三相電加熱管

        380伏(fu)(fu)三相(xiang)四線電(dian)(dian)(dian)(dian)路中，任意兩根火(huo)(huo)線之(zhi)間的(de)電(dian)(dian)(dian)(dian)壓都是(shi)380伏(fu)(fu)，任意一根火(huo)(huo)線與零線之(zhi)間都可(ke)以組成(cheng)220伏(fu)(fu)。這個系統(tong)可(ke)以形成(cheng)三種電(dian)(dian)(dian)(dian)源：即單相(xiang)220伏(fu)(fu)電(dian)(dian)(dian)(dian)源，單相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源，三相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源，第 I 種家用(yong)比較多，第三種工廠里電(dian)(dian)(dian)(dian)機類用(yong)得多，第二種用(yong)得少，只有交流(liu)電(dian)(dian)(dian)(dian)焊機經常(chang)用(yong)到單相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)(dian)源。