Mike Krzyzewski is really a famous coach of Dream Team. She has coached north america men's basketball team for some time, that's clinched numerous medals for his country. Following Londonfl jerseys supplyn Olympic was over, Krzyzewski told The Associated Press that this game will be his final one as national coach, a job he's held for seven years. He had left open the possibility of swomen nfl jerseystaying with the team beyond the London Games, when practice on Saturday said these will be his last Olympics.When asked if he was sure, Krzyzewski didn't hesitate before again saying, "yecheap nfl jerseys wholesales," this will be his last game "If we could win it, then it might be three major championships in a row, i always do not know when that has been done because we haven't usually won http://govoriotkrito.bg/libs/nflcn08.htmthe globe championships," Krzyzewski said. "It becomes an enormous thing for the program." Whatever, he's an awesome coach. His achievement are going to be remembered by the country.cheap nfl jerseys

        電力變壓器

        2019/9/3 8:30:54      點(diǎn)擊:

        電力變壓器是一種靜止的電氣設(shè)備,是用來將某一數(shù)值的交流電壓(電流)變成頻率相同的另一種或幾種數(shù)值不同的電壓(電流)的設(shè)備。當(dāng)一次繞組通以交流電時(shí),就產(chǎn)生交變的磁通,交變的磁通通過鐵芯導(dǎo)磁作用,就在二次繞組中感應(yīng)出交流電動(dòng)勢。二次感應(yīng)電動(dòng)勢的高低與一二次繞組匝數(shù)的多少有關(guān),即電壓大小與匝數(shù)成正比。主要作用是傳輸電能,因此,額定容量是它的主要參數(shù)。額定容量是一個(gè)表現(xiàn)功率的慣用值,它是表征傳輸電能的大小,以kVA或MVA表示,當(dāng)對(duì)變壓器施加額定電壓時(shí),根據(jù)它來確定在規(guī)定條件下不超過溫升限值的額定電流。較為節(jié)能的電力變壓器是非晶合金鐵心配電變壓器,其最大優(yōu)點(diǎn)是,空載損耗值特低。最終能否確?蛰d損耗值,是整個(gè)設(shè)計(jì)過程中所要考慮的核心問題。當(dāng)在產(chǎn)品結(jié)構(gòu)布置時(shí),除要考慮非晶合金鐵心本身不受外力的作用外,同時(shí)在計(jì)算時(shí)還須精確合理選取非晶合金的特性參數(shù)。

        電力變壓器是發(fā)電廠和變電所的主要設(shè)備之一。變壓器的作用是多方面的不僅能升高電壓把電能送到用電地區(qū),還能把電壓降低為各級(jí)使用電壓,以滿足用電的需要?傊龎号c降壓都必須由變壓器來完成。在電力系統(tǒng)傳送電能的過程中,必然會(huì)產(chǎn)生電壓和功率兩部分損耗,在輸送同一功率時(shí)電壓損耗與電壓成反比,功率損耗與電壓的平方成反比。利用變壓器提高電壓,減少了送電損失。
        變壓器是由繞在同一鐵芯上的兩個(gè)或兩個(gè)以上的線圈繞組組成,繞組之間是通過交變磁場而聯(lián)系著并按電磁感應(yīng)原理工作。變壓器安裝位置應(yīng)考慮便于運(yùn)行、檢修和運(yùn)輸,同時(shí)應(yīng)選擇安全可靠的地方。在使用變壓器時(shí)必須合理地選用變壓器的額定容量。變壓器空載運(yùn)行時(shí),需用較大的無功功率。這些無功功率要由供電系統(tǒng)供給。變壓器的容量若選擇過大,不但增加了初投資,而且使變壓器長期處于空載或輕載運(yùn)行,使空載損耗的比重增大,功率因數(shù)降低,網(wǎng)絡(luò)損耗增加,這樣運(yùn)行既不經(jīng)濟(jì)又不合理。變壓器容量選擇過小,會(huì)使變壓器長期過負(fù)荷,易損壞設(shè)備。因此,變壓器的額定容量應(yīng)根據(jù)用電負(fù)荷的需要進(jìn)行選擇,不宜過大或過小。
        99热这里只有精品色综合,2018AV无码视频在线播放,国产美女一级a爱,久久人人超碰精品CAOPOREN 看国产精品美女黄片 日本熟妇牲交视频在线观看,国产在线播放99,国产一级无码视频,国产在线观看添荫蒂视频|www.tjnx.com.cn/ 日本熟妇牲交视频在线观看,国产在线播放99,国产一级无码视频,国产在线观看添荫蒂视频|www.zzshanglu.com http://www.tjnx.com.cn/ http://www.zzshanglu.com