農用(yong)機(ji)(ji)械通(tong)常在(zai)農忙(mang)季節使用(yong)，每年(nian)使用(yong)的時間很短(duan)，因(yin)此為農用(yong)機(ji)(ji)械提供動力(li)的電(dian)動機(ji)(ji)一般一機(ji)(ji)多(duo)用(yong)，在(zai)一機(ji)(ji)多(duo)用(yong)時常常出現(xian)大馬拉小車(che)的現(xian)象(xiang)，浪費電(dian)能，為節約電(dian)能，避免大馬拉小車(che)，以下介紹兩種降低三(san)相異步(bu)電(dian)動機(ji)(ji)輸出功率的方法。

一、三(san)角形連(lian)接(jie)的(de)電動機改星形接(jie)法

正常(chang)運轉(zhuan)采用三(san)角形接(jie)法的(de)三(san)相(xiang)異步電(dian)動機(ji)(ji)，為(wei)降低功(gong)(gong)率使(shi)用，可把三(san)相(xiang)繞組(zu)接(jie)成(cheng)星形后接(jie)在(zai)線電(dian)壓為(wei)380V的(de)電(dian)源(yuan)上(shang)，此時電(dian)動機(ji)(ji)的(de)功(gong)(gong)率是額定功(gong)(gong)率的(de)34%左(zuo)右。例如380V三(san)角形接(jie)法10KW的(de)三(san)相(xiang)異步電(dian)動機(ji)(ji)改接(jie)成(cheng)星形，接(jie)在(zai)線電(dian)壓為(wei)380V的(de)三(san)相(xiang)電(dian)源(yuan)上(shang)使(shi)用，此時該(gai)電(dian)動機(ji)(ji)的(de)輸出功(gong)(gong)率是3.4KW左(zuo)右。

二、三相異步電(dian)動(dong)(dong)機(ji)改單相異步電(dian)動(dong)(dong)機(ji)

星形(xing)接(jie)(jie)(jie)法(fa)(fa)與三(san)(san)角形(xing)接(jie)(jie)(jie)法(fa)(fa)的(de)三(san)(san)相(xiang)(xiang)電(dian)(dian)(dian)動(dong)機(ji)(ji)改接(jie)(jie)(jie)方(fang)法(fa)(fa)相(xiang)(xiang)同。打開(kai)三(san)(san)相(xiang)(xiang)異(yi)步(bu)電(dian)(dian)(dian)動(dong)機(ji)(ji)的(de)接(jie)(jie)(jie)線(xian)盒，在任意兩相(xiang)(xiang)電(dian)(dian)(dian)源(yuan)接(jie)(jie)(jie)線(xian)端子之(zhi)(zhi)間(jian)接(jie)(jie)(jie)入(ru)一(yi)電(dian)(dian)(dian)容器。例如(ru)把電(dian)(dian)(dian)容器接(jie)(jie)(jie)在V1和(he)W1之(zhi)(zhi)間(jian)，此時(shi)將單相(xiang)(xiang)電(dian)(dian)(dian)源(yuan)接(jie)(jie)(jie)在U1和(he)V1或W1之(zhi)(zhi)間(jian)(假設(she)電(dian)(dian)(dian)源(yuan)接(jie)(jie)(jie)在U1和(he)V1之(zhi)(zhi)間(jian)電(dian)(dian)(dian)動(dong)機(ji)(ji)正傳，則電(dian)(dian)(dian)源(yuan)接(jie)(jie)(jie)在U1和(he)W1之(zhi)(zhi)間(jian)電(dian)(dian)(dian)動(dong)機(ji)(ji)會反轉，)即可把原來的(de)三(san)(san)相(xiang)(xiang)異(yi)步(bu)電(dian)(dian)(dian)動(dong)機(ji)(ji)改裝成了單相(xiang)(xiang)異(yi)步(bu)電(dian)(dian)(dian)動(dong)機(ji)(ji)。此法(fa)(fa)特別適合(he)沒(mei)有三(san)(san)相(xiang)(xiang)電(dian)(dian)(dian)源(yuan)的(de)場合(he)使(shi)用三(san)(san)相(xiang)(xiang)異(yi)步(bu)電(dian)(dian)(dian)動(dong)機(ji)(ji)。

其中電(dian)(dian)容(rong)器的(de)容(rong)量可用C=KP求得，這里C是電(dian)(dian)容(rong)器的(de)容(rong)量，單(dan)(dan)位是微法(μF)；P是電(dian)(dian)動機(ji)(ji)的(de)功率，單(dan)(dan)位是千(qian)瓦(wa)(KW)；K是經(jing)驗系數，三(san)相異(yi)步(bu)(bu)電(dian)(dian)動機(ji)(ji)星(xing)形連接(jie)(jie)時(shi)取0.06，三(san)角(jiao)性連接(jie)(jie)時(shi)取0.1。例(li)如10KW的(de)三(san)相異(yi)步(bu)(bu)電(dian)(dian)動機(ji)(ji)星(xing)形連接(jie)(jie)時(shi)C=KP=0.06×10=0.6μF；10KW的(de)三(san)相異(yi)步(bu)(bu)電(dian)(dian)動機(ji)(ji)三(san)角(jiao)形連接(jie)(jie)時(shi)C=KP=0.1×10=1μF。

