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概念解釋

旋(xuan)轉(zhuan)磁(ci)(ci)場是一種大(da)小不變，而(er)以一定轉(zhuan)速(su)在(zai)空間(jian)旋(xuan)轉(zhuan)的磁(ci)(ci)場。在(zai)對(dui)稱三(san)相繞組中流過對(dui)稱三(san)相電流時會產生一種旋(xuan)轉(zhuan)磁(ci)(ci)場，該磁(ci)(ci)場隨電流交變而(er)在(zai)空間(jian)不斷地旋(xuan)轉(zhuan)著(zhu)。

交流電機(ji)氣隙中的磁場。因其沿定、轉(zhuan)子(zi)鐵心圓柱面不斷(duan)旋(xuan)轉(zhuan)而得名。旋(xuan)轉(zhuan)磁場是電能和轉(zhuan)動機(ji)械能之間互相轉(zhuan)換的基本條件。

通常三相(xiang)(xiang)交流電(dian)(dian)機的(de)(de)(de)定子都有(you)對稱的(de)(de)(de)三相(xiang)(xiang)繞(rao)組(zu)（見電(dian)(dian)樞繞(rao)組(zu)）。任意(yi)一相(xiang)(xiang)繞(rao)組(zu)通以交流電(dian)(dian)流時產生的(de)(de)(de)是(shi)脈(mo)振磁(ci)(ci)場(chang)。但(dan)若(ruo)以平衡(heng)三相(xiang)(xiang)電(dian)(dian)流通入(ru)三相(xiang)(xiang)對稱繞(rao)組(zu)，就會(hui)產生一個在空間(jian)(jian)旋轉(zhuan)的(de)(de)(de)磁(ci)(ci)場(chang)。磁(ci)(ci)場(chang)的(de)(de)(de)對稱軸線φ隨時間(jian)(jian)而轉(zhuan)動(dong)，其轉(zhuan)速(su)ns由電(dian)(dian)流頻(pin)率(lv)f和磁(ci)(ci)極(ji)對數P決定 ns稱為同(tong)步轉(zhuan)速(su)或同(tong)步速(su)（以轉(zhuan)每分(fen)表(biao)示）。中國應用的(de)(de)(de)工業電(dian)(dian)源的(de)(de)(de)頻(pin)率(lv)f為50赫,于是(shi)兩(liang)極(ji)電(dian)(dian)機(P=1)的(de)(de)(de)ns=3000轉(zhuan)/分(fen)；四極(ji)電(dian)(dian)機(P=2)的(de)(de)(de)ns=1500轉(zhuan)/分(fen)；余類推。

在一般情況下，電流變(bian)化(hua)一個周(zhou)期，磁場軸(zhou)線在空(kong)間就轉過一對極。

若(ruo)近似地(di)認為磁(ci)(ci)(ci)場沿圓(yuan)(yuan)周作正弦形(xing)分布，并用磁(ci)(ci)(ci)場軸線(xian)處(chu)的(de)(de)(de)空間矢量(liang)Ø來(lai)代表，用矢量(liang)長度表示磁(ci)(ci)(ci)場振(zhen)幅，則理論(lun)分析證明，三相(xiang)對(dui)稱繞組(zu)通以(yi)平(ping)(ping)衡的(de)(de)(de)三相(xiang)電流時，產(chan)生(sheng)的(de)(de)(de)是(shi)一(yi)個(ge)振(zhen)幅不變(bian)的(de)(de)(de)旋(xuan)轉(zhuan)磁(ci)(ci)(ci)場。這(zhe)時矢量(liang)Ø在(zai)旋(xuan)轉(zhuan)過程中它的(de)(de)(de)末端(duan)軌跡為一(yi)圓(yuan)(yuan)形(xing)，故名圓(yuan)(yuan)形(xing)旋(xuan)轉(zhuan)磁(ci)(ci)(ci)場。這(zhe)個(ge)結論(lun)可以(yi)推(tui)廣到一(yi)般的(de)(de)(de)多相(xiang)（包括兩相(xiang)）系統(tong)。即多相(xiang)電機對(dui)稱繞組(zu)通以(yi)平(ping)(ping)衡多相(xiang)交(jiao)流電流，則產(chan)生(sheng)圓(yuan)(yuan)形(xing)旋(xuan)轉(zhuan)磁(ci)(ci)(ci)場。

