在電(dian)阻、電(dian)感及電(dian)容(rong)所組成的串聯(lian)電(dian)路內，當容(rong)抗XC與感抗XL相(xiang)等時，即(ji)XC=XL，電(dian)路中的電(dian)壓(ya)U與電(dian)流(liu)I的相(xiang)位相(xiang)同，電(dian)路呈現純電(dian)阻性，這種現象叫。當電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)發生串(chuan)聯(lian)(lian)諧振時電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的阻(zu)(zu)(zu)抗(kang)(kang)Z=√R^2 +(XC-XL)^2=R，電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中總阻(zu)(zu)(zu)抗(kang)(kang)最小(xiao)，電(dian)(dian)(dian)(dian)流將(jiang)達到(dao)最大值(zhi)。 阻(zu)(zu)(zu)抗(kang)(kang)條(tiao)件(jian)，諧振后虛(xu)部(bu)相等(deng)符號相反。串(chuan)聯(lian)(lian)阻(zu)(zu)(zu)抗(kang)(kang)等(deng)于(yu)(yu)0，并聯(lian)(lian)阻(zu)(zu)(zu)抗(kang)(kang)等(deng)于(yu)(yu)無窮(qiong)大。就(jiu)是在變頻(pin)串(chuan)聯(lian)(lian)諧振試驗裝置(zhi)的時候，串(chuan)聯(lian)(lian)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)諧振電(dian)(dian)(dian)(dian)流無窮(qiong)大;并聯(lian)(lian)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)諧振電(dian)(dian)(dian)(dian)壓(ya)無窮(qiong)大(理論值(zhi))。在電(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)、、電(dian)(dian)(dian)(dian)感(gan)(gan)串(chuan)聯(lian)(lian)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中，出現電(dian)(dian)(dian)(dian)源、電(dian)(dian)(dian)(dian)壓(ya)、電(dian)(dian)(dian)(dian)流同(tong)相位現象，叫做串(chuan)聯(lian)(lian)諧振，其特點是:電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)呈純電(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)性(xing)，電(dian)(dian)(dian)(dian)源、電(dian)(dian)(dian)(dian)壓(ya)和電(dian)(dian)(dian)(dian)流同(tong)相位，電(dian)(dian)(dian)(dian)抗(kang)(kang)X等(deng)于(yu)(yu)0，阻(zu)(zu)(zu)抗(kang)(kang)Z等(deng)于(yu)(yu)電(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)R，此時電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的阻(zu)(zu)(zu)抗(kang)(kang)最小(xiao)，電(dian)(dian)(dian)(dian)流最大，在電(dian)(dian)(dian)(dian)感(gan)(gan)和電(dian)(dian)(dian)(dian)容(rong)上可能(neng)產生比電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)壓(ya)大很多倍的高電(dian)(dian)(dian)(dian)壓(ya)，因(yin)此串(chuan)聯(lian)(lian)諧振也(ye)稱電(dian)(dian)(dian)(dian)壓(ya)諧振。
35KV變頻串聯諧(xie)振(zhen)裝置產生諧(xie)振(zhen)的(de)原(yuan)因
在電(dian)阻(zu)、電(dian)容和(he)電(dian)感(gan)串(chuan)聯(lian)的電(dian)路(lu)中(zhong)，感(gan)抗Xl和(he)Xc的作用是直接相減(jian)的。如果滿足一定條件，恰好(hao)使Xl=Xc，則電(dian)路(lu)的電(dian)抗等于零，電(dian)路(lu)中(zhong)的電(dian)流和(he)電(dian)壓(ya)相位(wei)相同(tong)，沒有無功(gong)功(gong)率在電(dian)阻(zu)與電(dian)感(gan)、電(dian)容間(jian)交換。電(dian)路(lu)的這種狀態稱為串(chuan)聯(lian)諧振。
電路諧振條件是Xc=Xl，即ωL=1/ωC，由此可得(de)電路固有諧振條件為f0=1/(2π√LC)。
阻抗(kang)(kang)條件(jian):諧(xie)振后(hou)虛部相(xiang)等符號相(xiang)反。串(chuan)聯阻抗(kang)(kang)等于(yu)0，并聯阻抗(kang)(kang)等于(yu)無(wu)窮(qiong)(qiong)大(da)(da)。就是在諧(xie)振的時(shi)候，串(chuan)聯電路諧(xie)振電流(liu)無(wu)窮(qiong)(qiong)大(da)(da);并聯電路諧(xie)振電壓無(wu)窮(qiong)(qiong)大(da)(da)(理論值)。或者說:
串聯電路中(zhong):總的輸入阻抗的虛(xu)部等于零(諧振就是輸出(chu)的電壓和(he)電流(liu)同(tong)相(xiang))
在(zai)具有電(dian)(dian)阻(zu)R、電(dian)(dian)感L和電(dian)(dian)容(rong)C元件的(de)(de)交(jiao)流電(dian)(dian)路中，電(dian)(dian)路兩(liang)端的(de)(de)電(dian)(dian)壓與其(qi)中電(dian)(dian)流位相一般是不同的(de)(de)。如果我們調節電(dian)(dian)路元件(L或C)的(de)(de)參數或電(dian)(dian)源頻率，可以使它(ta)們位相相同，整(zheng)個電(dian)(dian)路呈(cheng)現為純電(dian)(dian)阻(zu)性。電(dian)(dian)路達到這(zhe)種狀態稱之為諧振(zhen)。
