1　軸承電流產生原因及危害

在(zai)(zai)感(gan)應電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)機(ji)中，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)的(de)(de)(de)(de)(de)(de)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)是(shi)始終存在(zai)(zai)的(de)(de)(de)(de)(de)(de)。正(zheng)弦(xian)波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源驅動(dong)下(xia)，因(yin)(yin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)定(ding)轉(zhuan)(zhuan)子(zi)齒槽尺(chi)寸的(de)(de)(de)(de)(de)(de)偏差，磁性(xing)材料定(ding)向屬性(xing)的(de)(de)(de)(de)(de)(de)改變(bian)(bian)(bian)，或者(zhe)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源三(san)相(xiang)不(bu)(bu)平衡(heng)等(deng)(deng)原(yuan)因(yin)(yin)，都會引(yin)起電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)磁通(tong)(tong)的(de)(de)(de)(de)(de)(de)不(bu)(bu)平衡(heng)，在(zai)(zai)轉(zhuan)(zhuan)子(zi)軸(zhou)(zhou)(zhou)(zhou)上產生軸(zhou)(zhou)(zhou)(zhou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)和軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。這種(zhong)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)幅值(zhi)較小，危(wei)害不(bu)(bu)大(da)。在(zai)(zai)變(bian)(bian)(bian)頻(pin)器驅動(dong)下(xia)，因(yin)(yin)產生原(yuan)理(li)的(de)(de)(de)(de)(de)(de)不(bu)(bu)同，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)(de)危(wei)害大(da)大(da)增加。通(tong)(tong)用(yong)(yong)變(bian)(bian)(bian)頻(pin)器多采用(yong)(yong)PWM調制(zhi)方式(shi)，逆變(bian)(bian)(bian)回路(lu)用(yong)(yong)高(gao)(gao)頻(pin)功(gong)率(lv)元件（如IGBT等(deng)(deng)），在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)上得到(dao)近似正(zheng)弦(xian)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)波形(xing)。三(san)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)基波分(fen)量的(de)(de)(de)(de)(de)(de)合成(cheng)(cheng)矢(shi)量為零，但(dan)實(shi)際(ji)上每一(yi)瞬間(jian)(jian)三(san)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)矢(shi)量和不(bu)(bu)為零，三(san)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)是(shi)不(bu)(bu)平衡(heng)的(de)(de)(de)(de)(de)(de)。該(gai)合成(cheng)(cheng)共模電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)幅值(zhi)等(deng)(deng)于變(bian)(bian)(bian)頻(pin)器直流(liu)(liu)側(ce)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，頻(pin)率(lv)等(deng)(deng)于逆變(bian)(bian)(bian)器開關頻(pin)率(lv)。該(gai)共模電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經定(ding)轉(zhuan)(zhuan)子(zi)之間(jian)(jian)的(de)(de)(de)(de)(de)(de)靜電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容耦合在(zai)(zai)轉(zhuan)(zhuan)子(zi)軸(zhou)(zhou)(zhou)(zhou)上也產生相(xiang)同頻(pin)率(lv)的(de)(de)(de)(de)(de)(de)軸(zhou)(zhou)(zhou)(zhou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，通(tong)(tong)常(chang)變(bian)(bian)(bian)頻(pin)器逆變(bian)(bian)(bian)側(ce)載(zai)波頻(pin)率(lv)很(hen)高(gao)(gao)，在(zai)(zai)10kHz以上，過高(gao)(gao)的(de)(de)(de)(de)(de)(de)頻(pin)率(lv)和定(ding)子(zi)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜相(xiang)感(gan)應，產生很(hen)高(gao)(gao)的(de)(de)(de)(de)(de)(de)dv/dt前后沿，加大(da)波形(xing)畸變(bian)(bian)(bian)。由于靜電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)耦合，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)各(ge)部分(fen)之間(jian)(jian)有大(da)小不(bu)(bu)等(deng)(deng)的(de)(de)(de)(de)(de)(de)分(fen)布(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容，構成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)的(de)(de)(de)(de)(de)(de)零序(xu)回路(lu)，其中流(liu)(liu)經軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)的(de)(de)(de)(de)(de)(de)對地放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)就形(xing)成(cheng)(cheng)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。正(zheng)常(chang)狀(zhuang)態(tai)下(xia)，軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)滾珠(zhu)懸浮(fu)在(zai)(zai)潤(run)滑脂形(xing)成(cheng)(cheng)的(de)(de)(de)(de)(de)(de)油(you)膜中，潤(run)滑油(you)膜起到(dao)絕緣作用(yong)(yong)，當油(you)膜因(yin)(yin)某種(zhong)原(yuan)因(yin)(yin)被破壞或過高(gao)(gao)的(de)(de)(de)(de)(de)(de)dv/dt軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)都會擊穿油(you)膜形(xing)成(cheng)(cheng)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)在(zai)(zai)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)內外圈和滾珠(zhu)上形(xing)成(cheng)(cheng)燒(shao)蝕，長時間(jian)(jian)運行(xing)會發展(zhan)成(cheng)(cheng)延軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)內外圈一(yi)周的(de)(de)(de)(de)(de)(de)象搓衣(yi)板樣的(de)(de)(de)(de)(de)(de)條紋，并(bing)升(sheng)高(gao)(gao)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)溫度(du)，溶化潤(run)滑脂，更加劣化軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)的(de)(de)(de)(de)(de)(de)運行(xing)。

