Fuji变频调速器起动跳闸问题的解决

比较详细地介绍了Fuji变频调速器起动过程中跳闸问题的解决过程。     

船舶轴带发电机自动合闸及动力负荷自起动设计

在论述船舶轴带发电机DW98断路器的跳闸和合闸特性的基础上,设计了当因负载故障跳闸时通过PC控制选择性地自动合闸,及当船舶动力负荷恢复供电后又能自起动的综合系统,该设计具有很好的实用性．     

使用新型延时器件的星/三角起动线路

船舶电网需要有效地控制起动电流,本文讨论了一种使用新型延时器件的星／三角起动线路,该线路能够可靠地完成星形线路到三角线路的转换,抑制“飞弧短路”的出现。     

三相异步电动机自耦变压器降压起动控制电路分析

为减小大容量三相异步电动机的起动电流,常用自耦变压器进行降压起动,然而,在实际使用过程中,却出现了自耦变压器的烧毁以及过电流导致空气开关跳闸的现象。作者在实践中对此进行了改进,消除了这种现象。     

某船舵机启动箱断路器跳闸故障 分析及排除

针对某船舵机启动箱断路器频繁跳闸的故障现象,对断路器自身状态、电机正常起动时的电流冲击、电机瞬间断电再上电及电网压降等因素进行了分析,给出了有效的解决方案。为今后此类问题的解决及相关设计提供借鉴和参考。     

“霸王岭”轮主空压机防主触头熔焊故障电路的设计

根据某轮主空压机电机主电路主触头经常熔焊,而又经常引起主配电板总开关跳闸这一严重故障现象,设计一个双主触头短延时先后接通或断开的保护电路,从根本上解除了该熔焊故障的危害。     

主空压机防主触头熔焊故障电路的设计

根据“霸王岭”轮主空压机电机主电路主触头经常熔焊,而又经常引起总配电板主开关跳闸这一严重故障现象,设计一个短延时先后接通或断开的保护电路,从而解除了该熔焊故障的危害,为确定双主触头运行时主触点熔焊状态,设计一个指示电路便于维护。     

一种大功率逆变电源的软起控制方法

大功率逆变电源的母线电容较大,直接起动会产生较大的冲击电流,会导致器件损坏、断路器跳闸保护,因此必须进行软起动。基于绝缘栅双极性型晶体管的输出特性,提出了一种新的大功率逆变电源软起控制方法,通过控制绝缘栅双极性型晶体管的驱动电压,自动调节绝缘栅双极性型晶体管的导通电阻来限制冲击电流,实现软起动的功能。研制了一台原理样机,试验验证了该控制方法的可行性和先进性。     

船用柴油机起动空气管系零部件设计分析

根据MAN、Wrtsil柴油机起动空气管系零部件的设计特点,重点阐述起动空气管系的设计压力、管子选用、法兰选型、压力试验和防爆片设计计算,并对起动阀螺母拧紧方法及起动空气管系安全装置进行了分析,提出了起动空气管系设计的一些注意事项。     

某船柴油主机空气起动异常的研究及修理

针对某船柴油主机空气起动出现的异常问题,对空气起动系统和配气定时进行研究。了解起动系统组成及部件功能,分析起动异常的可能原因,提出相应的解决方案;校核起动系统供气能力、检查管路阀件密性,确保起动次数满足船检规范要求;研究进气相位特点和空气分配器结构,熟悉配气原理,掌握配气规律;研究正倒车配气定时,检查进气起动相位,调整起动凸轮位置并周向、轴向固定,解决因起动凸轮配气定时错误引起的空气起动异常问题。修理结果表明有关研究和分析可行有效,可供同行借鉴。     

海洋工程船推进电动机的启动方式探讨

结合武昌船舶重工有限责任公司制造的一系列海洋工程船的推进装置电动机的启动方案,总结船用交流大功率电动机的启动方式,比较自耦变压器、软启动和变频启动方式的优缺点及应用范围。     

三相永磁无刷电机起动控制研究

本文分析了的120°导通三相逆变器的SVPWM控制特性,提出了基于SVPWM控制和电流调节控制的无位置传感器的三相永磁无刷直流电机（BLDCM）的起动控制方法。在Matlab/Simlink环境下,建立了三相永磁BLDCM起动控制系统的仿真模型并进行了仿真。仿真结果表明该起动控制方法不但能有效控制起动电流大小,而且能改...     

