活塞支撑杆测量仪的设计

活塞支撑杆测量仪的设计及应用,代替了传统的测量法,实现了不同种类大批量支撑杆快速测量,降低了工人的劳动强度,提高了测量的准确性及活塞盐芯的位置精度,减少了测量时间,提高了生产效率。     

棉纺行业设备节能探讨

<正> 近几年来,节能工作在棉纺行业已引起了足够的重视,通过认真宣传和贯彻国务院《节约能源管理暂行条例》,提高了广大干部职工的节能意识。相继成立了专职节能机构,建立了能源管理制度,狠抓了节能基础管理工作,加强了能源统计,实行了定额考核,开展了企     

复合式空气干燥器在压缩空气后处理中的成功应用

文中简单介绍了复合式空气干燥器的特点和在压缩空气后处理中的使用情况,并证明使用了该干燥器后,保证了净化风的质量,从而确保了全厂装置的安全用风,有效降低了能耗,取得了显著的经济效益,同时也提出了以后改进发展的方向。     

750 kV两站两线科研项目管理

针对兰州超高压输变电公司科研项目管理模式进行了研究与分析,提出了科研项目分解的方案,通过本方案明确了基本课题,可以较为全面、系统指导科研工作的开展,增强了科研项目实施的可操作性。构建了矩阵式科研项目管理组织结构,优化配置了公司各科研资源,明确了科研项目的各主要责任主体。确立了科研项目管理流程,做到闭环控制,加强了科研项目过程管理。     

有限元弹性动力分析与优化在某气门机构中的应用

对某发动机气门机构建立了混合刚体-弹性体的参数化非线性有限元模型,进行了弹性动力学计算。通过回归方程对模型进行了优化,降低了摇臂的质量,在保证摇臂强度的同时改善了凸轮-滚子的接触性能,从而降低了磨损,提高了耐久性。     

实施PDM系统为企业带来的价值

阐述了PDM系统的功能,现代企业利用该系统对数据进行分类管理,缩短了新产品开发周期,降低了产品成本,提高了企业的管理能力,促进了企业的发展.     

棉纺行业设备节能探讨

近几年来,节能工作在棉纺行业,已引起了足够的重视。通过认真宣传和贯彻国务院《节能条例》,提高了广大干部职工的节能意识,建立了专职节能机构,健全了能源管理制度,加强了节能基础管理工作,实行定额考核目标管理,开展了企业能量平衡工作,以及实行了不同形式的用能承包经济责任制,均取得了显著的节能效果。因此,摆在棉纺企业面前的重要任务是如何将企业的     

低压终端隔离开关的可靠性改进

分析了传统低压终端隔离开关的结构特点、存在的可靠性问题,并针对此提出了一种改进的结构。改进方案简化了产品电路机构,解决了触头运动不平衡问题,改进了触头烧损问题。并采用快速闭合机构和引弧角,大大减少了电弧产生,显著减小了隔离开关的熔焊问题,从而提高了隔离开关的可靠性和使用寿命。     

300MW煤粉煤气混烧发电锅炉的节能研究

某钢铁公司发电厂通过建设300MW的煤粉煤气混烧发电机组,充分利用钢铁厂生产过程中产生的大量富裕高炉煤气和焦炉煤气,进行煤、气混烧发电,基本杜绝了高炉煤气的放散,有效利用了低热值的二次能源,而且保证了发电负荷的稳定,为企业提供了供电保证,达到了节能、减排、保障供电的目标,实现了钢铁工业和发电行业的有机结合,践行了循环经济理念,取得了良好的经济效益和环保效益。     

超临界600MW等级汽轮机高中压整体内缸研究

主要介绍了上海汽轮机厂超临界600MW等级汽轮机高中压整体内缸技术方案。新型内缸整合了高中压模块的主要部套,改善了高、中压平衡活塞结构,改变了喷嘴连接形式,优化了蒸汽室型线,并通过CAE分析严格考核了恶劣工作环境下内缸的强度、刚度、密封及蠕变特性。实践表明,新的结构使机组高中压模块得到了精简,缩短了安装检修工期,降低了工艺成本,极大地提高了机组运行的经济性。     

