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一、內部主電路結構

        采用(yong)“交-直-交”結構(gou)的(de)低壓(ya)變頻器，其內部主電路(lu)由整流(liu)和逆變兩(liang)大(da)部分組成，如圖1所(suo)示。從R、S、T端輸(shu)入(ru)的(de)三(san)(san)相(xiang)(xiang)交流(liu)電，經三(san)(san)相(xiang)(xiang)整流(liu)橋(qiao)（由二極(ji)管(guan)D1～D6構(gou)成）整流(liu)成直流(liu)電，電壓(ya)為UD。電容器C1和C2是(shi)濾波(bo)電容器。6個IGBT管(guan)（絕緣柵雙(shuang)極(ji)性(xing)晶體管(guan)）V1～V6構(gou)成三(san)(san)相(xiang)(xiang)逆變橋(qiao)，把直流(liu)電逆變成頻率和電壓(ya)任意可(ke)調的(de)三(san)(san)相(xiang)(xiang)交流(liu)電。

圖1 變頻器內部主電路

二、均(jun)壓電阻(zu)和限流(liu)電阻(zu)

        圖(tu)1中，濾(lv)(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)C1和C2兩端(duan)各并聯了一(yi)(yi)個(ge)(ge)(ge)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，是為(wei)(wei)了使(shi)兩只電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)上(shang)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)基(ji)本相等，防止電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)在(zai)(zai)(zai)工作(zuo)中損壞（目前，由于(yu)技(ji)術(shu)的(de)(de)(de)進步(bu)，低壓(ya)(ya)（380V）變(bian)頻器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容大(da)多數(shu)可(ke)以不需要串(chuan)聯使(shi)用了）。在(zai)(zai)(zai)整流橋(qiao)和濾(lv)(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)之間接有(you)一(yi)(yi)個(ge)(ge)(ge)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R和一(yi)(yi)對(dui)接觸(chu)(chu)器(qi)(qi)(qi)(qi)(qi)觸(chu)(chu)點KM，其(qi)緣(yuan)由是：變(bian)頻器(qi)(qi)(qi)(qi)(qi)剛接通(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)時，濾(lv)(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)上(shang)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)(wei)0V，而電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)(wei)380V時的(de)(de)(de)整流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)峰值是537V，這(zhe)樣(yang)在(zai)(zai)(zai)接通(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)瞬間將(jiang)有(you)很大(da)的(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)沖擊(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，有(you)可(ke)能(neng)損壞整流二(er)極管(guan)；另外，端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)(wei)0的(de)(de)(de)濾(lv)(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)會使(shi)整流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)瞬間降低至0V，形成對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)網絡(luo)的(de)(de)(de)干(gan)擾。為(wei)(wei)了解決上(shang)述問題，在(zai)(zai)(zai)整流橋(qiao)和濾(lv)(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)之間接入一(yi)(yi)個(ge)(ge)(ge)限(xian)流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R，可(ke)將(jiang)濾(lv)(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流限(xian)制在(zai)(zai)(zai)一(yi)(yi)個(ge)(ge)(ge)允許(xu)范圍內。但是，如果(guo)限(xian)流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R始(shi)終(zhong)接在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路內，其(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)降將(jiang)影響變(bian)頻器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)輸出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，也(ye)會降低變(bian)頻器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)轉(zhuan)換效(xiao)率(lv)，因此，濾(lv)(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)完畢(bi)后，由接觸(chu)(chu)器(qi)(qi)(qi)(qi)(qi)KM將(jiang)限(xian)流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R短接，使(shi)之退出運行(xing)。

三、主電路的對外連接端(duan)子

        各(ge)種變(bian)(bian)頻器主電(dian)路(lu)的(de)(de)對外(wai)連(lian)接(jie)(jie)(jie)(jie)端(duan)(duan)子大致相同，如圖2所示。其(qi)中，R、S、T是變(bian)(bian)頻器的(de)(de)電(dian)源端(duan)(duan)子，接(jie)(jie)(jie)(jie)至交流(liu)三相電(dian)源；U、V、W為變(bian)(bian)頻器的(de)(de)輸(shu)出(chu)端(duan)(duan)子，接(jie)(jie)(jie)(jie)至電(dian)動(dong)機；P+是整流(liu)橋輸(shu)出(chu)的(de)(de)+端(duan)(duan)，出(chu)廠時P+端(duan)(duan)與P端(duan)(duan)之間(jian)用一塊(kuai)截(jie)面(mian)積足夠大的(de)(de)銅片短接(jie)(jie)(jie)(jie)，當需要接(jie)(jie)(jie)(jie)入(ru)直流(liu)電(dian)抗器DL時，拆去銅片，將DL接(jie)(jie)(jie)(jie)在P+和P之間(jian)；P、N是濾波(bo)后直流(liu)電(dian)路(lu)的(de)(de)+、-端(duan)(duan)子，可以連(lian)接(jie)(jie)(jie)(jie)制(zhi)動(dong)單元和制(zhi)動(dong)電(dian)阻；PE是接(jie)(jie)(jie)(jie)地端(duan)(duan)子。

