三相電加熱管

        380伏(fu)(fu)三相四線(xian)電(dian)(dian)(dian)路中，任(ren)意(yi)兩根火線(xian)之間的電(dian)(dian)(dian)壓(ya)都(dou)是380伏(fu)(fu)，任(ren)意(yi)一根火線(xian)與零線(xian)之間都(dou)可(ke)(ke)以(yi)組成(cheng)220伏(fu)(fu)。這個(ge)系(xi)統可(ke)(ke)以(yi)形成(cheng)三種(zhong)(zhong)電(dian)(dian)(dian)源：即(ji)單相220伏(fu)(fu)電(dian)(dian)(dian)源，單相380伏(fu)(fu)電(dian)(dian)(dian)源，三相380伏(fu)(fu)電(dian)(dian)(dian)源，第 I 種(zhong)(zhong)家用比較多(duo)(duo)，第三種(zhong)(zhong)工廠(chang)里電(dian)(dian)(dian)機類用得(de)多(duo)(duo)，第二種(zhong)(zhong)用得(de)少，只有交流電(dian)(dian)(dian)焊機經(jing)常用到單相380伏(fu)(fu)電(dian)(dian)(dian)源。