1　轴承电流产生原因及危害

在(zai)(zai)(zai)感应电(dian)(dian)(dian)(dian)(dian)动机(ji)中，电(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)流(liu)是始终(zhong)存在(zai)(zai)(zai)的(de)(de)(de)。正弦(xian)波(bo)电(dian)(dian)(dian)(dian)(dian)源(yuan)驱(qu)动下，因(yin)电(dian)(dian)(dian)(dian)(dian)机(ji)定转子(zi)齿槽尺(chi)寸的(de)(de)(de)偏差(cha)，磁性材料定向属性的(de)(de)(de)改变(bian)(bian)(bian)(bian)，或(huo)者供电(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)源(yuan)三(san)(san)相(xiang)(xiang)不(bu)(bu)平(ping)衡(heng)等(deng)(deng)原(yuan)因(yin)，都会引起电(dian)(dian)(dian)(dian)(dian)机(ji)磁通(tong)的(de)(de)(de)不(bu)(bu)平(ping)衡(heng)，在(zai)(zai)(zai)转子(zi)轴(zhou)(zhou)(zhou)(zhou)(zhou)上(shang)产(chan)(chan)(chan)生轴(zhou)(zhou)(zhou)(zhou)(zhou)电(dian)(dian)(dian)(dian)(dian)压(ya)和轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)流(liu)。这(zhei)种轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)压(ya)幅(fu)值(zhi)较小，危害不(bu)(bu)大。在(zai)(zai)(zai)变(bian)(bian)(bian)(bian)频(pin)(pin)(pin)(pin)器(qi)驱(qu)动下，因(yin)产(chan)(chan)(chan)生原(yuan)理的(de)(de)(de)不(bu)(bu)同，电(dian)(dian)(dian)(dian)(dian)机(ji)轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)危害大大增加(jia)。通(tong)用(yong)变(bian)(bian)(bian)(bian)频(pin)(pin)(pin)(pin)器(qi)多采用(yong)PWM调制方(fang)式，逆变(bian)(bian)(bian)(bian)回(hui)(hui)路用(yong)高(gao)(gao)(gao)频(pin)(pin)(pin)(pin)功率(lv)(lv)(lv)元件（如IGBT等(deng)(deng)），在(zai)(zai)(zai)电(dian)(dian)(dian)(dian)(dian)机(ji)上(shang)得(de)到近似(si)正弦(xian)的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)压(ya)波(bo)形(xing)。三(san)(san)相(xiang)(xiang)电(dian)(dian)(dian)(dian)(dian)压(ya)基波(bo)分(fen)量的(de)(de)(de)合成(cheng)(cheng)矢量为(wei)零(ling)(ling)，但实际上(shang)每一瞬(shun)间三(san)(san)相(xiang)(xiang)电(dian)(dian)(dian)(dian)(dian)压(ya)矢量和不(bu)(bu)为(wei)零(ling)(ling)，三(san)(san)相(xiang)(xiang)电(dian)(dian)(dian)(dian)(dian)压(ya)是不(bu)(bu)平(ping)衡(heng)的(de)(de)(de)。该合成(cheng)(cheng)共模(mo)电(dian)(dian)(dian)(dian)(dian)压(ya)幅(fu)值(zhi)等(deng)(deng)于(yu)变(bian)(bian)(bian)(bian)频(pin)(pin)(pin)(pin)器(qi)直(zhi)流(liu)侧(ce)电(dian)(dian)(dian)(dian)(dian)压(ya)，频(pin)(pin)(pin)(pin)率(lv)(lv)(lv)等(deng)(deng)于(yu)逆变(bian)(bian)(bian)(bian)器(qi)开关频(pin)(pin)(pin)(pin)率(lv)(lv)(lv)。该共模(mo)电(dian)(dian)(dian)(dian)(dian)压(ya)经定转子(zi)之间的(de)(de)(de)静电(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)容(rong)耦合在(zai)(zai)(zai)转子(zi)轴(zhou)(zhou)(zhou)(zhou)(zhou)上(shang)也产(chan)(chan)(chan)生相(xiang)(xiang)同频(pin)(pin)(pin)(pin)率(lv)(lv)(lv)的(de)(de)(de)轴(zhou)(zhou)(zhou)(zhou)(zhou)电(dian)(dian)(dian)(dian)(dian)压(ya)，通(tong)常变(bian)(bian)(bian)(bian)频(pin)(pin)(pin)(pin)器(qi)逆变(bian)(bian)(bian)(bian)侧(ce)载波(bo)频(pin)(pin)(pin)(pin)率(lv)(lv)(lv)很高(gao)(gao)(gao)，在(zai)(zai)(zai)10kHz以上(shang)，过高(gao)(gao)(gao)的(de)(de)(de)频(pin)(pin)(pin)(pin)率(lv)(lv)(lv)和定子(zi)、电(dian)(dian)(dian)(dian)(dian)缆相(xiang)(xiang)感应，产(chan)(chan)(chan)生很高(gao)(gao)(gao)的(de)(de)(de)dv/dt前(qian)后沿，加(jia)大波(bo)形(xing)畸变(bian)(bian)(bian)(bian)。