圖2 主電路對外連接端子

四、變(bian)頻(pin)系統的共(gong)用直流母線

        電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)機(ji)在(zai)制(zhi)動(dong)(dong)(dong)(dong)（發電(dian)(dian)(dian)(dian)(dian)(dian)）狀(zhuang)態時(shi)，變(bian)頻(pin)(pin)器(qi)(qi)從電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)機(ji)吸收的(de)(de)(de)能(neng)(neng)(neng)量(liang)(liang)都會保存在(zai)變(bian)頻(pin)(pin)器(qi)(qi)直(zhi)流環節的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)容中，并導致(zhi)變(bian)頻(pin)(pin)器(qi)(qi)中的(de)(de)(de)直(zhi)流母(mu)線(xian)(xian)(xian)電(dian)(dian)(dian)(dian)(dian)(dian)壓升高(gao)。如(ru)果(guo)變(bian)頻(pin)(pin)器(qi)(qi)配備制(zhi)動(dong)(dong)(dong)(dong)單(dan)元和(he)制(zhi)動(dong)(dong)(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（這兩種元件屬(shu)于選(xuan)配件），變(bian)頻(pin)(pin)器(qi)(qi)就(jiu)可(ke)以(yi)(yi)通過短(duan)時(shi)間接(jie)通電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，使再(zai)(zai)(zai)生電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)(neng)(neng)以(yi)(yi)熱方(fang)式消(xiao)耗(hao)掉，稱做(zuo)能(neng)(neng)(neng)耗(hao)制(zhi)動(dong)(dong)(dong)(dong)。當(dang)然，采取再(zai)(zai)(zai)生能(neng)(neng)(neng)量(liang)(liang)回(hui)饋(kui)(kui)方(fang)案也可(ke)解決(jue)變(bian)頻(pin)(pin)調速系(xi)統(tong)的(de)(de)(de)再(zai)(zai)(zai)生能(neng)(neng)(neng)量(liang)(liang)問(wen)題(ti)，并可(ke)達(da)到節約能(neng)(neng)(neng)源的(de)(de)(de)目的(de)(de)(de)。而標準通用PWM變(bian)頻(pin)(pin)器(qi)(qi)沒(mei)有(you)(you)設(she)計使再(zai)(zai)(zai)生能(neng)(neng)(neng)量(liang)(liang)反饋(kui)(kui)到三相電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)功能(neng)(neng)(neng)。如(ru)果(guo)將(jiang)多(duo)臺(tai)(tai)變(bian)頻(pin)(pin)器(qi)(qi)的(de)(de)(de)直(zhi)流環節通過共(gong)用直(zhi)流母(mu)線(xian)(xian)(xian)互連，則一(yi)臺(tai)(tai)或(huo)多(duo)臺(tai)(tai)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)機(ji)產生的(de)(de)(de)再(zai)(zai)(zai)生能(neng)(neng)(neng)量(liang)(liang)就(jiu)可(ke)以(yi)(yi)被其他電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)機(ji)以(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)的(de)(de)(de)方(fang)式消(xiao)耗(hao)吸收。或(huo)者，在(zai)直(zhi)流母(mu)線(xian)(xian)(xian)上(shang)設(she)置一(yi)組(zu)一(yi)定容量(liang)(liang)的(de)(de)(de)制(zhi)動(dong)(dong)(dong)(dong)單(dan)元和(he)制(zhi)動(dong)(dong)(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，用以(yi)(yi)吸收不能(neng)(neng)(neng)被電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)狀(zhuang)態電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)機(ji)吸收的(de)(de)(de)再(zai)(zai)(zai)生能(neng)(neng)(neng)量(liang)(liang)。若共(gong)用直(zhi)流母(mu)線(xian)(xian)(xian)與能(neng)(neng)(neng)量(liang)(liang)回(hui)饋(kui)(kui)單(dan)元組(zu)合，就(jiu)可(ke)以(yi)(yi)將(jiang)直(zhi)流母(mu)線(xian)(xian)(xian)上(shang)的(de)(de)(de)多(duo)余能(neng)(neng)(neng)量(liang)(liang)直(zhi)接(jie)反饋(kui)(kui)到電(dian)(dian)(dian)(dian)(dian)(dian)網(wang)中來，從而提高(gao)系(xi)統(tong)的(de)(de)(de)節能(neng)(neng)(neng)效果(guo)。綜(zong)上(shang)所述，在(zai)具有(you)(you)多(duo)臺(tai)(tai)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)(dong)機(ji)的(de)(de)(de)變(bian)頻(pin)(pin)調速系(xi)統(tong)中，選(xuan)用共(gong)用直(zhi)流母(mu)線(xian)(xian)(xian)方(fang)案，配置一(yi)組(zu)制(zhi)動(dong)(dong)(dong)(dong)單(dan)元、制(zhi)動(dong)(dong)(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)和(he)能(neng)(neng)(neng)量(liang)(liang)回(hui)饋(kui)(kui)單(dan)元，是一(yi)種提高(gao)系(xi)統(tong)性(xing)能(neng)(neng)(neng)并節約投資的(de)(de)(de)較好方(fang)案。

