武钢CCPP起动变频器组成及起动工序

武汉钢铁（集团）公司CCPP（燃气-蒸汽联合循环发电）电厂配置两台燃气轮发电机,为提高运行效率,减小起动过程中对设备造成的冲击,都采用变频器进行起动。本文重点研究对起动变频器的选型和工艺要求,介绍在燃气轮机起动过程中起动变频器的工序要求,包括吹扫、盘车、正常起动、重起动、多台机组起动等过程,介绍起动变频器的整体结构和控制器组成,描述燃气轮机起动过程中起动变频器的实际运行工序,给出起动变频器运行过程中的输出实时曲线和特性。武钢CCPP电厂通过采用起动变频器起动发电机,提高了机组运行效率,实现了快速倒机操作,并减小了起动过程中对电网和设备的冲击,提高了电网的利用率。     

连铸机回转台起动性能的分析与研究

根据连铸机回转台的负荷特点以及对起动性能的要求，进行了各工况的负荷计算。分析了传统起动控制方式设计中，参数的选取对起动性能的影响。对较理想的起动运行方式作了推介。     

煤气鼓风机起动过程分析计算

分析了鼓风机的起动过程，给出了起动时间的计算方法，讨论了电压波动和起始静态阻矩对起动过程的影响，以把握煤气鼓风机的开车起动过程。     

感应电动机起动方式的选择

阐述笼型感应电动机全压起动的优点及条件，讨论了影响电动机起动的因素。对几种降压起动方式进行了分析比较，以便合理选择。对绕线转子电动机的起动方式及应用范围进行了说明。     

降补固态软起动装置在风机起动中的应用

对在AV63-15大风机电机起动选用降补固态软起动装置工作原理和技术配置方案进行了简单说明,和其他起动装置在性能上进行了对比。结合厂家技术配置方案和供电系统情况,对起动过程进行了初步的仿真计算。对于计算结果结合现场起动情况,对使用过程中应注意事项进行了说明。     

大功率电机起动过程实践

介绍19000kW大功率电机降压起动原理、热变电阻工作原理和起动特性,分析影响电机起动性能的主要因素;通过起动实践和录制起动曲线,了解热变电阻的实际温度、电网电压等参数对电机起动过程的影响,以期合理地调节参数,优化起动曲线。     

Y-△电机重载起动受阻分析和改善

1987年5月,某轧钢厂一台J02型、55kW、Y-△起动的电动机在起动时,引起变电所总空气开关越级跳闸(起动时,本身保护跳闸回路短接),5分钟后第二次起动仍旧失败。而在脱开轧机(即空载)时,则能正常起动。为此,对起动受阻原因进行了分析,并提出了相应的改善措施。     

高压同步电动机液态软启动及其自动控制

本文介绍了液体软启动的原理,以及使用Ouantum系列PLC实现高压大功率同步电动机起动过程的自动控制,及其运行过程中的自动监控。对比分析了全压起动与降压起动对电网电压及电机的影响。     

浅谈大容量电动机的起动方式

通过实例对大容量笼型电动机的各种起动方式进行比较,明确电动机全压起动、降压起动及变频起动方式的条件及优缺点,以供选择.     

基于DSP的异步电机变频起动技术研究

本文首先分析了船舶辅机中异步电动机的应用现状。并指出了起动过程中存在问题。然后分析了异步电劫机常用的起动技术，指出了其中存在的缺点和不足。最后对变频起动技术展开研究，设计了一种基于DSP的变频起动装置，并编写了调试软件方便参数整定与调试，变频起动技术是一种很有研究价值的技术。     

Translation of the flagellar gene fliO of Salmonella typhimurium from putative tandem starts

The flagellar gene fliO of Salmonella typhimurium can be translated from an AUG codon that overlaps the termination codon of fliN (K. Ohnishi et al., J. Bacteriol. 179:6092-6099, 1997). However, it had been concluded on the basis of complementation analysis that in Escherichia coli a second start codon 60 bp downstream was the authentic one (J. Malakooti et al., J. Bacteriol. 176:189-197, 1994). This raised the possibility of tandem translational starts, such as occur for the chemotaxis gene cheA; this possibility was increased by the existence of a stem-loop sequence covering the second start, a feature also found with cheA. Protein translated from the first start codon was detected regardless of whether the second start codon was present; it was also detected when the stem-loop structure was disrupted or deleted. Translation from the second start codon, either as the natural one (GUG) or as AUG, was not detected when the first start and intervening sequence were intact. Nor was it detected when the first codon was attenuated (by conversion of AUGAUG to AUAAUA; in S. typhimurium there is a second, adjacent, AUG) or eliminated (by conversion to CGCCGC); disruption of the stem-loop structure still did not yield detectable translation from the second start. When the entire sequence up to the second start was deleted, translation from the second start was detected provided the natural codon GUG had been converted to AUG. A fliO null mutant could be fully complemented in swarm assays whenever the first start and intervening sequence were present, regardless of the state of the second start. Reasonably good complementation occurred when the first start and intervening sequence were absent provided the second start was intact, either as AUG or as GUG; thus translation from the GUG codon must have been occurring even though protein levels were too low to be detected. The translated intervening sequence is rather divergent between S. typhimurium and E. coli and corresponds to a substantial cytoplasmic domain prior to the sole transmembrane segment, which is highly conserved; the sequence following the second start begins immediately prior to that transmembrane segment. The significance of the data for FliO is discussed and compared to the equivalent data for CheA. Attention is also drawn to the fact that given an optimal ribosome binding site, AUA can serve as a fairly efficient start codon even though it seldom if ever appears to be used in nature.     

