異步(bu)電機(ji)(ji)和(he)同步(bu)電機(ji)(ji)的區別 異步(bu)電機(ji)(ji)和(he)同步(bu)電機(ji)(ji)哪個好(hao)
異步電動機(asynchronous motor)
異步電動機是由定子側接入三相交流電源,定子繞組流過的三相對稱電流產生三相磁動勢(定子旋轉磁動勢)并產生旋轉磁場。該旋轉磁場與轉子導體有相對切割運動,根據(ju)電磁感應(ying)原理(li),轉(zhuan)子(zi)導體(ti)產(chan)生(sheng)感(gan)應(ying)電(dian)(dian)動(dong)勢并產(chan)生(sheng)感(gan)應(ying)電(dian)(dian)流(liu)。根據電(dian)(dian)磁(ci)(ci)力定律,載流(liu)的(de)(de)(de)轉(zhuan)子(zi)導體(ti)在磁(ci)(ci)場(chang)中(zhong)受到電(dian)(dian)磁(ci)(ci)力作用,形成電(dian)(dian)磁(ci)(ci)轉(zhuan)矩,驅動(dong)轉(zhuan)子(zi)旋(xuan)轉(zhuan)。異步(bu)電(dian)(dian)動(dong)機的(de)(de)(de)轉(zhuan)速小于定子(zi)旋(xuan)轉(zhuan)磁(ci)(ci)場(chang)的(de)(de)(de)轉(zhuan)速,有個轉(zhuan)差(cha)(轉(zhuan)差(cha)與定子(zi)所產(chan)生(sheng)的(de)(de)(de)旋(xuan)轉(zhuan)磁(ci)(ci)場(chang)的(de)(de)(de)轉(zhuan)速的(de)(de)(de)比值叫轉(zhuan)差(cha)率),從而叫做異步(bu)電(dian)(dian)動(dong)機。因其轉(zhuan)子(zi)繞組電(dian)(dian)流(liu)是(shi)感(gan)應(ying)產(chan)生(sheng)的(de)(de)(de),又稱(cheng)感(gan)應(ying)電(dian)(dian)動(dong)機。
異步電動機的同步轉速,即旋轉磁場的轉速為:n=60f/p
其中:
n——異步(bu)電動機的同步(bu)轉速;
f——電源頻率(lv);
p——磁極對數。
由(you)上式可以看出,改(gai)變(bian)(bian)異(yi)步電動機的供(gong)電頻率就可以改(gai)變(bian)(bian)其同步轉速,從而實現(xian)調速運行,即變(bian)(bian)頻調速。
異步電動機按照轉子結構分為兩種形式:有鼠(shu)籠式(鼠(shu)籠式異(yi)步(bu)電機)、繞線式異(yi)步(bu)電動機。
特點:
優點:結構簡單,制造方便,價格便宜,運行方便。
缺點(dian):功率因數滯后,輕載功率因數低(di),調(diao)速性能稍(shao)差。
主要做電(dian)(dian)動(dong)機用,一般不做發電(dian)(dian)機。
同步電動機是由定子側送入三相交流電,不同的只是在轉子側同時通一個直流電流,產生相對定子方向不變的磁場,這個磁場旋轉的速度和由定子產生的旋轉磁場的速度是相等的,所以稱為同步電動機。其轉子轉速n與磁(ci)極對數p、電(dian)源頻(pin)率f之間滿足n=60f/p。轉(zhuan)速n決定于電源頻率(lv)f,故電源頻(pin)率一定(ding)時,轉速(su)不變,且與負載無關。具有運(yun)行(xing)穩定(ding)性(xing)高和過載能力大等特點(dian)。
過去(qu)的(de)電(dian)(dian)(dian)(dian)(dian)力拖(tuo)動(dong)(dong)中(zhong),很(hen)少采用同(tong)(tong)(tong)步(bu)電(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji),同(tong)(tong)(tong)步(bu)電(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)主要作為(wei)發電(dian)(dian)(dian)(dian)(dian)機(ji)使用,其主要原(yuan)因(yin)是同(tong)(tong)(tong)步(bu)電(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)不能在電(dian)(dian)(dian)(dian)(dian)網電(dian)(dian)(dian)(dian)(dian)壓下自(zi)行起(qi)動(dong)(dong),靜止的(de)轉子磁極在旋轉磁場的(de)作用下,平均轉矩為(wei)零。但是近年來,隨著(zhu)電(dian)(dian)(dian)(dian)(dian)力電(dian)(dian)(dian)(dian)(dian)子技術的(de)發展,解(jie)決了同(tong)(tong)(tong)步(bu)電(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)起(qi)動(dong)(dong)和調(diao)速的(de)問題,使同(tong)(tong)(tong)步(bu)電(dian)(dian)(dian)(dian)(dian)動(dong)(dong)機(ji)在電(dian)(dian)(dian)(dian)(dian)力拖(tuo)動(dong)(dong)中(zhong)作為(wei)原(yuan)動(dong)(dong)機(ji)出現。
