三相電加熱管

        380伏(fu)(fu)三(san)相(xiang)四線(xian)(xian)電(dian)(dian)(dian)(dian)路中，任意兩(liang)根火線(xian)(xian)之間的電(dian)(dian)(dian)(dian)壓(ya)都是380伏(fu)(fu)，任意一根火線(xian)(xian)與(yu)零線(xian)(xian)之間都可以組成(cheng)220伏(fu)(fu)。這個系統可以形(xing)成(cheng)三(san)種電(dian)(dian)(dian)(dian)源：即單相(xiang)220伏(fu)(fu)電(dian)(dian)(dian)(dian)源，單相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源，三(san)相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源，第 I 種家用比較多，第三(san)種工廠里電(dian)(dian)(dian)(dian)機類用得多，第二種用得少，只有交流電(dian)(dian)(dian)(dian)焊機經常用到單相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源。