Ten MVA air-gap armature winding: thermal, structural anddielectric results

This paper describes the armature winding built as part of MIT's 10 MVA superconducting generator project. The winding has a helical winding form, is an air-gap winding having no iron teeth in the active region, employs a limited voltage gradient insulation scheme and is cooled by an insulating fluid. Structurally, the winding employs bonded joints between the conductors and structural tubes, which are of filament-wound fiber-reinforced plastic. Preliminary tests indicated that thermal performance of this winding was satisfactory. On the other hand, the winding suffered a catastrophic insulation failure after only a short time at high voltage. The resulting fault gave the structural system of the armature winding (and the rest of the machine) a good test. In this paper the authors review the major aspects of the design of the winding, describe the thermal tests and then tell of the insulation failure. They can, at best, speculate about the cause of that failure, but they can, on the basis of this experience, make recommendations for further development of machines of this type     

Performance evaluations of 50 MVA airgap winding stator forsuperconducting generator

Structural features of a trial-manufactured air-gap winding stator for a 50 MVA superconducting generator and results of various characteristic tests are described. The stator has an improved winding section, strengthened against electromagnetic force and smaller due to use of a four-layer water-cooled helical air-gap armature winding. The axial flux through the stator core, assumed to be generated by the circumferential current of the helical winding, is too low to pose any practical problems, as shown by a three-dimensional magnetic-field analysis taking into account the magnetic anisotropy due to the laminated iron core. The air-gap armature winding electromagnetic force in the radial and axial directions (which does not contribute to the generator output) increases when the running power factor decreases. The helical winding is shown to be applicable to the armature winding of large superconducting generators     

Rotor design of a 1000 MW superconducting generator

A conceptual rotor design was developed for a 1000 MW superconducting generator having a high-initial-response excitation system. Field winding design, magnetic field analysis of the field winding, and loss calculations and force and stress analyses for the rotor body were carried out. The results are as follows: (1) the operating point of the field winding at the transient state is 72% of the short sample characteristics; (3) the stress in the rotor teeth at the steady state is 405 Pa; and (4) high initial response excitation can cause quenching of the field winding, so the shaft should have a higher resistivity. The maximum flux density at the field winding end region can be small due to optimum magnetometer force distribution     

Development status of superconducting motors

The article gives a brief history of the development of superconducting motors with emphasis on the use of high temperature superconductors. At present, effort is directed toward the demonstration of a 1000 hp HTS motor, the test of which will mark another significant milestone in HTS motor development. For the first time, a closed-loop refrigeration system will be used to maintain an operating temperature near 30 K for the HTS field winding. Following the conclusion of the 1000 hp HTS motor project, a 5000 hp HTS motor will be constructed and tested to demonstrate its economical viability. The progress in developing HTS motors to date is shown. The rotor for the 1000 hp motor was designed to accommodate other coils and can provide a test bed for wire developed in the future     

Application of superconducting magnetic energy storage unit toimprove the damping of synchronous generator

A systematic approach to the design of a controller for superconducting magnetic energy storage (SMES) units to improve the dynamic stability of a power system is presented. The scheme employs a proportional-integral (PI) controller to enhance the damping of the electromechanical mode oscillation of synchronous generators. The parameters of the PI controller are determined by the pole assignment method based on modal control theory. Eigenvalue analysis and nonlinear computer simulations show that SMES with the PI controller can greatly improve the damping of the system under various operating conditions. Although the PI controller is designed for a special load condition, it can also provide good damping under other load conditions     

Conceptual design of coupled nonequilibrium disk MHD generator and superconducting magnet system

The authors propose a new conceptual design method for a coupled nonequilibrium disk MHD generator and superconducting magnet system. At first, a generator with constant magnetic flux density is conceptually designed by using the new generator design method recently developed by the authors, and several superconducting magnets suitable for the generator are conceptually designed. Next, considering the obtained magnetic flux density distribution of each magnet, the design calculation of the generator is performed again, and the specifications of the generator are corrected. From the obtained coupled systems, the optimum system is finally selected through synthetical consideration of various requirements. The procedure of the proposed method is very simple, and no iterative calculation is contained in the correction process. Incorporating the new generator design method makes this advantage possible because the generator size can be fixed in the correction process. In the conventional method, a change of magnetic flux density distribution leads directly to a change in the generator size, and therefore, design calculations of the generator and magnet should be iterated in the correction process until they converge to consistent sizes. The procedure of the new conceptual design method is explained in detail by taking the case of a supersonic generator with a caesium seeded helium plasma and 100 MW thermal input.     

The end of cheap oil: Current status and prospects

This paper, analyses the factors impacting the price of crude oil in order to examine the likely evolution of the oil market and attempts to answer the question, whether cheap oil is already a thing of the past. Based on data made publicly available mostly by the major oil companies, it examines the effects of demand and supply, the evolution of world oil reserves, the trends in new discoveries of new oilfields, the evolution of world Gross Domestic Product (GDP), and the depletion of oil resources. The analysis concludes that the world peak in conventional oil production—the point beyond which oil production will irreversibly start declining—is approaching and will be reached, even according to the most optimistic scenarios, before 2040 and quite possibly much sooner. If the appropriate solutions for substituting crude oil and for conserving the use of energy are not implemented in time, then the current upward trend in oil prices is bound to continue.     

