三相電加熱管

        380伏(fu)(fu)(fu)三相(xiang)四線(xian)電(dian)(dian)路中，任意兩根(gen)火(huo)(huo)線(xian)之(zhi)間(jian)的電(dian)(dian)壓都是380伏(fu)(fu)(fu)，任意一(yi)根(gen)火(huo)(huo)線(xian)與零線(xian)之(zhi)間(jian)都可(ke)以組(zu)成(cheng)220伏(fu)(fu)(fu)。這個系統可(ke)以形成(cheng)三種(zhong)電(dian)(dian)源(yuan)：即單相(xiang)220伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，單相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，三相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，第(di) I 種(zhong)家用(yong)比較多，第(di)三種(zhong)工(gong)廠里電(dian)(dian)機類用(yong)得多，第(di)二(er)種(zhong)用(yong)得少，只有交流電(dian)(dian)焊機經常用(yong)到單相(xiang)380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)。