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变频器应用之电机漏电原因及解决方法

  • 2017-04-10

有(you)的现场使(shi)用变(bian)频器控制(zhi)电(dian)机会(hui)出现漏(lou)电(dian)问题,漏(lou)电(dian)电(dian)压(ya)有(you)几十伏到200伏不等,在(zai)这里针对此故障的原因进(jin)行理论的分析和(he)说(shuo)明(ming)如下。 

漏电问题产生的原因

我们都知(zhi)道电(dian)(dian)(dian)(dian)(dian)(dian)动(dong)(dong)机(ji)(ji)的(de)(de)(de)(de)三相定子绕组流过(guo)电(dian)(dian)(dian)(dian)(dian)(dian)流产(chan)(chan)生(sheng)旋转磁场,根据磁电(dian)(dian)(dian)(dian)(dian)(dian)感(gan)应(ying)(ying)(ying)(ying)的(de)(de)(de)(de)原理(li)(li),电(dian)(dian)(dian)(dian)(dian)(dian)动(dong)(dong)机(ji)(ji)的(de)(de)(de)(de)外壳(qiao)就(jiu)(jiu)(jiu)会产(chan)(chan)生(sheng)感(gan)应(ying)(ying)(ying)(ying)电(dian)(dian)(dian)(dian)(dian)(dian)动(dong)(dong)势,此(ci)电(dian)(dian)(dian)(dian)(dian)(dian)动(dong)(dong)势的(de)(de)(de)(de)大小就(jiu)(jiu)(jiu)取决(jue)于变频(pin)器(qi)IGBT的(de)(de)(de)(de)开(kai)关频(pin)率的(de)(de)(de)(de)大小,由(you)于高(gao)性能的(de)(de)(de)(de)控(kong)制(zhi)要求高(gao)的(de)(de)(de)(de)开(kai)关频(pin)率,其开(kai)关速(su)度很快,则DV/DT偏(pian)(pian)大,同时(shi)这个感(gan)应(ying)(ying)(ying)(ying)电(dian)(dian)(dian)(dian)(dian)(dian)动(dong)(dong)势就(jiu)(jiu)(jiu)偏(pian)(pian)大,人触(chu)摸(mo)(mo)(mo)上(shang)就(jiu)(jiu)(jiu)有电(dian)(dian)(dian)(dian)(dian)(dian)击的(de)(de)(de)(de)感(gan)觉(jue)。理(li)(li)论上(shang)IGBT的(de)(de)(de)(de)开(kai)关速(su)度越(yue)快,电(dian)(dian)(dian)(dian)(dian)(dian)机(ji)(ji)外壳(qiao)上(shang)的(de)(de)(de)(de)感(gan)应(ying)(ying)(ying)(ying)电(dian)(dian)(dian)(dian)(dian)(dian)动(dong)(dong)势就(jiu)(jiu)(jiu)越(yue)高(gao),而变频(pin)器(qi)对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)机(ji)(ji)的(de)(de)(de)(de)控(kong)制(zhi)精度和响(xiang)应(ying)(ying)(ying)(ying)就(jiu)(jiu)(jiu)越(yue)高(gao),人触(chu)摸(mo)(mo)(mo)之后被电(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)感(gan)觉(jue)就(jiu)(jiu)(jiu)越(yue)高(gao),反(fan)之,IGBT的(de)(de)(de)(de)开(kai)关频(pin)率慢,感(gan)应(ying)(ying)(ying)(ying)电(dian)(dian)(dian)(dian)(dian)(dian)就(jiu)(jiu)(jiu)小,人触(chu)摸(mo)(mo)(mo)的(de)(de)(de)(de)感(gan)觉(jue)就(jiu)(jiu)(jiu)小,所以国内的(de)(de)(de)(de)低端(duan)变频(pin)器(qi)设计(ji)的(de)(de)(de)(de)开(kai)关频(pin)率偏(pian)(pian)低,控(kong)制(zhi)电(dian)(dian)(dian)(dian)(dian)(dian)机(ji)(ji)后感(gan)应(ying)(ying)(ying)(ying)电(dian)(dian)(dian)(dian)(dian)(dian)小,人摸(mo)(mo)(mo)上(shang)没啥感(gan)觉(jue),但其控(kong)制(zhi)性较差,动(dong)(dong)态响(xiang)应(ying)(ying)(ying)(ying)较慢。


