三相電加熱管

        380伏(fu)(fu)(fu)三相(xiang)四線電(dian)(dian)路中，任意兩根(gen)火線之間的電(dian)(dian)壓都是380伏(fu)(fu)(fu)，任意一根(gen)火線與零(ling)線之間都可(ke)以組成(cheng)220伏(fu)(fu)(fu)。這個(ge)系統可(ke)以形(xing)成(cheng)三種(zhong)電(dian)(dian)源(yuan)：即(ji)單(dan)(dan)相(xiang)220伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，單(dan)(dan)相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，三相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，第 I 種(zhong)家用(yong)(yong)比較多，第三種(zhong)工廠里(li)電(dian)(dian)機(ji)(ji)類用(yong)(yong)得多，第二種(zhong)用(yong)(yong)得少(shao)，只有交流電(dian)(dian)焊(han)機(ji)(ji)經(jing)常(chang)用(yong)(yong)到單(dan)(dan)相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)。