三相電加熱管

        380伏(fu)(fu)(fu)三(san)(san)相四線(xian)電(dian)(dian)路中，任意兩根(gen)火(huo)線(xian)之(zhi)間的電(dian)(dian)壓都是380伏(fu)(fu)(fu)，任意一根(gen)火(huo)線(xian)與零線(xian)之(zhi)間都可(ke)以(yi)組成220伏(fu)(fu)(fu)。這個系統可(ke)以(yi)形成三(san)(san)種(zhong)(zhong)電(dian)(dian)源(yuan)：即單(dan)相220伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，單(dan)相380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，三(san)(san)相380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)，第(di) I 種(zhong)(zhong)家用(yong)比較多(duo)，第(di)三(san)(san)種(zhong)(zhong)工(gong)廠里電(dian)(dian)機(ji)(ji)類用(yong)得多(duo)，第(di)二種(zhong)(zhong)用(yong)得少，只(zhi)有交(jiao)流電(dian)(dian)焊機(ji)(ji)經常用(yong)到單(dan)相380伏(fu)(fu)(fu)電(dian)(dian)源(yuan)。