Metal fuel cells [Zn-air fuel cells]

The author describes a zinc-air fuel cell system which may be used for everything from electric vehicles (EVs) to backup generators, and may also provide practical and efficient energy storage     

Mighty mites [fuel cell power supplies]

In this article, the author examines how the fuel cell's first big market success may be alcohol-fed units small enough to power cellphones, laptops, and PDAs.     

New machines for old [manufacturing computer control]

ICL is currently implementing a phased CIM strategy at its printed circuit board (PCB) manufacturing site at Kidsgrove. The manufacturing process begins with laminate and components entering the factory, and ends with tested PCBs leaving to be fitted into products at ICL's assembly plants or stored for field spares. The author shows that one of the major problems in installing computer-integrated and flexible manufacturing systems (for PCB production applications) is the integration of existing numerically controlled machines     

电池、燃料电池、UPS产品厂商信息

~~电池、燃料电池、UPS产品厂商信息     

Meter power [electricity metering]

The author discusses the problems caused by the privatisation of the UK electricity supply industry in the area of metering. The minimum requirements for changes in metering suggested by Offer (Office of Electricity Regulation) to improve demand side management, are discussed. The author then discusses communication techniques for improved metering. The author describes mains signalling and radio techniques for remote meter reading. The practical implications of using such technology and its benefits are discussed     

Tighter controls for busier systems [power systems]

A variety of new technologies are becoming available that will help utilities maintain power system reliability while handling the larger volume of transactions. For example, power electronic systems can provide unprecedented control over electricity flow on transmission networks, preventing or containing cascading disturbances. In addition, new sensor technology, faster communications between control centers, and advanced software tools can enable utilities to monitor system conditions in real time, letting them respond more quickly to disturbances and minimize their impact. Over the next decade, these technologies will facilitate increased power transfers through power delivery systems that are presently constrained, providing power at lower cost to a greater number of customers. It is a question of how to optimize power flow through an entire network by integrating multiple technologies and coordinating control over wide areas. Such integration and coordination will be necessary for deregulation to proceed smoothly toward its twin goals: reducing electricity costs to US consumers, while maintaining the high levels of reliability they have come to expect. The authors discuss the following technologies to help achieve these goals including: flexible AC transmission systems (FACTS), the next generation of FACTS controllers, hierarchical control of FACTS, on-line power systems analysis, control centre communications, and wide area measurement system     

Power struggle [power supplies for portable equipment]

Gadgets bristling with hardware and applications in smaller packages are forcing designers to consider new power sources. The leading candidate is a form of fuel cell based on methanol as fuel. A methanol based fuel cell produced by Toshiba to power a notebook computer is described in this article.     

The power within [Internet]

The public Internet has revolutionised the world's communications. Now companies are rushing to build their own private intranets. The author explains some of the attractions that intranets provide: cross-platform functionality; a consistent view of information; an enabling technology path; ease of integration; ease of communication; relatively low-cost installation; and increased effectiveness of information     

Nonstop monitoring [power quality]

A power failure could spell disaster for a large financial institution. The author describes the role of fixed power quality monitoring systems in ensuring that the trading never has to stop. Consulting engineers and site facility managers are increasingly of the opinion that supply quality in a modern commercial building demands the installation of a fully integrated, fixed power quality monitoring system, operating 24 hours a day, 365 days a year. The PegaSys system, manufactured in Canada by Power Measurement Ltd of Victoria, British Columbia, and marketed in the UK by C-Matic Systems is an example of a modern, highly flexible, power monitoring system. A typical installation consists of one or more monitoring PCs connected to a network of fixed power quality instruments installed at all of the key supply points throughout a building. The PC's graphical interface depicts the electrical layout of the building, indicating the location of each monitoring instrument, together with the status of load levels or approaching alarm limits. Typically, a user will have one main screen where system condition can be viewed at a glance. More detailed information is available by navigating down through the hierarchy of screen layers. The objective of the system is to provide load trending for system planning together with pre-fault alarming, so that, as far as is humanly possible, power outages are avoided     

Redesigning the old 555 [timer circuit]

It is rare that an integrated circuit stays on the market for 25 years. And it is surprising that, except for a CMOS derivative, the 555 timer has never been updated. It has been shrunk somewhat, but the original schematic and layout have remained intact. For a long time this situation could be explained by the versatility of the 555, whose speed, current draw and voltage range sit right in the middle of a vast field of applications. But in the last few years, supply voltages have moved downward, well below the 4.5 V at which the 555 cuts off, and the unit's 5-10 mA current requirement now seems wasteful. A better design is clearly needed. The author describes the features of the original timer before discussing the redesign. The voltage versus current design and output stage are discussed     