根據變頻串聯諧振原理，我們知道當前電抗器L的感抗值X1與回路中的容抗值Xc相等時，回路達到諧振狀態，此時回路中僅回路電阻R消耗有功功率，而無功功率則在電抗器與試品電容之間來回振蕩，從而在試品上產生高壓。
產生串(chuan)聯(lian)諧振的原因:
XL =X C
由于串聯(lian)諧振要(yao)在 L、C 中產生高壓(ya)，可能造成擊穿線圈或(huo)電(dian)(dian)容的(de)危害，因此，在電(dian)(dian)力工(gong)程中應盡量避免串聯(lian)諧振，而利用串聯(lian)諧振試驗(yan)裝置進行檢(jian)測電(dian)(dian)力系統就顯得(de)尤為重要(yao)了。
在(zai)具有R、L、C元(yuan)(yuan)件(jian)的(de)(de)(de)正(zheng)弦交流(liu)(liu)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)中,電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)兩端(duan)的(de)(de)(de)電(dian)(dian)(dian)(dian)壓與(yu)電(dian)(dian)(dian)(dian)流(liu)(liu)一般是不(bu)同(tong)(tong)相(xiang)(xiang)的(de)(de)(de).如果改變電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)元(yuan)(yuan)件(jian)的(de)(de)(de)參(can)數值或(huo)調節電(dian)(dian)(dian)(dian)源的(de)(de)(de)頻率,可使(shi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)的(de)(de)(de)電(dian)(dian)(dian)(dian)壓與(yu)電(dian)(dian)(dian)(dian)流(liu)(liu)同(tong)(tong)相(xiang)(xiang),使(shi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)的(de)(de)(de)阻抗(kang)呈現(xian)電(dian)(dian)(dian)(dian)阻的(de)(de)(de)性(xing)質,處(chu)在(zai)這種(zhong)狀態下的(de)(de)(de)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)稱為(wei)諧(xie)(xie)振.根據電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)的(de)(de)(de)不(bu)同(tong)(tong)連接(jie)形式(shi),諧(xie)(xie)振現(xian)象(xiang)可分為(wei)串聯諧(xie)(xie)振和并聯諧(xie)(xie)振.。在(zai)R、L、C串聯電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)中,當電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)中的(de)(de)(de)XL=XC時,阻抗(kang)角∮=0,即電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)壓 和電(dian)(dian)(dian)(dian)流(liu)(liu) 同(tong)(tong)相(xiang)(xiang),這種(zhong)現(xian)象(xiang)稱為(wei)串聯諧(xie)(xie)振。
串聯(lian)諧(xie)振的(de)特點:
(1)諧振(zhen)發生時,因感(gan)抗XL等于容抗XC,所(suo)以,阻(zu)抗達(da)到最小值(zhi),電路呈電阻(zu)性。
(2)在電壓U不(bu)變的(de)情況下,電路中的(de)電流I達到最大(da)值。
(3)由于串(chuan)聯(lian)諧(xie)(xie)振(zhen)(zhen)時(shi)(shi)XL=XC,所以(yi)UL=UC,而UL和Uc的(de)(de)(de)相位相反,相加時(shi)(shi)互相抵消,所以(yi)電(dian)(dian)阻上(shang)(shang)的(de)(de)(de)電(dian)(dian)壓(ya)等于電(dian)(dian)源電(dian)(dian)壓(ya)。串(chuan)聯(lian)電(dian)(dian)路諧(xie)(xie)振(zhen)(zhen)時(shi)(shi)具有某些(xie)特(te)點,了解諧(xie)(xie)振(zhen)(zhen)現(xian)象(xiang)可以(yi)利(li)(li)用這(zhe)些(xie)特(te)點,又可防止某些(xie)特(te)點所帶來(lai)(lai)的(de)(de)(de)危害(hai)。LC諧(xie)(xie)波(bo)濾除裝(zhuang)置就是(shi)(shi)利(li)(li)用串(chuan)聯(lian)諧(xie)(xie)振(zhen)(zhen)的(de)(de)(de)特(te)點,分別慮(lv)除主要各次諧(xie)(xie)波(bo).在(zai)普通無功(gong)補償裝(zhuang)置中應避免串(chuan)聯(lian)諧(xie)(xie)振(zhen)(zhen),這(zhe)是(shi)(shi)因為,當(dang)串(chuan)聯(lian)諧(xie)(xie)振(zhen)(zhen)發(fa)生時(shi)(shi),電(dian)(dian)容元件上(shang)(shang)的(de)(de)(de)電(dian)(dian)壓(ya)將增高,可能導致(zhi)電(dian)(dian)容器絕(jue)緣(yuan)層(ceng)被擊穿。但在(zai)無線電(dian)(dian)工程中,利(li)(li)用串(chuan)聯(lian)諧(xie)(xie)振(zhen)(zhen)現(xian)象(xiang)的(de)(de)(de)選擇(ze)性(xing)和所獲得的(de)(de)(de)較(jiao)高電(dian)(dian)壓(ya),可將所需要接收的(de)(de)(de)信號(hao)提取(qu)出(chu)來(lai)(lai)，對LC選頻(pin)諧(xie)(xie)振(zhen)(zhen)回路中的(de)(de)(de)品質因數Q,它的(de)(de)(de)定(ding)義是(shi)(shi):Qo=WoL/r,Wo是(shi)(shi)回路的(de)(de)(de)諧(xie)(xie)振(zhen)(zhen)頻(pin)率,r是(shi)(shi)電(dian)(dian)感L的(de)(de)(de)消耗電(dian)(dian)阻。
