380伏(fu)(fu)(fu)(fu)(fu)三(san)相四線(xian)(xian)電(dian)路中,任意兩根火線(xian)(xian)之(zhi)間(jian)(jian)的電(dian)壓都是380伏(fu)(fu)(fu)(fu)(fu),任意一(yi)根火線(xian)(xian)與零(ling)線(xian)(xian)之(zhi)間(jian)(jian)都可以組成220伏(fu)(fu)(fu)(fu)(fu)。這(zhe)個系統可以形(xing)成三(san)種(zhong)電(dian)源(yuan):即單(dan)相220伏(fu)(fu)(fu)(fu)(fu)電(dian)源(yuan),單(dan)相380伏(fu)(fu)(fu)(fu)(fu)電(dian)源(yuan),三(san)相380伏(fu)(fu)(fu)(fu)(fu)電(dian)源(yuan),第 I 種(zhong)家用(yong)(yong)比較多(duo),第三(san)種(zhong)工廠里電(dian)機類用(yong)(yong)得多(duo),第二種(zhong)用(yong)(yong)得少,只有交(jiao)流電(dian)焊機經(jing)常用(yong)(yong)到(dao)單(dan)相380伏(fu)(fu)(fu)(fu)(fu)電(dian)源(yuan)。