三相電加熱管

        380伏(fu)三(san)(san)相(xiang)四線(xian)電(dian)(dian)路中(zhong)，任意兩根火線(xian)之間的電(dian)(dian)壓都是380伏(fu)，任意一根火線(xian)與零(ling)線(xian)之間都可(ke)以組(zu)成(cheng)220伏(fu)。這個系統可(ke)以形成(cheng)三(san)(san)種(zhong)電(dian)(dian)源(yuan)(yuan)：即(ji)單(dan)相(xiang)220伏(fu)電(dian)(dian)源(yuan)(yuan)，單(dan)相(xiang)380伏(fu)電(dian)(dian)源(yuan)(yuan)，三(san)(san)相(xiang)380伏(fu)電(dian)(dian)源(yuan)(yuan)，第 I 種(zhong)家用(yong)(yong)比較(jiao)多，第三(san)(san)種(zhong)工廠里(li)電(dian)(dian)機(ji)類(lei)用(yong)(yong)得多，第二種(zhong)用(yong)(yong)得少，只(zhi)有交流電(dian)(dian)焊機(ji)經(jing)常用(yong)(yong)到單(dan)相(xiang)380伏(fu)電(dian)(dian)源(yuan)(yuan)。