晶闸管中频电源倍压式负载电路的设计计算

本文介绍了晶闸管中频电源倍压式谐振负载电路的基本原理、电压关系、工作频率、谐振元件参数设计计算。经过实践，基本上与实际相符，可作为并联式谐振、倍压式谐振负载电路的工程设计计算方法选用。     

新型晶闸管逆变电桥的分析计算

介绍一种新型晶闸管中频感应电炉的逆变电桥，分析了对该电桥逆变晶闸管采用阻容保护电路的必要性。建立了该阻容保护电路中电容电压的二阶微分方程，解出电压随时间变化关系，推导出逆变晶闸管上的电压上升率，为元件参数的选择提供了依据。     

A solid state direct on line starter for medium voltage inductionmotors with minimized current and torque pulsations

This paper describes a thyristorized static switch which is designed and implemented specifically for frequent direct-on-line starting of medium voltage large induction motors. The circuit configuration chosen utilizes back-to-back connected series thyristor strings on two of the supply lines. Both the starting current and the torque pulsations of the induction motor are minimized by a controlled, nonsimultaneous switching of motor phases to the supply. This reduces the electrical stresses on the power system and the mechanical stresses on the shaft as compared to conventional switching elements. The optimum switching strategy is found by the use of a hybrid mathematical model in ABC/dqO form. The validity of the results obtained for medium voltage, squirrel-cage induction machine are verified by the use of a physical simulator consisting of a low voltage, small induction machine and a shaft torque measuring system. The system has been in operation successfully in an iron and steel plant since 1991     

一种高性能快速晶闸管串联使用保护技术及其应用

在中频电源领域,由于晶闸管的开关频率高,在关断过程中,产生很大的反向di/dt,严重威胁器件的安全.由于国外生产的快速晶闸管性能高,能承受比较高的dv/dt、di/dt;而国内dv/dt最高达500 V/μs、di/dt达200A/μs、tq：12μs.所以,一般RC吸收回路在国产中频电源中的保护就显得有些欠缺.介绍了一种快速晶闸管换相缓冲技术的设计原理,及其在国产中频并联谐振逆变器的应用.实践证明,该技术可改善多个串联快速晶闸管的动态均压特性,能有效地保证国产快速晶闸管在中频电源中的稳定运行.     

Voltage and Frequency Controller for a Three-Phase Four-Wire Autonomous Wind Energy Conversion System

This paper deals with control of voltage and frequency of an autonomous wind energy conversion system (AWECS) based on capacitor-excited asynchronous generator and feeding three-phase four-wire loads. The proposed controller consists of three single-phase insulated gate bipolar junction transistor (IGBT)-based voltage source converters (VSCs) and a battery at dc link. These three single-phase VSCs are connected to each phase of the generator through three single-phase transformers. The proposed controller is having bidirectional flow capability of active and reactive powers by which it controls the system voltage and frequency with variation of consumer loads and the speed of the wind. VSCs along with transformer function as a voltage regulator, a harmonic eliminator, a load balancer, and a neutral current compensator while the battery is used to control the active power flow which, in turn, maintains the constant system frequency. The complete electromechanical system is modeled and simulated in the MATLAB using the Simulink and the power system blockset (PSB) toolboxes. The simulated results are presented to demonstrate the capability of the proposed controller as a voltage and frequency regulator, harmonic eliminator, load balancer, and neutral current compensator for different electrical (varying consumer loads) and mechanical (varying wind speed) dynamic conditions in an autonomous wind energy conversion system.     

Characterization methods and modelling of ultracapacitors for use as peak power sources

This paper suggests both a methodology to characterize ultracapacitors and to model their electrical behaviour. Current levels, frequency intervals, and voltage ranges are adapted to ultracapacitors testing. Experimental data results in the determination of the ultracapacitors performances in terms of energy and power densities, the quantification of the capacitance dependence on voltage, and the modelling of the dynamic behaviour of the device. Then, an electric model is proposed taking into account the ultracapacitors characteristics and their future use as peak power source for hybrid and electric vehicles. After, the parameters identification procedure is explained. Finally, the model validation, both in frequency and time domains, proves the validity of this methodology and the performances of the proposed model.     

