CPG三(san)相電(dian)動(dong)機(ji)，具(ju)有(you)一定的(de)過(guo)載(zai)能力，短時間過(guo)載(zai)對電(dian)動(dong)機(ji)的(de)影響不大，但是，電(dian)動(dong)機(ji)的(de)電(dian)流(liu)(liu)長時間超過(guo)額定電(dian)流(liu)(liu)，就(jiu)會使(shi)(shi)電(dian)動(dong)機(ji)嚴重(zhong)發(fa)熱(re)而損壞，如果電(dian)動(dong)機(ji)定子(zi)繞組內部發(fa)生短路，也(ye)會使(shi)(shi)繞組電(dian)流(liu)(liu)增加而燒毀(hui)電(dian)機(ji)。所以三(san)相電(dian)動(dong)機(ji)需(xu)要有(you)的(de)保(bao)護(hu)(hu)裝置包(bao)括，過(guo)載(zai)保(bao)護(hu)(hu)，短路保(bao)護(hu)(hu)、缺相保(bao)護(hu)(hu)，漏電(dian)保(bao)護(hu)(hu)，過(guo)熱(re)保(bao)護(hu)(hu)等，下(xia)面就(jiu)來具(ju)體介紹(shao)下(xia)這幾種(zhong)保(bao)護(hu)(hu)。

1.電動(dong)機的(de)過載(zai)保護(hu)，在(zai)電動(dong)機的(de)控制回路安裝EOCR電機保護(hu)器，在(zai)過載(zai)運行時EOCR檢測三相電流并判(pan)斷(duan)是(shi)否過流。一般(ban)選擇EOCR時，動(dong)作電流按電動(dong)機額定(ding)電流的(de)1.1~1.2倍(bei)選擇。

2. 三(san)相(xiang)電(dian)(dian)(dian)動(dong)機(ji)的短路(lu)(lu)保(bao)護，電(dian)(dian)(dian)動(dong)機(ji)繞組或(huo)者是線(xian)路(lu)(lu)短路(lu)(lu)時，短路(lu)(lu)電(dian)(dian)(dian)流很(hen)大，熱繼電(dian)(dian)(dian)器(qi)還(huan)來不(bu)及動(dong)作，電(dian)(dian)(dian)動(dong)機(ji)可能(neng)已損(sun)壞。因此，EOCR短路(lu)(lu)保(bao)護具(ju)有速斷功能(neng)，可直(zhi)接控制斷路(lu)(lu)器(qi)的脫(tuo)扣線(xian)圈動(dong)作。

3.三相(xiang)電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)缺(que)相(xiang)保護，若電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)在運(yun)行(xing)中斷一(yi)相(xiang)電(dian)源，雖(sui)然能(neng)繼續(xu)運(yun)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)，但轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速降低，電(dian)流增大(da)，當(dang)(dang)電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)兩相(xiang)運(yun)行(xing)時(shi)，定子磁(ci)場(chang)(chang)由三相(xiang)旋(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場(chang)(chang)變為單(dan)相(xiang)脈動(dong)(dong)(dong)磁(ci)場(chang)(chang)，這個脈動(dong)(dong)(dong)磁(ci)場(chang)(chang)可分(fen)為兩個旋(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)方(fang)向(xiang)相(xiang)反的(de)旋(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場(chang)(chang)，其中正(zheng)向(xiang)旋(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場(chang)(chang)將產生一(yi)個正(zheng)向(xiang)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩使(shi)電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)繼續(xu)運(yun)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)，因(yin)(yin)為反方(fang)向(xiang)磁(ci)場(chang)(chang)產生的(de)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩抵(di)消了一(yi)部分(fen)正(zheng)向(xiang)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩，因(yin)(yin)此使(shi)電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)的(de)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)距比原來轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩降低了許多，另外，兩相(xiang)運(yun)行(xing)時(shi)產生的(de)附(fu)加(jia)損耗使(shi)電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)發(fa)(fa)熱，兩相(xiang)電(dian)流過(guo)大(da)也(ye)容易燒壞(huai)電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)繞(rao)組。所以電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)不允許長時(shi)間(jian)缺(que)相(xiang)運(yun)行(xing)，應當(dang)(dang)裝設保護裝置，使(shi)電(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)在發(fa)(fa)生缺(que)相(xiang)時(shi)退出運(yun)行(xing)。

4.電(dian)動(dong)機(ji)(ji)漏(lou)(lou)電(dian)保護，當電(dian)動(dong)機(ji)(ji)絕緣(yuan)老化或者是(shi)溫度過高(gao)引起損(sun)壞(huai)絕緣(yuan)，或者受潮，浸水都(dou)會使繞(rao)組(zu)對地絕緣(yuan)降(jiang)低導致(zhi)外(wai)殼帶電(dian)，繞(rao)組(zu)絕緣(yuan)降(jiang)低極易導致(zhi)繞(rao)組(zu)局部短路產(chan)生(sheng)高(gao)溫，燒壞(huai)繞(rao)組(zu)，外(wai)殼帶電(dian)危及人身(shen)安全，所以電(dian)動(dong)機(ji)(ji)必須安裝漏(lou)(lou)電(dian)保護裝置。

5.電(dian)機過(guo)熱保護，電(dian)機繞(rao)組溫(wen)度(du)過(guo)高是引起(qi)繞(rao)組絕緣老化，相間和匝間短(duan)路的主要(yao)原因(yin)。最(zui)直(zhi)接的辦(ban)法就(jiu)是在定(ding)子(zi)繞(rao)組內安裝溫(wen)度(du)保護裝置，使(shi)電(dian)動機接近允(yun)許溫(wen)度(du)時便自(zi)動切斷電(dian)路。