什(shen)么是發(fa)電(dian)機勵磁(ci)系統 

　　供給同步

發電機

勵(li)(li)磁(ci)電(dian)流的(de)(de)(de)電(dian)源(yuan)及其(qi)附屬(shu)設(she)備統(tong)(tong)(tong)稱(cheng)為勵(li)(li)磁(ci)系統(tong)(tong)(tong)。它一般由(you)勵(li)(li)磁(ci)功率單(dan)(dan)元(yuan)和勵(li)(li)磁(ci)調(diao)(diao)(diao)節(jie)(jie)(jie)器(qi)(qi)兩個主(zhu)要(yao)部(bu)分組(zu)成(cheng)(cheng)。勵(li)(li)磁(ci)功率單(dan)(dan)元(yuan)向(xiang)同(tong)步(bu)發(fa)電(dian)機轉子(zi)提供勵(li)(li)磁(ci)電(dian)流；而勵(li)(li)磁(ci)調(diao)(diao)(diao)節(jie)(jie)(jie)器(qi)(qi)則(ze)根據輸(shu)入(ru)信(xin)號和給定(ding)(ding)的(de)(de)(de)調(diao)(diao)(diao)節(jie)(jie)(jie)準(zhun)則(ze)控制勵(li)(li)磁(ci)功率單(dan)(dan)元(yuan)的(de)(de)(de)輸(shu)出。勵(li)(li)磁(ci)系統(tong)(tong)(tong)的(de)(de)(de)自(zi)動勵(li)(li)磁(ci)調(diao)(diao)(diao)節(jie)(jie)(jie)器(qi)(qi)對提高電(dian)力(li)系統(tong)(tong)(tong)并聯機組(zu)的(de)(de)(de)穩定(ding)(ding)性具有相當大的(de)(de)(de)作(zuo)用。尤其(qi)是現(xian)代電(dian)力(li)系統(tong)(tong)(tong)的(de)(de)(de)發(fa)展(zhan)導致機組(zu)穩定(ding)(ding)極限降(jiang)低的(de)(de)(de)趨(qu)勢，也促使勵(li)(li)磁(ci)技術(shu)不斷(duan)發(fa)展(zhan)。同(tong)步(bu)發(fa)電(dian)機的(de)(de)(de)勵(li)(li)磁(ci)系統(tong)(tong)(tong)主(zhu)要(yao)由(you)功率單(dan)(dan)元(yuan)和調(diao)(diao)(diao)節(jie)(jie)(jie)器(qi)(qi)（裝置）兩大部(bu)分組(zu)成(cheng)(cheng)。 