漏电问题的解决方案

为了避免这(zhei)个(ge)问题的(de)(de)(de)(de)发生,在硬件设(she)计的(de)(de)(de)(de)时候,就加入了感应电(dian)(dian)(dian)(dian)(dian)浪涌(yong)滤波器电(dian)(dian)(dian)(dian)(dian)路(lu),并将浪涌(yong)滤波器的(de)(de)(de)(de)接(jie)地(di)(di)(di)(di)(di)端(duan)(duan)于变(bian)(bian)(bian)频(pin)(pin)器的(de)(de)(de)(de)外壳相连(lian),同(tong)(tong)时在变(bian)(bian)(bian)频(pin)(pin)器的(de)(de)(de)(de)配线说明中,要(yao)求将电(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)(de)接(jie)地(di)(di)(di)(di)(di)端(duan)(duan)同(tong)(tong)变(bian)(bian)(bian)频(pin)(pin)器的(de)(de)(de)(de)接(jie)地(di)(di)(di)(di)(di)B相连(lian),将输入电(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)地(di)(di)(di)(di)(di)(大地(di)(di)(di)(di)(di))同(tong)(tong)变(bian)(bian)(bian)频(pin)(pin)器的(de)(de)(de)(de)接(jie)地(di)(di)(di)(di)(di)A相连(lian),从而使电(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)(de)感应电(dian)(dian)(dian)(dian)(dian)通过电(dian)(dian)(dian)(dian)(dian)机(ji)与变(bian)(bian)(bian)频(pin)(pin)器的(de)(de)(de)(de)接(jie)地(di)(di)(di)(di)(di)和(he)变(bian)(bian)(bian)频(pin)(pin)器与电(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)接(jie)地(di)(di)(di)(di)(di)线形成回路(lu),使电(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)(de)地(di)(di)(di)(di)(di)变(bian)(bian)(bian)频(pin)(pin)器的(de)(de)(de)(de)地(di)(di)(di)(di)(di)和(he)电(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)地(di)(di)(di)(di)(di)在同(tong)(tong)一电(dian)(dian)(dian)(dian)(dian)位上(shang),他(ta)们之间的(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)位差是为0伏电(dian)(dian)(dian)(dian)(dian)压,这(zhei)样人站在大地(di)(di)(di)(di)(di)上(shang)面接(jie)触到(dao)电(dian)(dian)(dian)(dian)(dian)机(ji)的(de)(de)(de)(de)外壳、设(she)备的(de)(de)(de)(de)机(ji)架、变(bian)(bian)(bian)频(pin)(pin)器的(de)(de)(de)(de)外壳就不(bu)会有(you)被电(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)感觉了。

但(dan)是(shi)(shi)有(you)(you)些工厂内为(wei)了配线方便,高压(ya)配电房内没(mei)有(you)(you)把(ba)地(di)(di)线拉入车间,甚(shen)至错误的(de)(de)认(ren)为(wei)大地(di)(di)就是(shi)(shi)地(di)(di)线,这种想(xiang)法是(shi)(shi)错误的(de)(de),大家不妨(fang)想(xiang)一想(xiang),如果大地(di)(di)可以当地(di)(di)线,那我们日常生活中何

必拉N线(xian)(xian)(xian)盒(he)地(di)(di)线(xian)(xian)(xian)呢(ni)?发电站里的N线(xian)(xian)(xian)也(ye)是和地(di)(di)线(xian)(xian)(xian)连(lian)在一起的啊?我们不用拉N线(xian)(xian)(xian)盒(he)地(di)(di)线(xian)(xian)(xian)不是省(sheng)很(hen)多(duo)电线(xian)(xian)(xian)吗?为啥浪费人力、物(wu)力、时间呢(ni)?然而(er)现实中(zhong)有很(hen)多(duo)工厂没有拉电源地(di)(di)线(xian)(xian)(xian)的,设备没法(fa)找到接地(di)(di)点,而(er)电机在使用中(zhong)却有感应漏电的情况(kuang),遇到这种情况(kuang),我们提(ti)供两种方案:

方案1:电机、变频器、机架三个电线连在一起之后,使他们处于同一电位,并经过变频器内部的浪涌吸收、泄放,使感应电压大大减小,这样不至于让人又触电的感觉,也就是说没有地线也没有关系,只要就几个的地连在一起就好了,这样变频器内部的浪涌滤波器才起作用到作用。

方案2:一般情况下经过方案1的处理,不至于会有电人的现象,但由于特殊的原因,感应电压还是比较高,还可以电人,那就在方案1的前提下再在变频器的输入电源端增加一个感应电浪涌滤波器。

并将感应(ying)电(dian)(dian)浪(lang)(lang)(lang)涌(yong)滤(lv)波(bo)(bo)器的(de)地与电(dian)(dian)动机的(de)地、变频器的(de)地接在(zai)一起(如图4中(zhong)的(de)红色线(xian)所示)让(rang)感应(ying)电(dian)(dian)浪(lang)(lang)(lang)涌(yong)滤(lv)波(bo)(bo)器再一次对电(dian)(dian)机的(de)感应(ying)电(dian)(dian)进行吸收(shou)和泄(xie)放,进一步减小感应(ying)电(dian)(dian)压,达到防止漏电(dian)(dian)电(dian)(dian)人的(de)目前的(de)。增加(jia)的(de)感应(ying)电(dian)(dian)浪(lang)(lang)(lang)涌(yong)滤(lv)波(bo)(bo)器的(de)电(dian)(dian)路(lu)原理与变频器内(nei)部(bu)的(de)浪(lang)(lang)(lang)涌(yong)滤(lv)波(bo)(bo)电(dian)(dian)路(lu)是一样的(de),是由于体积太大,没法设计安(an)装在(zai)变频器内(nei)部(bu)电(dian)(dian)路(lu)里面,因此做(zuo)成外(wai)接方式。

