三相電加熱管

        380伏(fu)三(san)(san)(san)相四線電(dian)(dian)路(lu)中，任(ren)意(yi)兩根(gen)火線之間(jian)的電(dian)(dian)壓(ya)都是380伏(fu)，任(ren)意(yi)一(yi)根(gen)火線與零線之間(jian)都可(ke)以組成220伏(fu)。這(zhe)個系統(tong)可(ke)以形成三(san)(san)(san)種電(dian)(dian)源：即單(dan)相220伏(fu)電(dian)(dian)源，單(dan)相380伏(fu)電(dian)(dian)源，三(san)(san)(san)相380伏(fu)電(dian)(dian)源，第(di) I 種家用(yong)比較(jiao)多，第(di)三(san)(san)(san)種工廠里電(dian)(dian)機類用(yong)得(de)多，第(di)二種用(yong)得(de)少，只有交流電(dian)(dian)焊機經常用(yong)到單(dan)相380伏(fu)電(dian)(dian)源。