A new power converter for fuel cells with high system efficiency

This paper presents a new high-efficiency grid-connected single-phase converter for fuel cells. It consists of a two-stage power conversion topology. Since the fuel cell operates with a low voltage in a wide voltage range (25?V–45?V) this voltage must be transformed to around 350–400?V in order to be able to invert this dc power into ac power to the grid. The proposed converter consists of an isolated dc–dc converter cascaded with a single-phase H-bridge inverter. The dc–dc converter is a current-fed push-pull converter. The inverter is controlled as a standard single-phase power factor controller with resistor emulation at the output. Experimental results of converter efficiency, grid performance and fuel cell dynamic response are shown for a 1?kW prototype. The proposed converter exhibits a high efficiency in a wide power range (higher than 92%) and the inverter operates with a near-unity power factor and a low current THD.     

Efficient algorithm for glitch power reduction [CMOS logiccircuits]

An efficient algorithm is proposed for reducing glitch power dissipation in CMOS logic circuits. The proposed algorithm takes a path balancing approach that is achieved using gate sizing and buffer insertion methods. The gate sizing technique reduces not only glitches but also the effective circuit capacitance. After gate sizing, buffers are inserted into the remaining unbalanced paths which have not been subjected to gate sizing. ILP has been employed to determine the location of inserted buffers. The proposed algorithm has been tested on LGSynth91 benchmark circuits. Experimental results show that 61.5% of glitches are reduced on average     

The CEO problem [multiterminal source coding]

We consider a new problem in multiterminal source coding motivated by the following decentralized communication/estimation task. A firm's Chief Executive Officer (CEO) is interested in the data sequence {X(t)} _t=1^∞ which cannot be observed directly, perhaps because it represents tactical decisions by a competing firm. The CEO deploys a team of L agents who observe independently corrupted versions of {X(t)}_t=1^∞. Because {X(t)} is only one among many pressing matters to which the CEO must attend, the combined data rate at which the agents may communicate information about their observations to the CEO is limited to, say, R bits per second. If the agents were permitted to confer and pool their data, then in the limit as L→∞ they usually would be able to smooth out their independent observation noises entirely. Then they could use their R bits per second to provide the CEO with a representation of {X(t)} with fidelity D(R), where D(·) is the distortion-rate function of {X(t)}. In particular, with such data pooling D can be made arbitrarily small if R exceeds the entropy rate H of {X(t)}. Suppose, however, that the agents are not permitted to convene, Agent i having to send data based solely on his own noisy observations {Y_i(t)}. We show that then there does not exist a finite value of R for which even infinitely many agents can make D arbitrarily small. Furthermore, in this isolated-agents case we determine the asymptotic behavior of the minimal error frequency in the limit as L and then R tend to infinity     

Kilowatts on order [power amplifiers]

The development of pulse-width-modulation (PWM) power amplifiers based on fast-switching MOSFETs and their applications are described. Their ability to drive magnets efficiently, neutralize power line harmonics, and control motion with precision is examined. Active filter and active magnetic bearing implementations are discussed     

Appropriate technologies [photovoltaic power generation]

The use of technology to improve health and general well-being of much of the world's population-and do so at affordable cost-presents electrical and electronics engineers with unusual challenges and opportunities. The topic covered in this paper is photovoltaics, which has the potential of bringing electric energy to millions of remote rural households, greatly enhancing their quality of life. Photovoltaics is attractive because it can help countries avoid the huge expense of expanding electric grids into rural areas     

Breaking the mould [power transmission]

The liberalisation of energy industries has become a major international concern. In this article, the author charts the experience of National Grid (NGC)-the world's first privately owned independent transmission company-in developing the complex roles of network manager and system controller within the radically changing electricity market in England and Wales     

Wheeling and dealing [power transmission]

Within a few years the transmission network will remain the last outpost of regulation within the electricity industry for England and Wales. The need for the long-term regulation of the transmission business raises important issues in the economic management of the electricity industry. In particular, what form of regulation will best help to promote the overall goal of economic efficiency within the industry? How should the services of the transmission business be priced? And how can the long-term security of the network be guaranteed? The author describes some of the challenges of combining a regulated transmission business with the quest for market-led economic efficiency