三相電加熱管

        380伏三(san)(san)相四線(xian)電(dian)(dian)(dian)路中，任意(yi)兩根(gen)火(huo)線(xian)之間的電(dian)(dian)(dian)壓(ya)都是380伏，任意(yi)一根(gen)火(huo)線(xian)與零線(xian)之間都可以組成220伏。這個系統可以形(xing)成三(san)(san)種(zhong)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)：即單(dan)相220伏電(dian)(dian)(dian)源(yuan)(yuan)(yuan)，單(dan)相380伏電(dian)(dian)(dian)源(yuan)(yuan)(yuan)，三(san)(san)相380伏電(dian)(dian)(dian)源(yuan)(yuan)(yuan)，第 I 種(zhong)家用(yong)比較多，第三(san)(san)種(zhong)工廠里電(dian)(dian)(dian)機類用(yong)得多，第二種(zhong)用(yong)得少，只有交流電(dian)(dian)(dian)焊機經(jing)常用(yong)到單(dan)相380伏電(dian)(dian)(dian)源(yuan)(yuan)(yuan)。