一般說(shuo)來(lai)，旋轉(zhuan)磁場的(de)(de)轉(zhuan)向(xiang)(xiang)總是從電流超前的(de)(de)相(xiang)(xiang)(xiang)移(yi)向(xiang)(xiang)電流滯后的(de)(de)相(xiang)(xiang)(xiang)。如果將三(san)相(xiang)(xiang)(xiang)的(de)(de)3個引出線任意兩個對調再(zai)接向(xiang)(xiang)電源，即通入三(san)相(xiang)(xiang)(xiang)繞組的(de)(de)電流相(xiang)(xiang)(xiang)序(xu)相(xiang)(xiang)(xiang)反，則(ze)旋轉(zhuan)磁場的(de)(de)轉(zhuan)向(xiang)(xiang)也跟著相(xiang)(xiang)(xiang)反。

如果三相(xiang)電(dian)流(liu)不平衡，可(ke)用對(dui)稱(cheng)分(fen)量法(fa)把三相(xiang)電(dian)流(liu)系(xi)統(tong)(tong)(tong)分(fen)解(jie)為(wei)正序電(dian)流(liu)系(xi)統(tong)(tong)(tong)和(he)負序電(dian)流(liu)系(xi)統(tong)(tong)(tong)。正序電(dian)流(liu)系(xi)統(tong)(tong)(tong)產生一(yi)個(ge)正向圓形(xing)旋轉磁場(chang)，負序電(dian)流(liu)系(xi)統(tong)(tong)(tong)產生一(yi)個(ge)反(fan)向圓形(xing)旋轉磁場(chang)。一(yi)般(ban)情況(kuang)，兩個(ge)磁場(chang)振幅大小不等，其合(he)成磁場(chang)矢量的(de)末端軌(gui)跡為(wei)一(yi)橢圓形(xing)，故(gu)名橢圓形(xing)旋轉磁場(chang)。這個(ge)結論也可(ke)以推廣到一(yi)般(ban)的(de)多相(xiang)(包括兩相(xiang))電(dian)機。

分類

圓旋轉磁場

磁感應(ying)強度矢量(liang)B的箭(jian)頭末(mo)端沿圓(yuan)周移動(dong)的旋轉磁場。

順時(shi)針旋轉磁場(chang)：三個(ge)完全(quan)一(yi)樣的(de)(de)(de)線圈(quan)AX、BY、CZ在(zai)(zai)(zai)空(kong)間沿著順時(shi)針方(fang)向(xiang)(xiang)(xiang)(xiang)彼此(ci)間隔120°，其中(zhong)BY在(zai)(zai)(zai)AX之后，CZ又(you)在(zai)(zai)(zai)BY之后(圖2)。若對(dui)這三個(ge)線圈(quan)的(de)(de)(de)始端A、B、C通入正序的(de)(de)(de)對(dui)稱三相電(dian)(dian)流，則在(zai)(zai)(zai)三個(ge)線圈(quan)的(de)(de)(de)中(zhong)心處(chu)O所產(chan)生的(de)(de)(de)磁感應(ying)強(qiang)度(du)矢(shi)量(liang)B的(de)(de)(de)模B=3/2Bmp(Bmp為每一(yi)相電(dian)(dian)流在(zai)(zai)(zai)O處(chu)產(chan)生的(de)(de)(de)正弦磁感應(ying)強(qiang)度(du)的(de)(de)(de)振(zhen)幅)，矢(shi)量(liang)B與x軸(zhou)的(de)(de)(de)夾(jia)角β=π-ωt。這樣，隨著時(shi)間的(de)(de)(de)增(zeng)加，磁感應(ying)強(qiang)度(du)矢(shi)量(liang)B的(de)(de)(de)大小保持(chi)為3/2Bmp不變，同時(shi)以角速度(du)ω在(zai)(zai)(zai)空(kong)間作(zuo)順時(shi)針旋轉，故該磁場(chang)為順時(shi)針旋轉的(de)(de)(de)圓旋轉磁場(chang)。圖3是該磁場(chang)中(zhong)在(zai)(zai)(zai)t=0、T/4、T/2和3/4T時(shi)的(de)(de)(de)磁感應(ying)強(qiang)度(du)矢(shi)量(liang)B的(de)(de)(de)示(shi)意圖(設(she)A相電(dian)(dian)流iA的(de)(de)(de)初相位為零)。其中(zhong)周期(qi)T=2π/ω，rA0、rB0和rC0是指示(shi)方(fang)向(xiang)(xiang)(xiang)(xiang)的(de)(de)(de)單(dan)位矢(shi)量(liang)，長(chang)度(du)為1，方(fang)向(xiang)(xiang)(xiang)(xiang)則與所對(dui)應(ying)的(de)(de)(de)線圈(quan)的(de)(de)(de)繞行方(fang)向(xiang)(xiang)(xiang)(xiang)成右手螺旋關系。