从操作过电压谈高压电机软起动装置的选择

从操作过电压产生机理出发，阐述操作过电压对高压电动机的危害，通过对高压电机在各种情况下操作过电压的探讨分析，指出高压电动机采用传统起动方式存在的问题，分析了高压电动机采用软起动的必要性，通过对当前各种软起动装置的比较，提出了选择依据。     

软启动装置在风机中的应用

随着工业化规模的不断扩大,大容量电机的应用急剧增加。而大容量电机启动时产生的大电流冲击严重影响着工业设备的正常运行和使用寿命。本文主要分析了当今工业中为解决电机启动过程中的大电流冲击问题而产生的软启动装置。简要的介绍了电动机软启动的启动方式,软启动装置的种类和组成以及特点。并结合酒钢烧结厂抽风机简要的介绍了液阻式软启动装置的原理,特点。最后分析了未来软启动的发展方向。     

On negative selection against ATG triplets near start codons in eukaryotic and prokaryotic genomes

The frequencies of ATG triplets in the genomes of various species were systematically analyzed, and the frequency of ATG triplets was significantly low around start codons in both prokaryotic and eukaryotic genomes. In eukaryotes, however, the frequency decrease before the start codon is much more evident than that after the start codon. In prokaryotes, on the other hand, the ATG frequency pattern around the start codon is less evident, and-more importantly-symmetric. We also computed average distances between a start codon and its nearest upstream-located ATG triplet and found a general tendency for the average distances to be longer in higher organisms.     

梅钢4号烧结机主抽风机变频软启动系统

介绍一个采用一台西门子GL150型LC I变频器依次启动两台6 900 kW同步电动机拖动的主抽风机的变频软启动系统。变频器的控制方式为转矩控制,启动方式为分段加速,变频软启动系统通过降压变压器-GL150变频器-升压变压器启动10 kV同步电动机。GL150型变频器采用大功率晶闸管元件,变频软启动系统在启动中通过直接检测定子电压、电流来计算转子位置,不需要外置的测速编码器。采用变频软启动方式启动大型高压电动机,避免了传统的不变频异步启动方式必然带来的电动机电枢发热严重的现象。采用GL150型变频器的变频软启动系统,在整个启动-并网过程中对电动机完全可控,对风机无冲击。     

交流电动机的软起动技术

交流电动机的软起动是一种综合技术，它克服了发鼠笼异步机传统降压起动方式的许多缺点，通过采用软起动器可以实现交流电动机的软起动。本文介绍了交流电动机主要的几种软起动方式以及交流电动机软起动的特点，并指出了软起动器的其他一些应用。     

IF钢开浇阶段铸坯洁净度分析

由于IF钢生产过程中对开浇阶段铸坯质量判定不明确,因此在利用时容易导致产品质量问题而增加生产成本。通过对头坯不同位置进行取样,研究IF钢开浇阶段铸坯沿拉坯方向的洁净度变化。实验结果表明,IF钢开浇阶段铸坯中大型夹杂物主要来源于结晶器卷渣和中间包中来不及上浮的脱氧或二次氧化产物;从距离头坯头部2.5m位置开始,由结晶器卷渣所引入的大型夹杂物含量接近正常坯水平;距离头坯头部7.5m位置处开始N含量与正常坯含量基本持平,簇状Al_2O_3夹杂物数量及尺寸接近正常坯水平;距离头坯头部8.5m位置处开始全氧质量分数保持在20×10~(-6)左右。     

Where am I? Distal cues use requires sensitivity to start location change in the rat.

Place learning is impaired when a single plus maze is moved between adjacent locations 33-120 cm apart. This maze translation creates distinct start locations but maintains a single goal location with respect to distal cues. Hippocampal cell recording data suggest the majority of place fields are tied to apparatus boundaries, not to distal cues, when an apparatus is moved these distances to the left or right. Thus, rats may fail to appreciate the existence of multiple start locations with respect to distal cues when the maze is moved in this way and their start location on the surface is constant. Performance on the single plus maze problem was improved when texture cues were correlated with different start locations. Place learning was supported when multiple start locations were provided on a single large surface (double plus maze), even though rats did not explore the entire surface. Place learning was also supported when random extensions were added to a double plus maze such that start locations, relative to surface boundaries, were not informative as to goal location. This outcome suggests sensitivity to multiple start locations is required for distal cue use in translational place problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

高碳帘线钢72A连续冷却转变(CCT)的特性

采用热膨胀法,通过THERMECMASTOR-Z热模拟实验机测试了高碳帘线钢72A(%:0.72C、0.53Mn、0.22Si)的连续冷却转变(CCT)曲线,并分析了开始冷却温度(840～930℃)和冷却速度(0.8～22℃/s)对钢组织的影响。结果表明,相同开始冷却温度条件下,冷却速度越快,相变时间越短;相同冷速条件下,随着开始冷却温度的升高,到达相变开始转变温度的时间和到达转变终了温度的时间会延后;提高开始冷却温度,珠光体的百分含量增加,珠光体片层间距减少,有利于提高线材力学性能。     

宝钢1450板坯连铸中间包自动开浇过程控制技术

提出了中间包自动开浇控制的两个阶段.介绍了宝钢1450板坯连铸中间包自动开浇技术的发展及粘合式开浇管的开发;阐述了自动开浇的理论计算、硬件配置和系统流程,通过试验,找到了软件设置的要点以及对硬件管理的要求,在自动控制精度上取得了突破.