變頻器的核心它主要是通過高速電力電子開關來產生一定寬度和極性的PWM或SPWM控(kong)製(zhi)信(xin)號(hao)。這(zhe)種(zhong)具(ju)有(you)很(hen)陡(dou)邊(bian)沿(yan)的(de)脈(mai)衝(chong)信(xin)號(hao)會(hui)產(chan)生(sheng)很(hen)強(qiang)的(de)電(dian)磁(ci)輻(fu)射(she),尤(you)其(qi)是(shi)輸(shu)出(chu)電(dian)路(lu),它(ta)們(men)將(jiang)以(yi)各(ge)種(zhong)方(fang)式(shi)把(ba)自(zi)已(yi)的(de)能(neng)量(liang)傳(chuan)播(bo)出(chu)去(qu),幹(gan)攏(long)周(zhou)邊(bian)設(she)備(bei)的(de)正(zheng)常(chang)工(gong)作(zuo),嚴(yan)重(zhong)地(di)超(chao)出(chu)了(le)電(dian)磁(ci)兼(jian)客(ke)標(biao)準(zhun)的(de)極(ji)限(xian)值(zhi)要(yao)求(qiu)。因(yin)此(ci),變(bian)頻(pin)器(qi)生(sheng)產(chan)廠(chang)家(jia)為(wei)用(yong)戶(hu)製(zhi)造(zao)了(le)一(yi)些(xie)專(zhuan)用(yong)設(she)備(bei)來(lai)抑(yi)製(zhi)變(bian)頻(pin)器(qi)產(chan)生(sheng)的(de)電(dian)磁(ci)幹(gan)擾(rao),以(yi)達(da)到(dao)質(zhi)檢(jian)標(biao)準(zhun),確(que)保(bao)變(bian)頻(pin)器(qi)及(ji)其(qi)它(ta)設(she)備(bei)的(de)安(an)全(quan)運(yun)行(xing)。諧(xie)波(bo)的(de)傳(chuan)播(bo)途(tu)徑(jing)大(da)致(zhi)為(wei)兩(liang)種(zhong),一(yi)種(zhong)是(shi)傳(chuan)導(dao);另一種是輻射。解決傳導幹擾的辦法主要是在電路中把傳導的高頻電流濾掉或者隔離;解決輻射幹擾就是對輻射源或被幹擾的線路進行屏蔽。
變(bian)頻(pin)係(xi)統(tong)的(de)供(gong)電(dian)電(dian)源(yuan)與(yu)其(qi)他(ta)設(she)備(bei)的(de)供(gong)電(dian)電(dian)源(yuan)相(xiang)互(hu)獨(du)立(li),或(huo)在(zai)變(bian)頻(pin)器(qi)和(he)其(qi)他(ta)用(yong)電(dian)設(she)備(bei)的(de)輸(shu)入(ru)側(ce)安(an)裝(zhuang)隔(ge)離(li)變(bian)壓(ya)器(qi),切(qie)斷(duan)諧(xie)波(bo)電(dian)流(liu)。電(dian)動(dong)機(ji)和(he)變(bian)頻(pin)器(qi)之(zhi)間(jian)電(dian)纜(lan)應(ying)穿(chuan)鋼(gang)管(guan)敷(fu)設(she)或(huo)用(yong)鎧(kai)裝(zhuang)電(dian)纜(lan),並(bing)與(yu)其(qi)他(ta)弱(ruo)電(dian)信(xin)號(hao)在(zai)不(bu)同(tong)的(de)電(dian)纜(lan)溝(gou)分(fen)別(bie)敷(fu)設(she),避(bi)免(mian)輻(fu)射(she)幹(gan)擾(rao)。信(xin)號(hao)線(xian)采(cai)用(yong)屏(ping)蔽(bi)線(xian),且(qie)布(bu)線(xian)時(shi)與(yu)變(bian)頻(pin)器(qi)主(zhu)回(hui)路(lu)控(kong)製(zhi)線(xian)錯(cuo)開(kai)一(yi)定(ding)距(ju)離(li)(至少20cm以上),qieduanfusheganrao。bianpinqishiyongzhuanyongjiedixian,qieyongcuduanxianjiedi,linjinqitadianqishebeidedixianbixuyubianpinqipeixianfenkai,shiyongduanxian。zheyangnengyouxiaoyizhidianliuxieboduilinjinshebeidefusheganrao。shiyongbianpinqishi,yinjiedibuzhengqueeryinqideganlongjiantishiyoufasheng,weicishouxianyaozaigainianshangfenqingshenmeshi“安全接地”和“電磁幹擾接地”,尤其是在高頻區域,由於“趨膚效應”在接頭處將呈現高阻狀態,造成接地不良,使係統對外幹擾信號增強,對外影響變得敏感。
