三相電加熱管

        380伏三(san)相(xiang)(xiang)四線(xian)電(dian)(dian)(dian)路中，任意兩根火線(xian)之間(jian)的電(dian)(dian)(dian)壓都是380伏，任意一根火線(xian)與(yu)零(ling)線(xian)之間(jian)都可以(yi)組成(cheng)220伏。這個系統可以(yi)形(xing)成(cheng)三(san)種電(dian)(dian)(dian)源(yuan)(yuan)：即單(dan)相(xiang)(xiang)220伏電(dian)(dian)(dian)源(yuan)(yuan)，單(dan)相(xiang)(xiang)380伏電(dian)(dian)(dian)源(yuan)(yuan)，三(san)相(xiang)(xiang)380伏電(dian)(dian)(dian)源(yuan)(yuan)，第 I 種家用(yong)比(bi)較多(duo)，第三(san)種工廠里電(dian)(dian)(dian)機類用(yong)得(de)多(duo)，第二種用(yong)得(de)少，只有(you)交流電(dian)(dian)(dian)焊機經(jing)常用(yong)到單(dan)相(xiang)(xiang)380伏電(dian)(dian)(dian)源(yuan)(yuan)。