三相異步電動機的過載分析

2020-12-27

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　　三相異步電動機在使用過程中，如果拖動的負載超過其額定容量，就會過載。電動機過載一般會出現以下異常現象:①電動機過熱②電動機運行電流超過額定電流③電動機運行中自身產生異常的音響④電動機及其拖動的設備發出異常振動，電動機的轉速下降。

　　電動機(ji)過載(zai)的(de)主要原因(yin)有以下(xia)幾個方(fang)面(mian):

　　1.電(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)太(tai)低(di)。電(dian)(dian)(dian)動機(ji)起動或滿載(zai)運行時(shi)進線(xian)(xian)端電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)不是線(xian)(xian)路的空載(zai)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)，負(fu)載(zai)時(shi)，若電(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)降低(di)，如380伏電(dian)(dian)(dian)動機(ji)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)低(di)于360伏，電(dian)(dian)(dian)流必然增加，造成電(dian)(dian)(dian)動機(ji)溫升過高(gao)。電(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)低(di)的原因(yin)，一(yi)是高(gao)壓(ya)(ya)(ya)(ya)電(dian)(dian)(dian)源(yuan)本身偏低(di)，需要調(diao)節變(bian)壓(ya)(ya)(ya)(ya)器(qi)分(fen)接開關，分(fen)有載(zai)調(diao)壓(ya)(ya)(ya)(ya)和(he)無載(zai)調(diao)壓(ya)(ya)(ya)(ya)兩(liang)種。二(er)是電(dian)(dian)(dian)動機(ji)距離變(bian)壓(ya)(ya)(ya)(ya)器(qi)太(tai)遠，供電(dian)(dian)(dian)電(dian)(dian)(dian)纜截面太(tai)小，負(fu)載(zai)重，線(xian)(xian)路壓(ya)(ya)(ya)(ya)降太(tai)大(da)，此時(shi)需增大(da)導線(xian)(xian)截面或減小線(xian)(xian)路負(fu)荷。

　　2.接法有(you)誤。例如380伏(fu)星(xing)形(xing)接法電(dian)動機，若(ruo)錯接為(wei)三角形(xing)，則(ze)相(xiang)電(dian)壓(ya)提高到原來的√3倍，則(ze)電(dian)流大增(zeng)，反之380伏(fu)三角形(xing)接法錯接成(cheng)星(xing)形(xing)Y，則(ze)相(xiang)電(dian)壓(ya)下(xia)降(jiang)至220伏(fu)，滿載時電(dian)流大大增(zeng)加，以上兩(liang)種情況均會(hui)造(zao)成(cheng)電(dian)動杌燒毀。

　　3.機械方面的(de)原因。機械故障(zhang)種類很多(duo)，故障(zhang)復雜，常見的(de)有軸承(cheng)損壞，設備堵轉(zhuan)。

　　4.電機選型不當，起動時間長。如離心脫水機，球磨機等起動時阻力矩大，起動時間長，極易燒毀電動機。此類機械應選用起動電流小，起動轉矩大的雙鼠籠式、深槽式異步電動機或繞線式異步電動機。另外功率選擇方面留有余量。從電氣控制方式上可酌情選擇變頻器或軟啟動器。

三相異步電動機