三相電加熱管

        380伏(fu)(fu)(fu)三(san)相(xiang)四線(xian)(xian)電(dian)(dian)(dian)路中，任(ren)意(yi)兩根火線(xian)(xian)之間的(de)電(dian)(dian)(dian)壓都是380伏(fu)(fu)(fu)，任(ren)意(yi)一根火線(xian)(xian)與零線(xian)(xian)之間都可以(yi)組成220伏(fu)(fu)(fu)。這個(ge)系統可以(yi)形成三(san)種(zhong)電(dian)(dian)(dian)源：即單(dan)(dan)相(xiang)220伏(fu)(fu)(fu)電(dian)(dian)(dian)源，單(dan)(dan)相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)(dian)源，三(san)相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)(dian)源，第(di) I 種(zhong)家用(yong)比較(jiao)多，第(di)三(san)種(zhong)工廠里(li)電(dian)(dian)(dian)機類用(yong)得多，第(di)二種(zhong)用(yong)得少(shao)，只有交流電(dian)(dian)(dian)焊機經常用(yong)到單(dan)(dan)相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)(dian)源。