三相電加熱管

        380伏(fu)三(san)相(xiang)四線(xian)電(dian)(dian)(dian)路中，任(ren)意(yi)兩(liang)根火(huo)線(xian)之間(jian)的電(dian)(dian)(dian)壓都(dou)是380伏(fu)，任(ren)意(yi)一(yi)根火(huo)線(xian)與(yu)零線(xian)之間(jian)都(dou)可以組(zu)成(cheng)220伏(fu)。這個系統可以形成(cheng)三(san)種電(dian)(dian)(dian)源(yuan)(yuan)：即(ji)單相(xiang)220伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，單相(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，三(san)相(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，第 I 種家用(yong)比較多(duo)，第三(san)種工(gong)廠里電(dian)(dian)(dian)機類用(yong)得多(duo)，第二(er)種用(yong)得少，只(zhi)有交流電(dian)(dian)(dian)焊(han)機經常用(yong)到單相(xiang)380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)。