UPS工頻機和高頻機的區別
用戶在購買大功率UPS的(de)時候(hou),常(chang)常(chang)面(mian)(mian)臨在工(gong)頻(pin)(pin)(pin)(pin)機和(he)(he)高(gao)(gao)頻(pin)(pin)(pin)(pin)機之間(jian)進行選擇的(de)困惑。就UPS廠商(shang)方面(mian)(mian)而言,當然都認為是(shi)自己的(de)好,“公說(shuo)公有(you)理,婆說(shuo)婆有(you)理”。提(ti)供工(gong)頻(pin)(pin)(pin)(pin)機的(de)廠商(shang)說(shuo)工(gong)頻(pin)(pin)(pin)(pin)機穩定(ding)性(xing)和(he)(he)可靠性(xing)高(gao)(gao);提(ti)供高(gao)(gao)頻(pin)(pin)(pin)(pin)機的(de)廠商(shang)會(hui)說(shuo)高(gao)(gao)頻(pin)(pin)(pin)(pin)機節省(sheng)空間(jian),成本(ben)相對較低等諸如此類的(de)說(shuo)法(fa)。其實,工(gong)頻(pin)(pin)(pin)(pin)機和(he)(he)高(gao)(gao)頻(pin)(pin)(pin)(pin)機到底孰優孰劣,很(hen)難一(yi)概而論,可以(yi)說(shuo)各有(you)利弊。用戶應當在全面(mian)(mian)認識這兩種UPS機型的(de)基礎上(shang),客觀審視自身(shen)的(de)應用和(he)(he)需求,選擇適合自己需要(yao)的(de)產品。
工頻機和高頻機的原理分析
工(gong)(gong)(gong)頻(pin)機和(he)高(gao)頻(pin)機是(shi)按UPS的設計電(dian)路(lu)工(gong)(gong)(gong)作頻(pin)率(lv)來(lai)區(qu)分的。工(gong)(gong)(gong)頻(pin)機是(shi)以傳統的模擬電(dian)路(lu)原理設計,由晶閘管(SCR)整流(liu)器(qi)(qi)、IGBT逆(ni)(ni)變器(qi)(qi)、旁(pang)路(lu)和(he)工(gong)(gong)(gong)頻(pin)升壓(ya)隔(ge)離(li)變壓(ya)器(qi)(qi)組成。因(yin)其整流(liu)器(qi)(qi)和(he)變壓(ya)器(qi)(qi)工(gong)(gong)(gong)作頻(pin)率(lv)均為工(gong)(gong)(gong)頻(pin)50Hz,顧名思義叫(jiao)工(gong)(gong)(gong)頻(pin)UPS。高(gao)頻(pin)機通(tong)(tong)常由IGBT高(gao)頻(pin)整流(liu)器(qi)(qi)、電(dian)池變換器(qi)(qi)、逆(ni)(ni)變器(qi)(qi)和(he)旁(pang)路(lu)組成。IGBT可以通(tong)(tong)過控制加在(zai)門極的驅動來(lai)控制其開通(tong)(tong)與(yu)關斷,IGBT整流(liu)器(qi)(qi)開關頻(pin)率(lv)通(tong)(tong)常在(zai)幾千赫到幾十千赫,甚至高(gao)達(da)上百千赫,遠遠高(gao)于工(gong)(gong)(gong)頻(pin)機,因(yin)此(ci)稱為高(gao)頻(pin)UPS。
在工(gong)頻UPS電(dian)(dian)路中,主路三相(xiang)交流(liu)(liu)輸入(ru)經(jing)過換相(xiang)電(dian)(dian)感,接到三個SCR橋臂組成的整流(liu)(liu)器之(zhi)后變(bian)(bian)換成直流(liu)(liu)電(dian)(dian)壓(ya)(ya),通(tong)過控制整流(liu)(liu)橋SCR的導通(tong)角來調節輸出(chu)直流(liu)(liu)電(dian)(dian)壓(ya)(ya)值。由于SCR屬(shu)于半(ban)控器件,控制系統只能(neng)控制開通(tong)點(dian),一(yi)旦SCR導通(tong)之(zhi)后,即使門極(ji)驅動(dong)撤消,也無法關斷(duan),只有(you)等到其電(dian)(dian)流(liu)(liu)為零(ling)之(zhi)后才能(neng)自然(ran)關斷(duan),所(suo)以其開通(tong)和關斷(duan)均是基于一(yi)個工(gong)頻周期,不(bu)存在高頻的開通(tong)和關斷(duan)控制。