三相電加熱管

        380伏(fu)(fu)(fu)(fu)三(san)相四線(xian)(xian)電(dian)(dian)路中，任(ren)(ren)意兩根(gen)火線(xian)(xian)之間(jian)的電(dian)(dian)壓都是380伏(fu)(fu)(fu)(fu)，任(ren)(ren)意一根(gen)火線(xian)(xian)與零線(xian)(xian)之間(jian)都可以(yi)組成220伏(fu)(fu)(fu)(fu)。這個(ge)系統可以(yi)形成三(san)種電(dian)(dian)源(yuan)(yuan)：即單相220伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan)(yuan)，單相380伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan)(yuan)，三(san)相380伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan)(yuan)，第 I 種家用(yong)比較多(duo)，第三(san)種工廠里電(dian)(dian)機類用(yong)得(de)(de)多(duo)，第二種用(yong)得(de)(de)少，只有交流電(dian)(dian)焊機經常用(yong)到單相380伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan)(yuan)。