異步電機和(he)(he)同步電機的區別(bie) 異步電機和(he)(he)同步電機哪個好(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,轉(zhuan)(zhuan)子(zi)(zi)導體產生感(gan)應電動(dong)勢并(bing)產生感(gan)應電流(liu)。根據(ju)電磁(ci)力(li)定律(lv)，載流(liu)的(de)(de)轉(zhuan)(zhuan)子(zi)(zi)導體在磁(ci)場(chang)中受到(dao)電磁(ci)力(li)作用，形成電磁(ci)轉(zhuan)(zhuan)矩(ju)，驅(qu)動(dong)轉(zhuan)(zhuan)子(zi)(zi)旋轉(zhuan)(zhuan)。異步電動(dong)機的(de)(de)轉(zhuan)(zhuan)速小于定子(zi)(zi)旋轉(zhuan)(zhuan)磁(ci)場(chang)的(de)(de)轉(zhuan)(zhuan)速，有個轉(zhuan)(zhuan)差（轉(zhuan)(zhuan)差與定子(zi)(zi)所產生的(de)(de)旋轉(zhuan)(zhuan)磁(ci)場(chang)的(de)(de)轉(zhuan)(zhuan)速的(de)(de)比值叫轉(zhuan)(zhuan)差率），從而叫做(zuo)異步電動(dong)機。因其轉(zhuan)(zhuan)子(zi)(zi)繞組(zu)電流(liu)是感(gan)應產生的(de)(de)，又稱(cheng)感(gan)應電動(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)(bu)電動機的同步(bu)(bu)轉速；

f——電源頻率(lv)；

p——磁(ci)極對數。

由上式(shi)可以(yi)看出，改(gai)變異步(bu)(bu)電動機的供(gong)電頻(pin)率就可以(yi)改(gai)變其同步(bu)(bu)轉速，從而實現調速運行(xing)，即變頻(pin)調速。

異步電動機按照轉子結構分為兩種形式:有鼠(shu)籠(long)式（鼠(shu)籠(long)式異(yi)步電機(ji)）、繞線(xian)式異(yi)步電動機(ji)。

特點:

優點：結(jie)構簡單，制造方便，價(jia)格便宜，運(yun)行方便。

缺(que)點：功率因數(shu)滯后(hou)，輕載功率因數(shu)低，調(diao)速性(xing)能稍差(cha)。

主要做電動機(ji)用，一般不做發(fa)電機(ji)。

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與磁極對數(shu)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f，故電源頻(pin)率(lv)一定時(shi)，轉速不變，且與負(fu)載無關。具有運行(xing)穩定性高和過載能力大等特點。

過去(qu)的電(dian)(dian)力拖動(dong)中，很少采(cai)用(yong)同(tong)(tong)步電(dian)(dian)動(dong)機，同(tong)(tong)步電(dian)(dian)動(dong)機主要(yao)作(zuo)(zuo)為發電(dian)(dian)機使用(yong)，其主要(yao)原因是(shi)同(tong)(tong)步電(dian)(dian)動(dong)機不能在電(dian)(dian)網電(dian)(dian)壓下自行起動(dong)，靜止的轉子(zi)磁極在旋轉磁場的作(zuo)(zuo)用(yong)下，平均轉矩為零。但是(shi)近年來，隨著(zhu)電(dian)(dian)力電(dian)(dian)子(zi)技術的發展，解決了同(tong)(tong)步電(dian)(dian)動(dong)機起動(dong)和(he)調速(su)的問題，使同(tong)(tong)步電(dian)(dian)動(dong)機在電(dian)(dian)力拖動(dong)中作(zuo)(zuo)為原動(dong)機出現(xian)。

同(tong)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機和(he)異(yi)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機的(de)(de)(de)區別(bie)在(zai)于：從供(gong)電(dian)(dian)(dian)(dian)(dian)方面說(shuo)(shuo)，異(yi)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機只是(shi)(shi)在(zai)定(ding)子(zi)(zi)側加上(shang)電(dian)(dian)(dian)(dian)(dian)壓(ya)（也有轉(zhuan)(zhuan)(zhuan)子(zi)(zi)上(shang)加電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)），而(er)同(tong)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機要在(zai)定(ding)子(zi)(zi)和(he)轉(zhuan)(zhuan)(zhuan)子(zi)(zi)上(shang)都加上(shang)電(dian)(dian)(dian)(dian)(dian)壓(ya)。也就是(shi)(shi)說(shuo)(shuo)異(yi)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機是(shi)(shi)單(dan)邊勵磁，同(tong)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機是(shi)(shi)雙邊勵磁。同(tong)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機就是(shi)(shi)靠勵磁電(dian)(dian)(dian)(dian)(dian)流運行的(de)(de)(de)，如果沒(mei)有勵磁，電(dian)(dian)(dian)(dian)(dian)機就是(shi)(shi)異(yi)步(bu)(bu)(bu)(bu)(bu)(bu)的(de)(de)(de)。從轉(zhuan)(zhuan)(zhuan)速(su)方面說(shuo)(shuo)，異(yi)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機的(de)(de)(de)轉(zhuan)(zhuan)(zhuan)速(su)只與(yu)負荷大(da)小(xiao)有關(guan)（當然(ran)有一(yi)(yi)(yi)定(ding)的(de)(de)(de)范圍），而(er)同(tong)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機的(de)(de)(de)轉(zhuan)(zhuan)(zhuan)速(su)只與(yu)定(ding)子(zi)(zi)供(gong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)頻(pin)率有關(guan)。從結構上(shang)說(shuo)(shuo)，同(tong)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機與(yu)異(yi)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機轉(zhuan)(zhuan)(zhuan)子(zi)(zi)的(de)(de)(de)構造也不一(yi)(yi)(yi)樣。異(yi)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機的(de)(de)(de)轉(zhuan)(zhuan)(zhuan)子(zi)(zi)是(shi)(shi)有夕(xi)鋼片和(he)鋁條（或夕(xi)鋼片和(he)線(xian)圈組成），而(er)同(tong)步(bu)(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)機一(yi)(yi)(yi)般由(you)數塊磁鋼和(he)線(xian)圈組成（也有隱(yin)極式(shi)的(de)(de)(de)不太一(yi)(yi)(yi)樣）。