陕西小水电世纪末的回眸与展望

５０ 年来,陕西小水电及电气化事业得到了长足的发展,为工农业生产和贫困地区脱贫致富发挥了积极作用。本文对５０ 年的发展历程作以回顾,总结基本经验并提出新世纪小水电发展的方针     

Estimation of peak transient voltages at wind turbine generator terminals

This paper proposes equivalent circuits and a method for the estimation of the peak transient voltages at generator terminals in wind turbines equipped with back‐to‐back converters. Equivalent circuits as well as a way of phase‐to‐phase and phase‐to‐ground voltages estimation in back‐to‐back converter are presented. Proposed theoretical background is well confirmed by small‐scale measurements. It is shown and proven that phase‐to‐ground voltages represent a dominating threat for the wind turbine generators insulation. Copyright © 2014 John Wiley & Sons, Ltd.     

论绿色印刷的现状及发展

面对全球气候变化的挑战,节能减排、低碳经济等已成为人类社会可持续发展的重要内容.对于我国印刷行业来说,使用绿色原料、实施绿色工艺的绿色印刷已经是印刷企业的共识.阐述了绿色印刷目前在国内外的发展现状,预测绿色印刷的未来发展方向将是对印刷工业废气、废液和固体废弃物的清洁、降解处理的先进环保技术,印刷废料的回收以及整个流程中...     

管腔内支架研究和开发的现状及展望

【摘要】 为了使临床医师,特别是介入放射学、心血管学和肿瘤学等专科医师,掌握更多有关各类新型支架的研发信息,进而在血管成形术中能更精确地应用最适宜的支架,并对支架的进一步研究提出有意义的建议,该文对支架研发的现状和展望,包括支架材料的更新和支架构型的改进以及其国内市场的分析等进行图文相结合的全面详细阐述。
     

李家峡水电站4#发电机定子下线的监理

介绍了大型水轮发电机的新型冷却方式——蒸发冷却方式在李家峡水电站4#发电机定子绕组中的原理、应用及优点,对李家峡水电站4#发电机定子下线的整个工艺过程、定子下线安装过程中发现的问题及时分析、总结,以及解决的办法。     

多年调节水库年末水位研究

建立了预测多年调节水库年末水位的ANN预测模型,针对GA、BP算法的优缺点,运用GA-BP算法求解网络模型.通过黄河龙羊峡水库实例计算证明,该方法可为水库调度提供一定依据.     

Nuclear power for sustainable development: Current status and future prospects

Interest in nuclear power has been revived as a result of volatile fossil fuel prices, concerns about the security of energy supplies, and global climate change. This paper describes the current status and future plans for expansion of nuclear power, the advances in nuclear reactor technology, and their impacts on the associated risks and performance of nuclear power. Advanced nuclear reactors have been designed to be simpler and safer, and to have lower costs than currently operating reactors. By addressing many of the public health and safety risks that plagued the industry since the accidents at Three Mile Island and Chernobyl, these reactors may help break the current deadlock over nuclear power. In that case, nuclear power could make a significant contribution towards reducing greenhouse gas emissions. However, significant issues persist, fueling reservations among the public and many decision makers. Nuclear safety, disposal of radioactive wastes, and proliferation of nuclear explosives need to be addressed in an effective and credible way if the necessary public support is to be obtained.     

Introduction: Natural gas development begins at home

International trade in natural gas by pipeline and as LNG was the fastest growing element in the world gas business during the last two decades. However, less than 15% of world gas output crosses frontiers, a proportion closer to that of coal (10%) than of oil (50%). Gas, like coal, should be considered a “market locating” fuel, since its transport cost often far exceeds that of other manufacturing inputs. Moreover, gas export projects suffer from heavy front-end investment costs and from uncertain demand growth in the importing countries. For these reasons, developing countries with a potential for natural gas production must seriously consider all opportunities for local gas utilization. In order to maximize the availability of gas for domestic uses, policies which provide adequate incentives for gas development are required. Imaginative formulae to encourage exploration specifically for gas, and imaginative technology to make local gas development commercial on a smaller scale than most developers have considered so far, are the current prerequisites for natural gas in developing countries.     

风力发电技术讲座(四) 风力发电机组(2)

4调速 装置自然界的风速经常变化。风轮的转速随风速的增大而变快，发电机的输出电压、频率、功率也增加；当风轮的转速超过额定值时，有可能影响机组的使用寿命，甚至造成设备的毁坏。为使风轮能以一定的转速稳定地工作，风力发电机上设有调速装置。调速装置是在风速大于设计额定风速时才起作用，因此，又被称为限速装置。当风速增至停机风速时，调速装置能使风轮顺桨（风向与风轮旋转平面平行）停机。     

风力发电技术讲座(一)风力发电机组(1)

风力发电机是将风能转换成机械能,再把机械能转换成电能的机电设备.风力发电机通常由风轮、对风装置、调速装置、传动装置、发电机、塔架、停车机构等组成。     

State-of-the-art research and development status of sodium batteries

钠硫电池,钠-氯化镍电池(ZEBRA电池)和钠-空气电池等一类以金属钠作负极,通过钠离子在正负极之间传导和得失电子而实现电能和化学能转换的电池,统称为钠电池.本文综述了钠硫电池,ZEBRA电池和钠-空气电池等钠电池的研究和开发现状,包括各种钠电池的结构,工作原理和性能特性以及目前研发进展的介绍,它们面临的主要问题的分析,最后指出它们今后的发展趋势.