三相電加熱管

        380伏(fu)三相(xiang)(xiang)(xiang)四(si)線(xian)電(dian)(dian)路中，任(ren)意(yi)兩根火線(xian)之間(jian)的(de)電(dian)(dian)壓(ya)都是(shi)380伏(fu)，任(ren)意(yi)一根火線(xian)與(yu)零線(xian)之間(jian)都可(ke)以組成(cheng)220伏(fu)。這個系統可(ke)以形成(cheng)三種(zhong)電(dian)(dian)源(yuan)：即(ji)單(dan)(dan)相(xiang)(xiang)(xiang)220伏(fu)電(dian)(dian)源(yuan)，單(dan)(dan)相(xiang)(xiang)(xiang)380伏(fu)電(dian)(dian)源(yuan)，三相(xiang)(xiang)(xiang)380伏(fu)電(dian)(dian)源(yuan)，第(di) I 種(zhong)家用(yong)比(bi)較多(duo)，第(di)三種(zhong)工廠里電(dian)(dian)機類用(yong)得多(duo)，第(di)二(er)種(zhong)用(yong)得少(shao)，只有(you)交流電(dian)(dian)焊機經常用(yong)到(dao)單(dan)(dan)相(xiang)(xiang)(xiang)380伏(fu)電(dian)(dian)源(yuan)。