三相電加熱管

        380伏(fu)三相四線(xian)(xian)電(dian)(dian)路(lu)中，任意(yi)兩根火線(xian)(xian)之(zhi)(zhi)間的(de)電(dian)(dian)壓都是380伏(fu)，任意(yi)一(yi)根火線(xian)(xian)與零線(xian)(xian)之(zhi)(zhi)間都可(ke)以組成220伏(fu)。這(zhe)個系(xi)統可(ke)以形成三種電(dian)(dian)源(yuan)：即(ji)單相220伏(fu)電(dian)(dian)源(yuan)，單相380伏(fu)電(dian)(dian)源(yuan)，三相380伏(fu)電(dian)(dian)源(yuan)，第 I 種家用(yong)比較多，第三種工廠里電(dian)(dian)機類(lei)用(yong)得(de)多，第二種用(yong)得(de)少，只有交流電(dian)(dian)焊機經常用(yong)到單相380伏(fu)電(dian)(dian)源(yuan)。