三相電加熱管

        380伏(fu)三(san)(san)相四線電(dian)(dian)(dian)路(lu)中，任意(yi)兩根(gen)火線之間的電(dian)(dian)(dian)壓都是380伏(fu)，任意(yi)一根(gen)火線與零線之間都可以組成(cheng)220伏(fu)。這(zhe)個系統可以形成(cheng)三(san)(san)種(zhong)電(dian)(dian)(dian)源(yuan)：即單(dan)相220伏(fu)電(dian)(dian)(dian)源(yuan)，單(dan)相380伏(fu)電(dian)(dian)(dian)源(yuan)，三(san)(san)相380伏(fu)電(dian)(dian)(dian)源(yuan)，第 I 種(zhong)家用比較多，第三(san)(san)種(zhong)工廠里電(dian)(dian)(dian)機(ji)類(lei)用得多，第二種(zhong)用得少，只有交流電(dian)(dian)(dian)焊機(ji)經常用到單(dan)相380伏(fu)電(dian)(dian)(dian)源(yuan)。