電機電流過大的原因

2018-08-30

次

　　電動機空載電流過大的原因有如下幾種：電源電壓太高：當電源電壓太高時，電機鐵芯會產生磁飽和現象，導致空載電流過大。②、電動機因修理后裝配不當或空隙過大。③、定子繞組匝數不夠或Ｙ型連接誤接成△形接線。④、對于一些舊電動機，由于硅鋼片腐蝕或老化，使磁場強度減弱或片間絕緣損壞而造成空載電流太大。對于小型電動機，空載電流只要不坡過額定電流的 50% 就可以繼續使用。

　　所謂電動機的啟動是指電動機從接入電源開始轉動起，到達到額定轉速為止的這一過程。根據理論分析和實際測定，異步電動機啟動瞬間；定子繞組啟動電流很大，可達額定值的4-7倍。

　　為什么會(hui)有(you)這么大的(de)啟動(dong)電(dian)(dian)(dian)(dian)流呢？因為異步(bu)電(dian)(dian)(dian)(dian)動(dong)機在啟動(dong)瞬間轉子(zi)并(bing)不能(neng)(neng)立(li)馬就(jiu)轉動(dong)起來，此(ci)時轉子(zi)電(dian)(dian)(dian)(dian)磁感應的(de)反電(dian)(dian)(dian)(dian)勢(shi)尚未建立(li)起來，所(suo)以外電(dian)(dian)(dian)(dian)壓全部加(jia)在沒有(you)反電(dian)(dian)(dian)(dian)勢(shi)的(de)定子(zi)繞(rao)組(zu)上，其電(dian)(dian)(dian)(dian)路電(dian)(dian)(dian)(dian)流就(jiu)是外電(dian)(dian)(dian)(dian)壓除以繞(rao)組(zu)的(de)阻抗（用符號Z表(biao)示(shi)，是一種對(dui)電(dian)(dian)(dian)(dian)流其阻礙作用的(de)能(neng)(neng)力，單(dan)位為歐姆公式Z=V/I表(biao)示(shi)），所(suo)以定子(zi)繞(rao)組(zu)電(dian)(dian)(dian)(dian)流很大。

　　這么大的(de)(de)啟動(dong)電(dian)(dian)流(liu)將帶來以下不良后果：使電(dian)(dian)網電(dian)(dian)壓產(chan)生波(bo)動(dong)（特別是(shi)容量較大的(de)(de)電(dian)(dian)動(dong)機啟動(dong)時），從而影響到接在電(dian)(dian)網上的(de)(de)其(qi)它設備(bei)的(de)(de)正(zheng)常(chang)運行。

　　使(shi)電(dian)(dian)(dian)動(dong)(dong)機(ji)繞組發熱，絕(jue)緣老化(hua)，從而縮(suo)短了電(dian)(dian)(dian)動(dong)(dong)機(ji)的使(shi)用(yong)壽命(ming)。特別是對經常需(xu)要(yao)啟(qi)(qi)動(dong)(dong)的電(dian)(dian)(dian)動(dong)(dong)機(ji)影響(xiang)較大(da)。啟(qi)(qi)動(dong)(dong)瞬間，由于(yu)電(dian)(dian)(dian)動(dong)(dong)機(ji)轉子電(dian)(dian)(dian)路功率因素較低，啟(qi)(qi)動(dong)(dong)轉矩并(bing)不很大(da)。如果啟(qi)(qi)動(dong)(dong)轉矩小于(yu)負(fu)載(zai)轉矩則電(dian)(dian)(dian)動(dong)(dong)機(ji)將無法啟(qi)(qi)動(dong)(dong)。綜(zong)上所述，異(yi)步電(dian)(dian)(dian)動(dong)(dong)機(ji)啟(qi)(qi)動(dong)(dong)時的主要(yao)缺點(dian)是啟(qi)(qi)動(dong)(dong)電(dian)(dian)(dian)流(liu)較大(da)。為了減小啟(qi)(qi)動(dong)(dong)電(dian)(dian)(dian)流(liu)，須采用(yong)適(shi)當的啟(qi)(qi)動(dong)(dong)方(fang)法。

電動機