380伏(fu)三相(xiang)(xiang)四線(xian)電(dian)(dian)(dian)路中(zhong),任意兩(liang)根火線(xian)之間(jian)的(de)電(dian)(dian)(dian)壓(ya)都(dou)是380伏(fu),任意一根火線(xian)與零(ling)線(xian)之間(jian)都(dou)可以組成(cheng)220伏(fu)。這個(ge)系統可以形成(cheng)三種電(dian)(dian)(dian)源:即單(dan)(dan)相(xiang)(xiang)220伏(fu)電(dian)(dian)(dian)源,單(dan)(dan)相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源,三相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源,第 I 種家用比(bi)較多(duo)(duo),第三種工(gong)廠里電(dian)(dian)(dian)機類(lei)用得多(duo)(duo),第二種用得少,只有交流電(dian)(dian)(dian)焊機經常用到單(dan)(dan)相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源。