三相電加熱管

        380伏(fu)(fu)三(san)(san)相(xiang)四線(xian)電(dian)(dian)(dian)路中，任意兩(liang)根(gen)火(huo)線(xian)之間的(de)電(dian)(dian)(dian)壓都是380伏(fu)(fu)，任意一根(gen)火(huo)線(xian)與零線(xian)之間都可(ke)(ke)以組成220伏(fu)(fu)。這個系統可(ke)(ke)以形成三(san)(san)種(zhong)電(dian)(dian)(dian)源(yuan)：即單(dan)相(xiang)220伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，單(dan)相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，三(san)(san)相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，第 I 種(zhong)家用(yong)(yong)比較多，第三(san)(san)種(zhong)工廠里電(dian)(dian)(dian)機類用(yong)(yong)得多，第二種(zhong)用(yong)(yong)得少，只有(you)交(jiao)流電(dian)(dian)(dian)焊機經常用(yong)(yong)到單(dan)相(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)。