380伏(fu)三(san)(san)(san)相四線電(dian)路中,任意兩根(gen)火線之(zhi)間(jian)的電(dian)壓都是380伏(fu),任意一根(gen)火線與(yu)零線之(zhi)間(jian)都可以組(zu)成220伏(fu)。這(zhe)個系統可以形成三(san)(san)(san)種電(dian)源(yuan):即單(dan)相220伏(fu)電(dian)源(yuan),單(dan)相380伏(fu)電(dian)源(yuan),三(san)(san)(san)相380伏(fu)電(dian)源(yuan),第(di)(di) I 種家用(yong)(yong)比較多(duo)(duo),第(di)(di)三(san)(san)(san)種工廠里(li)電(dian)機類用(yong)(yong)得多(duo)(duo),第(di)(di)二種用(yong)(yong)得少,只(zhi)有交流電(dian)焊機經常用(yong)(yong)到單(dan)相380伏(fu)電(dian)源(yuan)。