同(tong)(tong)(tong)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)和異(yi)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)的(de)區(qu)別在(zai)(zai)于:從供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)方(fang)面說,異(yi)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)只是在(zai)(zai)定子(zi)側加(jia)上(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(也有轉(zhuan)(zhuan)子(zi)上(shang)加(jia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)),而同(tong)(tong)(tong)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)要在(zai)(zai)定子(zi)和轉(zhuan)(zhuan)子(zi)上(shang)都加(jia)上(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。也就是說異(yi)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)是單邊勵磁(ci),同(tong)(tong)(tong)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)是雙邊勵磁(ci)。同(tong)(tong)(tong)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)就是靠(kao)勵磁(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流運(yun)行的(de),如果沒有勵磁(ci),電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)就是異(yi)步(bu)(bu)的(de)。從轉(zhuan)(zhuan)速方(fang)面說,異(yi)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)的(de)轉(zhuan)(zhuan)速只與(yu)負(fu)荷大小有關(當然有一定的(de)范圍),而同(tong)(tong)(tong)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)的(de)轉(zhuan)(zhuan)速只與(yu)定子(zi)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)頻率有關。從結構(gou)(gou)上(shang)說,同(tong)(tong)(tong)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)與(yu)異(yi)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)轉(zhuan)(zhuan)子(zi)的(de)構(gou)(gou)造(zao)也不一樣。異(yi)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)的(de)轉(zhuan)(zhuan)子(zi)是有夕鋼(gang)(gang)片和鋁條(tiao)(或夕鋼(gang)(gang)片和線(xian)圈組成),而同(tong)(tong)(tong)步(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)(ji)(ji)一般由數塊(kuai)磁(ci)鋼(gang)(gang)和線(xian)圈組成(也有隱極式的(de)不太一樣)。
結構
