380伏(fu)三(san)相(xiang)(xiang)(xiang)四線電(dian)(dian)路中,任(ren)意(yi)兩根(gen)火線之(zhi)間的電(dian)(dian)壓都是380伏(fu),任(ren)意(yi)一根(gen)火線與零線之(zhi)間都可以組成220伏(fu)。這個系統(tong)可以形成三(san)種(zhong)電(dian)(dian)源(yuan):即單相(xiang)(xiang)(xiang)220伏(fu)電(dian)(dian)源(yuan),單相(xiang)(xiang)(xiang)380伏(fu)電(dian)(dian)源(yuan),三(san)相(xiang)(xiang)(xiang)380伏(fu)電(dian)(dian)源(yuan),第(di) I 種(zhong)家用比較多(duo),第(di)三(san)種(zhong)工廠里(li)電(dian)(dian)機類用得(de)多(duo),第(di)二種(zhong)用得(de)少,只有交流電(dian)(dian)焊機經常用到單相(xiang)(xiang)(xiang)380伏(fu)電(dian)(dian)源(yuan)。