我(wo)们曾经(jing)过大量的(de)(de)(de)实验证明,通过方(fang)案二这种接法的(de)(de)(de)现(xian)场整改,在没有(you)接电(dian)源的(de)(de)(de)地线的(de)(de)(de)应用(yong)场合(he)下(xia)(xia),都能(neng)将(jiang)电(dian)动(dong)机运转产生的(de)(de)(de)感应电(dian)压减小到(dao)20V以下(xia)(xia),确保现(xian)场操作(zuo)人(ren)员的(de)(de)(de)安(an)全,不(bu)会再有(you)被漏电(dian)电(dian)人(ren)的(de)(de)(de)感觉(jue)。但是,方(fang)案二中(zhong)如果接有(you)电(dian)源线的(de)(de)(de)地线,那么也就不(bu)用(yong)外接感应电(dian)浪涌(yong)滤波器都可(ke)以了。

另外,如果现(xian)场是有(you)多台(tai)(tai)变(bian)频(pin)(pin)器(qi)(qi)控制电(dian)动(dong)(dong)机(ji)运转时,且不方便安(an)装多个感(gan)应(ying)(ying)电(dian)浪(lang)(lang)涌(yong)(yong)滤(lv)波(bo)器(qi)(qi)的(de)(de),并不一(yi)定是要求每台(tai)(tai)变(bian)频(pin)(pin)器(qi)(qi)都(dou)配一(yi)下感(gan)应(ying)(ying)电(dian)浪(lang)(lang)涌(yong)(yong)滤(lv)波(bo)器(qi)(qi),也可以只接(jie)(jie)一(yi)个或两个感(gan)应(ying)(ying)电(dian)浪(lang)(lang)涌(yong)(yong)滤(lv)波(bo)器(qi)(qi),并将滤(lv)波(bo)器(qi)(qi)的(de)(de)接(jie)(jie)地(di)(di)(di)端(duan)(duan)与现(xian)场几台(tai)(tai)变(bian)频(pin)(pin)器(qi)(qi)的(de)(de)接(jie)(jie)地(di)(di)(di)端(duan)(duan)、现(xian)场电(dian)动(dong)(dong)机(ji)的(de)(de)接(jie)(jie)地(di)(di)(di)端(duan)(duan)、设(she)备机(ji)架接(jie)(jie)在一(yi)起(qi),如图(tu)5所示:由于每台(tai)(tai)变(bian)频(pin)(pin)器(qi)(qi)内部都(dou)有(you)感(gan)应(ying)(ying)电(dian)浪(lang)(lang)涌(yong)(yong)滤(lv)波(bo)器(qi)(qi)电(dian)路,但(dan)如果电(dian)机(ji)的(de)(de)接(jie)(jie)地(di)(di)(di)线没(mei)有(you)接(jie)(jie)回到(dao)(dao)变(bian)频(pin)(pin)器(qi)(qi)的(de)(de)接(jie)(jie)地(di)(di)(di)端(duan)(duan)子去(qu)的(de)(de)话(hua),感(gan)应(ying)(ying)电(dian)浪(lang)(lang)涌(yong)(yong)滤(lv)波(bo)器(qi)(qi)也就不起(qi)作用了,所以现(xian)场应(ying)(ying)用中电(dian)动(dong)(dong)机(ji)的(de)(de)接(jie)(jie)地(di)(di)(di)端(duan)(duan)一(yi)定要与变(bian)频(pin)(pin)器(qi)(qi)的(de)(de)接(jie)(jie)地(di)(di)(di)端(duan)(duan)接(jie)(jie)到(dao)(dao)一(yi)起(qi)。

当(dang)然(ran)有(you)(you)些(xie)设备在某些(xie)场合电(dian)机不接(jie)(jie)地(di)(di)线(xian)也不会有(you)(you)漏电(dian)的(de)(de)(de)(de)感觉,这(zhei)与(yu)本文前面所说的(de)(de)(de)(de)大地(di)(di)虽(sui)然(ran)也是(shi)属于导体,但(dan)大地(di)(di)毕竟是(shi)有(you)(you)阻(zu)(zu)值(zhi)的(de)(de)(de)(de),而且(qie)根(gen)据(ju)不同(tong)的(de)(de)(de)(de)土地(di)(di)的(de)(de)(de)(de)土壤成份,阻(zu)(zu)值(zhi)也大小不一原理是(shi)一样的(de)(de)(de)(de)。但(dan)是(shi)按照(zhao)正确的(de)(de)(de)(de)用(yong)电(dian)安全(quan)规范,是(shi)要求(qiu)电(dian)机良好(hao)接(jie)(jie)地(di)(di)的(de)(de)(de)(de),但(dan)条件不允许(如(ru)没有(you)(you)电(dian)源(yuan)接(jie)(jie)地(di)(di)端)的(de)(de)(de)(de),电(dian)动机的(de)(de)(de)(de)地(di)(di)、电(dian)柜外壳与(yu)变频(pin)器的(de)(de)(de)(de)地(di)(di)总可以接(jie)(jie)在一起的(de)(de)(de)(de)。

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