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Comparison of transfer functions using estimated rational functions to detect winding mechanical faults in transformers
, Article Archives of Electrical Engineering ; Volume 61, Issue 1 , 2012 , Pages 85-99 ; 00040746 (ISSN) ; Vakilian, M ; Rahimpour, E ; Sharif University of Technology
2012
Abstract
As it is found in the related published literatures, the transfer function (TF) evaluation method is the most feasible method for detection of winding mechanical faults in transformers. Therefore, investigation of an accurate method for evaluation of the TFs is very important. This paper presents three new indices to compare the transformer TFs and consequently to detect the winding mechanical faults. These indices are based on estimated rational functions. To develop the method, the necessary measurements are carried out on a 1.3 MVA transformer winding, under intact condition, as well as different fault conditions (axial displacement of winding). The obtained results demonstrate the high...
Evaluating fuzzy earned value indices and estimates by applying alpha cuts
, Article Expert Systems with Applications ; Volume 38, Issue 7 , 2011 , Pages 8193-8198 ; 09574174 (ISSN) ; Salehipour, A ; Sharif University of Technology
2011
Abstract
The earned value technique is an essential technique in analyzing and controlling the performance of a project by providing a more accurate measurement of both project performance and project progress. This paper presents an approach to deal with fuzzy earned value indices. This includes developing new indices under fuzzy circumstances and evaluating them using alpha cut method. The model improves the applicability of the earned value techniques under real-life and uncertain conditions. A small example illustrates how the new model can be implemented in reality
Transformer winding diagnosis using comparison of transfer function coefficients
, Article ECTI-CON 2011 - 8th Electrical Engineering/ Electronics, Computer, Telecommunications and Information Technology (ECTI) Association of Thailand - Conference 2011, 17 May 2011 through 19 May 2011, Khon Kaen ; 2011 , Pages 681-683 ; 9781457704246 (ISBN) ; Vakilian, M ; Rahimpour, E ; Azizian, D ; Sharif University of Technology
2011
Abstract
In this work, a new model of transformer winding is developed. The components in the model are determined by the geometric and electric data of the winding. Under different degrees of axial displacement and radial deformation in the winding, circuit parameters in the model will be changed and thus the character of the circuit will be influenced. After acquiring the model parameters in the intact and faulted cases, transfer function coefficients derived in model from nodal analysis. Then using introduce the new index based on coefficients we can specify the type and extent of penetration of the fault in the winding. Results presented demonstrate the potential of this method
Fuzzy-small degrees of freedom representation of linear and angular variations in mechanical assemblies for tolerance analysis and allocation
, Article Mechanism and Machine Theory ; Volume 46, Issue 4 , April , 2011 , Pages 558-573 ; 0094114X (ISSN) ; Movahhedy, M. R ; Foumani, M. S ; Sharif University of Technology
2011
Abstract
Tolerances naturally generate an uncertain environment for design and manufacturing. In this paper, a novel fuzzy based tolerance representation approach for modeling the variations of geometric features due to dimensional tolerances is presented. The two concepts of fuzzy theory and small degrees of freedom are combined to introduce the fuzzy-small degrees of freedom model (F-SDOF). This model is suitable for tolerance analysis of mechanical assemblies with linear and angular tolerances. Based on the fuzzy concept, a new index (called the assemblability index) is introduced which signifies the fitting quality of parts in the assembly. Graphical and numerical representations of tolerance...
The effect of source motion on contaminant distribution in the cleanrooms
, Article Energy and Buildings ; Volume 43, Issue 4 , April , 2011 , Pages 966-970 ; 03787788 (ISSN) ; Sajadi, B ; Molaeimanesh, G. R ; Sharif University of Technology
2011
Abstract
In the recent decades, cleanrooms have found growing applications in broad range of industries such as pharmacy and microelectronics. Concerns about negative effects of the contaminant exposure on the human health and product quality motivate many researchers towards understanding of the airflow and contaminant distribution though these environments. With an improvement in computational capacity of the computers, computational fluid dynamics (CFD) technique has become a powerful tool to study the engineering problems including indoor air quality (IAQ). In this research, indoor airflow in a full-scale cleanroom is investigated numerically using Eulerian-Eulerian approach. To evaluate the...