三相電加熱管

        380伏(fu)(fu)三(san)(san)相(xiang)四線(xian)(xian)電(dian)(dian)路中，任(ren)意兩根火(huo)線(xian)(xian)之(zhi)間(jian)的電(dian)(dian)壓都(dou)是380伏(fu)(fu)，任(ren)意一根火(huo)線(xian)(xian)與(yu)零線(xian)(xian)之(zhi)間(jian)都(dou)可(ke)以組成220伏(fu)(fu)。這個系(xi)統可(ke)以形成三(san)(san)種電(dian)(dian)源：即單相(xiang)220伏(fu)(fu)電(dian)(dian)源，單相(xiang)380伏(fu)(fu)電(dian)(dian)源，三(san)(san)相(xiang)380伏(fu)(fu)電(dian)(dian)源，第(di)(di)(di) I 種家用(yong)(yong)比較多(duo)，第(di)(di)(di)三(san)(san)種工廠里電(dian)(dian)機類用(yong)(yong)得(de)(de)多(duo)，第(di)(di)(di)二種用(yong)(yong)得(de)(de)少，只有交流電(dian)(dian)焊機經(jing)常用(yong)(yong)到單相(xiang)380伏(fu)(fu)電(dian)(dian)源。