1,720,997 research outputs found
Misure e Fidatezza; Sistemi riparabili
No full textFor repairable devices, such as systems, sub-systems, etc., availability requirements
have to be defined. Availability takes into account, in fact, not only
the concept of reliability, extensively discussed in previous papers, but integrates
this concept with information on the repair and restoration of the performed
functions, with the activities associated to them. In other words,
given a device, it is possible to estimate the fault status and, consequently,
the related maintenance issues
L'affidabilità nella moderna progettazione: un elemento competitivo che collega sicurezza e certificazione
No full textEffects 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 by means of numerical simulations and then validated through an experimental activity
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
Fault classification tool for high pressure water jet pumps
No full textIn this work a set of indexes able to define a suitable “footprint” of a Waterjet system has been investigated. A on-line and non-intrusive monitoring and diagnostic system has been designed implementing an algorithm defined on the basis of the proposed indexes
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
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
A Novel Method for the Rotor Fault Detection in Small Inverter-Fed Induction Motors
No full textIt is known that when a rotor fault occurs, an induction machine draws an alternative power at twice the rotor frequency. In previous work the authors have shown how to employ this phenomenon in order to detect rotor faults in small inverter fed induction machines. In particular, a rotor fault index has been presented and tested supposing that the AC drive main supply is single phase. Starting from this approach, in the present paper two new rotor fault indexes suitable for three-phase input AC drives will be proposed. Furthermore, their capability to detect early rotor faults in different conditions has been evaluated through an extensive experimental activity. Some results will be presented
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