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介绍了利用西门子S7-200系列可编程序控制器(PLC)实现的真空断路器机械寿命试验自动控制,该设备功能完善,操作简便,可靠性好. 相似文献
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针对高速列车真空断路器(VCB)在列车运行中处于频繁开断的状态,开断过程中电弧反复烧蚀触头产生尖端、毛刺、金属蒸汽,扩散的金属蒸汽又使灭弧室真空度降低,首次提出了通过测量VCB在分断不同次数正常电流下接触电阻表征其电寿命的试验方法,并得到了不同分断次数下耐受冲击电压和工频工作电压的特性.研究表明:VCB初期接触电阻随分断次数增加而增加,之后接触电阻基本保持不变;在VCB使用初期瞬态恢复电压不能导致电弧重燃,长期工作后可能导致电弧多次重燃,但即使长期工作后工频工作电压仍不能击穿灭弧室. 相似文献
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A driving restriction policy, as one of the control-and-command rationing measures, is a politically acceptable policy tool to address traffic congestion and air pollution in some countries and cities in the world. Beijing is the first city in China to implement this policy. A one-day-a-week driving restriction scheme was expected to take 20% of cars off the road every week day. Using household survey and travel diary data, we analyze the short-term effect of this driving restriction policy on individual travel mode choice. The data also allow us to identify which demographic groups are more likely to break the restriction rule. The estimates reveal that the restriction policy in Beijing does not have significant influence on individuals’ decisions to drive, as compared with the policy’s influence on public transit. The rule-breaking behavior is constant and pervasive. We found that 47.8% of the regulated car owners didn’t follow the restriction rules, and drove “illegally” to their destination places. On average, car owners who traveled during peak hours and/or for work trips, and whose destinations were farther away from the city center or subway stations, were more likely to break the driving restriction rules. Therefore, Beijing is probably in need of more comprehensive and palatable policy instruments (e.g., a combination of congestion tolls, parking fees, fuel taxes, and high-speed transit facilities) to effectively alleviate traffic congestion and air pollution. 相似文献
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Roberto?MuscariEmail author Andrea Di?Mascio 《Journal of Marine Science and Technology》2003,8(2):61-67
A numerical model for the simulation of two dimensional spilling breaking waves is described. It is derived from a previous model which, in turn, takes its underlying ideas from the Cointe and Tulin theory of steady breakers. With respect to the former model, the present one is local, i.e., the inception, extension, and geometry of the breakers are determined through the local shape of the water surface. The model has been implemented in a RANSE code, which was developed for the simulation of ship flows, through a modification in the boundary conditions. This yields a simple and effective way to reproduce the breakers influence on the underlying flow. The resulting code has been used to simulate the flow past a submerged hydrofoil. The numerical results are compared with those of the previous model and with the experimental data obtained by Duncan. 相似文献
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破碎压实技术能将旧水泥混凝土路面破碎与压实后,直接作为新路面的基层或底基层使用,它在旧水泥混凝土路面改造中有越来越广泛的应用。然而,破碎机械对城镇道路地下管道会产生冲击振动,影响管道的安全。作者以MHB(多锤头破碎)机械为研究对象,分析冲击波的传递规律和面层结构的振动,并给出了振动引起的附加动应力和Steverding... 相似文献
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直流电网发生短路故障时其短路电流巨大,可能超过现有保护设备分断能力,利用超快速开关技术,设计出一种新型的直流短路限流装置,阐述了其工作原理,研制出实验样机,完成了大电流分断实验,实验结果表明该型限流保护装置能有效抑制短路电流。 相似文献
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文章介绍了SS 5机车的TZZ 6型制动电阻装置和TDZ 1A-250/25 A型空气断路器的技术参数、结构特点,以及该型断路器的开断容量试验结果。 相似文献
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本文介绍了几种典型的直流固态断路器拓扑结构,总结了各自的特点,分析了直流固态断路器的应用前景,最后设计了1500V/4000A原理样机的相关参数,并给出了样机分断仿真研究结果。 相似文献
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基于对真空断路器凸轮操作机构的分析,建立了相应的数学模型,并通过所建立的模型,对凸轮机构进行了优化设计。结果表明,所建立的数学模型为真空断路器凸轮操作机构提供了一种有效的优化设计方法。 相似文献