三相逆变器供电单相永磁同步电动机的起动性能分析

本文对采用三相逆变器供电的单相永磁同步电动机变频起动过程的转矩进行了深入的分析,提出了用于单相永磁同步电动机变频起动分析的简化等值电路,分别用拟稳态法和简化等值电路法计算了单相永磁同步电动机变频起动过程中的异步起动转矩,两者计算结果相一致,证明了该简化等值电路法的正确性。根据简化等值电路法推出了变频起动时保证最大异步转矩保持恒定的完全补偿法,用拟稳态法计算了采用完全补偿法变频起动时的异步转矩和平均转矩,验证了完全补偿法的正确性。     

Numerical simulation of flow around a smooth circular cylinder at very high Reynolds numbers

High Reynolds number flows (Re = 1 × 10⁶, 2 × 10⁶ and 3.6 × 10⁶, based on the free stream velocity and cylinder diameter) covering the supercritical to upper-transition flow regimes around a two-dimensional (2D) smooth circular cylinder, have been investigated numerically using 2D Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with a standard high Reynolds number k ? ? turbulence model. The objective of the present study is to evaluate whether the model is applicable for engineering design within these flow regimes. The results are compared with published experimental data and numerical results. Although the k ? ? model is known to yield less accurate predictions of flows with strong anisotropic turbulence, satisfactory results for engineering design purposes are obtained for high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. Re > 10⁶. This is based on the comparison with published experimental data and numerical results.     

Modelling the ecosystem dynamics of the Barents Sea including the marginal ice zone: II. Carbon flux and interannual variability

An upgraded and revised physically–biologically coupled, nested 3D model with 4 km grid size is applied to investigate the seasonal carbon flux and its interannual variability. The model is validated using field data from the years for which the carbon flux was modelled, focussing on its precision in space and time, the adequacy of the validation data, suspended biomass and vertical export. The model appears to reproduce the space and time (± 1 week and 10 nautical miles) distribution of suspended biomass well, but it underestimates vertical export of carbon at depth. The modelled primary production ranges from 79 to 118 g C m^− 2 year^− 1 (average 93 g C m^− 2 year^− 1) between 4 different years with higher variability in the ice-covered Arctic (± 26%) than in the Atlantic (± 7%) section. Meteorological forcing has a strong impact on the vertical stratification of the regions dominated by Atlantic water and this results in significant differences in seasonal variability in primary production. The spatially integrated primary production in the Barents Sea is 42–49% greater during warm years than the production during the coolest and most ice-covered year.     

托辊皮带机起动过程仿真研究

建立模拟托辊皮带机起动过程的数学模型,进行仿真研究,并通过实例分析计算,着重探讨减速比和液力耦合器限制扭矩的取值对皮带机起动过程的影响,指出降压起动时电机的负载状态和液力耦合器的工作条件优于直接起动时.     

对一起应急发电机启动失败的特别关注

文章通过一个应急发电机启动失败的实际案例,结合《国际海上人命安全公约》中对于应急发电机启动方式的要求,剖析该典型应急发电机启动控制系统设计所存在的缺陷,同时分析可行的解决方案。旨在为应急发电机启动系统的设计提供参考。     

Synoptic transects on the distribution of trace elements (Hg,Pb, Cd,Cu, Ni,Zn, Co,Mn, Fe,and Al) in surface waters of the Northern- and Southern East Atlantic

