三相電加熱管

        380伏(fu)(fu)(fu)三相四線電(dian)(dian)(dian)路中，任(ren)意(yi)兩根火線之間(jian)的(de)電(dian)(dian)(dian)壓都(dou)是380伏(fu)(fu)(fu)，任(ren)意(yi)一根火線與零線之間(jian)都(dou)可以(yi)組成220伏(fu)(fu)(fu)。這(zhe)個系統可以(yi)形(xing)成三種電(dian)(dian)(dian)源(yuan)(yuan)：即單相220伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，單相380伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，三相380伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，第 I 種家用(yong)比較(jiao)多，第三種工廠(chang)里電(dian)(dian)(dian)機類用(yong)得多，第二種用(yong)得少(shao)，只有交流電(dian)(dian)(dian)焊機經常用(yong)到單相380伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)。