380伏三(san)相四(si)線(xian)電路中,任意兩根火線(xian)之(zhi)間(jian)的電壓都是380伏,任意一(yi)根火線(xian)與零線(xian)之(zhi)間(jian)都可以組成220伏。這個系統可以形(xing)成三(san)種(zhong)(zhong)電源(yuan)(yuan)(yuan):即單相220伏電源(yuan)(yuan)(yuan),單相380伏電源(yuan)(yuan)(yuan),三(san)相380伏電源(yuan)(yuan)(yuan),第 I 種(zhong)(zhong)家用(yong)比(bi)較多(duo),第三(san)種(zhong)(zhong)工廠里電機類(lei)用(yong)得(de)多(duo),第二種(zhong)(zhong)用(yong)得(de)少,只有交(jiao)流電焊(han)機經常用(yong)到單相380伏電源(yuan)(yuan)(yuan)。