380伏三相四線電(dian)(dian)路(lu)中,任意兩根火線之(zhi)間(jian)的電(dian)(dian)壓都是(shi)380伏,任意一根火線與零線之(zhi)間(jian)都可以(yi)(yi)組成220伏。這個系統(tong)可以(yi)(yi)形成三種電(dian)(dian)源(yuan)(yuan):即單相220伏電(dian)(dian)源(yuan)(yuan),單相380伏電(dian)(dian)源(yuan)(yuan),三相380伏電(dian)(dian)源(yuan)(yuan),第 I 種家用(yong)(yong)比較多,第三種工廠里(li)電(dian)(dian)機(ji)類(lei)用(yong)(yong)得多,第二種用(yong)(yong)得少,只有交(jiao)流(liu)電(dian)(dian)焊機(ji)經常用(yong)(yong)到單相380伏電(dian)(dian)源(yuan)(yuan)。