三相電加熱管

        380伏(fu)(fu)三(san)相四(si)線(xian)(xian)電(dian)(dian)路中，任意(yi)(yi)兩根火線(xian)(xian)之(zhi)間的(de)電(dian)(dian)壓都是380伏(fu)(fu)，任意(yi)(yi)一(yi)根火線(xian)(xian)與(yu)零(ling)線(xian)(xian)之(zhi)間都可(ke)以組成(cheng)220伏(fu)(fu)。這(zhe)個系統(tong)可(ke)以形成(cheng)三(san)種(zhong)(zhong)電(dian)(dian)源：即單(dan)相220伏(fu)(fu)電(dian)(dian)源，單(dan)相380伏(fu)(fu)電(dian)(dian)源，三(san)相380伏(fu)(fu)電(dian)(dian)源，第(di) I 種(zhong)(zhong)家(jia)用比(bi)較(jiao)多，第(di)三(san)種(zhong)(zhong)工廠里電(dian)(dian)機(ji)類用得(de)多，第(di)二種(zhong)(zhong)用得(de)少，只有交流電(dian)(dian)焊機(ji)經常用到單(dan)相380伏(fu)(fu)電(dian)(dian)源。