三相電加熱管

        380伏(fu)三(san)相四線(xian)電(dian)(dian)(dian)路中，任(ren)意兩根火線(xian)之間的電(dian)(dian)(dian)壓都是380伏(fu)，任(ren)意一根火線(xian)與零線(xian)之間都可(ke)以組成220伏(fu)。這個系統可(ke)以形成三(san)種(zhong)電(dian)(dian)(dian)源(yuan)：即單(dan)相220伏(fu)電(dian)(dian)(dian)源(yuan)，單(dan)相380伏(fu)電(dian)(dian)(dian)源(yuan)，三(san)相380伏(fu)電(dian)(dian)(dian)源(yuan)，第(di) I 種(zhong)家用(yong)比較多，第(di)三(san)種(zhong)工廠(chang)里電(dian)(dian)(dian)機類用(yong)得多，第(di)二種(zhong)用(yong)得少，只有交流電(dian)(dian)(dian)焊機經常(chang)用(yong)到單(dan)相380伏(fu)電(dian)(dian)(dian)源(yuan)。