逆時(shi)(shi)針(zhen)旋轉的(de)(de)磁(ci)場：三個(ge)線圈(quan)的(de)(de)始端A、B、C處通入負序的(de)(de)三相對稱電(dian)流(liu)，則(ze)在三個(ge)線圈(quan)的(de)(de)中心處O的(de)(de)磁(ci)感(gan)應(ying)強(qiang)度矢量B的(de)(de)模B=3Bmp/2，但矢量B與x軸的(de)(de)夾角β=ωt。隨(sui)著時(shi)(shi)間的(de)(de)增(zeng)加(jia)，磁(ci)感(gan)應(ying)強(qiang)度矢量B的(de)(de)大(da)小不(bu)變，卻以角速(su)度ω作逆時(shi)(shi)針(zhen)旋轉，故該磁(ci)場是逆時(shi)(shi)針(zhen)旋轉的(de)(de)圓旋轉磁(ci)場。

三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)動(dong)機(ji)(ji)的(de)(de)正(zheng)轉(zhuan)(zhuan)與反(fan)轉(zhuan)(zhuan)：三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)動(dong)機(ji)(ji)定(ding)(ding)子上三(san)(san)個線(xian)圈叫做定(ding)(ding)子繞組(zu)(zu)。將(jiang)該(gai)電(dian)(dian)動(dong)機(ji)(ji)接于用戶端(duan)的(de)(de)三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)源線(xian)上，若通入定(ding)(ding)子繞組(zu)(zu)AX、BY、CZ始端(duan)的(de)(de)是(shi)(shi)正(zheng)序的(de)(de)對稱(cheng)(cheng)三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)流(liu)，繞組(zu)(zu)電(dian)(dian)流(liu)會在電(dian)(dian)機(ji)(ji)內產生旋(xuan)轉(zhuan)(zhuan)磁場，使電(dian)(dian)機(ji)(ji)正(zheng)轉(zhuan)(zhuan);若通入的(de)(de)是(shi)(shi)負序的(de)(de)對稱(cheng)(cheng)三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)流(liu)，則三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)動(dong)機(ji)(ji)反(fan)轉(zhuan)(zhuan)。三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)動(dong)機(ji)(ji)正(zheng)常工作時一般是(shi)(shi)正(zheng)轉(zhuan)(zhuan)的(de)(de)。這樣，三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)動(dong)機(ji)(ji)接到三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)源線(xian)之前，需(xu)先用相(xiang)(xiang)(xiang)(xiang)序指示(shi)器確定(ding)(ding)好三(san)(san)相(xiang)(xiang)(xiang)(xiang)電(dian)(dian)源線(xian)的(de)(de)A、B、C的(de)(de)相(xiang)(xiang)(xiang)(xiang)序。

