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    A control strategy for reducing the torque ripple in low speed operation of direct torque controlled induction motor

    , Article 2004 IEEE International Symposium on Industrial Electronics, IEEE-ISlE, 4 May 2004 through 7 May 2004 ; Volume 2 , 2004 , Pages 1203-1208 Kaboli, F. S ; Zolghadri, S. M. R ; Haghbin, T. S ; Homaifar, F. A ; Sharif University of Technology
    2004
    Abstract
    A new switching table is proposed for decreasing the torque ripple in DTC especially in low speed. Each sector is divided to two half sector and a proper vector set is defined for each. Through this new switching table, the torque response is smooth even in the beginning of each sector and it leads to the reduction of torque ripple. None of motor parameters are used in this switching strategy and there is no need to shorten the sampling period. Simulation and experimental results confirm the ability of this method in reducing the torque ripple. ©2004 IEEE  

    A reliable and fast response buck converter based on interleaved converter

    , Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 804-807 ; 9781728115085 (ISBN) Keshtkar Teeula, A ; Kaboli, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Power Distribution Unit (PDU) is a power supply unit that supplies various DC voltage levels for electric equipment. Reliability of PDU is very important in electrical systems. Buck converter is frequently used in PDU to provide the lower voltage levels than the source voltage level. The output capacitor of the buck converter is the main factor of failure. In this paper, we present a method to design a buck converter with almost no inductor current ripple. If the inductor current ripple is eliminated, the output capacitor can be removed from the converter. By removing the capacitor, the reliability and transient response of the converter can be improved considerably. The proposed method is... 

    Torque ripple minimization in DTC of induction motor based on optimized flux value determination

    , Article The 29th Annual Conference of the IEEE Industrial Electronics Society, Roanoke, VA, 2 November 2003 through 6 November 2003 ; Volume 1 , 2003 , Pages 431-435 Kaboli, S ; Zolghadri, M. R ; Haghbin, S ; Emadi, A ; Sharif University of Technology
    2003
    Abstract
    Torque ripple is a major difficulty in direct torque controlled induction motors. The reference value of the motor flux greatly influences the torque ripple. On the other hand, many motors work in an operating cycle, which includes load intervals of less than their nominal power. In these situations, it is not necessary to set their flux value as the nominal value. In this paper, the effect of the reference value of the motor flux on the motor torque ripple is investigated. A new control algorithm is proposed to determine the reference value of the flux according to the value of the motor torque. Simulation and experimental results justify the validity of the proposed method to reduce the... 

    Effects of the flux value on the torque ripple of the direct torque controlled induction motor drives determination

    , Article 5th International Conference on Power Electronics and Drive Systems, PEDS 2003, 17 November 2003 through 20 November 2003 ; Volume 1 , 2003 , Pages 439-444 ; 0780378857 (ISBN) Kaboli, S ; Zolghadri, M. R ; Haghbin, S ; Homaifar, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    Abstract
    Torque ripple is a major difficulty in direct torque control of induction motors. The reference value of the motor flux greatly influences the torque ripple. On the other hand, many motors work in an operating cycle, which includes load intervals of less than their nominal power. In these situations, it is not necessary to set their flux value as the nominal value. In this paper, the effect of the reference value of the motor flux on the motor torque ripple is investigated. The effect of the flux reference variation on the motor power factor as well as torque dynamics is also presented. Simulation results as well as experimental results justify the validity of the proposed method on the... 

    Structural Disorders of Graphene and Its Effects on Electronic Properties

    , M.Sc. Thesis Sharif University of Technology Abedpour, Nima (Author) ; Rahimi Tabar, Mohammad Reza (Supervisor)
    Abstract
    In this thesis we would like to investigate structural disorder of Graphene and its effect on electronic properties. Graphene is a one-layer crystal of Carbon atoms which was the first two dimensional crystal observed experimentally. Low energy current carriers on Graphene behave like mass-less Dirac fermions and this interesting electronic property attracts much attention on studying Graphene. Structural disorder of Graphene highly affects its electronic properties. We study thermal fluctuations of Graphene sheet, disorder super lattice, and static ripples, as structural disorders of Graphene. Disorders due to thermal fluctuations of graphene induce a disordered gauge field on the graphene... 

