380伏(fu)(fu)三相(xiang)(xiang)四線電(dian)(dian)路中,任(ren)意兩根火(huo)線之間的電(dian)(dian)壓都是380伏(fu)(fu),任(ren)意一根火(huo)線與零線之間都可以(yi)組成220伏(fu)(fu)。這個系統可以(yi)形成三種(zhong)電(dian)(dian)源(yuan):即單相(xiang)(xiang)220伏(fu)(fu)電(dian)(dian)源(yuan),單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan),三相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan),第 I 種(zhong)家用(yong)比(bi)較多,第三種(zhong)工廠里電(dian)(dian)機類用(yong)得多,第二種(zhong)用(yong)得少,只有交(jiao)流電(dian)(dian)焊機經常用(yong)到單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan)。