三相電加熱管

        380伏(fu)三(san)相(xiang)(xiang)四線電(dian)(dian)(dian)(dian)(dian)路中，任意兩(liang)根(gen)火線之(zhi)間的(de)電(dian)(dian)(dian)(dian)(dian)壓都是380伏(fu)，任意一根(gen)火線與零線之(zhi)間都可以組成220伏(fu)。這個系統可以形成三(san)種電(dian)(dian)(dian)(dian)(dian)源：即單相(xiang)(xiang)220伏(fu)電(dian)(dian)(dian)(dian)(dian)源，單相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)(dian)(dian)源，三(san)相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)(dian)(dian)源，第 I 種家用(yong)比較(jiao)多(duo)，第三(san)種工廠里電(dian)(dian)(dian)(dian)(dian)機(ji)類用(yong)得多(duo)，第二種用(yong)得少，只有(you)交流電(dian)(dian)(dian)(dian)(dian)焊(han)機(ji)經常用(yong)到單相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)(dian)(dian)源。