三相電加熱管

        380伏(fu)(fu)三(san)(san)相四線(xian)電(dian)(dian)路中，任意兩根(gen)火線(xian)之(zhi)間(jian)的電(dian)(dian)壓都是380伏(fu)(fu)，任意一根(gen)火線(xian)與零線(xian)之(zhi)間(jian)都可以(yi)組(zu)成220伏(fu)(fu)。這個系統(tong)可以(yi)形成三(san)(san)種(zhong)(zhong)電(dian)(dian)源：即(ji)單相220伏(fu)(fu)電(dian)(dian)源，單相380伏(fu)(fu)電(dian)(dian)源，三(san)(san)相380伏(fu)(fu)電(dian)(dian)源，第 I 種(zhong)(zhong)家用(yong)(yong)比較多，第三(san)(san)種(zhong)(zhong)工廠里電(dian)(dian)機類用(yong)(yong)得多，第二種(zhong)(zhong)用(yong)(yong)得少(shao)，只有交流電(dian)(dian)焊(han)機經常用(yong)(yong)到單相380伏(fu)(fu)電(dian)(dian)源。