380伏三(san)相(xiang)四線(xian)電(dian)(dian)路中,任(ren)意兩根火(huo)線(xian)之(zhi)間的電(dian)(dian)壓都是(shi)380伏,任(ren)意一根火(huo)線(xian)與零線(xian)之(zhi)間都可以(yi)組成(cheng)220伏。這個系統可以(yi)形成(cheng)三(san)種(zhong)(zhong)(zhong)電(dian)(dian)源(yuan):即(ji)單(dan)相(xiang)220伏電(dian)(dian)源(yuan),單(dan)相(xiang)380伏電(dian)(dian)源(yuan),三(san)相(xiang)380伏電(dian)(dian)源(yuan),第 I 種(zhong)(zhong)(zhong)家(jia)用(yong)比較多(duo),第三(san)種(zhong)(zhong)(zhong)工廠里電(dian)(dian)機類用(yong)得多(duo),第二種(zhong)(zhong)(zhong)用(yong)得少,只(zhi)有交(jiao)流電(dian)(dian)焊機經常用(yong)到單(dan)相(xiang)380伏電(dian)(dian)源(yuan)。