在防止電磁幹擾接地時,需要實現低阻抗連接。具體操作時應注意以下兩點:在使用機殼作為公共地時,需要除淨連接點處的油漆或其它塗料,以確保低阻抗連接。不同接地點間盡可能使用短的扁平線連接在一起(因扁平線的高頻低阻特性較好),並bing要yao經jing常chang檢jian查zha所suo有you的de接jie地di點dian,以yi防fang止zhi脫tuo落luo或huo鬆song動dong現xian象xiang發fa生sheng。變bian頻pin器qi安an裝zhuang於yu控kong製zhi櫃gui內nei,既ji能neng屏ping蔽bi向xiang外wai輻fu射she能neng量liang,又you能neng防fang止zhi外wai界jie電dian磁ci幹gan擾rao的de進jin入ru。具ju體ti施shi工gong時shi應ying注zhu意yi機ji殼ke、電纜屏蔽層及電動機外殼三者應可靠連接在一起。
zengjiashurudiankangqi,yibanyingcaiyongwuyuandiankangqi,mudezaiyuzhiyunxutedingdepinlvxinhaotongguo,zuzhiganraoxinhaoyuan。bingbangzhuxishouzhongzaishebeitourushichanshengdelangyongdianyahezhudianyuandedianyajianfeng。2%阻zu抗kang進jin線xian電dian抗kang器qi通tong常chang已yi足zu以yi能neng夠gou吸xi收shou電dian壓ya峰feng值zhi並bing在zai多duo數shu應ying用yong情qing況kuang下xia能neng避bi免mian變bian頻pin器qi有you害hai的de停ting機ji。還hai能neng保bao護hu變bian頻pin器qi內nei部bu直zhi流liu回hui路lu電dian容rong器qi不bu至zhi於yu過guo熱re和he由you於yu吸xi收shou浪lang湧yong漏lou電dian壓ya,而er減jian少shao壽shou命ming,並bing且qie增zeng加jia電dian源yuan阻zu抗kang。4%zukangjinxiandiankangqizuishiyijiangdiyoubianpinqichanshengdexiebopinlvdianliu,hainengshiganlongxinhaobunengtongguodixianchuanboerbeifanshehuiganraoyuan。anzhuangshurudiankangqishiyingjinliangkaojinbianpinqi,bingyuqigongjiban。ruoliangzhejulichaoguobianpinqishiyongshuomingshuguidingdebiaozhun,yingyongbianpingxianlianjie。
輸出電抗器裝於變頻器的輸出端(U﹑V&W),以yi允yun許xu電dian機ji在zai長chang電dian纜lan的de情qing況kuang下xia運yun行xing。在zai變bian頻pin器qi輸shu出chu端duan串chuan接jie電dian抗kang器qi,可ke以yi解jie決jue電dian機ji過guo熱re和he噪zao聲sheng汙wu染ran。采cai用yong了le輸shu出chu電dian抗kang器qi,可ke省sheng去qu在zai變bian頻pin器qi與yu電dian機ji之zhi問wen的de屏ping蔽bi電dian纜lan。這zhe樣yang做zuo不bu僅jin降jiang低di了le成cheng本ben,而er且qie能neng很hen好hao的de抑yi製zhi變bian頻pin器qi對dui外wai產chan生sheng的de幹gan擾rao,這zhe是shi使shi用yong電dian抗kang器qi的de主zhu耍shua優you點dian。
輸出電抗器的電感補償可使電機電纜相-對-相和相-對-地的分布電容。由於電機電纜長度增加,電機電纜的總分布電容也隨時增加,該分布電容與變頻器輸出端的殘餘電壓峰值(由於變頻器輸出器件IGBT切換),導致電流峰值流回變頻器。這些電流峰值會引起變頻器有害的跳閘,安裝了輸出電抗器都可以避免。
電抗器被裝於變頻器的輸出端,以允許帶長電纜運行,電抗器補償了電纜中的分布電容。
其它措施:1)使用屏蔽電纜削弱電磁感應和靜電感應。2)在逆變電路直流側的正、負端到地線間跨接100n以下的電容器。此種方法特別適用幹7.5KW以下的用電設備。3)將控製線、信號線與電源線分開,通常距離應在200mm以上,如果控製線必須與電源線交叉,則應盡量使交叉角接近90度。
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