三相電加熱管

        380伏三(san)相(xiang)四線(xian)電(dian)(dian)路中，任意兩根火線(xian)之(zhi)(zhi)間的電(dian)(dian)壓(ya)都(dou)是(shi)380伏，任意一根火線(xian)與(yu)零線(xian)之(zhi)(zhi)間都(dou)可(ke)以組成220伏。這個(ge)系統可(ke)以形成三(san)種電(dian)(dian)源：即(ji)單相(xiang)220伏電(dian)(dian)源，單相(xiang)380伏電(dian)(dian)源，三(san)相(xiang)380伏電(dian)(dian)源，第(di)(di) I 種家用(yong)比(bi)較多，第(di)(di)三(san)種工廠里電(dian)(dian)機(ji)(ji)類用(yong)得(de)多，第(di)(di)二(er)種用(yong)得(de)少，只有交(jiao)流(liu)電(dian)(dian)焊(han)機(ji)(ji)經常用(yong)到單相(xiang)380伏電(dian)(dian)源。