380伏三(san)相(xiang)四線(xian)電(dian)路中,任意兩根(gen)火線(xian)之間(jian)的電(dian)壓都(dou)是380伏,任意一根(gen)火線(xian)與零線(xian)之間(jian)都(dou)可(ke)以組成(cheng)220伏。這個系統可(ke)以形成(cheng)三(san)種電(dian)源(yuan)(yuan):即(ji)單相(xiang)220伏電(dian)源(yuan)(yuan),單相(xiang)380伏電(dian)源(yuan)(yuan),三(san)相(xiang)380伏電(dian)源(yuan)(yuan),第(di)(di) I 種家用(yong)比較多(duo),第(di)(di)三(san)種工廠(chang)里電(dian)機(ji)類用(yong)得(de)多(duo),第(di)(di)二種用(yong)得(de)少,只有交流電(dian)焊機(ji)經常用(yong)到單相(xiang)380伏電(dian)源(yuan)(yuan)。