電(dian)(dian)(dian)流(liu)形成(cheng)的(de)基(ji)本條件是，電(dian)(dian)(dian)壓(ya)(ya)和閉合(he)回(hui)(hui)路。產(chan)生軸(zhou)電(dian)(dian)(dian)流(liu)的(de)前提是有軸(zhou)電(dian)(dian)(dian)壓(ya)(ya)，并且有一(yi)個閉合(he)的(de)回(hui)(hui)路。防爆電(dian)(dian)(dian)機運(yun)行(xing)過程中為何會有軸(zhou)電(dian)(dian)(dian)壓(ya)(ya)呢？產(chan)生軸(zhou)電(dian)(dian)(dian)壓(ya)(ya)的(de)原因(yin)有兩(liang)種，一(yi)種是交(jiao)變磁(ci)通，另一(yi)種是靜電(dian)(dian)(dian)荷積(ji)累。

前者產生(sheng)(sheng)的(de)(de)(de)軸電(dian)(dian)(dian)(dian)壓是(shi)連續的(de)(de)(de)、周期性的(de)(de)(de)。通常(chang)情況下，防爆電(dian)(dian)(dian)(dian)機(ji)的(de)(de)(de)轉(zhuan)(zhuan)子在(zai)對(dui)稱(cheng)的(de)(de)(de)、正弦交(jiao)變(bian)(bian)磁(ci)場中運行(xing)，電(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)轉(zhuan)(zhuan)子切割磁(ci)場感(gan)應的(de)(de)(de)交(jiao)變(bian)(bian)電(dian)(dian)(dian)(dian)勢(shi)，所(suo)(suo)產生(sheng)(sheng)的(de)(de)(de)交(jiao)變(bian)(bian)電(dian)(dian)(dian)(dian)流也是(shi)對(dui)稱(cheng)的(de)(de)(de)，所(suo)(suo)以，正常(chang)時轉(zhuan)(zhuan)子兩端間不會有(you)不對(dui)稱(cheng)電(dian)(dian)(dian)(dian)壓。但是(shi)，當(dang)電(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)的(de)(de)(de)定子鐵心，在(zai)圓周方向(xiang)上的(de)(de)(de)磁(ci)阻出(chu)現不平衡時，就會產生(sheng)(sheng)不對(dui)稱(cheng)交(jiao)變(bian)(bian)電(dian)(dian)(dian)(dian)勢(shi)，也就產生(sheng)(sheng)了軸電(dian)(dian)(dian)(dian)壓，這種電(dian)(dian)(dian)(dian)壓是(shi)沿軸向(xiang)而產生(sheng)(sheng)的(de)(de)(de)。而靜電(dian)(dian)(dian)(dian)荷產生(sheng)(sheng)的(de)(de)(de)軸電(dian)(dian)(dian)(dian)壓是(shi)間歇(xie)的(de)(de)(de)，并且是(shi)非周期的(de)(de)(de)。電(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)在(zai)運行(xing)過程中，負(fu)載方面的(de)(de)(de)流體(ti)會與運行(xing)的(de)(de)(de)旋轉(zhuan)(zhuan)體(ti)摩擦而在(zai)旋轉(zhuan)(zhuan)體(ti)上產生(sheng)(sheng)靜電(dian)(dian)(dian)(dian)荷，電(dian)(dian)(dian)(dian)荷逐漸(jian)積(ji)累(lei)便(bian)產生(sheng)(sheng)軸電(dian)(dian)(dian)(dian)壓。

軸電流對電機的危害(hai)

電機運(yun)行中，轉(zhuan)子軸(zhou)電壓(ya)一旦形成回路，就會產生(sheng)軸(zhou)電流，是(shi)一種典型的(de)(de)低電壓(ya)大(da)電流模式。軸(zhou)與軸(zhou)瓦之間采用油(you)潤滑，電機軸(zhou)承是(shi)壓(ya)在油(you)膜(mo)上的(de)(de)。由于軸(zhou)電壓(ya)幅值較(jiao)低，油(you)膜(mo)的(de)(de)絕緣一般是(shi)不會被擊穿的(de)(de)。

