三相電加熱管

        380伏三(san)相四線電(dian)(dian)路中，任意兩根(gen)火線之間(jian)的電(dian)(dian)壓都是380伏，任意一根(gen)火線與零線之間(jian)都可以(yi)組成220伏。這(zhe)個系統(tong)可以(yi)形成三(san)種(zhong)(zhong)(zhong)電(dian)(dian)源：即單相220伏電(dian)(dian)源，單相380伏電(dian)(dian)源，三(san)相380伏電(dian)(dian)源，第 I 種(zhong)(zhong)(zhong)家(jia)用(yong)比較多，第三(san)種(zhong)(zhong)(zhong)工廠里(li)電(dian)(dian)機類用(yong)得多，第二種(zhong)(zhong)(zhong)用(yong)得少，只有交流電(dian)(dian)焊機經常用(yong)到單相380伏電(dian)(dian)源。