三相電加熱管

        380伏(fu)三(san)相四(si)線(xian)(xian)電(dian)(dian)路中，任(ren)意兩(liang)根火線(xian)(xian)之間的(de)電(dian)(dian)壓都是(shi)380伏(fu)，任(ren)意一根火線(xian)(xian)與零線(xian)(xian)之間都可以(yi)組成(cheng)220伏(fu)。這個系統(tong)可以(yi)形成(cheng)三(san)種(zhong)電(dian)(dian)源(yuan)：即單(dan)相220伏(fu)電(dian)(dian)源(yuan)，單(dan)相380伏(fu)電(dian)(dian)源(yuan)，三(san)相380伏(fu)電(dian)(dian)源(yuan)，第(di)(di) I 種(zhong)家(jia)用(yong)比較多，第(di)(di)三(san)種(zhong)工(gong)廠里電(dian)(dian)機類用(yong)得多，第(di)(di)二種(zhong)用(yong)得少，只(zhi)有(you)交(jiao)流電(dian)(dian)焊(han)機經常用(yong)到單(dan)相380伏(fu)電(dian)(dian)源(yuan)。