Wind farm—A power source in future power systems

The paper describes modern wind power systems, introduces the issues of large penetration of wind power into power systems, and discusses the possible methods of making wind turbines/farms act as a power source, like conventional power plants in power systems. Firstly, the paper describes modern wind turbines and wind farms, and then introduces the wind power development and wind farms. An optimization platform for designing electrical systems of offshore wind farms is briefed. The major issues related to the grid connection requirements and the operation of wind turbines/farms in power systems are illustrated.     

An optimized SVPWM switching strategy for three-level NPC VSI and a novel switching strategy for three-level two-quadrant chopper to stabilize the voltage of capacitors

Voltage source inverter (VSI) can produce single and three-phase (3P) AC voltages from a constant or variable DC voltage. There are many ways to control the VSI output voltage. Each control way produces some harmonics at the VSI output voltage. The space vector pulse width modulation (SVPWM) may be more effective than other modulation methods, e.g. harmonic injection, phase shifting, multi career pulse width modulation, in decreasing the low order harmonics (LOH). Different switching strategies (SSs) of power electronic devices in SVPWM have some specific advantages and disadvantages with regard to one another. In this paper, a comparative study between different SVPWM SSs is carried out by considering some objective functions such as total harmonic distortion (THD), power and switching losses, the ratio of the harmonic components to the fundamental component, distortion factor (DF). It is also shown that by selecting an optimized and appropriate SS for SVPWM, the harmonic orders, which are the multiples of the frequency index (FI), are eliminated. Then, to investigate the impact of variations of the capacitors voltage and switching frequency on power quality criteria, the most appropriate and optimized SS is applied to a 3P three-level (3L) neutral-point-clamped (NPC) VSI to supply a 3P load.     

An improved thermal and electrical model for a solar photovoltaic thermal (PV/T) air collector

In this paper, an attempt is made to investigate the thermal and electrical performance of a solar photovoltaic thermal (PV/T) air collector. A detailed thermal and electrical model is developed to calculate the thermal and electrical parameters of a typical PV/T air collector. The thermal and electrical parameters of a PV/T air collector include solar cell temperature, back surface temperature, outlet air temperature, open-circuit voltage, short-circuit current, maximum power point voltage, maximum power point current, etc. Some corrections are done on heat loss coefficients in order to improve the thermal model of a PV/T air collector. A better electrical model is used to increase the calculations precision of PV/T air collector electrical parameters. Unlike the conventional electrical models used in the previous literature, the electrical model presented in this paper can estimate the electrical parameters of a PV/T air collector such as open-circuit voltage, short-circuit current, maximum power point voltage, and maximum power point current. Further, an analytical expression for the overall energy efficiency of a PV/T air collector is derived in terms of thermal, electrical, design and climatic parameters. A computer simulation program is developed in order to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. Since some corrections have been down on thermal and electrical models, it is observed that the thermal and electrical simulation results obtained in this paper is more precise than the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency and overall energy efficiency of PV/T air collector is about 17.18%, 10.01% and 45%, respectively, for a sample climatic, operating and design parameters.     

Fuel cell early markets: Techno-economic feasibility study of PEMFC-based drivetrains in materials handling vehicles

The current benchmark technology for electric materials handling vehicles uses lead-acid batteries as power source that cause productivity, space and safety issues. This paper evaluates, from a technical and economical point of view, the feasibility of using hydrogen fueled PEMFC as an alternative power source for the forklift drivetrain. The reduction in idle time thanks to lower refueling time and constant power generation have been acknowledged to impact the productivity related costs in such way that the fuel cell option shows better financial results for medium to big fleets, operating three working shifts per day, and using market hydrogen or onsite natural gas reforming. Net present values over 450,000 $ and internal rates of return over 30% for several scenarios bear witness to it. However, a complementary sensitivity analysis has shown important variations in the results that suggest case-by-case analysis before considering the investment.