1　轴承电流产生原因及危害

在(zai)(zai)(zai)感(gan)应电(dian)(dian)(dian)(dian)(dian)(dian)(dian)动(dong)机(ji)中(zhong)，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)(de)(de)(de)(de)轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)是(shi)始终存在(zai)(zai)(zai)的(de)(de)(de)(de)(de)(de)(de)。正(zheng)弦波(bo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源驱动(dong)下(xia)，因电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机(ji)定(ding)(ding)转子齿槽(cao)尺(chi)寸的(de)(de)(de)(de)(de)(de)(de)偏差(cha)，磁(ci)性材料定(ding)(ding)向(xiang)属性的(de)(de)(de)(de)(de)(de)(de)改变(bian)(bian)(bian)，或者供电(dian)(dian)(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源三相(xiang)不(bu)平(ping)衡等原因，都(dou)会(hui)引起(qi)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机(ji)磁(ci)通(tong)的(de)(de)(de)(de)(de)(de)(de)不(bu)平(ping)衡，在(zai)(zai)(zai)转子轴(zhou)(zhou)(zhou)上(shang)产(chan)生轴(zhou)(zhou)(zhou)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)和轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。这(zhei)种轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)幅(fu)值较小(xiao)，危(wei)害不(bu)大(da)。在(zai)(zai)(zai)变(bian)(bian)(bian)频(pin)器(qi)(qi)(qi)(qi)驱动(dong)下(xia)，因产(chan)生原理的(de)(de)(de)(de)(de)(de)(de)不(bu)同，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机(ji)轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)(de)(de)危(wei)害大(da)大(da)增加。通(tong)用(yong)(yong)变(bian)(bian)(bian)频(pin)器(qi)(qi)(qi)(qi)多采用(yong)(yong)PWM调制方式(shi)，逆变(bian)(bian)(bian)回路用(yong)(yong)高(gao)频(pin)功率(lv)(lv)元件（如IGBT等），在(zai)(zai)(zai)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机(ji)上(shang)得到近似正(zheng)弦的(de)(de)(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)波(bo)形(xing)。三相(xiang)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)基波(bo)分(fen)量(liang)的(de)(de)(de)(de)(de)(de)(de)合成(cheng)(cheng)(cheng)矢量(liang)为(wei)零，但实际上(shang)每(mei)一瞬(shun)间(jian)三相(xiang)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)矢量(liang)和不(bu)为(wei)零，三相(xiang)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)是(shi)不(bu)平(ping)衡的(de)(de)(de)(de)(de)(de)(de)。该合成(cheng)(cheng)(cheng)共模(mo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)幅(fu)值等于变(bian)(bian)(bian)频(pin)器(qi)(qi)(qi)(qi)直流(liu)侧(ce)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，频(pin)率(lv)(lv)等于逆变(bian)(bian)(bian)器(qi)(qi)(qi)(qi)开(kai)关频(pin)率(lv)(lv)。该共模(mo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)经定(ding)(ding)转子之间(jian)的(de)(de)(de)(de)(de)(de)(de)静电(dian)(dian)(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)容耦(ou)合在(zai)(zai)(zai)转子轴(zhou)(zhou)(zhou)上(shang)也产(chan)生相(xiang)同频(pin)率(lv)(lv)的(de)(de)(de)(de)(de)(de)(de)轴(zhou)(zhou)(zhou)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，通(tong)常变(bian)(bian)(bian)频(pin)器(qi)(qi)(qi)(qi)逆变(bian)(bian)(bian)侧(ce)载波(bo)频(pin)率(lv)(lv)很(hen)高(gao)，在(zai)(zai)(zai)10kHz以上(shang)，过(guo)高(gao)的(de)(de)(de)(de)(de)(de)(de)频(pin)率(lv)(lv)和定(ding)(ding)子、电(dian)(dian)(dian)(dian)(dian)(dian)(dian)缆(lan)相(xiang)感(gan)应，产(chan)生很(hen)高(gao)的(de)(de)(de)(de)(de)(de)(de)dv/dt前后(hou)沿，加大(da)波(bo)形(xing)畸变(bian)(bian)(bian)。由于静电(dian)(dian)(dian)(dian)(dian)(dian)(dian)耦(ou)合，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机(ji)各(ge)部分(fen)之间(jian)有大(da)小(xiao)不(bu)等的(de)(de)(de)(de)(de)(de)(de)分(fen)布电(dian)(dian)(dian)(dian)(dian)(dian)(dian)容，构(gou)成(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)(de)(de)(de)(de)零序回路，其中(zhong)流(liu)经轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)的(de)(de)(de)(de)(de)(de)(de)对(dui)地放(fang)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)就形(xing)成(cheng)(cheng)(cheng)轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。正(zheng)常状态下(xia)，轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)滚(gun)珠悬浮在(zai)(zai)(zai)润滑脂(zhi)形(xing)成(cheng)(cheng)(cheng)的(de)(de)(de)(de)(de)(de)(de)油(you)(you)膜(mo)中(zhong)，润滑油(you)(you)膜(mo)起(qi)到绝缘作用(yong)(yong)，当油(you)(you)膜(mo)因某(mou)种原因被破坏或过(guo)高(gao)的(de)(de)(de)(de)(de)(de)(de)dv/dt轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)都(dou)会(hui)击穿油(you)(you)膜(mo)形(xing)成(cheng)(cheng)(cheng)放(fang)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)，放(fang)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)在(zai)(zai)(zai)轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)内外(wai)圈(quan)和滚(gun)珠上(shang)形(xing)成(cheng)(cheng)(cheng)烧(shao)蚀，长时间(jian)运行会(hui)发(fa)展成(cheng)(cheng)(cheng)延轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)内外(wai)圈(quan)一周的(de)(de)(de)(de)(de)(de)(de)象搓衣(yi)板样的(de)(de)(de)(de)(de)(de)(de)条纹(wen)，并升(sheng)高(gao)轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)温度，溶化润滑脂(zhi)，更加劣化轴(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)的(de)(de)(de)(de)(de)(de)(de)运行。

