三相電加熱管

        380伏(fu)三(san)(san)相四線(xian)電(dian)(dian)(dian)(dian)路中，任(ren)意兩根火(huo)線(xian)之間的電(dian)(dian)(dian)(dian)壓都(dou)是380伏(fu)，任(ren)意一(yi)根火(huo)線(xian)與零線(xian)之間都(dou)可以(yi)組成220伏(fu)。這(zhe)個(ge)系(xi)統可以(yi)形成三(san)(san)種(zhong)電(dian)(dian)(dian)(dian)源(yuan)(yuan)：即單(dan)相220伏(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)，單(dan)相380伏(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)，三(san)(san)相380伏(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)，第 I 種(zhong)家用(yong)比(bi)較(jiao)多(duo)，第三(san)(san)種(zhong)工廠里電(dian)(dian)(dian)(dian)機(ji)類用(yong)得多(duo)，第二種(zhong)用(yong)得少(shao)，只有交流電(dian)(dian)(dian)(dian)焊機(ji)經常用(yong)到單(dan)相380伏(fu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)。