一、什么是中頻爐？

中頻感應加熱爐(下稱中頻爐)是一種迅速平穩的金屬材料加溫設備，它靠直流變頻設備把三相直流交流電流變化為單相電高頻交流電流.直流變頻設備是中頻爐的關鍵機器設備，其造成的諧波能使轉動電動機造成額外輸出功率損耗和發燙，提升變電器和電力網的損耗，使電磁能計量檢定儀表盤造成偏差，對繼電保護裝置、自動控制系統設備等造成影響，比較嚴重時候造成錯誤操，諧波也有將會在無功補償，電容控制回路被變大，可能會導致電容過負載乃至毀壞;此外諧波還會對鄰近的通信路線造成影響，因而，功率大的中頻爐的諧波難題不容忽視。

二、中頻爐諧波原因來源以及諧波帶來的危害

1.中(zhong)頻爐(lu)諧波的(de)分析

中頻(pin)電(dian)源注人(ren)電(dian)網的(de)諧波主要(yao)由整(zheng)(zheng)(zheng)流(liu)(liu)裝(zhuang)置產生。以三相六脈動全控制橋(qiao)整(zheng)(zheng)(zheng)流(liu)(liu)電(dian)路(lu)為例，在理想的(de)條件下(xia)能夠(gou)用大(da)致方(fang)波表示整(zheng)(zheng)(zheng)流(liu)(liu)電(dian)路(lu)交流(liu)(liu)側的(de)各相電(dian)流(liu)(liu)，利用傅立(li)葉分析法(fa)積累交流(liu)(liu)側的(de)a相電(dian)流(liu)(liu)的(de)式子(zi)圖(tu)如下(xia)：

 

從式(shi)(1)所知，在逆變電(dian)(dian)(dian)路(lu)溝(gou)通(tong)(tong)交流(liu)(liu)(liu)側電(dian)(dian)(dian)流(liu)(liu)(liu)中(zhong)(zhong)僅帶有(you)(you)6k土1(k為(wei)正整(zheng)(zheng)(zheng)數)次(ci)諧(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)流(liu)(liu)(liu)，這種諧(xie)波(bo)(bo)(bo)稱(cheng)之(zhi)為(wei)三相(xiang)6脈動飲料橋式(shi)整(zheng)(zheng)(zheng)流(liu)(liu)(liu)電(dian)(dian)(dian)路(lu)的(de)特(te)點諧(xie)波(bo)(bo)(bo)，各次(ci)諧(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)流(liu)(liu)(liu)有(you)(you)效值與(yu)基波(bo)(bo)(bo)電(dian)(dian)(dian)流(liu)(liu)(liu)有(you)(you)效值的(de)比率(lv)(一(yi)般 稱(cheng)之(zhi)為(wei)n次(ci)諧(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)流(liu)(liu)(liu)帶有(you)(you)率(lv))都(dou)相(xiang)當于諧(xie)波(bo)(bo)(bo)頻次(ci)n的(de)后.在具體電(dian)(dian)(dian)源電(dian)(dian)(dian)路(lu)中(zhong)(zhong)，因(yin)為(wei)整(zheng)(zheng)(zheng)流(liu)(liu)(liu)變壓器中(zhong)(zhong)走(zou)電(dian)(dian)(dian)抗的(de)功(gong)效，促使整(zheng)(zheng)(zheng)流(liu)(liu)(liu)器閥的(de)導通(tong)(tong)和(he)關閉都(dou)必須有(you)(you)一(yi)個銜接全過程，逆變電(dian)(dian)(dian)路(lu)溝(gou)通(tong)(tong)交流(liu)(liu)(liu)側各相(xiang)電(dian)(dian)(dian)流(liu)(liu)(liu)的(de)波(bo)(bo)(bo)型將變為(wei)梯形波(bo)(bo)(bo)，而已不是理想化標準下(xia)的(de)方(fang)波(bo)(bo)(bo)，因(yin)而，在具體情(qing)況(kuang)下(xia)測出(chu)的(de)n次(ci)諧(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)流(liu)(liu)(liu)帶有(you)(you)率(lv)一(yi)般都(dou)低于1/n.

