三相電加熱管

        380伏(fu)(fu)(fu)三(san)相(xiang)四線電(dian)(dian)(dian)路中，任(ren)意(yi)兩根火(huo)線之間的電(dian)(dian)(dian)壓(ya)都是380伏(fu)(fu)(fu)，任(ren)意(yi)一根火(huo)線與零線之間都可(ke)以組成220伏(fu)(fu)(fu)。這個系(xi)統可(ke)以形成三(san)種(zhong)電(dian)(dian)(dian)源(yuan)(yuan)：即單相(xiang)220伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，單相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，三(san)相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，第 I 種(zhong)家用(yong)比較多(duo)，第三(san)種(zhong)工廠(chang)里電(dian)(dian)(dian)機(ji)類用(yong)得(de)多(duo)，第二種(zhong)用(yong)得(de)少，只(zhi)有交流電(dian)(dian)(dian)焊機(ji)經常用(yong)到單相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)。