Surface seawater samples were taken in the framework of the GEOTRACES program on “POLARSTERN” expedition ANT XXIII/1 in the Eastern Atlantic in 2005 to study the distribution of the trace elements Hg (mercury), Pb (lead), Cd (cadmium), Cu (copper), Ni (nickel), Zn (zinc), Co (cobalt), Mn (manganese), Fe (iron), and Al (aluminium). With the exception of Hg, results were compared to earlier datasets from 1989 to 1990. The particulate fraction averaged over the transect was calculated to be 49% for Cd, 23% for Mn and 50% for Fe indicating a release of these TEI's (trace elements and their isotopes) from a leachable SPM fraction in the stored and acidified samples.Total Pb concentrations ranged between 5 and 20 pmol kg^? 1 in 2005 with highest values in the ITCZ (intertropical convergence zone). In 1989 Pb concentrations were twice as high in the region of the ITCZ, while by a factor of 10–15 higher values were obtained in the North Atlantic.Total Cd and Co are dominated, by different seasonal upwelling regimes (Equatorial upwelling, Guinea Dome, Angola Dome).Total Cu, Ni, Fe, Mn and Al show nearly identical concentrations in 1990 and 2005. For total manganese and aluminium strong maxima (3–4 nmol kg^? 1 and 55 nmol kg^? 1 respectively) are observed between 23°N and 0°, while the Fe maximum (6–9 nmol kg^? 1) is located at 7°N. Total Hg concentrations ranged between 0.5 and 4.5 pmol kg^? 1.     

Density-dependent effects on seston dynamics and rates of filtering and biodeposition of the suspension-cultured scallop Chlamys farreri in a eutrophic bay (northern China): An experimental study in semi-in situ flow-through systems

Effects of stocking density on seston dynamics and filtering and biodeposition by the suspension-cultured Zhikong scallop Chlamys farreri Jones et Preston in a eutrophic bay (Sishili Bay, northern China), were determined in a 3-month semi-field experiment with continuous flow-through seawater from the bay. Results showed that the presence of the scallops could strongly decrease seston and chlorophyll a concentrations in the water column. Moreover, in a limited water column, increasing scallop density could cause seston depletion due to scallop's filtering and biodeposition process, and impair scallop growth. Both filtration rate and biodeposition rate of C. farreri showed significant negative correlation with their density and positive relationship with seston concentration. Calculation predicts that the daily removal of suspended matter from water column by the scallops in Sishili Bay ecosystem can be as high as 45% of the total suspended matter; and the daily production of biodeposits by the scallops in early summer in farming zone may amount to 7.78 g m^− 2, with daily C, N and P biodeposition rates of 3.06 × 10^− 1, 3.86 × 10^− 2 and 9.80 × 10^− 3 g m^− 2, respectively. The filtering and biodeposition by suspension-cultured scallops could substantially enhance the deposition of total suspended particulate material, suppress accumulation of particulate organic matter in water column, and increase the flux of C, N and P to benthos, strongly enhancing pelagic–benthic coupling. It was suggested that the filtering-biodeposition process by intensively suspension-cultured bivalve filter-feeders could exert strong top-down control on phytoplankton biomass and other suspended particulate material in coastal ecosystems. This study also indicated that commercially suspension-cultured bivalves may simultaneously and potentially aid in mitigating eutrophication pressures on coastal ecosystems subject to anthropogenic N and P loadings, serving as a eutrophic-environment bioremediator. The ecological services (e.g. filtering capacity, top-down control, and benthic–pelagic coupling) functioned by extractive bivalve aquaculture should be emphasized in coastal ecosystems.     

舰船大负载起动电网瞬态电压降计算和分析

介绍了根据感应电动机电抗、感应电动机起动电流及起动千伏安等常用电网瞬态压降计算方法,分析比较了直接起动、星形-三角形起动及自耦变压器补偿起动等舰船电力系统常用三种起动方式的优、缺点,并以实例计算三种起动方式时的电网瞬态电压降,指出了根据计算的电网瞬态电压降,选择合适起动方式,控制舰船用大容量电力负载起动对电网的影响。