三相電加熱管

        380伏三(san)相(xiang)四(si)線(xian)電(dian)(dian)路中，任意兩根火線(xian)之(zhi)間的電(dian)(dian)壓都是380伏，任意一根火線(xian)與零線(xian)之(zhi)間都可以(yi)組成220伏。這個系統(tong)可以(yi)形(xing)成三(san)種(zhong)電(dian)(dian)源(yuan)：即單(dan)相(xiang)220伏電(dian)(dian)源(yuan)，單(dan)相(xiang)380伏電(dian)(dian)源(yuan)，三(san)相(xiang)380伏電(dian)(dian)源(yuan)，第 I 種(zhong)家用(yong)比較(jiao)多，第三(san)種(zhong)工廠(chang)里電(dian)(dian)機類用(yong)得多，第二種(zhong)用(yong)得少，只有交流(liu)電(dian)(dian)焊機經常用(yong)到(dao)單(dan)相(xiang)380伏電(dian)(dian)源(yuan)。