三相電加熱管

        380伏三(san)(san)(san)相(xiang)四線電(dian)(dian)(dian)路中，任意兩根(gen)火線之(zhi)間的電(dian)(dian)(dian)壓都是380伏，任意一根(gen)火線與零線之(zhi)間都可以組成220伏。這(zhe)個系統可以形成三(san)(san)(san)種電(dian)(dian)(dian)源：即(ji)單相(xiang)220伏電(dian)(dian)(dian)源，單相(xiang)380伏電(dian)(dian)(dian)源，三(san)(san)(san)相(xiang)380伏電(dian)(dian)(dian)源，第 I 種家(jia)用(yong)(yong)比較多，第三(san)(san)(san)種工廠里電(dian)(dian)(dian)機類用(yong)(yong)得多，第二種用(yong)(yong)得少(shao)，只有(you)交流(liu)電(dian)(dian)(dian)焊(han)機經常用(yong)(yong)到單相(xiang)380伏電(dian)(dian)(dian)源。