假如中頻感應爐的(de)(de)逆變電(dian)(dian)路(lu)(lu)為(wei)12脈(mo)動(dong)飲料(liao)(liao)整(zheng)流(liu)器，其(qi)特點諧(xie)波(bo)(bo)的(de)(de)頻次(ci)為(wei)(12k土1).先后推(tui)導(dao)，p脈(mo)動(dong)飲料(liao)(liao)逆變電(dian)(dian)路(lu)(lu)的(de)(de)特點諧(xie)波(bo)(bo)頻次(ci)為(wei)(p左士1)，各次(ci)諧(xie)波(bo)(bo)有效(xiao)值與基(ji)波(bo)(bo)有效(xiao)值的(de)(de)比率也都(dou)相當(dang)于諧(xie)波(bo)(bo)頻次(ci)的(de)(de)后.因而，提升逆變電(dian)(dian)路(lu)(lu)的(de)(de)脈(mo)動(dong)飲料(liao)(liao)數，能夠降低注人電(dian)(dian)力網的(de)(de)高(gao)次(ci)諧(xie)波(bo)(bo).

2.中頻爐諧波的來源

諧波的造(zao)成關鍵是來源于非線性電器設備(bei)的應用(yong):

A.具備(bei)鐵磁飽(bao)和特點的變壓器鐵芯機(ji)器設(she)備(bei)，如:變電器、串聯電抗(kang)器等(deng);

B.以具備明顯非線性特點的(de)(de)電(dian)孤為(wei)工(gong)作中物(wu)質的(de)(de)機器(qi)設備，如:氣體放電(dian)燈、交流弧焊機、煉綱(gang)電(dian)弧爐、中頻感應(ying)爐等;

C.以(yi)電(dian)(dian)(dian)(dian)(dian)(dian)力(li)工(gong)(gong)(gong)程(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)子元(yuan)器(qi)件為(wei)基本的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)源變(bian)(bian)壓(ya)器(qi)機(ji)器(qi)設備(bei)，如:各(ge)(ge)種(zhong)各(ge)(ge)樣(yang)電(dian)(dian)(dian)(dian)(dian)(dian)力(li)工(gong)(gong)(gong)程(cheng)變(bian)(bian)流(liu)機(ji)器(qi)設備(bei)(鎮流(liu)器(qi)、逆變(bian)(bian)電(dian)(dian)(dian)(dian)(dian)(dian)源、軟啟動(dong)器(qi))、交流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)機(ji)調速和變(bian)(bian)壓(ya)設備(bei)、大空間的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)力(li)工(gong)(gong)(gong)程(cheng)可控(kong)硅(gui)可控(kong)性(xing)開關(guan)(guan)柜等(deng)，他們很多的(de)(de)(de)用以(yi)化工(gong)(gong)(gong)廠、電(dian)(dian)(dian)(dian)(dian)(dian)氣設備(bei)鐵路(lu)、冶金工(gong)(gong)(gong)業(ye)、礦(kuang)山開采(cai)等(deng)廠礦(kuang)企(qi)業(ye)及(ji)其(qi)各(ge)(ge)種(zhong)各(ge)(ge)樣(yang)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)產品中(zhong)。左右這種(zhong)非(fei)線(xian)(xian)(xian)性(xing)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)設備(bei)因為(wei)負(fu)載具備(bei)其(qi)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)不(bu)伴(ban)隨著工(gong)(gong)(gong)作(zuo)(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)同歩轉變(bian)(bian)的(de)(de)(de)非(fei)線(xian)(xian)(xian)性(xing)特點(dian)，促使(shi)穿過負(fu)載的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)呈非(fei)正弦波形，它由基波以(yi)及(ji)整數倍(bei)的(de)(de)(de)諧(xie)波組成(cheng)(cheng)。造(zao)(zao)成(cheng)(cheng)的(de)(de)(de)諧(xie)波使(shi)電(dian)(dian)(dian)(dian)(dian)(dian)力(li)網(wang)工(gong)(gong)(gong)作(zuo)(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)比較(jiao)嚴重失幀。如某鑄造(zao)(zao)公(gong)司，選用35kV路(lu)線(xian)(xian)(xian)供電(dian)(dian)(dian)(dian)(dian)(dian)系統，關(guan)(guan)鍵用電(dian)(dian)(dian)(dian)(dian)(dian)量機(ji)器(qi)設備(bei)是中(zhong)頻感(gan)應爐。電(dian)(dian)(dian)(dian)(dian)(dian)力(li)公(gong)司就該公(gong)司對公(gong)共電(dian)(dian)(dian)(dian)(dian)(dian)力(li)網(wang)電(dian)(dian)(dian)(dian)(dian)(dian)能質(zhi)量的(de)(de)(de)危害開展了檢測，檢測依(yi)據為(wei):該公(gong)司6單脈沖中(zhong)頻感(gan)應爐造(zao)(zao)成(cheng)(cheng)的(de)(de)(de)5、7次諧(xie)波電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)造(zao)(zao)成(cheng)(cheng)35kV母線(xian)(xian)(xian)槽的(de)(de)(de)工(gong)(gong)(gong)作(zuo)(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)崎變(bian)(bian)率超(chao)過國家標(biao)準控(kong)制(zhi)值。(見下數據圖表數據信(xin)息)

