為什么電動機過載保護器會不工作?
電動機過載保護器在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)工作(zuo)(zuo)(zuo)(zuo)正常時(shi)(shi)不動(dong)(dong)作(zuo)(zuo)(zuo)(zuo),而當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)超(chao)越某(mou)一(yi)(yi)整(zheng)定值時(shi)(shi)繼電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)才(cai)發作(zuo)(zuo)(zuo)(zuo)斷(duan)開(kai)動(dong)(dong)作(zuo)(zuo)(zuo)(zuo),給接觸器(qi)(qi)一(yi)(yi)個(ge)斷(duan)開(kai)信號,斷(duan)開(kai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源,從而保護電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)的(de)(de)作(zuo)(zuo)(zuo)(zuo)用。一(yi)(yi)般,溝通過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)過(guo)載(zai)保護器(qi)(qi)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)整(zheng)定規模一(yi)(yi)般為額定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu),當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)過(guo)載(zai)保護器(qi)(qi)的(de)(de)采樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)超(chao)過(guo)額定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)1.2倍(bei)時(shi)(shi),保護器(qi)(qi)才(cai)會斷(duan)開(kai)常閉(bi)觸點(dian)。由于過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)過(guo)載(zai)保護器(qi)(qi)在正常情況下(即電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)在額定值時(shi)(shi))是常閉(bi)的(de)(de),只有當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)時(shi)(shi)才(cai)動(dong)(dong)作(zuo)(zuo)(zuo)(zuo)。
運行時(shi),一般允(yun)許(xu)短(duan)時(shi)間過(guo)(guo)載(輸出功(gong)率超(chao)過(guo)(guo)額定值稱(cheng)為(wei)過(guo)(guo)載),但是(shi),如果負載時(shi)間太長,電動(dong)(dong)機(ji)的(de)溫升超(chao)過(guo)(guo)允(yun)許(xu)值,就(jiu)會(hui)造(zao)成(cheng)(cheng)絕緣老(lao)化(hua),縮短(duan)使用壽(shou)命,嚴重時(shi)甚至燒毀繞(rao)組。因此,為(wei)了防止電動(dong)(dong)機(ji)長時(shi)間過(guo)(guo)載運行而造(zao)成(cheng)(cheng)損(sun)壞,過(guo)(guo)載時(shi)間必須加以限制,這(zhe)種(zhong)保(bao)護就(jiu)是(shi)電動(dong)(dong)機(ji)的(de)過(guo)(guo)載保(bao)護。