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Analysis of a Ferromagnetic Segment using Magnetic Flux Leakage Method for Detecting Defect
, M.Sc. Thesis Sharif University of Technology ; Zohoor, Hassan (Supervisor)
Abstract
Magnetic flux leakage is one of the nondestructive testing methods used for ferromagnetic segments. The basis of performance of the magnetic flux leakage nondestructive testing is such that the ferromagnetic segment will be led to magnetic saturation by a powerful magnetic field, and if there was defect and decreasing in cross section, the segment's capability of transmitting magnetic flux will be decreased and therefore, some of passing magnetic flux from the under testing segment, will be leaked to the surrounding area. So the amount of magnetic flux leakage can be a criterion of existing defect in the segment. To estimate sizing of the defect, it's necessary to study the ingredients which...
Modeling and Control of Magnetically-Levitated Iron-Less Planar Actuators
, M.Sc. Thesis Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
Flying has fascinated mankind for ages. Nowadays, planar actuators are performing the same task as that, once a dream, of a flying magic carpet found in Persian mythology. Magnetically levitated planar actuators (MLPAs) consist of two parts; a moving part, and a stationary part. In most applications the moving part which is an array of permanent magnets (PMs) produces a magnetic flux density in the air-gap, and the stationary part, an array of current carrying coils, produces force and torque when it is exposed to the magnetic flux of the PM array. These actuators have been utilized in industry in applications where precise positioning is important. In recent years however, they have found...
Analytical modeling of magnetic flux in superconducting synchronous machine
, Article IEEE Transactions on Applied Superconductivity ; Volume 23, Issue 1 , 2013 ; 10518223 (ISSN) ; Elhaminia, P ; Zolghadri, M. R ; Fardmanesh, M ; Sharif University of Technology
2013
Abstract
A general model for superconducting synchronous machines in which the rotor can be considered as a magnetic or a nonmagnetic material is proposed and analytically investigated. Analytical equations for magnetic flux in different regions of the machine have been developed. Furthermore, nonlinear magnetization of the iron core is studied. In order to solve the equations in the case of the iron saturation, a reiterative algorithm is proposed. Finite-element simulation has also been performed to verify the equations and the proposed algorithm. The obtained analytical results show good agreement with finite-element method results
RSFQ logic circuits, a novel technology in integrated circuits based on superconductivity
, Article WSEAS Transactions on Circuits and Systems ; Volume 5, Issue 2 , 2006 , Pages 274-278 ; 11092734 (ISSN) ; Shakmohammadi, S ; Payandehjoo, K ; Kheirizad, I ; Sharif University of Technology
2006
Abstract
With thc advent of Superconductivity, a new category of Integrated Circuits' Technology has been represented called RSFQ (Rapid Single Flux Quantum) Superconductor 'technology, RSFQ superconducting circuits use Josephson Junctions (JJ) as electronic switches. In RSFQ superconducting circuits information is represented as discrete voltage pulses equivalent to the magnetic flux quanta. In this paper, we first describe the Josephson effect and then explain the basic building blocks used in RSFQ circuits and performance of some asynchronous logic gates
A diversity based reconfigurable method for fault tolerant control of induction motors
, Article International Symposium on Power Electronics, Electrical Drives, Automation and Motion, 2006. SPEEDAM 2006, Taormina, 23 May 2006 through 26 May 2006 ; Volume 2006 , 2006 , Pages 66-71 ; 1424401941 (ISBN); 9781424401949 (ISBN) ; Shojaei, A ; Ahmadi Khatir, D ; Sharif University of Technology
2006
Abstract
AC motor drive systems are sensitive to faults occurring at the power inverter, or at the control system. A novel fault tolerant Field Oriented Control system for induction motors is introduced. The system maintains speed control in the event of sensors malfunction and adverse signal conditions, providing enhanced reliability. The system comprises four different flux estimators which are fused by a Fuzzy aggregation system in order to give a reliable estimate of motor flux. The proposed control system is an effective and easy to implement method giving a potential for motor drive reliability enhancement. © 2006 IEEE
Approach for analytical modelling of axial-flux PM machines
, Article IET Electric Power Applications ; Volume 10, Issue 6 , 2016 , Pages 441-450 ; 17518660 (ISSN) ; Abedini Mohammadi, A ; Oraee, A ; Oraee, H ; Sharif University of Technology
Institution of Engineering and Technology
2016
Abstract
In the presented paper, an analytical model is developed for calculation of the air gap magnetic flux density in the axial-flux surface-mounted PM machines. The slotting effect is taken into account in the air gap magnetic flux distribution, accurately. The main novelty of this study is replacing the stator teeth by some surface currents at the border of the removed stator teeth. The uniqueness theorem is applied to find the surface currents. The two-dimensional (2D) field solution in the slotless machine is solved easily by separation of variables method. The multi-slice quasi-3D method is applied for taking 3D nature of field distribution into account. In addition, the back-EMF, armature...
