三相電加熱管

        380伏(fu)三相(xiang)(xiang)四線(xian)電(dian)路中，任意兩根(gen)火線(xian)之間的電(dian)壓都(dou)是(shi)380伏(fu)，任意一根(gen)火線(xian)與零(ling)線(xian)之間都(dou)可(ke)(ke)以(yi)組成(cheng)220伏(fu)。這個系統(tong)可(ke)(ke)以(yi)形(xing)成(cheng)三種(zhong)(zhong)電(dian)源(yuan)：即單相(xiang)(xiang)220伏(fu)電(dian)源(yuan)，單相(xiang)(xiang)380伏(fu)電(dian)源(yuan)，三相(xiang)(xiang)380伏(fu)電(dian)源(yuan)，第(di) I 種(zhong)(zhong)家用(yong)(yong)比較多，第(di)三種(zhong)(zhong)工廠(chang)里電(dian)機(ji)類用(yong)(yong)得多，第(di)二種(zhong)(zhong)用(yong)(yong)得少，只有交流電(dian)焊機(ji)經常用(yong)(yong)到單相(xiang)(xiang)380伏(fu)電(dian)源(yuan)。