由于SCR整流(liu)(liu)器屬(shu)于降(jiang)壓(ya)(ya)整流(liu)(liu),所(suo)以直流(liu)(liu)母(mu)線電(dian)(dian)壓(ya)(ya)經(jing)逆變(bian)(bian)輸出(chu)的交流(liu)(liu)電(dian)(dian)壓(ya)(ya)比(bi)輸入(ru)交流(liu)(liu)電(dian)(dian)壓(ya)(ya)低(di),要(yao)使輸出(chu)相(xiang)電(dian)(dian)壓(ya)(ya)能(neng)夠(gou)得(de)到恒定的220V電(dian)(dian)壓(ya)(ya),就(jiu)必須在逆變(bian)(bian)輸出(chu)增加升壓(ya)(ya)隔離變(bian)(bian)壓(ya)(ya)器。
相(xiang)比而言,高(gao)頻(pin)UPS整流屬于升壓(ya)(ya)(ya)整流,其輸出直流母線的電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)比輸入(ru)線電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的峰值(zhi)高(gao),一(yi)般典(dian)型值(zhi)為800V左(zuo)右,如果電(dian)(dian)(dian)(dian)池直接(jie)掛接(jie)母線,所需要(yao)(yao)的標配電(dian)(dian)(dian)(dian)池節數需要(yao)(yao)67節,這樣給實際(ji)應用帶來(lai)極大的限(xian)制。因此一(yi)般高(gao)頻(pin)UPS會單獨(du)配置一(yi)個電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)變(bian)(bian)換器(qi),市(shi)電(dian)(dian)(dian)(dian)正常的時(shi)候電(dian)(dian)(dian)(dian)池變(bian)(bian)換器(qi)把(ba)800V的母線電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)降到電(dian)(dian)(dian)(dian)池組(zu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya);市(shi)電(dian)(dian)(dian)(dian)故(gu)障或超限(xian)時(shi),電(dian)(dian)(dian)(dian)池變(bian)(bian)換器(qi)把(ba)電(dian)(dian)(dian)(dian)池組(zu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)升高(gao)到800V的母線電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。由(you)于高(gao)頻(pin)機(ji)母線電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)為800V左(zuo)右,所以逆(ni)(ni)變(bian)(bian)器(qi)輸出相(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)可以直接(jie)達(da)到220V,逆(ni)(ni)變(bian)(bian)器(qi)之后就(jiu)不再需要(yao)(yao)升壓(ya)(ya)(ya)變(bian)(bian)壓(ya)(ya)(ya)器(qi)。因此,有(you)無隔離變(bian)(bian)壓(ya)(ya)(ya)器(qi)是工頻(pin)機(ji)與高(gao)頻(pin)機(ji)在結構上的主要(yao)(yao)區別。
UPS輸出隔離變壓器的作用
隔離(li)變(bian)(bian)壓器(qi)(qi)(qi)是利用電(dian)磁感應原(yuan)理,對配電(dian)或信號(hao)進行(xing)電(dian)氣隔離(li)的裝置。隔離(li)變(bian)(bian)壓器(qi)(qi)(qi)在UPS中通(tong)常被設計在逆變(bian)(bian)器(qi)(qi)(qi)的輸出端,可以起到增(zeng)加UPS性(xing)能改善(shan)負載(zai)端供電(dian)質量的作用。通(tong)常,UPS的輸出隔離(li)變(bian)(bian)壓器(qi)(qi)(qi)有以下四大優點:
降低零地電壓,優化UPS末端供電網絡
