三相電加熱管

        380伏(fu)三(san)相(xiang)(xiang)四線(xian)(xian)電(dian)(dian)(dian)路(lu)中，任意兩根火線(xian)(xian)之(zhi)間(jian)的(de)電(dian)(dian)(dian)壓都是380伏(fu)，任意一根火線(xian)(xian)與零(ling)線(xian)(xian)之(zhi)間(jian)都可以組成220伏(fu)。這個系(xi)統可以形成三(san)種電(dian)(dian)(dian)源(yuan)(yuan)：即單相(xiang)(xiang)220伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，單相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，三(san)相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，第 I 種家用(yong)(yong)比較多，第三(san)種工(gong)廠里(li)電(dian)(dian)(dian)機類用(yong)(yong)得(de)多，第二(er)種用(yong)(yong)得(de)少(shao)，只有交(jiao)流電(dian)(dian)(dian)焊機經常用(yong)(yong)到單相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)。