　　勵磁(ci)變(bian)的作用 

　　勵(li)(li)磁(ci)(ci)(ci)(ci)變(bian)繞組(zu)(zu)的聯接(jie)組(zu)(zu)別，通(tong)(tong)常為(wei)Y，yo，對(dui)于副(fu)方(fang)電(dian)(dian)(dian)(dian)流大(da)的情況下(xia)，采用(yong)(yong)Y，dll組(zu)(zu)別。勵(li)(li)磁(ci)(ci)(ci)(ci)變(bian)就設計和結構來(lai)說，與普通(tong)(tong)配電(dian)(dian)(dian)(dian)變(bian)壓(ya)(ya)器(qi)(qi)(qi)一樣，短路電(dian)(dian)(dian)(dian)壓(ya)(ya)4％－8％。考慮到勵(li)(li)磁(ci)(ci)(ci)(ci)變(bian)必須(xu)可(ke)靠，強勵(li)(li)時(shi)要有一定(ding)的過載(zai)能力，且勵(li)(li)磁(ci)(ci)(ci)(ci)電(dian)(dian)(dian)(dian)源一般不(bu)設計備用(yong)(yong)電(dian)(dian)(dian)(dian)源，因此宜選用(yong)(yong)維(wei)護簡單、過載(zai)能力強的干式變(bian)壓(ya)(ya)器(qi)(qi)(qi)。從(cong)(cong)目(mu)前國內干式變(bian)壓(ya)(ya)器(qi)(qi)(qi)制造(zao)工藝(yi)水(shui)平來(lai)說，已能生產(chan)容量達16000kVA、電(dian)(dian)(dian)(dian)壓(ya)(ya)等級(ji)35KV的干式變(bian)壓(ya)(ya)器(qi)(qi)(qi)，以滿(man)足大(da)型機(ji)組(zu)(zu)的需要。若(ruo)從(cong)(cong)降低勵(li)(li)磁(ci)(ci)(ci)(ci)系統造(zao)價來(lai)說，采用(yong)(yong)油浸(jin)變(bian)壓(ya)(ya)器(qi)(qi)(qi)也是可(ke)行(xing)的。當(dang)勵(li)(li)磁(ci)(ci)(ci)(ci)變(bian)壓(ya)(ya)器(qi)(qi)(qi)安裝在(zai)戶外時(shi)，由(you)變(bian)壓(ya)(ya)器(qi)(qi)(qi)副(fu)方(fang)到整流橋之(zhi)間(jian)的饋線，由(you)于有電(dian)(dian)(dian)(dian)抗壓(ya)(ya)降，不(bu)宜太(tai)長，特別是在(zai)勵(li)(li)磁(ci)(ci)(ci)(ci)電(dian)(dian)(dian)(dian)流很大(da)的情況下(xia)，這一點必須(xu)考慮。還有不(bu)宜用(yong)(yong)單芯鎧裝電(dian)(dian)(dian)(dian)纜，而應選用(yong)(yong)橡皮電(dian)(dian)(dian)(dian)纜。因為(wei)單芯鎧裝電(dian)(dian)(dian)(dian)纜通(tong)(tong)以交流電(dian)(dian)(dian)(dian)時(shi)，在(zai)鋼(gang)甲中需要感應較高(gao)的電(dian)(dian)(dian)(dian)壓(ya)(ya)以及不(bu)能忽略的電(dian)(dian)(dian)(dian)流，并(bing)對(dui)通(tong)(tong)信電(dian)(dian)(dian)(dian)纜造(zao)成干擾。 

　　三相(xiang)勵磁(ci)變的選擇計算(suan)如下； 

　　計算變壓(ya)器的變比和容量用(yong)到(dao)以下參數(shu)：(鴨(ya)河口電廠實際值(zhi)) 

　　發電(dian)機額定勵(li)磁電(dian)流(liu)Ifn＝4469A 

　　發電機額(e)定(ding)勵磁電壓Ufn＝364V 

　　強(qiang)勵(li)倍數Kc＝2 

　　可(ke)控硅最小(xiao)控制角αmin＝10。 

　　變壓器漏抗Xk一(yi)般取4％一(yi)8％ 

　　饋(kui)電回路電壓(ya)降之(zhi)和∑△U：一般為2—4V 

　　按(an)照可控硅全(quan)控橋(qiao)整流計算方法計算勵(li)磁變低壓側(ce)Us： 

　　1.35UsCOSαmin=KcUfn+3KcIfnXk/π+∑△U 

　　由于在初設時Xk無法確認，∑△U也為估(gu)計值，因此可以把回路中總的(de)電壓損失估(gu)計為15％。 

　　由COSαmin≈COS0。=1 

　　則：上式可變為Us＝KcUfn／(85％×1.35)＝2×364／(85％×1.35)＝634．4V 

　　實際取勵(li)磁變副邊電壓(ya)Us＝650V 

　　發電機出口(kou)電壓為22000V，所以(yi)勵磁變(bian)變(bian)比為22000V／650V。 

　　勵磁變(bian)壓(ya)器也可以由直流(liu)側電流(liu)折算，取裕(yu)度系數為1.15，則副邊電流(liu)為： 

　　Is＝1.15×0.816×Ifn＝1.15×0.816×4469＝4193.7A 

　　實際取勵(li)磁變副邊電(dian)流Is＝4393.3A 

　　由Is、Us可以計算出(chu)勵(li)磁變容量(liang)： 

　　S＝√-3IsUs＝√-3×634.4×4193.7＝4608kVA 

　　實際變壓(ya)器(qi)容(rong)量(liang)S＝4950kVA，留有一定(ding)的容(rong)量(liang)。