Search results for "reliability"
showing 10 items of 1563 documents
A Low-Power Fully-Mosfet Voltage Reference Generator for 90 nm CMOS Technology
2006
An integrated voltage reference generator, designed for being incorporated in standard 90-nm CMOS technology flash memories, is described in this paper. A fully MOSFET based approach, using also subthreshold operated devices, has been adopted in order to achieve low-voltage and low-power requirements and to overcome the difficulties of conventional band-gap reference circuits. The proposed circuit, based on current signals, internally generates two currents with opposite dependence on temperature. The two currents are added, thus canceling almost completely temperature dependence, and then linearly converted into the output voltage. For a temperature variation between -20degC and 90degC, th…
On the reliability of ASHRAE conduction transfer function coefficients of walls
2000
The transfer function method recommended by the ASHRAE can be considered the most modern tool currently available for the thermal analysis of a building. It is particularly well suited for use with a computer as it makes it possible to describe with great accuracy the internal heat gain of walls using a small set of coefficients. The present paper shows how to calculate sets of coefficients diverse from that proposed by Mitalas who first developed the method and on the basis of an unequivocal criterion, to prove the advantages in using them. The authors also investigated some of the paramount mathematical and physical aspects which affect the approximation degree of the ASHRAE method and, w…
Monolithic integration of GMR sensors for standard CMOS-IC current sensing
2017
Abstract In this work we report on the development of Giant Magnetoresistive (GMR) sensors for off-line current measurements in standard integrated circuits. An ASIC has been specifically designed and fabricated in the well-known AMS-0.35 μm CMOS technology, including the electronic circuitry for sensor interfacing. It implements an oscillating circuit performing a voltage-to-frequency conversion. Subsequently, a fully CMOS-compatible low temperature post-process has been applied for depositing the GMR sensing devices in a full-bridge configuration onto the buried current straps. Sensitivity and resolution of these sensors have been investigated achieving experimental results that show a de…
Frequency stability in microgrid: control strategies and analysis of BESS aging effects
2016
In order to ensure a thorough analysis, all components placed in a microgrid would have to be considered to guarantee an effective energy management. To this aim, various algorithms are used both to preserve and restore power systems after significant disturbances. However, these models frequently do not evaluate components performance decline with the age and, consequently, they don't consider actual values during microgrid analysis, potentially affecting obtained results. In particular, evaluating energy storage systems aging and their effects has rarely been addressed in prior works. The present article proposes a model to maintain power system/microgrid stability after disturbances usin…
Experimental validation of a general model for three phase inverters operating in healthy and faulty modes
2012
The paper presents the experimental verification of a general mathematical model of Voltage Source Inverters (VSI) able to simulate fault conditions and which is also useful for the simulation of fault-tolerant systems for different applications. In general, in the past, the problem of faulty inverters modeling has been addressed specifically by considering faults on the different phases as separate cases. Furthermore, traditional models include only the faulty mode and not the healthy mode, so resulting then not able to predict transient phenomena. The model hereafter presented overcomes this drawback. It was formulated by introducing the concept of “healthy leg binary variables”. Such var…
Criticality and sensitivity analysis of the components of a system
2000
Abstract In the design of complex systems there is a great interest to know the relative importance of each of their elements. In this paper, we define a new method for measuring the relative importance of each element of the system. We have to specify that this paper concerns only non-repairable systems and components. We present a way of calculating the criticality of each component for a complex system no matter what the random distribution of the life of the component is. The paper also demonstrates a simple way of calculating how the system life improves when the life of a component is improved.
Simple Circuit Models for Studying Global Earthing Systems
2007
The paper proposes three simple circuit models for the simulation of the behaviour of a global earthing system during different fault events. The models allow one the evaluation of the maximum earth potential rise at every possible fault location and for every possible fault event. The three considered fault events are: single-line-to-earth fault inside a MV/LV substation, double-earth-fault in a MV line, single-line-to-earth fault inside a HV/MV station. After having illustrated the hypotheses at the basis of the study, the circuit models for the three fault events are presented and a numerical example shows how to use them in order to check the "global safety" of the interconnected earthi…
Can the effective number of bits be useful to assess the measurement uncertainty?
2003
The effective number of bits (ENOB) is a well know parameter, employed to characterize the overall behavior of an A/D converter. In order to verify if the ENOB can be also used to assess the measurement uncertainty of the A/D conversion based instruments, we use a developed software tool. The results show that using the ENOB can lead to an underestimate of the uncertainties.
Uncertainty evaluation in the measurements for the electric power quality analysis
2013
The paper deals with the uncertainty estimation in the measurements performed to assess the electric power quality. In a first steps, according to the 'ISO - Guide to Expression of the Uncertainty in Measurements' all the error sources, which give a significant contribution to the combined uncertainty associated to the measurement results, are identified. Successively, in order to analyze how the errors propagate through the measurement chain, a Monte Carlo based approach is proposed. The method exploits an ad-hoc developed simulator of the measurement process, which takes into account the particular way of propagation of all the identified error sources. Eventually, with the aim of validat…
Risk evaluation and creep in conventional conductors caused by high temperature operation
2008
The advent of electricity market deregulation, the increased operating and overload temperatures of transmission line conductors have caused concern among TSOs (Transmission System Operators) and DSOs (Distribution System Operators) about the effect of elevated temperatures on conventional bare conductors of existing line. Nowadays building new lines is very difficult cause of increased costs to obtain rights of way, public intervention, etc.... Cost and lead times required to place new lines into service are now increased and the business in electric market is reduced for the limited possibility of transmission. Therefore, utilities are attempting to gain as much capacity as possible modif…