三相電加熱管

        380伏(fu)三相四(si)線(xian)(xian)電(dian)(dian)路中(zhong)，任意兩根(gen)火線(xian)(xian)之(zhi)間(jian)的(de)電(dian)(dian)壓都是380伏(fu)，任意一根(gen)火線(xian)(xian)與零線(xian)(xian)之(zhi)間(jian)都可(ke)以組成220伏(fu)。這個系統可(ke)以形成三種電(dian)(dian)源：即單相220伏(fu)電(dian)(dian)源，單相380伏(fu)電(dian)(dian)源，三相380伏(fu)電(dian)(dian)源，第 I 種家用比較多，第三種工廠里電(dian)(dian)機類(lei)用得多，第二種用得少，只(zhi)有交流電(dian)(dian)焊機經常用到單相380伏(fu)電(dian)(dian)源。