)，RC參數要(yao)選(xuan)(xuan)擇(ze)適當，參數主要(yao)靠(kao)實(shi)驗來決(jue)定，通常(chang)電(dian)容C可按負載電(dian)流1A/1μF選(xuan)(xuan)擇(ze)。使(shi)用二(er)(er)極管時(shi)其正負極性應連(lian)接正確，且二(er)(er)極管V的(de)(de)耐壓(ya)要(yao)夠。需要(yao)指出的(de)(de)是(shi)RC消(xiao)(xiao)火(huo)花電(dian)路(lu)(lu)應緊靠(kao)電(dian)流繼電(dian)器(qi)觸(chu)(chu)點安(an)裝，并盡量使(shi)連(lian)接線短(duan)些，以保證消(xiao)(xiao)火(huo)花電(dian)路(lu)(lu)的(de)(de)效果(guo)。
如某廠(chang)熱(re)處(chu)理爐(lu)的(de)(de)(de)溫度自動(dong)控(kong)制系(xi)統，用(yong)(yong)(yong)溫控(kong)儀（控(kong)制輸出(chu)為(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)的(de)(de)(de)PID調節器(qi)）及中間(jian)(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)來控(kong)制接(jie)觸(chu)(chu)器(qi)的(de)(de)(de)通、斷進(jin)而控(kong)制電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)熱(re)器(qi)。但在(zai)(zai)(zai)使用(yong)(yong)(yong)中由(you)(you)于溫度儀表波(bo)動(dong)大(da)，尤(you)其(qi)控(kong)溫精度越高其(qi)波(bo)動(dong)越大(da)，致使中間(jian)(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)動(dong)作(zuo)(zuo)頻(pin)繁(fan)，由(you)(you)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)觸(chu)(chu)點(dian)(dian)在(zai)(zai)(zai)接(jie)通的(de)(de)(de)瞬間(jian)(jian)，觸(chu)(chu)點(dian)(dian)上(shang)將有數倍于正常工(gong)(gong)作(zuo)(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)的(de)(de)(de)沖擊，而在(zai)(zai)(zai)斷開瞬間(jian)(jian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中儲存的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)磁(ci)(ci)能將以火花的(de)(de)(de)形式在(zai)(zai)(zai)觸(chu)(chu)點(dian)(dian)間(jian)(jian)釋(shi)放。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)觸(chu)(chu)點(dian)(dian)過于頻(pin)繁(fan)的(de)(de)(de)動(dong)作(zuo)(zuo)造成電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)觸(chu)(chu)點(dian)(dian)的(de)(de)(de)發熱(re)、燒蝕、甚至熔焊，修磨幾次(ci)就(jiu)無法(fa)使用(yong)(yong)(yong)了，只能更換電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)。接(jie)觸(chu)(chu)器(qi)已由(you)(you)于經常流(liu)(liu)(liu)過數倍的(de)(de)(de)工(gong)(gong)作(zuo)(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)而發熱(re)，鐵芯(xin)由(you)(you)于頻(pin)繁(fan)動(dong)作(zuo)(zuo)使鐵芯(xin)位移和磁(ci)(ci)路(lu)(lu)(lu)氣隙增(zeng)大(da)，而產生很大(da)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)磁(ci)(ci)噪聲。上(shang)述問題不僅(jin)增(zeng)加了維(wei)修工(gong)(gong)作(zuo)(zuo)量，有時還(huan)影(ying)響(xiang)生產，為(wei)(wei)(wei)此該廠(chang)對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)進(jin)行(xing)了改造，使用(yong)(yong)(yong)RC消火花電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，RC電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)選擇的(de)(de)(de)參(can)數是(shi)：C為(wei)(wei)(wei)100pF/1000V，R的(de)(de)(de)為(wei)(wei)(wei)1.2kΩ/1W。把RC元件直接(jie)接(jie)在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)觸(chu)(chu)點(dian)(dian)上(shang)，再就(jiu)是(shi)設法(fa)減小接(jie)觸(chu)(chu)器(qi)的(de)(de)(de)工(gong)(gong)作(zuo)(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，采取這(zhe)些措施后，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)的(de)(de)(de)觸(chu)(chu)點(dian)(dian)使用(yong)(yong)(yong)壽命大(da)大(da)延長(chang)。效果明(ming)顯(xian)，在(zai)(zai)(zai)滿(man)足了生產要求的(de)(de)(de)同時，還(huan)減輕(qing)了維(wei)修工(gong)(gong)作(zuo)(zuo)量，節約了維(wei)修費用(yong)(yong)(yong)。
消(xiao)除電(dian)流(liu)繼電(dian)器接(jie)點火花的方法
由于電(dian)(dian)(dian)(dian)流繼電(dian)(dian)(dian)(dian)器接(jie)點(dian)通斷的(de)(de)電(dian)(dian)(dian)(dian)流較小，接(jie)點(dian)間(jian)(jian)不會(hui)出現電(dian)(dian)(dian)(dian)弧(hu)，但會(hui)出現“火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)”，這是由于接(jie)點(dian)電(dian)(dian)(dian)(dian)路(lu)中存在電(dian)(dian)(dian)(dian)感，則(ze)在斷開(kai)時(shi)電(dian)(dian)(dian)(dian)感上(shang)會(hui)出現過電(dian)(dian)(dian)(dian)壓，它與電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)壓一起加在接(jie)點(dian)間(jian)(jian)隙上(shang)，使剛分開(kai)一點(dian)距離的(de)(de)接(jie)點(dian)間(jian)(jian)隙擊穿而放(fang)電(dian)(dian)(dian)(dian)。由于能(neng)量(liang)所限(xian)，只會(hui)產生火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)，接(jie)點(dian)間(jian)(jian)存在的(de)(de)電(dian)(dian)(dian)(dian)容與電(dian)(dian)(dian)(dian)感中能(neng)量(liang)的(de)(de)交(jiao)替轉換(huan)，使火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)時(shi)隱時(shi)現，而成為一種(zhong)高頻信號(hao)，再者火(huo)花(hua)放(fang)電(dian)(dian)(dian)(dian)對接(jie)點(dian)也會(hui)造成損傷(shang)，而會(hui)降低(di)使用壽命，因此必須設法消除(chu)，實用的(de)(de)消火(huo)花(hua)電(dian)(dian)(dian)(dian)路(lu)有兩(liang)種(zhong)。
一(yi)、其(qi)基(ji)本作(zuo)用原理是，使電感中的能(neng)量不通過接點而通過rc；
二(er)(er)、在(zai)(zai)斷(duan)開時經過二(er)(er)極管v在(zai)(zai)負(fu)載r.l上消耗掉。在(zai)(zai)應用中(zhong)選擇(ze)(ze)一種就(jiu)行了(le)。但要(yao)注(zhu)意的是，rc參數(shu)要(yao)選擇(ze)(ze)適當，參數(shu)主要(yao)靠實驗來決(jue)定，通常電容(rong)c可按負(fu)載電流1a／1微法選擇(ze)(ze)。使用二(er)(er)極管時其(qi)正負(fu)極性應連(lian)接(jie)正確。
