380伏(fu)三(san)相(xiang)四(si)線電(dian)(dian)(dian)路中,任意兩根(gen)火線之間的電(dian)(dian)(dian)壓都(dou)是380伏(fu),任意一根(gen)火線與零線之間都(dou)可(ke)以組成220伏(fu)。這個系統可(ke)以形(xing)成三(san)種(zhong)電(dian)(dian)(dian)源(yuan):即單(dan)相(xiang)220伏(fu)電(dian)(dian)(dian)源(yuan),單(dan)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(di) I 種(zhong)家用(yong)比較多,第(di)三(san)種(zhong)工廠里(li)電(dian)(dian)(dian)機類用(yong)得多,第(di)二種(zhong)用(yong)得少,只有(you)交流(liu)電(dian)(dian)(dian)焊機經常(chang)用(yong)到(dao)單(dan)相(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)。