Transient heat transfer analysis of a layer by considering the effect of radiation
, Article Journal of Fusion Energy ; Volume 23, Issue 3 , 2005 , Pages 207-215 ; 01640313 (ISSN) ; Safavisohi, B ; Aghanajafi, C ; Sharif University of Technology
2005
Abstract
The transient heat transfer analysis of a layer has been studied much less than the steady state. However, transient temperature distribution resulted from including radiation and conduction simultaneously, is significantly different from those obtained by considering conduction alone. In order to include the effect of radiation heat transfer, we must insert the gradient of radiative flux in the energy equation. For this purpose, a variety of multi-flux methods have been suggested. A simplified procedure is the two-flux method, which is the one used in the present paper. This paper is focused on one-dimensional transient heat transfer of a layer using Finite Difference Method. To this end, a...
Computation of armature reaction field and full-load characteristics of an axial flux surface mounted pm machine using a new analytical approach
, Article 26th Iranian Conference on Electrical Engineering, ICEE 2018, 8 May 2018 through 10 May 2018 ; 2018 , Pages 1027-1031 ; 9781538649169 (ISBN) ; Sharifi, A. H ; Abedini Mohammadi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
In recent years axial flux permanent magnet (AFPM) machines have found industrial applications because of such characteristics as high power density, compact structure and disc-like shape. Like other electrical machines, prediction of flux density distribution in the air gap of AFPM is essential. In this paper, an analytical method for calculation of air gap flux density caused by armature reaction is presented. The solution is based on Maxwell's equations. Separation of variables method is applied to field equations and 2D distribution of magnetic flux density in the air gap calculated in term of Fourier series. The 2-D distribution of three-phase armature winding is modeled exactly....
Modeling and parametric studies of magnetic shape memory alloy–based energy harvester
, Article Journal of Intelligent Material Systems and Structures ; Volume 29, Issue 4 , 2018 , Pages 563-573 ; 1045389X (ISSN) ; Rostami Najafabadi, H ; Askari Farsangi, M. A ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
This article presents a model to simulate the behavior of a magnetic shape memory alloy while harvesting vibratory energy. In this type of energy harvester, magnetic shape memory alloy element is placed in the air gap of a ferromagnetic core which conducts the magnetic flux. Two apparent coils are wound around a ferromagnetic core: one to produce bias magnetic field by passing a rectified electric current and the other to serve as an energy pickup coil. Applying compressive time-variant strain field to magnetic shape memory alloy element changes its dimensions and magnetic properties as well. Presence of the bias magnetic field returns magnetic shape memory alloy element to its initial state...
Design-oriented modelling of axial-flux variable-reluctance resolver based on magnetic equivalent circuits and Schwarz-Christoffel mapping
, Article IEEE Transactions on Industrial Electronics ; Volume 65, Issue 5 , May , 2018 , Pages 4322-4330 ; 02780046 (ISSN) ; Nasiri Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Axial flux variable reluctance (AFVR) resolvers have substantial benefits that make them suitable for motion control drives. However, they suffer from insufficient accuracy, especially in high-accuracy applications. Hence, optimizing the AFVR resolver structure is necessary for improving its commercial usage. However, its accurate modelling needs three-dimensional (3-D) time stepping finite element analysis (TSFEA) that is computationally expensive and unsuitable for co-usage with optimization algorithms. The aim of this paper is to establish an accurate, yet computationally fast, model suitable for optimal design of AFVR resolvers. The working of the proposed model is based on magnetic...
