三相電加熱管

        380伏(fu)(fu)(fu)三(san)相四線(xian)(xian)電(dian)(dian)路中(zhong)，任意(yi)兩根火線(xian)(xian)之間的電(dian)(dian)壓(ya)都是380伏(fu)(fu)(fu)，任意(yi)一根火線(xian)(xian)與零(ling)線(xian)(xian)之間都可以組(zu)成220伏(fu)(fu)(fu)。這個系統(tong)可以形(xing)成三(san)種(zhong)電(dian)(dian)源：即單(dan)相220伏(fu)(fu)(fu)電(dian)(dian)源，單(dan)相380伏(fu)(fu)(fu)電(dian)(dian)源，三(san)相380伏(fu)(fu)(fu)電(dian)(dian)源，第 I 種(zhong)家用比較多(duo)，第三(san)種(zhong)工廠(chang)里電(dian)(dian)機(ji)(ji)類用得(de)多(duo)，第二種(zhong)用得(de)少，只有交(jiao)流電(dian)(dian)焊機(ji)(ji)經常用到單(dan)相380伏(fu)(fu)(fu)電(dian)(dian)源。