三相電加熱管

        380伏(fu)(fu)三(san)相(xiang)(xiang)四線電(dian)(dian)路中，任(ren)意(yi)兩根(gen)火(huo)線之(zhi)間的電(dian)(dian)壓(ya)都(dou)是380伏(fu)(fu)，任(ren)意(yi)一根(gen)火(huo)線與零線之(zhi)間都(dou)可(ke)以組成220伏(fu)(fu)。這(zhe)個(ge)系統(tong)可(ke)以形成三(san)種(zhong)電(dian)(dian)源：即單相(xiang)(xiang)220伏(fu)(fu)電(dian)(dian)源，單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)源，三(san)相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)源，第 I 種(zhong)家用(yong)(yong)比(bi)較(jiao)多，第三(san)種(zhong)工廠(chang)里電(dian)(dian)機類用(yong)(yong)得多，第二種(zhong)用(yong)(yong)得少，只有交流(liu)電(dian)(dian)焊(han)機經常用(yong)(yong)到單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)源。