從(cong)圖中可(ke)以看出，該客戶用電設備產生的(de)(de)5、7、11、13次諧波電流分別為允許值的(de)(de)321、14、123、1.16倍(bei)。尤其是五次諧波分量已經嚴重超標。

3.諧(xie)波帶來的危害

諧波對(dui)電力系(xi)統擁(yong)有(you) 比較普遍的各個(ge)方(fang)面傷害，具體表現(xian)為耗能提(ti)升(sheng)、電導體發燙、及其對(dui)保護(hu)器(qi)及計量檢(jian)定儀器(qi)設備精確性等危害。

A.諧波對變電器的(de)危害

當較高(gao)頻率(lv)的電流引入變電器(qi)(qi)時(shi)，將造成(cheng)趨膚效應和相鄰效用，在繞阻(zu)中造成(cheng)額外損耗，與變壓(ya)器(qi)(qi)線圈相關(guan)的鐵損亦有提升(sheng)。變電器(qi)(qi)將造成(cheng)超(chao)溫狀(zhuang)況。諧(xie)波工(gong)作(zuo)電壓(ya)還會使變電器(qi)(qi)勵(li)磁電流電流擴(kuo)大，高(gao)效率(lv)減(jian)少，功率(lv)因素值卜(bu)降(jiang)。當諧(xie)波工(gong)作(zuo)電壓(ya)長時(shi)間具(ju)有且比(bi)(bi)較比(bi)(bi)較嚴重時(shi)，將會嚴重危(wei)害變電器(qi)(qi)主絕(jue)緣層。

B.諧波對電力工(gong)程電容器的(de)危害

當電(dian)(dian)容(rong)器(qi)(qi)組(zu)控(kong)制回路特性阻抗(kang)呈溶性時(shi)，串(chuan)聯電(dian)(dian)容(rong)器(qi)(qi)對諧(xie)波(bo)電(dian)(dian)流起變大功效，非(fei)常是(shi)當系統軟件等價(jia)感抗(kang)和(he)電(dian)(dian)容(rong)器(qi)(qi)組(zu)控(kong)制回路容(rong)抗(kang)組(zu)成串(chuan)聯諧(xie)振(zhen)標準(zhun)，造(zao)(zao)成電(dian)(dian)流串(chuan)聯諧(xie)振(zhen)時(shi)，即便較小的(de)諧(xie)波(bo)電(dian)(dian)流也(ye)會變大若干倍，導致(zhi)電(dian)(dian)容(rong)器(qi)(qi)的(de)損耗大幅度提升(sheng)(sheng)，造(zao)(zao)成電(dian)(dian)容(rong)器(qi)(qi)的(de)超(chao)溫或毀壞(huai)。此外，諧(xie)波(bo)工作電(dian)(dian)壓(ya)值提高使電(dian)(dian)容(rong)器(qi)(qi)的(de)損耗指數和(he)額外損耗提升(sheng)(sheng)，造(zao)(zao)成非(fei)常容(rong)易產生常見故障和(he)減少電(dian)(dian)容(rong)器(qi)(qi)的(de)使用壽命。

C.對(dui)輸電(dian)線路的危害

當諧(xie)(xie)波電(dian)流根據(ju)架空電(dian)纜時，將會造成(cheng)并聯諧(xie)(xie)振，乃至導(dao)致風險的過(guo)壓(ya)。電(dian)線電(dian)纜在(zai)諧(xie)(xie)波工作(zuo)電(dian)壓(ya)功效卜，絕(jue)緣層抗壓(ya)強(qiang)度減(jian)(jian)少，泄露(lu)電(dian)流擴(kuo)大，使(shi)使(shi)用壽命減(jian)(jian)少。

除(chu)此之(zhi)外，諧(xie)波(bo)還(huan)會對轉動(dong)電動(dong)機、繼電保(bao)護裝置和保(bao)護裝置工作中(zhong)的(de)可(ke)信性(xing)、精確(que)測量和計量檢定儀器(qi)設備的(de)精確(que)性(xing)造成比較嚴重的(de)不好危害。