三相電加熱管

        380伏三(san)(san)相(xiang)(xiang)四線電(dian)路中，任意(yi)兩(liang)根(gen)火線之(zhi)間的電(dian)壓都是380伏，任意(yi)一(yi)根(gen)火線與(yu)零線之(zhi)間都可以(yi)組成(cheng)220伏。這個系統可以(yi)形成(cheng)三(san)(san)種(zhong)(zhong)(zhong)電(dian)源：即單相(xiang)(xiang)220伏電(dian)源，單相(xiang)(xiang)380伏電(dian)源，三(san)(san)相(xiang)(xiang)380伏電(dian)源，第(di)(di) I 種(zhong)(zhong)(zhong)家用(yong)(yong)比較多(duo)，第(di)(di)三(san)(san)種(zhong)(zhong)(zhong)工廠里(li)電(dian)機類用(yong)(yong)得多(duo)，第(di)(di)二種(zhong)(zhong)(zhong)用(yong)(yong)得少(shao)，只有(you)交(jiao)流電(dian)焊機經常用(yong)(yong)到單相(xiang)(xiang)380伏電(dian)源。