三相電加熱管

        380伏三(san)相四線(xian)電(dian)(dian)(dian)路中，任意(yi)兩根(gen)火線(xian)之(zhi)間(jian)的(de)電(dian)(dian)(dian)壓都是(shi)380伏，任意(yi)一根(gen)火線(xian)與零線(xian)之(zhi)間(jian)都可以組(zu)成220伏。這個系統可以形成三(san)種(zhong)電(dian)(dian)(dian)源(yuan)：即單(dan)(dan)相220伏電(dian)(dian)(dian)源(yuan)，單(dan)(dan)相380伏電(dian)(dian)(dian)源(yuan)，三(san)相380伏電(dian)(dian)(dian)源(yuan)，第 I 種(zhong)家用比較多(duo)，第三(san)種(zhong)工廠里電(dian)(dian)(dian)機(ji)類用得多(duo)，第二種(zhong)用得少，只(zhi)有(you)交(jiao)流電(dian)(dian)(dian)焊機(ji)經(jing)常(chang)用到單(dan)(dan)相380伏電(dian)(dian)(dian)源(yuan)。