三相電加熱管

        380伏(fu)三相四(si)線(xian)(xian)電(dian)(dian)路(lu)中，任意(yi)兩(liang)根(gen)火(huo)線(xian)(xian)之間的電(dian)(dian)壓都(dou)是380伏(fu)，任意(yi)一根(gen)火(huo)線(xian)(xian)與零線(xian)(xian)之間都(dou)可以組成220伏(fu)。這個系統可以形成三種電(dian)(dian)源：即(ji)單(dan)相220伏(fu)電(dian)(dian)源，單(dan)相380伏(fu)電(dian)(dian)源，三相380伏(fu)電(dian)(dian)源，第 I 種家用比(bi)較多，第三種工(gong)廠里電(dian)(dian)機類用得多，第二種用得少(shao)，只有(you)交流電(dian)(dian)焊機經常用到單(dan)相380伏(fu)電(dian)(dian)源。