在轉(zhuan)子(zi)高(gao)速運轉(zhuan)過程(cheng)中，如果出現潤滑油油質不合(he)要(yao)求，或(huo)缺油等情(qing)況時(shi)，會(hui)造成油膜破裂被擊(ji)(ji)穿，導致軸(zhou)與軸(zhou)瓦形成金屬性(xing)接觸，在接觸的(de)瞬(shun)間，軸(zhou)電(dian)壓(ya)會(hui)形成閉合(he)回路，形成低(di)電(dian)壓(ya)擊(ji)(ji)穿。這(zhe)時(shi)，產生(sheng)的(de)軸(zhou)電(dian)流相當大，瞬(shun)間可達到幾百安甚至上千安，它(ta)足以把軸(zhou)頸和軸(zhou)瓦燒壞。

由運(yun)行(xing)摩(mo)擦在軸(zhou)上產(chan)生的靜電(dian)(dian)荷(he)的逐(zhu)漸積(ji)累，使軸(zhou)的電(dian)(dian)位因被充電(dian)(dian)而(er)不斷(duan)升高(gao)。當運(yun)轉的軸(zhou)接觸(chu)到旋(xuan)轉體(ti)以外的任何部(bu)件時(shi)，便通過(guo)該(gai)部(bu)件進行(xing)放電(dian)(dian)。如(ru)(ru)果運(yun)轉的軸(zhou)一直(zhi)不接觸(chu)旋(xuan)轉體(ti)外的部(bu)件，會一直(zhi)積(ji)累電(dian)(dian)荷(he)，最后(hou)產(chan)生過(guo)高(gao)的電(dian)(dian)壓。如(ru)(ru)果該(gai)電(dian)(dian)壓超過(guo)軸(zhou)承(cheng)油膜的絕緣強度，則(ze)電(dian)(dian)荷(he)在極短(duan)的時(shi)間內(nei)放電(dian)(dian)，形(xing)成軸(zhou)電(dian)(dian)流。

軸(zhou)(zhou)(zhou)(zhou)電(dian)(dian)流會在轉(zhuan)(zhuan)軸(zhou)(zhou)(zhou)(zhou)、軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)內圈(quan)、軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)外(wai)圈(quan)、軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)室構成(cheng)的(de)(de)回路中流過，最(zui)顯著(zhu)的(de)(de)現(xian)象是(shi)在轉(zhuan)(zhuan)軸(zhou)(zhou)(zhou)(zhou)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)位(wei)置和(he)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)內圈(quan)表面(mian)因電(dian)(dian)弧放電(dian)(dian)產生(sheng)的(de)(de)小而深的(de)(de)圓(yuan)形(xing)蝕點。軸(zhou)(zhou)(zhou)(zhou)電(dian)(dian)流不(bu)但破壞(huai)油膜的(de)(de)穩定和(he)油膜形(xing)成(cheng)條(tiao)件，而且(qie)由于(yu)放電(dian)(dian)在轉(zhuan)(zhuan)軸(zhou)(zhou)(zhou)(zhou)和(he)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)內圈(quan)的(de)(de)表面(mian)，產生(sheng)很多(duo)蝕點，破壞(huai)了(le)轉(zhuan)(zhuan)軸(zhou)(zhou)(zhou)(zhou)與軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)的(de)(de)良好配合(he)，從而造成(cheng)軸(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)無法工作。在特殊情況下強大(da)的(de)(de)軸(zhou)(zhou)(zhou)(zhou)電(dian)(dian)流會在軸(zhou)(zhou)(zhou)(zhou)頸和(he)軸(zhou)(zhou)(zhou)(zhou)瓦的(de)(de)接觸面(mian)上產生(sheng)強烈的(de)(de)電(dian)(dian)弧，導致軸(zhou)(zhou)(zhou)(zhou)頸和(he)軸(zhou)(zhou)(zhou)(zhou)瓦損壞(huai)情況，造成(cheng)電(dian)(dian)機(ji)振動(dong)和(he)噪(zao)聲，最(zui)后使(shi)電(dian)(dian)機(ji)不(bu)能正常運轉(zhuan)(zhuan)。