380伏(fu)三(san)相(xiang)四線電(dian)(dian)(dian)路中(zhong),任(ren)(ren)意兩根火線之間的電(dian)(dian)(dian)壓都是380伏(fu),任(ren)(ren)意一根火線與零線之間都可以組成220伏(fu)。這個系統(tong)可以形成三(san)種電(dian)(dian)(dian)源(yuan):即單相(xiang)220伏(fu)電(dian)(dian)(dian)源(yuan),單相(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan),三(san)相(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan),第 I 種家用(yong)比較多(duo),第三(san)種工廠里電(dian)(dian)(dian)機類用(yong)得多(duo),第二(er)種用(yong)得少,只有(you)交(jiao)流電(dian)(dian)(dian)焊機經常用(yong)到單相(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)。