三相電加熱管

        380伏三(san)相(xiang)(xiang)四線(xian)(xian)(xian)(xian)電(dian)路(lu)中，任意兩根(gen)火(huo)線(xian)(xian)(xian)(xian)之間的電(dian)壓都(dou)是380伏，任意一根(gen)火(huo)線(xian)(xian)(xian)(xian)與零線(xian)(xian)(xian)(xian)之間都(dou)可以(yi)組成220伏。這(zhe)個(ge)系統可以(yi)形成三(san)種(zhong)(zhong)電(dian)源(yuan)(yuan)：即單相(xiang)(xiang)220伏電(dian)源(yuan)(yuan)，單相(xiang)(xiang)380伏電(dian)源(yuan)(yuan)，三(san)相(xiang)(xiang)380伏電(dian)源(yuan)(yuan)，第(di) I 種(zhong)(zhong)家用(yong)比較多，第(di)三(san)種(zhong)(zhong)工廠里電(dian)機類用(yong)得多，第(di)二種(zhong)(zhong)用(yong)得少(shao)，只有交(jiao)流(liu)電(dian)焊機經常用(yong)到單相(xiang)(xiang)380伏電(dian)源(yuan)(yuan)。