三相電加熱管

        380伏(fu)三(san)相四線(xian)(xian)電(dian)(dian)(dian)路中，任意(yi)兩(liang)根火線(xian)(xian)之間的電(dian)(dian)(dian)壓都(dou)(dou)是380伏(fu)，任意(yi)一根火線(xian)(xian)與零線(xian)(xian)之間都(dou)(dou)可(ke)以(yi)組成220伏(fu)。這個系統可(ke)以(yi)形成三(san)種電(dian)(dian)(dian)源(yuan)(yuan)：即(ji)單(dan)相220伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，單(dan)相380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，三(san)相380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)，第 I 種家(jia)用比較多，第三(san)種工廠里電(dian)(dian)(dian)機類用得多，第二種用得少，只有交流(liu)電(dian)(dian)(dian)焊機經常用到單(dan)相380伏(fu)電(dian)(dian)(dian)源(yuan)(yuan)。