結構

同(tong)步(bu)電(dian)機(ji)和異步(bu)電(dian)機(ji)的(de)(de)定子繞組(zu)(zu)是相(xiang)同(tong)的(de)(de)，主要(yao)區別在于轉(zhuan)子的(de)(de)結構。同(tong)步(bu)電(dian)機(ji)的(de)(de)轉(zhuan)子上有(you)直流勵磁(ci)(ci)繞組(zu)(zu)，所以需(xu)要(yao)外加(jia)勵磁(ci)(ci)電(dian)源(yuan)，通過滑(hua)環引入電(dian)流；而異步(bu)電(dian)機(ji)的(de)(de)轉(zhuan)子是短路的(de)(de)繞組(zu)(zu)，靠電(dian)磁(ci)(ci)感應(ying)產生電(dian)流。相(xiang)比之(zhi)下(xia)，同(tong)步(bu)電(dian)機(ji)較復(fu)雜，造價高。

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之間，因此在一些大的工(gong)(gong)廠(chang)，異步電機(ji)應用(yong)較多時，可附加一臺同(tong)(tong)步電機(ji)做調(diao)(diao)相機(ji)用(yong)，用(yong)來調(diao)(diao)節工(gong)(gong)廠(chang)與電網(wang)接口處的功(gong)率因數。但是，由于同(tong)(tong)步電機(ji)造(zao)價高，維護工(gong)(gong)作量大，現在一般都采用(yong)電容補(bu)償功(gong)率因數。

另(ling)外，一些(xie)早期采用晶閘(zha)管(guan)的變頻器(qi)，由于器(qi)件沒有(you)自(zi)關斷能力，需要(yao)依(yi)靠負載換流，這時需要(yao)用到同步(bu)電機。

同步電機效率較異步電機稍高，在2000KW以(yi)(yi)上的(de)(de)電動機(ji)選(xuan)型時(shi)，一般要(yao)考(kao)慮是(shi)否選(xuan)用(yong)同步電機(ji)。但(dan)是(shi)，同步機(ji)因為有勵(li)磁繞(rao)組和滑環，需要(yao)操作工人有較(jiao)高的(de)(de)水平來控制(zhi)勵(li)磁，另外(wai)，比起異(yi)步電機(ji)的(de)(de)免維護來，維護工作量較(jiao)大；所以(yi)(yi)，現在2500KW以下(xia)的(de)(de)電動機，現在(zai)(zai)大多選擇異(yi)步電機。在(zai)(zai)功率較小(xiao)時，效率的(de)(de)差別(bie)已經變(bian)得微不足道(dao)了。

在應用變頻器時

應用(yong)(yong)變(bian)頻(pin)(pin)器時(shi)，需要將電(dian)(dian)(dian)(dian)機(ji)和(he)電(dian)(dian)(dian)(dian)網斷開，將變(bian)頻(pin)(pin)器接入。接入變(bian)頻(pin)(pin)器后，電(dian)(dian)(dian)(dian)網側的功率與電(dian)(dian)(dian)(dian)機(ji)無關，只與變(bian)頻(pin)(pin)器有關。因此，除非用(yong)(yong)戶原來已經(jing)有同(tong)步電(dian)(dian)(dian)(dian)機(ji)，否則應該選(xuan)用(yong)(yong)異步電(dian)(dian)(dian)(dian)機(ji)，因為(wei)變(bian)頻(pin)(pin)器和(he)電(dian)(dian)(dian)(dian)機(ji)的造價都便宜。當然(ran)，如(ru)果選(xuan)用(yong)(yong)早期(qi)的負載換流型變(bian)頻(pin)(pin)器，則電(dian)(dian)(dian)(dian)機(ji)必須(xu)選(xuan)用(yong)(yong)同(tong)步電(dian)(dian)(dian)(dian)機(ji)，這是變(bian)頻(pin)(pin)器對電(dian)(dian)(dian)(dian)機(ji)的要求(qiu)。

簡單的說：同步和異步電機均屬交流動力電機,是靠50周交流電網供電而轉動.異(yi)步(bu)電(dian)機(ji)是定子送(song)入交(jiao)流電(dian),產生旋轉磁場,而轉(zhuan)子(zi)受感應而產生磁場,這(zhe)樣兩磁場作用(yong),使得轉(zhuan)子跟著(zhu)定子的(de)旋轉(zhuan)磁場而(er)轉(zhuan)動.其(qi)中轉子(zi)比定子(zi)旋轉磁(ci)場慢,有個(ge)轉差,不(bu)同步所以(yi)稱為異步機.而同步(bu)電機定子同異(yi)步(bu)電機,其轉子(zi)是人為加入直流(liu)電形成不(bu)變磁(ci)場,這(zhe)樣(yang)轉子就跟著定子旋轉磁(ci)場一起轉而同步,始稱同步電機.異步電(dian)機簡單,成本低.易(yi)于(yu)安(an)裝(zhuang),使用和維護.所以受到廣泛(fan)使用.缺點(dian)效率(lv)低,功率因數低(di)對電網不(bu)利(li).而同步電機效率高是容性負載,可改善電(dian)網功率(lv)因數.多用工礦(kuang)大型沒備。