三相電加熱管

        380伏(fu)三(san)(san)相四線電(dian)路(lu)中(zhong)，任意兩根火線之間的電(dian)壓都是380伏(fu)，任意一(yi)根火線與(yu)零線之間都可以組成220伏(fu)。這個系(xi)統(tong)可以形(xing)成三(san)(san)種(zhong)(zhong)(zhong)電(dian)源：即單相220伏(fu)電(dian)源，單相380伏(fu)電(dian)源，三(san)(san)相380伏(fu)電(dian)源，第 I 種(zhong)(zhong)(zhong)家用(yong)比較多，第三(san)(san)種(zhong)(zhong)(zhong)工(gong)廠里(li)電(dian)機類用(yong)得多，第二種(zhong)(zhong)(zhong)用(yong)得少，只有(you)交(jiao)流電(dian)焊機經常用(yong)到單相380伏(fu)電(dian)源。