三相電加熱管

        380伏(fu)(fu)三相(xiang)(xiang)四線電(dian)(dian)(dian)路中，任意兩(liang)根(gen)火線之間的電(dian)(dian)(dian)壓都(dou)是(shi)380伏(fu)(fu)，任意一(yi)根(gen)火線與零(ling)線之間都(dou)可以(yi)組成220伏(fu)(fu)。這個(ge)系統可以(yi)形成三種電(dian)(dian)(dian)源：即(ji)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(jiao)多，第三種工廠里電(dian)(dian)(dian)機類用得多，第二種用得少，只(zhi)有(you)交流電(dian)(dian)(dian)焊機經常(chang)用到(dao)單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源。