圖3所(suo)示(shi)為應用(yong)(yong)比(bi)較廣泛的(de)共用(yong)(yong)直流(liu)母線方(fang)案(an)，該方(fang)案(an)包(bao)括以下幾個部分(fen)。

圖3 變頻器的公用直流母線

1.三相交流電源進線

各(ge)變(bian)(bian)(bian)頻器的(de)(de)電(dian)源輸入(ru)端并聯于(yu)同一交(jiao)流母線(xian)上，并保證各(ge)變(bian)(bian)(bian)頻器的(de)(de)輸入(ru)端電(dian)源相位一致(zhi)。圖3中(zhong)(zhong)，斷路器QF是每臺變(bian)(bian)(bian)頻器的(de)(de)進(jin)線(xian)保護裝(zhuang)置(zhi)。LR是進(jin)線(xian)電(dian)抗器，當(dang)多臺變(bian)(bian)(bian)頻器在同一環境中(zhong)(zhong)運(yun)行時，相鄰變(bian)(bian)(bian)頻器會互相干(gan)(gan)擾(rao)，為了消除或減輕這種干(gan)(gan)擾(rao)，同時為了提高變(bian)(bian)(bian)頻器輸入(ru)側的(de)(de)功率因(yin)數，接入(ru)LR是必須的(de)(de)。

2.直流母線 

KM是變頻器的(de)直流(liu)(liu)環節與公(gong)用(yong)直流(liu)(liu)母線連(lian)接(jie)的(de)控(kong)制(zhi)開關(guan)。FU是半導體快速(su)熔斷器，其額(e)定電(dian)(dian)壓可選700V，額(e)定電(dian)(dian)流(liu)(liu)必須考慮驅動(dong)(dong)(dong)電(dian)(dian)動(dong)(dong)(dong)機在電(dian)(dian)動(dong)(dong)(dong)或制(zhi)動(dong)(dong)(dong)時的(de)最大電(dian)(dian)流(liu)(liu)，一般情況下，可以選擇額(e)定負載(zai)電(dian)(dian)流(liu)(liu)的(de)125%。

3.公(gong)共制動單元和(he)（或）能(neng)量回饋裝置 

回(hui)饋到公(gong)共直(zhi)流母線上(shang)的(de)再(zai)生能(neng)(neng)量，在(zai)不能(neng)(neng)完全被吸(xi)收的(de)情況(kuang)下，可(ke)通過共用的(de)制動電阻消耗未被吸(xi)收的(de)再(zai)生能(neng)(neng)量。若采(cai)用能(neng)(neng)量回(hui)饋裝置，則這部分再(zai)生能(neng)(neng)量將被回(hui)饋到電網中，從(cong)而提高(gao)節能(neng)(neng)的(de)效率(lv)。

4.控制單元 

各變頻器根據控制單(dan)元的指令，通過KM將其(qi)直流環節并(bing)聯(lian)到共用直流母線(xian)上，或是在變頻器故障后快速地與共用直流母線(xian)斷開。

（來源：網絡，版權(quan)歸原作者）