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

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              選購真空斷路器的要點

              2013/11/18 12:46:25      點擊:
                  目前真空開關在國內外各個領域得到了廣泛的應用,隨著真空開關使用的普及和提高,廣大用戶愈來愈急需了解和掌握真空開關的原理、結構、使用和維護等方面的知識。

              一、觸頭接觸行程
                觸頭接觸行程的選擇必須保證觸頭在磨損后仍能保持一定的壓力;在分閘時使動觸頭獲得一定的初始動能,提高開關的初始分閘速度,拉斷熔焊點,減小燃弧時間,提高介質恢復速度;在合閘時能利用觸頭彈簧得到平滑的緩沖,減小彈跳。
                開關的接觸行程太小,不能保證觸頭在燒毀后具有的觸頭壓力,開關的初始速度太小,影響真空斷路器的開斷和動熱穩定性,同時產生嚴重的合閘彈振。開關的接觸行程太大,將增加操作機構的合閘功,或者使合閘變的極不可靠。通常真空斷路器的觸頭接觸行程一般取額定開距的20%~40%,10kV真空斷路器的接觸行程一般取3~4mm。
              二、額定開距
                真空斷路器處于分閘狀態時,真空開關管動、靜觸頭之間的距離選擇與真空斷路器的額定電壓、使用條件、開斷電流的性質及觸頭材料、真空間隙的耐壓強度等因素有關,主要取決于額定電壓和觸頭材料。
                由于真空開關管的額定開距對絕緣性能的影響較大,當額定開距從零開距增大時,其絕緣水平也將提高,但當開距增大到一定數值時,開距對絕緣性能的影響就不大了,若進一步增大開距,將嚴重影響開關管的機械壽命。

              永久免费的无码中文影视
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