改(gai)(gai)接(jie)后的(de)(de)功(gong)(gong)(gong)率：改(gai)(gai)接(jie)成(cheng)(cheng)單(dan)(dan)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)，其有(you)效(xiao)功(gong)(gong)(gong)率是(shi)原(yuan)來(lai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)功(gong)(gong)(gong)率的(de)(de)70%左(zuo)(zuo)右，例(li)如(ru)(ru)：10KW的(de)(de)三(san)相(xiang)異步電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)改(gai)(gai)接(jie)成(cheng)(cheng)單(dan)(dan)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)有(you)效(xiao)功(gong)(gong)(gong)率為7KW左(zuo)(zuo)右。改(gai)(gai)接(jie)成(cheng)(cheng)單(dan)(dan)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)啟動(dong)(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)，其有(you)效(xiao)功(gong)(gong)(gong)率是(shi)原(yuan)來(lai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)功(gong)(gong)(gong)率的(de)(de)40%左(zuo)(zuo)右，例(li)如(ru)(ru)：10KW的(de)(de)三(san)相(xiang)異步電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)改(gai)(gai)接(jie)成(cheng)(cheng)單(dan)(dan)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)啟動(dong)(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)有(you)效(xiao)功(gong)(gong)(gong)率為4KW左(zuo)(zuo)右。改(gai)(gai)接(jie)后每相(xiang)繞(rao)組所加的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)不能超過該(gai)繞(rao)組的(de)(de)額(e)定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。具體改(gai)(gai)接(jie)成(cheng)(cheng)什么(me)樣的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)要看(kan)被拖動(dong)(dong)(dong)農(nong)用(yong)機(ji)(ji)(ji)械的(de)(de)功(gong)(gong)(gong)率情況(kuang)。當改(gai)(gai)接(jie)成(cheng)(cheng)單(dan)(dan)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)啟動(dong)(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)時(shi)(shi)(shi)(shi)，需再添加一個時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)，接(jie)線(xian)方(fang)法是(shi)：把時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)的(de)(de)延時(shi)(shi)(shi)(shi)斷(duan)開瞬時(shi)(shi)(shi)(shi)閉(bi)(bi)合常閉(bi)(bi)觸頭串聯(lian)在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)回路(lu)中(zhong)，時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)的(de)(de)線(xian)圈并(bing)聯(lian)在單(dan)(dan)相(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源兩端(時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)線(xian)圈的(de)(de)額(e)定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)要與(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)相(xiang)同(tong))。接(jie)好電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)后，調(diao)整(zheng)時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)的(de)(de)延時(shi)(shi)(shi)(shi)時(shi)(shi)(shi)(shi)間(jian)，就可以正(zheng)常工作(zuo)。它的(de)(de)工作(zuo)原(yuan)理是(shi)：當接(jie)通(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源時(shi)(shi)(shi)(shi)，時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)和電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)同(tong)時(shi)(shi)(shi)(shi)獲(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)回路(lu)接(jie)通(tong)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)啟動(dong)(dong)(dong)后，當轉(zhuan)速達到額(e)定(ding)轉(zhuan)速的(de)(de)80%左(zuo)(zuo)右時(shi)(shi)(shi)(shi)(通(tong)過調(diao)整(zheng)時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)的(de)(de)延時(shi)(shi)(shi)(shi)時(shi)(shi)(shi)(shi)間(jian)實現)時(shi)(shi)(shi)(shi)間(jian)繼(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)的(de)(de)延時(shi)(shi)(shi)(shi)斷(duan)開瞬時(shi)(shi)(shi)(shi)閉(bi)(bi)合常閉(bi)(bi)觸頭斷(duan)開，切(qie)斷(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)回路(lu)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)動(dong)(dong)(dong)機(ji)(ji)(ji)正(zheng)常運轉(zhuan)。

改接(jie)后的(de)(de)(de)轉向：不(bu)接(jie)電(dian)(dian)容器(qi)的(de)(de)(de)接(jie)線端子不(bu)動(dong)，例如上例中接(jie)U1的(de)(de)(de)電(dian)(dian)源(yuan)(yuan)線不(bu)動(dong)，另一根(gen)電(dian)(dian)源(yuan)(yuan)線由V1改接(jie)在W1上就(jiu)能實現反(fan)轉，即反(fan)轉原理同(tong)單相異步電(dian)(dian)動(dong)機的(de)(de)(de)反(fan)轉原理相同(tong)。