三相電加熱管

        380伏三(san)相(xiang)四線(xian)(xian)電(dian)(dian)(dian)(dian)路中，任(ren)意兩根(gen)火線(xian)(xian)之間的電(dian)(dian)(dian)(dian)壓都是380伏，任(ren)意一根(gen)火線(xian)(xian)與零(ling)線(xian)(xian)之間都可(ke)以(yi)組成220伏。這(zhe)個系統可(ke)以(yi)形成三(san)種(zhong)電(dian)(dian)(dian)(dian)源(yuan)：即單(dan)相(xiang)220伏電(dian)(dian)(dian)(dian)源(yuan)，單(dan)相(xiang)380伏電(dian)(dian)(dian)(dian)源(yuan)，三(san)相(xiang)380伏電(dian)(dian)(dian)(dian)源(yuan)，第 I 種(zhong)家用(yong)(yong)比較多，第三(san)種(zhong)工廠里(li)電(dian)(dian)(dian)(dian)機類用(yong)(yong)得多，第二種(zhong)用(yong)(yong)得少，只有(you)交(jiao)流電(dian)(dian)(dian)(dian)焊機經常用(yong)(yong)到單(dan)相(xiang)380伏電(dian)(dian)(dian)(dian)源(yuan)。