UPS的(de)(de)(de)(de)逆變(bian)輸(shu)出安裝(zhuang)隔(ge)(ge)離(li)變(bian)壓器(qi)(qi)可以隔(ge)(ge)離(li)輸(shu)入和(he)輸(shu)出之間的(de)(de)(de)(de)電(dian)氣連接(jie),從而(er)有效地(di)(di)(di)降(jiang)低輸(shu)出的(de)(de)(de)(de)零(ling)地(di)(di)(di)電(dian)壓。由于隔(ge)(ge)離(li)變(bian)壓器(qi)(qi)的(de)(de)(de)(de)副邊繞組(zu)采用Y型接(jie)法,中性(xing)點接(jie)地(di)(di)(di)后產(chan)生新的(de)(de)(de)(de)零(ling)線,從而(er)達到降(jiang)低零(ling)地(di)(di)(di)電(dian)壓的(de)(de)(de)(de)目的(de)(de)(de)(de)。事實上(shang),HP、IBM、SUN的(de)(de)(de)(de)小(xiao)型機因為要保(bao)證精(jing)密(mi)的(de)(de)(de)(de)計算能力與高可靠的(de)(de)(de)(de)數據處理傳(chuan)輸(shu)能力,都(dou)會對零(ling)地(di)(di)(di)電(dian)壓有極高的(de)(de)(de)(de)要求,加(jia)裝(zhuang)隔(ge)(ge)離(li)變(bian)壓器(qi)(qi)可以徹底解決(jue)因為零(ling)地(di)(di)(di)電(dian)壓偏高所(suo)造成的(de)(de)(de)(de)一些問題。
濾除負載端諧波,提高供電質量
隔(ge)離變壓器(qi)本身具有電感特(te)性,輸出隔(ge)離變壓器(qi)可(ke)以濾除負載端(duan)的大(da)量低次(ci)諧波,減少高(gao)(gao)頻*,并可(ke)以使高(gao)(gao)次(ci)諧波大(da)幅度衰減。采用電源(yuan)隔(ge)離變壓器(qi),可(ke)以有效地抑制竄入(ru)交流(liu)電源(yuan)中(zhong)的噪聲*,提高(gao)(gao)設備的電磁兼容性。
增強過載短路保護能力,保護負載與UPS主機
由(you)于其自身的(de)(de)(de)特(te)性,隔離(li)變壓(ya)器是UPS中工(gong)作最為(wei)穩定的(de)(de)(de)器件。UPS在正常工(gong)作過程中,如果遇到大的(de)(de)(de)短(duan)路電(dian)流,變壓(ya)器會(hui)產生反向電(dian)動勢,延緩(huan)短(duan)路電(dian)流對負載(zai)以及(ji)逆變器的(de)(de)(de)沖擊(ji)破壞,具有保護負載(zai)與UPS主機的(de)(de)(de)作用。
“通交流阻直流”,UPS故障時保護負載
高(gao)(gao)額UPS的(de)(de)(de)AC/DC變(bian)換部分采(cai)用高(gao)(gao)頻化(hua)設(she)計,提高(gao)(gao)了UPS的(de)(de)(de)輸(shu)入功(gong)率因(yin)數(shu)(0.98以(yi)上(shang))及輸(shu)入電壓(ya)(ya)范(fan)圍,DC/AC逆變(bian)部分高(gao)(gao)頻化(hua)減少了輸(shu)出(chu)濾波電感的(de)(de)(de)體(ti)積,功(gong)率密度大。由于(yu)無(wu)輸(shu)出(chu)隔離變(bian)壓(ya)(ya)器(qi),一旦逆變(bian)器(qi)橋臂的(de)(de)(de)IGBT被擊穿短路,BUS母線直(zhi)流高(gao)(gao)電壓(ya)(ya)將(jiang)加到負(fu)載上(shang),危及負(fu)載的(de)(de)(de)安全(quan)。輸(shu)出(chu)隔離變(bian)壓(ya)(ya)器(qi)具有“通交流阻直(zhi)流”的(de)(de)(de)能(neng)力(li),可以(yi)解決此類問題,在UPS發生故障時能(neng)夠使負(fu)載安全(quan)運行(xing)。
工頻機和高頻機的性能對比
在可靠性方面,工頻機要優于高頻機
工頻機采用晶(jing)閘(zha)管(SCR)整(zheng)流(liu)器,該技術經過半(ban)個多(duo)世(shi)紀的(de)(de)發展和革新,已經非(fei)常成(cheng)熟,其抗(kang)電(dian)(dian)流(liu)沖(chong)擊能(neng)力(li)非(fei)常強。由(you)于SCR屬于半(ban)控器件,不會出(chu)現直(zhi)通、誤(wu)觸發等故(gu)障。相比(bi)而(er)言,高(gao)頻機采用的(de)(de)IGBT高(gao)頻整(zheng)流(liu)器雖(sui)然開關頻率較高(gao),但是(shi)IGBT工作(zuo)時(shi)有嚴格的(de)(de)電(dian)(dian)壓、電(dian)(dian)流(liu)工作(zuo)區域,抗(kang)沖(chong)擊能(neng)力(li)較低。因此在總體可靠(kao)性(xing)方面,IGBT整(zheng)流(liu)器比(bi)SCR整(zheng)流(liu)器低。
