三相電加熱管

        380伏(fu)(fu)三相四(si)線電(dian)(dian)(dian)路中，任(ren)意兩(liang)根(gen)火線之(zhi)間(jian)的電(dian)(dian)(dian)壓都是380伏(fu)(fu)，任(ren)意一根(gen)火線與零線之(zhi)間(jian)都可以(yi)組成220伏(fu)(fu)。這個系統可以(yi)形成三種電(dian)(dian)(dian)源(yuan)：即單相220伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，單相380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，三相380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，第 I 種家用比較多，第三種工廠里(li)電(dian)(dian)(dian)機類用得多，第二種用得少，只有交(jiao)流電(dian)(dian)(dian)焊機經常用到單相380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)。