同步(bu)電(dian)(dian)(dian)機(ji)(ji)和異步(bu)電(dian)(dian)(dian)機(ji)(ji)的(de)定子繞(rao)(rao)組(zu)是相同的(de),主要(yao)區別在于轉(zhuan)子的(de)結構(gou)。同步(bu)電(dian)(dian)(dian)機(ji)(ji)的(de)轉(zhuan)子上有(you)直流(liu)勵(li)磁繞(rao)(rao)組(zu),所(suo)以需(xu)要(yao)外加(jia)勵(li)磁電(dian)(dian)(dian)源,通過滑環引入(ru)電(dian)(dian)(dian)流(liu);而異步(bu)電(dian)(dian)(dian)機(ji)(ji)的(de)轉(zhuan)子是短路的(de)繞(rao)(rao)組(zu),靠電(dian)(dian)(dian)磁感應產(chan)生電(dian)(dian)(dian)流(liu)。相比之下,同步(bu)電(dian)(dian)(dian)機(ji)(ji)較復雜(za),造(zao)價高。
用途
同步電機大多用在大型發電機的場合。而異步電機則幾乎全用在電動機場合。同步電機可以通過勵磁靈活調節輸入側的電壓和電流相位,即功率因數;異步電機的功率因數不可調,一般在0.75-0.85之(zhi)間(jian),因此在一(yi)(yi)些大的(de)工(gong)廠(chang),異步電(dian)(dian)機應用(yong)(yong)(yong)較多(duo)時,可附加一(yi)(yi)臺(tai)同步電(dian)(dian)機做調相(xiang)機用(yong)(yong)(yong),用(yong)(yong)(yong)來調節工(gong)廠(chang)與電(dian)(dian)網接口(kou)處的(de)功(gong)率(lv)因數(shu)。但(dan)是,由于同步電(dian)(dian)機造價(jia)高,維護工(gong)作量大,現在一(yi)(yi)般都采(cai)用(yong)(yong)(yong)電(dian)(dian)容補償功(gong)率(lv)因數(shu)。
另外,一些早(zao)期(qi)采用(yong)晶閘管的變頻器(qi),由于(yu)器(qi)件沒有自(zi)關斷能(neng)力,需要依(yi)靠負(fu)載(zai)換流,這(zhe)時需要用(yong)到同步電機。
同步電機效率較異步電機稍高,在2000KW以上的電動機(ji)選型(xing)時(shi),一般要考慮是否選用同步(bu)電機(ji)。但是,同步(bu)機(ji)因為(wei)有勵(li)磁繞組和滑環,需(xu)要操作(zuo)工人有較(jiao)高(gao)的水平來(lai)(lai)控制(zhi)勵(li)磁,另外,比起異步(bu)電機(ji)的免維護來(lai)(lai),維護工作(zuo)量(liang)較(jiao)大;所以,現在2500KW以(yi)下的(de)電動機(ji),現在大多選擇異步電機(ji)。在功(gong)率(lv)較小時,效率(lv)的(de)差別已經(jing)變得微不足道了(le)。
在應用變頻器時
應用(yong)變(bian)頻(pin)(pin)器(qi)時,需要(yao)(yao)將電機(ji)和(he)電網斷開,將變(bian)頻(pin)(pin)器(qi)接入。接入變(bian)頻(pin)(pin)器(qi)后,電網側(ce)的(de)功率與電機(ji)無關,只與變(bian)頻(pin)(pin)器(qi)有關。因(yin)此(ci),除非用(yong)戶原來已經有同步(bu)電機(ji),否(fou)則應該選用(yong)異步(bu)電機(ji),因(yin)為變(bian)頻(pin)(pin)器(qi)和(he)電機(ji)的(de)造價都便(bian)宜。當然,如果選用(yong)早期(qi)的(de)負載換流(liu)型變(bian)頻(pin)(pin)器(qi),則電機(ji)必須選用(yong)同步(bu)電機(ji),這(zhe)是變(bian)頻(pin)(pin)器(qi)對電機(ji)的(de)要(yao)(yao)求。
簡單的說:同步和異步電機均屬交流動力電機,是(shi)靠50周交流電網(wang)供電而轉動.異步電機是定子送入交流(liu)電,產生旋轉磁場,而轉子(zi)受感(gan)應(ying)而產生磁場,這樣兩磁場作用(yong),使(shi)得轉子(zi)跟著定子(zi)的(de)旋轉磁場(chang)而轉動.其中轉子比定(ding)子旋轉磁(ci)場(chang)慢,有個轉差,不同步(bu)所以稱為(wei)異步(bu)機.而(er)同步電機定子同異步電機,其(qi)轉子(zi)是人為加入直流電形成不變磁場,這樣轉子就(jiu)跟(gen)著定(ding)子旋轉磁場一起(qi)轉而(er)同步,始稱同步電機.異(yi)步(bu)電(dian)機(ji)簡單,成(cheng)本低(di).易于安裝,使(shi)用和維護(hu).所以受到廣泛使用.缺(que)點(dian)效率低,功率因(yin)數低對電網不利.而同步電機效率高是容性負載,可改善電網(wang)功(gong)率因(yin)數.多用工礦大型(xing)沒備。