三相電加熱管

        380伏(fu)(fu)(fu)(fu)三(san)相(xiang)四線電(dian)(dian)(dian)(dian)路中，任(ren)(ren)意兩(liang)根火線之間(jian)的(de)電(dian)(dian)(dian)(dian)壓(ya)都是380伏(fu)(fu)(fu)(fu)，任(ren)(ren)意一根火線與零線之間(jian)都可以(yi)組成(cheng)220伏(fu)(fu)(fu)(fu)。這個系(xi)統可以(yi)形成(cheng)三(san)種(zhong)(zhong)電(dian)(dian)(dian)(dian)源(yuan)(yuan)：即單相(xiang)220伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)，單相(xiang)380伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)，三(san)相(xiang)380伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)，第(di)(di) I 種(zhong)(zhong)家用比較多，第(di)(di)三(san)種(zhong)(zhong)工廠里電(dian)(dian)(dian)(dian)機類用得多，第(di)(di)二種(zhong)(zhong)用得少，只有交流電(dian)(dian)(dian)(dian)焊機經常用到單相(xiang)380伏(fu)(fu)(fu)(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)。