2　共模电流的路径

由于静电耦合，电机各部分间都有或大或小的分布电容，构成电机定子上共模电流的泄放路径。大部分共模电流经定子—机壳—地—变频器外壳这一路径，一小部分经定子—转子—转轴—轴承—机壳—地—变频器外壳这一路径。当变频器接地与电机外壳间阻抗高于变频器外壳与负载间阻抗时还会产生轴延伸电流，经定子—机壳—转轴—负荷端轴承（电机）—联轴器—轴承（负载）—地—变频器外壳这一回路泄放，不但危害电机负荷端轴承，还会危害负载轴承和联轴器。后两路共模电流流经电机轴承，造成危害并以第二种途径危害更大。

3　常见的轴承电流抑制措施

有多种方法抑制轴承电流，如在变频器输出侧加装正弦波滤波器，改善输出电流波形；将电机一端的轴承做绝缘处理，截断流经电机转轴和轴承的环流；在电机输出轴上安装接地碳刷，抑制经负荷接地的轴延伸电流等等。这多种方式能抑制相应的。

4　风机负荷端轴承损坏过程分析

基于以(yi)上的轴(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)流(liu)(liu)形成(cheng)原(yuan)(yuan)理，并结合电(dian)(dian)(dian)机的运(yun)行情况，我们(men)分(fen)析负荷端(duan)(duan)轴(zhou)(zhou)承(cheng)(cheng)(cheng)的损坏失效(xiao)是(shi)一(yi)个过程(cheng)(cheng)，轴(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)流(liu)(liu)是(shi)主要原(yuan)(yuan)因，同(tong)时(shi)机械(xie)震动、润(run)滑(hua)脂(zhi)消耗(hao)等是(shi)次要原(yuan)(yuan)因，促成(cheng)轴(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)流(liu)(liu)的形成(cheng)，并一(yi)定程(cheng)(cheng)度(du)上加(jia)重(zhong)了危害。风机电(dian)(dian)(dian)机投用后，由于轴(zhou)(zhou)承(cheng)(cheng)(cheng)间(jian)隙均(jun)匀(yun)，润(run)滑(hua)充(chong)分(fen)，润(run)滑(hua)油膜均(jun)匀(yun)，轴(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)流(liu)(liu)还不构(gou)成(cheng)很大(da)(da)(da)威胁，随着润(run)滑(hua)脂(zhi)的消耗(hao)，负荷端(duan)(duan)的震动加(jia)大(da)(da)(da)首(shou)先导致负荷端(duan)(duan)轴(zhou)(zhou)承(cheng)(cheng)(cheng)间(jian)隙加(jia)大(da)(da)(da)，轴(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)压击穿放电(dian)(dian)(dian)严(yan)重(zhong)，轴(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)流(liu)(liu)增大(da)(da)(da)，使得负荷端(duan)(duan)轴(zhou)(zhou)承(cheng)(cheng)(cheng)内道出现(xian)电(dian)(dian)(dian)烧蚀(shi)，温(wen)度(du)升高，润(run)滑(hua)脂(zhi)液化，直到轴(zhou)(zhou)承(cheng)(cheng)(cheng)磨损严(yan)重(zhong)，发热烧损。所以(yi)，我们(men)认为(wei)应采用综合治理，以(yi)多(duo)种方法减少和抑制轴(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)流(liu)(liu)。而绝缘(yuan)轴(zhou)(zhou)承(cheng)(cheng)(cheng)等方法由于实施难度(du)较大(da)(da)(da)暂不考虑(lv)。