三相電加熱管

        380伏(fu)(fu)三(san)相四線電(dian)(dian)路中，任(ren)(ren)意兩根火線之間的(de)電(dian)(dian)壓都是380伏(fu)(fu)，任(ren)(ren)意一根火線與零線之間都可(ke)以組成(cheng)220伏(fu)(fu)。這個系(xi)統可(ke)以形成(cheng)三(san)種(zhong)電(dian)(dian)源(yuan)：即單(dan)相220伏(fu)(fu)電(dian)(dian)源(yuan)，單(dan)相380伏(fu)(fu)電(dian)(dian)源(yuan)，三(san)相380伏(fu)(fu)電(dian)(dian)源(yuan)，第(di) I 種(zhong)家用(yong)(yong)比(bi)較(jiao)多，第(di)三(san)種(zhong)工廠里電(dian)(dian)機(ji)類用(yong)(yong)得多，第(di)二種(zhong)用(yong)(yong)得少，只有(you)交流電(dian)(dian)焊機(ji)經(jing)常用(yong)(yong)到單(dan)相380伏(fu)(fu)電(dian)(dian)源(yuan)。