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Operating small industrial equipment such as measuring instruments, sensors or weather stations, at remote locations requires reliable off-grid power supplies. The most common solution are large batteries, even though there are some inconveniences for the operator. Especially in northern regions, batteries can freeze during winter and suffer non-reparable damage. The exchange is strenuous at remote...
The direct methanol fuel cell is a power source that could produce reliable electrical energy at high efficiencies and low pollution levels. This paper describes some of the problems associated with the design of DMFCs as well as results obtained. The laboratory test configuration is briefly explained and test results are presented to assist the design process. The problems associated with the DMFC...
Data transmission networks are the backbone of modern telecommunications networks. They handle the transport of the constantly increasing volume of data between the various network elements of the fixed network and form the link between fixed network and mobile networks. The two technologies listed below are used: a) cable-based transmission (these days mostly involving optical fiber cables) b) point-to-point...
IEC Technical Committee (TC) 108 is developing an entirely new safety standard, applicable to consumer electronics, information technology equipment and telecommunications equipment. The standard will be performance based and technology independent. The standard is being developed using sound engineering principles and will clearly identify the hazards addressed. This is a "hazard-based safety...
The effect of load impedance on the dynamics and performance of a regulated converter is investigated. Theoretical formulation is derived utilizing two-port modelling technique. It is definitively shown that the load interactions are reflected into the converter dynamics via the internal open-loop output impedance. At the frequencies, where the loop gain is much higher than unity, the internal closed-loop...
In the highly competitive context of deregulated world energy, transmission utilities have a need for monitoring devices, using microprocessor based technology in order to optimize asset management within substations. A second-more sophisticated- generation of devices, adding protection and control to monitoring, is seen as the next step to decrease additionally the scheduled maintenance expenditures,...
This paper presents the comparative study for fuzzy regression model using linear programming, fuzzy regression model using genetic algorithms and standard regression model. The fuzzy and standard models were developed for estimation of electric power losses in electrical networks. Simulation was carried out with a tool developed in MATLAB
The bus architecture, consisting of bus converter and POLs (point of load), has become very popular since POL can respond to some demands of multi power supply voltage, low driving voltage and series sequence/tracking of LSI with more flexibility than isolated DC-DC solution. However, the customer suffers the system instability issue caused by impedance overlap between the bus converter and POL. Bus...
In liberalized electricity markets all players are driven to minimize costs respectively optimize profit considering public tasks to guarantee a safe, reliable and cost efficient supply with electricity. In 2003, worldwide major blackouts happened during a relatively short time frame putting electricity supply from a perception as "commodity" into a "high quality product" picture...
A new zero-current switching (ZCS) pulse-width modulated (PWM) boost converter is proposed in the paper. The main power switch in the proposed converter can operate with ZCS due to an active auxiliary circuit that diverts current away from the switch just before it is turned off. The circuit allows the converter to operate with ZCS without the disadvantages typically found in other, previously proposed...
A new ZCT-PWM cell, which reduces the current stress of the main switch and the rectifier diodes in DC-DC converter, is proposed and analyzed in this paper. Based on the ZCT-PWM cell a boost DC-DC converters is constructed, and it is analyzed to demonstrate the operation principle of the new ZCT cell. This type converter is suitable for high power high frequency application due to it's fully soft...
The evolution of telecom network architecture and new services have always had impact on powering architecture. The power consumption increases with the generalization of wireless, broadband IP, triple play and services based on computers, and applications are more sensitive to local failure because of high equipment concentration and interdependency. In a context of telecom unbundling, open electricity...
It is usually considered that if the ZVS performance of phase-shift (PS) ZVS full-bridge (FB) converter can be achieved with the help of auxiliary circuits at light load, then the ZVS performance can be achieved naturally at heavy load. However under certain circumstance, the drain to source capacitor will be recharged during the commutating period. Therefore, the ZVS performance of lagging leg may...
We estimated the lifetimes of large-capacity lithium-ion secondary cells in high-temperature-acceleration tests under variable maintaining voltages. The decrease in capacity was exacerbated by the temperature increase, and we found a strong correlation between the lifetime and temperature, in agreement with Arrhenius' law. The lifetime, which was effected by the charge voltage, was over 10 years at...
The SOFC converts by means of an electro chemical reaction the energy in fuel directly into electricity and heat, this conversion makes power generation using an SOFC significantly more efficient than conventional technology. The high efficiency of power generation is also maintained through part load operation conditions. The high temperature SOFC is environmentally friendly based on the high efficiency...
We estimated the capacity and life expectancy of 100-Ah-scale large nickel metal hydride backup batteries. The proposed method is based on the correlation between the voltage drop after charge cessation and the capacity of degraded batteries. The magnitude of the voltage drop varies with the environmental temperature, but a method of offsetting this temperature dependence is described. Capacity estimation...
Active power has introduced a new energy storage technology that could replace lead-acid batteries in many applications. The new product, which stores energy in the form of heat and compressed air, will initially be packaged for use with uninterruptible power systems. However, with a few modifications, the technology can also be applied to remote telecommunications sites, for mobile telephone and...
We developed small cycle VRLA batteries that have a longevity of 3000 cycles, and confirmed that a UPS with these installed can supply stable power as an electrical energy storage system. This paper describes the batteries we developed and a UPS with an electric energy storage function
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