变频器(qi)在(zai)调(diao)试与使用(yong)过(guo)(guo)程中(zhong)经(jing)常(chang)会(hui)遇到各种各样的(de)问题，其(qi)中(zhong)过(guo)(guo)电压现象最为常(chang)见。过(guo)(guo)电压产生后，变频器(qi)为了防止内部电路损坏，其(qi)过(guo)(guo)电压保(bao)护功能将动(dong)作(zuo)，使变频器(qi)停止运行，导(dao)致设备无法正常(chang)工作(zuo)。 

      所谓变频器的过电压(ya)，是指(zhi)由于种(zhong)(zhong)种(zhong)(zhong)原因造成(cheng)的变频器电压(ya)超(chao)过额定电压(ya)，集中表现(xian)在(zai)变频器直(zhi)流母线(xian)的直(zhi)流电压(ya)上。

      正常(chang)工作时，变频器直(zhi)流(liu)电(dian)压为三(san)相全波整流(liu)后(hou)的(de)平均(jun)值。若(ruo)以380V线(xian)(xian)电(dian)压计算，则(ze)平均(jun)直(zhi)流(liu)电(dian)压Ud=1.35U线(xian)(xian)=513V。

      在过电压(ya)(ya)发生时，直流母(mu)线上的储能电容将被充(chong)电，当电压(ya)(ya)上升至(zhi)700V左右时，(因机型而异(yi))变频器过电压(ya)(ya)保护动作。

      造成变(bian)频器过(guo)电压的(de)原因主要有两种：电源过(guo)电压和(he)再生过(guo)电压。

      电(dian)(dian)(dian)(dian)源(yuan)过电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)是指因(yin)电(dian)(dian)(dian)(dian)源(yuan)电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)过高而使直流母(mu)线电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)超(chao)过额(e)定值。而现在大(da)部分(fen)变频(pin)器(qi)的输入电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)最高可达460V，因(yin)此，电(dian)(dian)(dian)(dian)源(yuan)引起的过电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)极为少见。

      本(ben)文(wen)主要(yao)讨论的问题是再生过(guo)电压。

      产生(sheng)再(zai)生(sheng)过(guo)电(dian)(dian)(dian)(dian)压(ya)主(zhu)要有(you)以下原因：当大GD2(飞轮力矩)负(fu)(fu)(fu)载减(jian)速(su)(su)时变频器(qi)(qi)减(jian)速(su)(su)时间(jian)设定过(guo)短；电(dian)(dian)(dian)(dian)机受外力影响(xiang)(风机、牵(qian)伸机)或位能(neng)(neng)负(fu)(fu)(fu)载(电(dian)(dian)(dian)(dian)梯、起重机)下放。由于(yu)这些(xie)原因，使(shi)(shi)电(dian)(dian)(dian)(dian)机实际转(zhuan)(zhuan)(zhuan)(zhuan)速(su)(su)高于(yu)变频器(qi)(qi)的(de)指(zhi)令转(zhuan)(zhuan)(zhuan)(zhuan)速(su)(su)，也就是(shi)说(shuo)，电(dian)(dian)(dian)(dian)机转(zhuan)(zhuan)(zhuan)(zhuan)子转(zhuan)(zhuan)(zhuan)(zhuan)速(su)(su)超过(guo)了(le)同(tong)步转(zhuan)(zhuan)(zhuan)(zhuan)速(su)(su)，这时电(dian)(dian)(dian)(dian)机的(de)转(zhuan)(zhuan)(zhuan)(zhuan)差率为(wei)负(fu)(fu)(fu)，转(zhuan)(zhuan)(zhuan)(zhuan)子绕组(zu)切割旋转(zhuan)(zhuan)(zhuan)(zhuan)磁场的(de)方向与(yu)电(dian)(dian)(dian)(dian)动(dong)机状(zhuang)(zhuang)态时相反，其产生(sheng)的(de)电(dian)(dian)(dian)(dian)磁转(zhuan)(zhuan)(zhuan)(zhuan)矩为(wei)阻碍(ai)旋转(zhuan)(zhuan)(zhuan)(zhuan)方向的(de)制动(dong)转(zhuan)(zhuan)(zhuan)(zhuan)矩。所以电(dian)(dian)(dian)(dian)动(dong)机实际上处于(yu)发电(dian)(dian)(dian)(dian)状(zhuang)(zhuang)态，负(fu)(fu)(fu)载的(de)动(dong)能(neng)(neng)被"再(zai)生(sheng)"成为(wei)电(dian)(dian)(dian)(dian)能(neng)(neng)。再(zai)生(sheng)能(neng)(neng)量经逆变部续流二(er)极管对(dui)变频器(qi)(qi)直流储能(neng)(neng)电(dian)(dian)(dian)(dian)容器(qi)(qi)充电(dian)(dian)(dian)(dian)，使(shi)(shi)直流母线电(dian)(dian)(dian)(dian)压(ya)上升(sheng)，这就是(shi)再(zai)生(sheng)过(guo)电(dian)(dian)(dian)(dian)压(ya)。

       因(yin)再(zai)生(sheng)(sheng)过(guo)(guo)(guo)电(dian)压的(de)(de)过(guo)(guo)(guo)程中(zhong)产生(sheng)(sheng)的(de)(de)转矩(ju)与(yu)原(yuan)转矩(ju)相反，为制(zhi)(zhi)动转矩(ju)，因(yin)此再(zai)生(sheng)(sheng)过(guo)(guo)(guo)电(dian)压的(de)(de)过(guo)(guo)(guo)程也就(jiu)是再(zai)生(sheng)(sheng)制(zhi)(zhi)动的(de)(de)过(guo)(guo)(guo)程。换句话(hua)说，消除了再(zai)生(sheng)(sheng)能(neng)量(liang)，也就(jiu)提高了制(zhi)(zhi)动转矩(ju)。如(ru)果再(zai)生(sheng)(sheng)能(neng)量(liang)不大(da)，因(yin)变频器(qi)与(yu)电(dian)机(ji)本身具有(you)20的(de)(de)再(zai)生(sheng)(sheng)制(zhi)(zhi)动能(neng)力，这部分电(dian)能(neng)将(jiang)被变频器(qi)及电(dian)机(ji)消耗掉。若(ruo)这部分能(neng)量(liang)超过(guo)(guo)(guo)了变频器(qi)与(yu)电(dian)机(ji)的(de)(de)消耗能(neng)力，直流回路的(de)(de)电(dian)容将(jiang)被过(guo)(guo)(guo)充电(dian)，变频器(qi)的(de)(de)过(guo)(guo)(guo)电(dian)压保(bao)护(hu)功能(neng)动作，使运行(xing)停止。

      为避(bi)免这(zhei)种情况的发生(sheng)，必(bi)须将这(zhei)部分(fen)能量及时(shi)地(di)处理掉，同时(shi)也提高了(le)制动转(zhuan)矩，这(zhei)就是再生(sheng)制动的目(mu)的。

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