三相電加熱管

        380伏(fu)(fu)三(san)相(xiang)(xiang)四線電(dian)(dian)(dian)(dian)路(lu)中，任意(yi)兩根火線之(zhi)(zhi)間的(de)電(dian)(dian)(dian)(dian)壓(ya)都是380伏(fu)(fu)，任意(yi)一根火線與零線之(zhi)(zhi)間都可以組成220伏(fu)(fu)。這個(ge)系統(tong)可以形成三(san)種(zhong)(zhong)電(dian)(dian)(dian)(dian)源(yuan)：即單相(xiang)(xiang)220伏(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)，單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)，三(san)相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)，第 I 種(zhong)(zhong)家用比較多(duo)，第三(san)種(zhong)(zhong)工廠里(li)電(dian)(dian)(dian)(dian)機類用得(de)多(duo)，第二(er)種(zhong)(zhong)用得(de)少，只有交流電(dian)(dian)(dian)(dian)焊機經常用到單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)。