三相電加熱管

        380伏(fu)(fu)三(san)(san)(san)(san)相四線電(dian)(dian)(dian)路中，任意(yi)兩(liang)根火線之間(jian)(jian)的電(dian)(dian)(dian)壓都是380伏(fu)(fu)，任意(yi)一根火線與零線之間(jian)(jian)都可以(yi)組成(cheng)220伏(fu)(fu)。這個系統可以(yi)形成(cheng)三(san)(san)(san)(san)種(zhong)電(dian)(dian)(dian)源(yuan)(yuan)：即單(dan)相220伏(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，單(dan)相380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，三(san)(san)(san)(san)相380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)，第(di) I 種(zhong)家(jia)用(yong)比較多(duo)，第(di)三(san)(san)(san)(san)種(zhong)工(gong)廠里電(dian)(dian)(dian)機類用(yong)得多(duo)，第(di)二種(zhong)用(yong)得少，只有交流電(dian)(dian)(dian)焊(han)機經常用(yong)到單(dan)相380伏(fu)(fu)電(dian)(dian)(dian)源(yuan)(yuan)。