三相電加熱管

        380伏(fu)三相(xiang)(xiang)四線(xian)(xian)電(dian)(dian)(dian)路(lu)中，任意兩(liang)根火線(xian)(xian)之(zhi)間(jian)的電(dian)(dian)(dian)壓都是380伏(fu)，任意一(yi)根火線(xian)(xian)與零線(xian)(xian)之(zhi)間(jian)都可以(yi)組成(cheng)220伏(fu)。這個系統可以(yi)形成(cheng)三種(zhong)電(dian)(dian)(dian)源：即單相(xiang)(xiang)220伏(fu)電(dian)(dian)(dian)源，單相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源，三相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源，第(di) I 種(zhong)家(jia)用(yong)比較多，第(di)三種(zhong)工廠里電(dian)(dian)(dian)機(ji)類用(yong)得多，第(di)二種(zhong)用(yong)得少，只有交流電(dian)(dian)(dian)焊機(ji)經常(chang)用(yong)到單相(xiang)(xiang)380伏(fu)電(dian)(dian)(dian)源。