三相電加熱管

        380伏(fu)(fu)三相四(si)線(xian)(xian)(xian)電(dian)路中，任(ren)意兩根(gen)火線(xian)(xian)(xian)之(zhi)間的電(dian)壓都是380伏(fu)(fu)，任(ren)意一根(gen)火線(xian)(xian)(xian)與零線(xian)(xian)(xian)之(zhi)間都可以組成(cheng)220伏(fu)(fu)。這(zhe)個系(xi)統(tong)可以形成(cheng)三種(zhong)(zhong)電(dian)源(yuan)：即單相220伏(fu)(fu)電(dian)源(yuan)，單相380伏(fu)(fu)電(dian)源(yuan)，三相380伏(fu)(fu)電(dian)源(yuan)，第 I 種(zhong)(zhong)家(jia)用比較多，第三種(zhong)(zhong)工廠里電(dian)機類用得(de)多，第二種(zhong)(zhong)用得(de)少(shao)，只(zhi)有交流(liu)電(dian)焊機經常用到(dao)單相380伏(fu)(fu)電(dian)源(yuan)。