三相電加熱管

        380伏(fu)(fu)三相(xiang)(xiang)四線電(dian)(dian)(dian)路中(zhong)，任(ren)意兩根(gen)火(huo)線之間的電(dian)(dian)(dian)壓(ya)都是(shi)380伏(fu)(fu)，任(ren)意一(yi)根(gen)火(huo)線與(yu)零線之間都可以(yi)組(zu)成(cheng)220伏(fu)(fu)。這個系統可以(yi)形成(cheng)三種電(dian)(dian)(dian)源：即單相(xiang)(xiang)220伏(fu)(fu)電(dian)(dian)(dian)源，單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源，三相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源，第 I 種家用比較多(duo)，第三種工廠里電(dian)(dian)(dian)機類用得多(duo)，第二種用得少(shao)，只有交流電(dian)(dian)(dian)焊機經(jing)常用到(dao)單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源。