2　共模電流的路徑

由于靜電耦合，電機各部分間都有或大或小的分布電容，構成電機定子上共模電流的泄放路徑。大部分共模電流經定子—機殼—地—變頻器外殼這一路徑，一小部分經定子—轉子—轉軸—軸承—機殼—地—變頻器外殼這一路徑。當變頻器接地與電機外殼間阻抗高于變頻器外殼與負載間阻抗時還會產生軸延伸電流，經定子—機殼—轉軸—負荷端軸承（電機）—聯軸器—軸承（負載）—地—變頻器外殼這一回路泄放，不但危害電機負荷端軸承，還會危害負載軸承和聯軸器。后兩路共模電流流經電機軸承，造成危害并以第二種途徑危害更大。

3　常見的軸承電流抑制措施

有多種方法抑制軸承電流，如在變頻器輸出側加裝正弦波濾波器，改善輸出電流波形；將電機一端的軸承做絕緣處理，截斷流經電機轉軸和軸承的環流；在電機輸出軸上安裝接地碳刷，抑制經負荷接地的軸延伸電流等等。這多種方式能抑制相應的。

4　風機負荷端軸承損壞過程分析

基(ji)于以上(shang)的(de)(de)(de)軸(zhou)(zhou)(zhou)承電(dian)(dian)流(liu)形(xing)成原(yuan)(yuan)理(li)，并結(jie)合(he)電(dian)(dian)機(ji)(ji)的(de)(de)(de)運行(xing)情況，我(wo)們分(fen)析負荷(he)(he)端(duan)軸(zhou)(zhou)(zhou)承的(de)(de)(de)損(sun)壞失(shi)效是(shi)一個過程，軸(zhou)(zhou)(zhou)承電(dian)(dian)流(liu)是(shi)主(zhu)要原(yuan)(yuan)因，同(tong)時機(ji)(ji)械震動(dong)、潤(run)滑(hua)(hua)脂消耗等是(shi)次(ci)要原(yuan)(yuan)因，促成軸(zhou)(zhou)(zhou)承電(dian)(dian)流(liu)的(de)(de)(de)形(xing)成，并一定程度上(shang)加重了危害。風機(ji)(ji)電(dian)(dian)機(ji)(ji)投(tou)用(yong)后(hou)，由于軸(zhou)(zhou)(zhou)承間(jian)隙均(jun)勻(yun)(yun)，潤(run)滑(hua)(hua)充分(fen)，潤(run)滑(hua)(hua)油(you)膜均(jun)勻(yun)(yun)，軸(zhou)(zhou)(zhou)承電(dian)(dian)流(liu)還不構成很大(da)威脅，隨著潤(run)滑(hua)(hua)脂的(de)(de)(de)消耗，負荷(he)(he)端(duan)的(de)(de)(de)震動(dong)加大(da)首先導致(zhi)負荷(he)(he)端(duan)軸(zhou)(zhou)(zhou)承間(jian)隙加大(da)，軸(zhou)(zhou)(zhou)承電(dian)(dian)壓擊穿放電(dian)(dian)嚴重，軸(zhou)(zhou)(zhou)承電(dian)(dian)流(liu)增大(da)，使得負荷(he)(he)端(duan)軸(zhou)(zhou)(zhou)承內道(dao)出(chu)現電(dian)(dian)燒蝕，溫度升高，潤(run)滑(hua)(hua)脂液化，直到軸(zhou)(zhou)(zhou)承磨損(sun)嚴重，發熱(re)燒損(sun)。所以，我(wo)們認為應(ying)采用(yong)綜(zong)合(he)治(zhi)理(li)，以多種方(fang)法(fa)減少和抑制軸(zhou)(zhou)(zhou)承電(dian)(dian)流(liu)。而絕緣軸(zhou)(zhou)(zhou)承等方(fang)法(fa)由于實施難度較大(da)暫不考慮。