380伏(fu)三相四線(xian)(xian)電(dian)路(lu)中(zhong),任(ren)(ren)意(yi)兩(liang)根火線(xian)(xian)之(zhi)間的電(dian)壓都是380伏(fu),任(ren)(ren)意(yi)一根火線(xian)(xian)與零線(xian)(xian)之(zhi)間都可(ke)以組(zu)成(cheng)220伏(fu)。這個系統可(ke)以形成(cheng)三種(zhong)電(dian)源(yuan):即單相220伏(fu)電(dian)源(yuan),單相380伏(fu)電(dian)源(yuan),三相380伏(fu)電(dian)源(yuan),第(di) I 種(zhong)家用比(bi)較多(duo),第(di)三種(zhong)工廠里電(dian)機(ji)類用得(de)多(duo),第(di)二種(zhong)用得(de)少(shao),只有(you)交流電(dian)焊(han)機(ji)經常用到單相380伏(fu)電(dian)源(yuan)。