在環境適應性方面,高頻機要優于工頻機
高頻(pin)機(ji)是(shi)以微處(chu)(chu)理(li)器作為處(chu)(chu)理(li)控(kong)制中(zhong)心,將繁雜的(de)(de)(de)硬件(jian)模擬電路燒錄(lu)于微處(chu)(chu)理(li)器中(zhong),以軟件(jian)程(cheng)序的(de)(de)(de)方(fang)式(shi)來控(kong)制UPS的(de)(de)(de)運行。因(yin)此,體(ti)積、重(zhong)量等方(fang)面都有明顯的(de)(de)(de)降低(di),噪音也較(jiao)(jiao)小,對空間、環境影響小,因(yin)此比較(jiao)(jiao)適合于對可靠(kao)性要求不(bu)太(tai)苛刻的(de)(de)(de)辦公場所。正因(yin)為如此,許多廠(chang)家的(de)(de)(de)中(zhong)小功率UPS普遍推出(chu)了高頻(pin)機(ji)。
在負載對零地電壓的要求方面,工頻機要優于高頻機
大功率(lv)三相高頻機(ji)(ji)零線(xian)(xian)會(hui)引入整流器(qi)(qi)并作為正負(fu)母線(xian)(xian)的中(zhong)性點(dian),這種結構就不(bu)可(ke)避(bi)免(mian)地(di)造成(cheng)(cheng)整流器(qi)(qi)和逆變器(qi)(qi)高頻諧波耦合在零線(xian)(xian)上,抬升零地(di)電(dian)(dian)壓(ya)(ya),造成(cheng)(cheng)負(fu)載端零地(di)電(dian)(dian)壓(ya)(ya)抬高,很難(nan)滿足IBM、HP等服務器(qi)(qi)廠家對零地(di)電(dian)(dian)壓(ya)(ya)小(xiao)于1V的場地(di)需求(qiu)。另外(wai),在市電(dian)(dian)和發電(dian)(dian)機(ji)(ji)切換時(shi),高頻機(ji)(ji)往(wang)往(wang)因零線(xian)(xian)缺失而必須(xu)轉旁路工作,在特定工況下可(ke)能造成(cheng)(cheng)負(fu)載閃斷(duan)的重大故(gu)障。工頻機(ji)(ji)因整流器(qi)(qi)不(bu)需要零線(xian)(xian)參與工作,在零線(xian)(xian)斷(duan)開時(shi),UPS可(ke)以保持正常供電(dian)(dian)。
結束語
從結構上(shang)講,工(gong)頻(pin)機(ji)(ji)(ji)UPS和(he)高(gao)頻(pin)機(ji)(ji)(ji)UPS的(de)(de)差(cha)異主(zhu)要(yao)(yao)表(biao)現在隔(ge)離(li)變壓(ya)器上(shang),而工(gong)頻(pin)機(ji)(ji)(ji)對隔(ge)離(li)變壓(ya)器的(de)(de)使用(yong),在很大程度(du)上(shang)提升了UPS的(de)(de)可(ke)靠性。從綜合性能方面來講,工(gong)頻(pin)機(ji)(ji)(ji)和(he)高(gao)頻(pin)機(ji)(ji)(ji)則(ze)各有優劣,至少在當前(qian),不存在誰取代誰的(de)(de)問題(ti)。用(yong)戶在選購設備的(de)(de)時候應(ying)當立(li)足于自身(shen)的(de)(de)實際需要(yao)(yao),而不是(shi)盲(mang)目跟從。比如(ru),用(yong)戶要(yao)(yao)建設中大型的(de)(de)數據中心,那(nei)么對可(ke)靠性和(he)穩定性的(de)(de)要(yao)(yao)求就應(ying)當放在第一(yi)位,大功(gong)率的(de)(de)工(gong)頻(pin)機(ji)(ji)(ji)UPS就應(ying)當是(shi)首(shou)選;如(ru)果是(shi)一(yi)般的(de)(de)辦(ban)公場所應(ying)用(yong),或者(zhe)主(zhu)要(yao)(yao)考慮(lv)到(dao)設備對空間(jian)的(de)(de)占用(yong),則(ze)可(ke)以采用(yong)高(gao)頻(pin)機(ji)(ji)(ji)UPS。
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