三相電加熱管

        380伏(fu)三(san)相四線電(dian)(dian)路中，任(ren)意(yi)兩根(gen)火線之間的電(dian)(dian)壓都是380伏(fu)，任(ren)意(yi)一根(gen)火線與零線之間都可以組成(cheng)220伏(fu)。這個系(xi)統(tong)可以形成(cheng)三(san)種(zhong)電(dian)(dian)源(yuan)(yuan)(yuan)：即單(dan)(dan)相220伏(fu)電(dian)(dian)源(yuan)(yuan)(yuan)，單(dan)(dan)相380伏(fu)電(dian)(dian)源(yuan)(yuan)(yuan)，三(san)相380伏(fu)電(dian)(dian)源(yuan)(yuan)(yuan)，第 I 種(zhong)家(jia)用(yong)(yong)比(bi)較多(duo)，第三(san)種(zhong)工(gong)廠(chang)里電(dian)(dian)機類用(yong)(yong)得多(duo)，第二種(zhong)用(yong)(yong)得少，只有交流(liu)電(dian)(dian)焊機經常(chang)用(yong)(yong)到單(dan)(dan)相380伏(fu)電(dian)(dian)源(yuan)(yuan)(yuan)。