Approximating the distribution of flaws in magnetic materials using the generalized inverse
, Article 2011 IEEE International Conference on Imaging Systems and Techniques, IST 2011 - Proceedings, 17 May 2011 through 18 May 2011, Batu Ferringhi ; May , 2011 , Pages 137-141 ; 9781612848969 (ISBN) ; Abdollahi Jahdi, S ; Norouzi, E ; Sharif University of Technology
2011
Abstract
Non-destructive identification of voids in ferromagnetic materials is of great importance for industrial applications. Magnetic flux leakage technique is used here to examine the defected structure. To this end, an inverse problem should be solved in order to infer the location and depth of internal flaws from the measured leaked magnetic signals. Currently generalized inverse method and singular value decomposition are used for solving such inverse problem. Considering the cracks separation has significant effect on the absolute value of magnetic flux leakage signals, we study different distributions of cracks. In this paper, the magnetic dipole model is proposed to reconstruct the extent...
A novel method for modeling the magnetizing yoke
, Article Electromagnetics ; Volume 30, Issue 3 , 2010 , Pages 297-308 ; 02726343 (ISSN) ; Norouzi, E
2010
Abstract
Magnetic flux leakage is the most widely used method for oil and gas pipeline non destructive testing. The saturation level of the sample under test has a significant effect on its efficiency; therefore, the magnetizing yoke requires an elaborate design. The finite element method is the conventional approach used for this purpose, but it is very time consuming. In this article, a neuro-fuzzy method is presented to model the behavior of the magnetizing yoke. Modeling a few different designs with the finite element method and using the results for training the neuro-fuzzy model eradicates the necessity of modeling a huge number of designs with the finite element method. The acquired...
Developing an adaptive fractional model of a magnetic structure using evolutionary algorithm
, Article ICCC 2008 - IEEE 6th International Conference on Computational Cybernetics, Stara Lesna, 27 November 2008 through 29 November 2008 ; 2008 , Pages 189-192 ; 9781424428755 (ISBN) ; Hajihasani, M ; Farjami, Y ; Norouzi, E ; Sharif University of Technology
2008
Abstract
Magnetic flux leakage technique is used extensively to detect and characterize defects in natural gas and oil transmission pipelines. The amount of magnetic flux introduced into the test sample is an important factor in the resolution of flaw detection. It depends on the power of permanent magnets and the geometrical design of the magnetic yoke. Finite element method (FEM) is the most widely used method of analyzing magnetic yoke due to its power, accuracy and straightforwardness. On the other hand its calculations are so complicated and time consuming, and every single modification in the parameters of the problem requires a new run. In this paper, we present an innovative method to...
Developing a neural network model for magnetic yoke structure
, Article 2008 IEEE International Conference on Computational Intelligence for Measurement Systems and Applications, IEEE CIMSA 2008, Istanbul, 14 July 2008 through 16 July 2008 ; 2008 , Pages 75-78 ; 9781424423064 (ISBN) ; Norouzi, E ; Sharif University of Technology
2008
Abstract
Magnetic flux leakage technique is used extensively to detect and characterize defects in natural gas and oil transmission pipelines. The amount of magnetic flux introduced into the test sample is an important factor in the resolution of flaw detection. It depends on the power of permanent magnets and the geometrical design of the magnetic yoke. Finite element method (FEM) is the most widely used method of analyzing magnetic yoke due to its power, accuracy and straightforwardness. On the other hand its calculations are so complicated and time consuming, and every single modification in the parameters of the problem requires a new run. In this paper, we present an innovative method to...
Optimization of the flux distribution in magnetic flux leakage Testing
, Article Materials Evaluation ; Volume 68, Issue 3 , 2010 , Pages 360-364 ; 00255327 (ISSN) ; Ravanbod, H ; Sharif University of Technology
2010
Abstract
Many factors cause degeneration of the measured signal in magnetic flux leakage (MFL). One of these factors is non-uniformity of the magnetic flux inside the sample under test. Uniformity of the magnetic flux results in smoother and more predictable signals from various discontinuity types and also a reduction in the eddy current distortions induced because of the movement of the magnetizing yoke. The goal of this research is to find a near-optimal length for the magnetizing yoke. Toward this end, yokes with different lengths are simulated with the finite element method and the quality of the distribution of the flux lines inside the sample is studied. In this way a criterion for...
