三相電加熱管

        380伏(fu)(fu)三相(xiang)(xiang)四(si)線電(dian)(dian)(dian)路中(zhong)，任意(yi)兩根(gen)火線之間的電(dian)(dian)(dian)壓都是380伏(fu)(fu)，任意(yi)一根(gen)火線與零(ling)線之間都可以組成220伏(fu)(fu)。這個系統(tong)可以形成三種(zhong)(zhong)電(dian)(dian)(dian)源(yuan)：即單相(xiang)(xiang)220伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，三相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)，第 I 種(zhong)(zhong)家用比較多，第三種(zhong)(zhong)工廠里電(dian)(dian)(dian)機類用得(de)多，第二種(zhong)(zhong)用得(de)少，只有交流電(dian)(dian)(dian)焊機經常用到單相(xiang)(xiang)380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)。