橢圓旋轉磁場

磁(ci)(ci)感(gan)(gan)應強度(du)矢量(liang)B的(de)(de)(de)末端移動(dong)的(de)(de)(de)軌跡(ji)為(wei)橢(tuo)圓(yuan)的(de)(de)(de)旋轉磁(ci)(ci)場(chang)。當三個線圈不一樣或者是(shi)通入(ru)三個線圈始端的(de)(de)(de)是(shi)正序(xu)(負序(xu))不對稱三相電流，則隨著(zhu)時(shi)間的(de)(de)(de)增加磁(ci)(ci)感(gan)(gan)應強度(du)矢量(liang)B末端移動(dong)的(de)(de)(de)軌跡(ji)為(wei)橢(tuo)圓(yuan)，故該(gai)磁(ci)(ci)場(chang)為(wei)橢(tuo)圓(yuan)旋轉磁(ci)(ci)場(chang)。

產生條件

產生(sheng)的基(ji)本條件：兩(liang)個(ge)磁(ci)軛的幾何夾(jia)角與兩(liang)相激磁(ci)電流的相位(wei)差均(jun)不(bu)等于0度或180度。

應用實例

三(san)相感(gan)應(ying)電動機(ji)(ji)：定子繞(rao)組由三(san)相交流電源(yuan)供電，轉子繞(rao)組中的電流靠電磁感(gan)應(ying)產生，從而把電能(neng)變成機(ji)(ji)械能(neng)的裝置。又稱異步電動機(ji)(ji)。

所謂二極(ji)是指(zhi)定(ding)(ding)(ding)(ding)子(zi)繞(rao)(rao)組(zu)通電后將定(ding)(ding)(ding)(ding)子(zi)鐵(tie)心(xin)內(nei)(nei)壁(bi)(bi)劃分(fen)為(wei)(wei)一對(dui)磁極(ji)，磁感應(ying)線(xian)發出(chu)的極(ji)面(mian)稱(cheng)為(wei)(wei)N極(ji)，磁感應(ying)線(xian)進入的極(ji)面(mian)稱(cheng)為(wei)(wei)S極(ji)。三(san)相感應(ying)電動(dong)機主要由定(ding)(ding)(ding)(ding)子(zi)(電動(dong)機不動(dong)部分(fen))和轉子(zi)構成(cheng)。定(ding)(ding)(ding)(ding)子(zi)包(bao)括(kuo)鐵(tie)心(xin)和繞(rao)(rao)組(zu)。定(ding)(ding)(ding)(ding)子(zi)鐵(tie)心(xin)由硅鋼(gang)片疊壓而成(cheng)，鐵(tie)心(xin)內(nei)(nei)壁(bi)(bi)開槽(cao)，槽(cao)內(nei)(nei)安(an)放定(ding)(ding)(ding)(ding)子(zi)繞(rao)(rao)組(zu)。定(ding)(ding)(ding)(ding)子(zi)繞(rao)(rao)組(zu)是定(ding)(ding)(ding)(ding)子(zi)的電路(lu)部分(fen)，由漆包(bao)銅(tong)(或鋁)線(xian)繞(rao)(rao)成(cheng)，是三(san)組(zu)材料、匝數(shu)、線(xian)徑、繞(rao)(rao)法、形狀、大小完全相同的線(xian)圈，且(qie)空間位(wei)置互成(cheng)120°，稱(cheng)為(wei)(wei)對(dui)稱(cheng)三(san)相繞(rao)(rao)組(zu)。

由(you)于旋轉(zhuan)磁場的轉(zhuan)速(su)與(yu)電(dian)源(yuan)頻率(lv)有固定的關系，所以旋轉(zhuan)磁場的轉(zhuan)速(su)稱(cheng)為(wei)同步(bu)轉(zhuan)速(su)。旋轉(zhuan)方向(xiang)是順時針。說(shuo)明是由(you)電(dian)流(liu)超前的相轉(zhuan)向(xiang)電(dian)流(liu)落后的相。

