三相電加熱管

        380伏(fu)(fu)(fu)(fu)三(san)(san)(san)相(xiang)四線電(dian)(dian)(dian)(dian)路中(zhong)，任(ren)意(yi)兩(liang)根(gen)火(huo)線之(zhi)間的(de)電(dian)(dian)(dian)(dian)壓都(dou)是380伏(fu)(fu)(fu)(fu)，任(ren)意(yi)一(yi)根(gen)火(huo)線與零線之(zhi)間都(dou)可(ke)以(yi)組(zu)成(cheng)220伏(fu)(fu)(fu)(fu)。這個系統可(ke)以(yi)形成(cheng)三(san)(san)(san)種電(dian)(dian)(dian)(dian)源：即單相(xiang)220伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源，單相(xiang)380伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源，三(san)(san)(san)相(xiang)380伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源，第(di) I 種家用(yong)比較(jiao)多，第(di)三(san)(san)(san)種工廠(chang)里電(dian)(dian)(dian)(dian)機(ji)類用(yong)得多，第(di)二種用(yong)得少，只有交(jiao)流電(dian)(dian)(dian)(dian)焊機(ji)經常用(yong)到單相(xiang)380伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源。