三相電加熱管

        380伏三相(xiang)(xiang)四線(xian)電(dian)(dian)(dian)路中(zhong)，任意兩根火線(xian)之(zhi)間(jian)的電(dian)(dian)(dian)壓都是380伏，任意一根火線(xian)與(yu)零線(xian)之(zhi)間(jian)都可以(yi)組(zu)成(cheng)(cheng)220伏。這個系統可以(yi)形(xing)成(cheng)(cheng)三種(zhong)(zhong)電(dian)(dian)(dian)源(yuan)：即單(dan)相(xiang)(xiang)220伏電(dian)(dian)(dian)源(yuan)，單(dan)相(xiang)(xiang)380伏電(dian)(dian)(dian)源(yuan)，三相(xiang)(xiang)380伏電(dian)(dian)(dian)源(yuan)，第 I 種(zhong)(zhong)家用(yong)比較(jiao)多，第三種(zhong)(zhong)工廠(chang)里(li)電(dian)(dian)(dian)機類(lei)用(yong)得多，第二(er)種(zhong)(zhong)用(yong)得少，只有交(jiao)流(liu)電(dian)(dian)(dian)焊機經常用(yong)到單(dan)相(xiang)(xiang)380伏電(dian)(dian)(dian)源(yuan)。