High-fidelity magnetic characterization and analytical model development for switched reluctance machines
, Article IEEE Transactions on Magnetics ; Volume 49, Issue 4 , 2013 , Pages 1505-1515 ; 00189464 (ISSN) ; Kaboli, S ; Davoudi, A ; Moayedi, S ; Sharif University of Technology
2013
Abstract
This paper proposes a new experimental procedure for magnetic characterization of switched reluctance machines. In the existing methods, phase voltage and current data are captured and further processed to find the flux linkage. Conventionally, assuming zero initial flux value, the flux linkage can be found by integrating the corresponding voltage term. However, the initial flux value is usually unknown, e.g., it can be nonzero when the current is zero due to the residual flux effect, and, thus, imposes error in magnetic characterization. The proposed method addresses this issue by considering an additional equation in steady state. This method injects a low-frequency sinusoidal current to...
Rotary magnetohydrodynamic micropump based on slug trapping valve
, Article Journal of Microelectromechanical Systems ; Volume 20, Issue 1 , December , 2011 , Pages 260-269 ; 10577157 (ISSN) ; Shafii, M. B ; Sharif University of Technology
2011
Abstract
A novel rotary magnetohydrodynamic (MHD) (RMHD) micropump is presented in this paper in order to both benefit exclusive advantages from the MHD micropumps and eliminate the current obstacles in their implementation. Lorentz force, which is the actuation mechanism in RMHD, is used to propel a mercury slug in a circular microchannel in order to suck the working fluid from the inlet and pump it to the outlet. This idea is integrated with a valve which prevents the working fluid from passing through, while allowing the mercury slug to pass, during each pumping loop. The performance of a fabricated RMHD is evaluated, considering parameters such as pressure difference, running duration, electric...
Peculiar transport properties in Z-shaped graphene nanoribbons: A nanoscale NOR gate
, Article Thin Solid Films ; Volume 548 , 2013 , Pages 443-448 ; 00406090 (ISSN) ; Khoeini, F ; Shokri, A ; Sharif University of Technology
2013
Abstract
A nanoscale logic NOR gate has been theoretically designed by magnetic flux inputs in a Z-shaped graphene nanoribbon composed of an armchair ribbon device sandwiched between two semi-infinite metallic zigzag ribbon leads. The calculations are based on the tight-binding model and iterative Green's function method, in which the conductance as well as current-voltage characteristics of the nanosystem are calculated, numerically. We show that the current and conductance are highly sensitive to both the magnetic fluxes subject to the device and the size of the system. Our results may have important applications for building blocks in the nanoelectronic devices based on graphene nanoribbons
Analytical and numerical study of quantum transport in an array of nanorings: A case study with double rings
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 47 , January , 2013 , Pages 297-302 ; 13869477 (ISSN) ; Khoeini, F ; Sharif University of Technology
2013
Abstract
We present an analytical method to obtain an expression for electron transmission through an array of disordered nanorings (ADNRs) sandwiched between two semi-infinite metallic leads in different lead-ring coupling strengths. Our approach is based on the nearest-neighbor tight-binding approximation and transfer matrix method. First, we derive an analytical formula for electron transmission across the system. Next, we apply our approach to study of the electron transport in a perfect double nanoring (PDNR) and design a NOR gate using the magnetic fluxes inputs. The conductance, current-voltage characteristics and threshold voltage of the system are calculated in the weak and strong coupling...
Experimental study of a novel Magneto Mercury Reciprocating (MMR) micropump, fabrication and operation
, Article Sensors and Actuators, A: Physical ; Volume 194 , 2013 , Pages 277-284 ; 09244247 (ISSN) ; Salari, A ; Shafii, M. B ; Sharif University of Technology
2013
Abstract
Today, MEMS have wide applications in modern technologies. Magneto hydro dynamic (MHD) micropumps play an important role in the MEMS industry and have been thoroughly studied in the recent years. In this study, the idea of classic reciprocating micropumps was combined with magneto hydro dynamics (MHD) to develop a novel Magneto Mercury Reciprocating (MMR) micropump. To attain this goal, the Lorentz force, as the actuation mechanism, was used to move a conductive liquid (mercury) slug in a reciprocating manner in order to suck the working fluid (air) from the inlet and pump it to the outlet. The performance of the fabricated MMR micropump was examined in terms of parameters such as pressure...