1,721,020 research outputs found
Condition based maintenance through electrical signature analysis : a case study
No full textIn modern industrial applications, because of the increasing requirements in term of quality and efficiency, the employment of an effective maintenance strategy is becoming crucial. As a consequence, the service activity is moving towards the development of diagnostics and prognostics techniques aiming to minimize the impact of the failures on the production. In previous papers two simple diagnostic indexes has been presented. It has been shown that under some hypothesis they are effective to detect rotor faults of inverter-fed asynchronous machines. In this work, the effect on indexes due to the accuracy of the current measurement chain has been investigated. This has led to the development of a low-cost diagnostic device employing. Hall-effect current transducers and a dsPIC microcontroller. Finally, it will be shown that the indexes computed by means of this economical hardware are close to that obtained employing a PC interfaced with a much more accurate current acquisition system
Design and implementation of a on-board device for photovoltaic panels monitoring
No full textNowadays the world energy infrastructure is subjected to a progressive transformation. In fact it is already possible to notice the growing number of distributed small
generation units, based on different technologies, directly connected to the power grid. At present the energy that can be produced by the sun and wind seem to be the most promising renewable energy sources. The use of the solar energy requires to optimize the efficiency of the converting chain and to maintain the performances of the system. These requirements highlight the
need to equip photovoltaic (PV) plants with efficient condition monitoring tools. In this paper a hardware solution for monitoring system that allows implementing algorithm devoted
to check the dependability of the PV panels and to improve the overall system efficiency is presented
Effects of the speed loop on the diagnosis of rotor faults in induction machines
No full textThe development of high-performance static converters and advanced control techniques has led to a widespread diffusion of asynchronous drive systems in industrial plants. One of the strong points of the induction machines is their reliability; however, an unexpected failure may still result in a considerable economic loss. This fact has stimulated a prolific research activity concerning the continuous monitoring of the wear status of induction machines. The knowledge of their condition allows implementing condition-based maintenance techniques, which have proven to be very effective in critical processes. In previous papers, the authors have focused their attention on the detection of broken rotor bars in inverter-fed induction machines. Two indexes have been defined: Both of them are simple methods to estimate the same fault indicator, namely, the ratio between the amplitude of the power oscillation and the average power draw of the drive system.
However, this fault indicator exhibits a noticeable dependence on the mechanical load as well as on the speed loop parameters.
In this paper, a deep investigation about these dependences is provided. The study suggests introducing a new fault indicator which is much less sensitive with respect to the torque developed by the motor. Furthermore, the analysis allows predicting how the speed loop affects the fault detection techniques. The results of the study and the effectiveness of the new fault indicator have been first verified bymeans of numerical simulations and then validated through an experimental activity
A VI based tool for inverter fed induction motor diagnostic
No full textNowadays Virtual Instruments (more briefly called VIs) are very useful tools both in research and industrial applications.
Their greatflexibility, re-configurability, reliability and ease of use allow an effective implementation of complex measurements architectures. In particular, the capability to manage long measurement processes without staff presence makes the VIs a powerful support for the development of diagnostic techniques which require a continuous monitoring ofthe system. In this paper a novel VI-based diagnostic monitoring technique which permits the identification of rotor faults in small inverter-fed induction motors will be presented
Maintenance scheduling by means of electrical signature analysis technology
No full textThe increasing demand for efficiency and quality greatly influences the way in which assets and services are produced and managed. As a consequence, the maintenance of equipment is one of the key drivers for increasing the competitiveness in the market nowadays. This paper introduces ESA (Electric Signature Analysis), a technique that can act as a low cost and reliable tool for diagnostics and, for some applications, prognostics purpose. The effectiveness of the technique is discussed and, finally, demonstrated in a case study carried out for the monitoring of a Photovoltaic (PV) plant
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dust effects on the PV plant efficiency: A new monitoring strategy
No full textAs well known dust deposition on PV panels results in a decrease of the electrical power produced by the panel/photovoltaic system. In order to assess this decrease and carry out a long-term economic analysis, it is desirable to make an accurate prediction of the efficiency of the system and of the maintenance costs. Starting from this assumption, an economic model that takes into account the relationship between the losses in the energy production and the cost of maintenance is very useful. In this paper the losses due to the dust will be evaluated considering radiation data provided by public meteorological stations installed which are few kilometers far from the considered PV system
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Photovoltaic plant maintenance : a method base on economic evaluation of PV system losses
No full textIn literature few studies analyze the efficiency degradation due to the presence of dust on Photovoltaic (PV) modules (e.g. Meyer and Van Dyk, 2004; Hamdy et al. 2006; Powers et al. 2010; Mani and Pillai 2010). Since photovoltaic panels have to work in open space, the dust deposition cannot be avoided thus determining a reduction of energy production with respect to the clean condition. In order to quantify the effect of the reduced energy production on the payback ratio and to evaluate the long-term system performances of a photovoltaic plant, an accurate prediction of the plant efficiency and of the maintenance cost is mandatory.
In this paper an economical model that takes into account the relation between the losses in the energy production (predicted by means of an electric model of a PV reference panel) and the maintenance operations cost will be presented. The opportunity of using environmental data, acquired by means of public weather station will be also discussed
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