由(you)于(yu)静电(dian)(dian)(dian)(dian)(dian)耦合，电(dian)(dian)(dian)(dian)(dian)机(ji)各部分(fen)之间有大小不(bu)(bu)等(deng)(deng)的(de)(de)(de)分(fen)布电(dian)(dian)(dian)(dian)(dian)容(rong)，构成(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)零(ling)(ling)序回(hui)(hui)路，其中流(liu)经轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)的(de)(de)(de)对(dui)地放(fang)电(dian)(dian)(dian)(dian)(dian)就形(xing)成(cheng)(cheng)轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)流(liu)。正常状态下，轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)滚珠悬浮在(zai)(zai)(zai)润滑(hua)脂形(xing)成(cheng)(cheng)的(de)(de)(de)油膜(mo)中，润滑(hua)油膜(mo)起到绝缘作用(yong)，当油膜(mo)因(yin)某种原(yuan)因(yin)被破坏或(huo)过高(gao)(gao)(gao)的(de)(de)(de)dv/dt轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)电(dian)(dian)(dian)(dian)(dian)压(ya)都会击穿油膜(mo)形(xing)成(cheng)(cheng)放(fang)电(dian)(dian)(dian)(dian)(dian)，放(fang)电(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)流(liu)在(zai)(zai)(zai)轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)内(nei)外(wai)圈和滚珠上(shang)形(xing)成(cheng)(cheng)烧蚀，长时间运行会发(fa)展(zhan)成(cheng)(cheng)延轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)内(nei)外(wai)圈一周的(de)(de)(de)象搓(cuo)衣板样的(de)(de)(de)条纹，并升高(gao)(gao)(gao)轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)温度，溶(rong)化(hua)润滑(hua)脂，更加(jia)劣化(hua)轴(zhou)(zhou)(zhou)(zhou)(zhou)承(cheng)(cheng)(cheng)的(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(shang)的(de)(de)(de)轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)电(dian)流形成(cheng)(cheng)(cheng)原理，并(bing)结合(he)电(dian)机(ji)的(de)(de)(de)运行(xing)情(qing)况，我(wo)们分析负(fu)(fu)荷端(duan)轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)的(de)(de)(de)损(sun)(sun)坏(huai)失效(xiao)是(shi)一个过程，轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)电(dian)流是(shi)主(zhu)要原因，同时机(ji)械震动、润(run)滑(hua)脂(zhi)消(xiao)耗等(deng)是(shi)次要原因，促成(cheng)(cheng)(cheng)轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)电(dian)流的(de)(de)(de)形成(cheng)(cheng)(cheng)，并(bing)一定程度(du)(du)上(shang)加重了危害。风机(ji)电(dian)机(ji)投用(yong)后，由(you)于轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)间(jian)隙均(jun)匀(yun)，润(run)滑(hua)充分，润(run)滑(hua)油膜均(jun)匀(yun)，轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)电(dian)流还不(bu)构成(cheng)(cheng)(cheng)很(hen)大威胁，随着润(run)滑(hua)脂(zhi)的(de)(de)(de)消(xiao)耗，负(fu)(fu)荷端(duan)的(de)(de)(de)震动加大首先导致(zhi)负(fu)(fu)荷端(duan)轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)间(jian)隙加大，轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)电(dian)压击穿放电(dian)严重，轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)电(dian)流增(zeng)大，使得负(fu)(fu)荷端(duan)轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)内道(dao)出现电(dian)烧蚀，温度(du)(du)升(sheng)高，润(run)滑(hua)脂(zhi)液化，直到(dao)轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)磨(mo)损(sun)(sun)严重，发热烧损(sun)(sun)。所以(yi)，我(wo)们认为应采用(yong)综合(he)治理，以(yi)多(duo)种(zhong)方(fang)(fang)法减(jian)少(shao)和抑制(zhi)轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)电(dian)流。而绝缘轴(zhou)(zhou)承(cheng)(cheng)(cheng)(cheng)等(deng)方(fang)(fang)法由(you)于实施(shi)难(nan)度(du)(du)较大暂(zan)不(bu)考虑。