當定子(zi)(zi)(zi)(zi)(zi)三(san)相(xiang)繞(rao)組通入三(san)相(xiang)對稱電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)后(hou)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)內就產生(sheng)一個圖4所(suo)(suo)示的旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場。磁(ci)場順(shun)時(shi)針旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)就相(xiang)當于(yu)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)籠(long)條(即鑄鋁的鋁條，籠(long)條有很(hen)多根，圖4中(zhong)只(zhi)畫出兩根a1、a2作代表)a1、a2逆時(shi)針去切割磁(ci)感(gan)(gan)應(ying)(ying)(ying)線(xian)，于(yu)是(shi)(shi)在(zai)(zai)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)籠(long)條中(zhong)產生(sheng)感(gan)(gan)應(ying)(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)勢和感(gan)(gan)應(ying)(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)其方(fang)(fang)(fang)向(xiang)(xiang)(xiang)圖4所(suo)(suo)示。由于(yu)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)不(bu)(bu)是(shi)(shi)靠通電(dian)(dian)(dian)(dian)(dian)(dian)而是(shi)(shi)靠感(gan)(gan)應(ying)(ying)(ying)產生(sheng)，所(suo)(suo)以稱為(wei)三(san)相(xiang)感(gan)(gan)應(ying)(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)。由安培定律可(ke)判斷出轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)籠(long)條所(suo)(suo)受磁(ci)力方(fang)(fang)(fang)向(xiang)(xiang)(xiang)。轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)在(zai)(zai)這個電(dian)(dian)(dian)(dian)(dian)(dian)磁(ci)力矩(ju)的作用(yong)下(xia)也(ye)將(jiang)順(shun)時(shi)針轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)，即轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)向(xiang)(xiang)(xiang)與(yu)(yu)旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)向(xiang)(xiang)(xiang)是(shi)(shi)一致的。轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)與(yu)(yu)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)軸所(suo)(suo)帶負載輕重有關，但轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)總要小于(yu)旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)，否則(ze)它(ta)將(jiang)因不(bu)(bu)受電(dian)(dian)(dian)(dian)(dian)(dian)磁(ci)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩(ju)在(zai)(zai)阻力矩(ju)作用(yong)下(xia)慢下(xia)來。因而三(san)相(xiang)感(gan)(gan)應(ying)(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)又稱三(san)相(xiang)異步電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)。二極電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)中(zhong)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)一般在(zai)(zai)2800轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)/分以上(shang)，與(yu)(yu)旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)相(xiang)差(cha)很(hen)小。旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)用(yong)n1表示，轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)用(yong)n表示，則(ze)S=1-n/n1稱為(wei)感(gan)(gan)應(ying)(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)差(cha)率。二極電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)差(cha)率大約(yue)在(zai)(zai)0.02～0.06之間，可(ke)見它(ta)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速(su)變化范圍不(bu)(bu)大。由于(yu)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)向(xiang)(xiang)(xiang)與(yu)(yu)旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)向(xiang)(xiang)(xiang)一致，而旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)向(xiang)(xiang)(xiang)又由電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的相(xiang)序決定，所(suo)(suo)以當調換(huan)兩根電(dian)(dian)(dian)(dian)(dian)(dian)源線(xian)時(shi)由于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相(xiang)序的改(gai)變旋(xuan)(xuan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)磁(ci)場的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)向(xiang)(xiang)(xiang)就要反(fan)向(xiang)(xiang)(xiang)，從而轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)的轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)向(xiang)(xiang)(xiang)也(ye)就反(fan)向(xiang)(xiang)(xiang)。可(ke)見三(san)相(xiang)感(gan)(gan)應(ying)(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)可(ke)通過任意調換(huan)兩根電(dian)(dian)(dian)(dian)(dian)(dian)源線(xian)方(fang)(fang)(fang)便(bian)地使(shi)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)子(zi)(zi)(zi)(zi)(zi)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)軸改(gai)變轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)方(fang)(fang)(fang)向(xiang)(xiang)(xiang)。

三相感應電(dian)動(dong)機(ji)是(shi)靠通電(dian)后轉軸(zhou)上帶負(fu)載把電(dian)能變成(cheng)機(ji)械能的裝置(zhi)。它(ta)有堅固耐用、價格便宜、便于(yu)維(wei)修(xiu)、使(shi)用簡便等(deng)優(you)點，但它(ta)也有起動(dong)轉矩不大(da)、調速性(xing)能不好(hao)等(deng)缺點，在這方(fang)面直流(liu)電(dian)動(dong)機(ji)有明顯(xian)的優(you)越性(xing)。