三相電加熱管

        380伏(fu)三(san)相(xiang)四線(xian)電(dian)(dian)(dian)路中，任意(yi)兩根火(huo)線(xian)之(zhi)間(jian)(jian)的電(dian)(dian)(dian)壓都是380伏(fu)，任意(yi)一根火(huo)線(xian)與零線(xian)之(zhi)間(jian)(jian)都可(ke)以組(zu)成(cheng)220伏(fu)。這(zhe)個系統可(ke)以形成(cheng)三(san)種電(dian)(dian)(dian)源：即單(dan)相(xiang)220伏(fu)電(dian)(dian)(dian)源，單(dan)相(xiang)380伏(fu)電(dian)(dian)(dian)源，三(san)相(xiang)380伏(fu)電(dian)(dian)(dian)源，第 I 種家(jia)用(yong)比較多，第三(san)種工廠里(li)電(dian)(dian)(dian)機類用(yong)得多，第二種用(yong)得少，只有(you)交流(liu)電(dian)(dian)(dian)焊機經常用(yong)到(dao)單(dan)相(xiang)380伏(fu)電(dian)(dian)(dian)源。