三相電加熱管

        380伏(fu)(fu)三(san)(san)相四(si)線電(dian)(dian)路中，任(ren)意兩根(gen)(gen)火(huo)線之(zhi)(zhi)間(jian)的電(dian)(dian)壓都(dou)是380伏(fu)(fu)，任(ren)意一根(gen)(gen)火(huo)線與(yu)零線之(zhi)(zhi)間(jian)都(dou)可(ke)以組成220伏(fu)(fu)。這個系統可(ke)以形成三(san)(san)種電(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)(san)相380伏(fu)(fu)電(dian)(dian)源，第(di) I 種家用(yong)(yong)比較多，第(di)三(san)(san)種工廠里電(dian)(dian)機類用(yong)(yong)得多，第(di)二種用(yong)(yong)得少，只有交流電(dian)(dian)焊機經(jing)常用(yong)(yong)到(dao)單(dan)相380伏(fu)(fu)電(dian)(dian)源。