    Irreversibility in response to forces acting on graphene sheets

    , Article Physical Review Letters ; Volume 104, Issue 19 , May , 2010 ; 00319007 (ISSN) Abedpour, N ; Asgari, R ; Tabar, M. R. R ; Sharif University of Technology
    2010
    Abstract
    The amount of rippling in graphene sheets is related to the interactions with the substrate or with the suspending structure. Here, we report on an irreversibility in the response to forces that act on suspended graphene sheets. This may explain why one always observes a ripple structure on suspended graphene. We show that a compression-relaxation mechanism produces static ripples on graphene sheets and determine a peculiar temperature Tc, such that for T

    Reduction of the torque ripple in brushless doubly-fed machine

    , Article Proceedings of the 2011 3rd International Youth Conference on Energetics, IYCE 2011, 7 July 2011 through 9 July 2011 ; July , 2011 , Page(s):1 - 7 ; 9781457714948 (ISBN) Gorginpour, H ; Jandaghi, B ; Oraee, A ; Saket, M. A ; Ahmadian, M ; Oraee, H ; Sharif University of Technology
    2011
    Abstract
    In this paper, a new structure for the rotor of the Brushless Doubly-Fed Machine (BDFM) is introduced to reduce the machine's torque ripple. The ripple has a considerable effect on the machine start up. At the first section of the paper, analytical expressions for the air gap permeance distribution, the air gap MMF distribution, cogging torque and back EMF are presented. Then, the effects of skewing the rotor loops are analyzed. Finally, the relation between non-skewed quantities and their values in skewed coordinate are introduced  

    Space vector modulation for four-switch rectifier with compensating the effect of capacitors voltage ripple

    , Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009 ; 2009 ; 9789948427155 (ISBN) Ounie, S ; Zolghadri, M. R ; Sharif University of Technology
    Abstract
    A space vector modulation (SVM) approach is proposed to control a four-switch rectifier with power factor correction and compensating the effect of capacitors voltage ripple. The theory and performance of this method are presented, and the method effectiveness is demonstrated by extensive simulations. The simulation results show that the capacitor voltage ripple effects in the output voltage and current shaping can be omitted and the rectifier can work agreeably under high power factor condition although capacitors voltage is not balance. The allowable amount of this unbalanced value of filter capacitors is determined  

    A new modeling and control scheme for cascaded split-source converter cells

    , Article IEEE Transactions on Industrial Electronics ; 2021 ; 02780046 (ISSN) Montazeri, S. H ; Milimonfared, J ; Zolghadri, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Cascaded split-source inverter (CSSI) is a new single-stage modular multilevel topology. Each cell of this converter converts DC to AC power in the buck or boost operation mode without any additional power switch. This paper develops a design method based on a detailed model for CSSI. This model shows that energy storage elements experience double-fundamental frequency ripples besides high-frequency ones. It accurately calculates voltage gains and capacitor voltage and inductor current ripples. On the other hand, common carrier-based multilevel modulations have been modified in terms of both reference and carrier signals to control the inverter under symmetric and asymmetric conditions. With... 

    10KV High Voltgage DC Power Supply by Diode Rectifier and Switching Regulator to Reduce Output Capacitor

    , M.Sc. Thesis Sharif University of Technology Jannati, Mohammad Kazem (Author) ; Kaboli, Shahriyar (Supervisor)
    Abstract
    High voltage dc power supplies are commonly used in medical equipment, microwave lamps, X-ray equipment and radio transmission systems. In radio Transmission power supplies the output voltage quality is of great importance and the output voltage ripple must be very low. In addition usage of low frequency transformer and rectifier needs large bulk capacitors to reduce output voltage ripple. Moreover, to reduce energy discharged into load in load short circuit faults the output capacitance should be as low as possible. An approach to solve this problem is to use a diode rectifier and a switching power supply in series configuration. The Advantage is that the switching power supply provides a... 

    Design and Implement of an Ultra Low Ripple Power Supply for Cathode of Microwave Tube

    , M.Sc. Thesis Sharif University of Technology Jalali, Saeed (Author) ; Kaboli, Shahryar (Supervisor)
    Abstract
    The purpose of this Thesis is designing and constructing of high voltage power supply with very low ripple. Proposed method of this thesis is formed of two sections. In this proposed structure, in first section, structure is on basis of diodes rectifier that has been used for producing main portion of output load energy. Second section uses with aim of regulating of first stage voltage. In attention to existence of noises and available offsets in different sections of proposed circuits, model is basis of two stages structure. Sampling of output voltage by using of resistance divider for main loop of circuit has been done. So noises and offsets available in circuit act as prevented factor... 

    Molecular Dynamics Simulation of Nanocar Motion on Carbon Structures

    , Ph.D. Dissertation Sharif University of Technology Mofidi, Mahsa (Author) ; Nejat Pishkenari, Hossein (Supervisor) ; Ejtehadi, Mohammad Reza (Supervisor)
    Abstract
    Nanomachines are molecules inspired by natural molecular machines and are able to move and transport at the nanoscale. Due to the advancement of nanotechnology, the need to move materials and energy on a small scale is necessary more than ever. Nanocars are artificial molecular machines with chassis, axles, and wheels designed for nanoscale transport at materials’ surfaces. Understanding the dependence of surface dynamics of nanocars on the substrate’s physico-chemical properties is critical to the design of the transport properties of such man-made nanoscale devices. Among the multitude of potential substrates for the nanotransporters, graphene exhibits intrinsic ripples on its surface,... 

    Design and Implement of Voltage Ripple Measuring System for Power Supply of Microwave Tubes

    , M.Sc. Thesis Sharif University of Technology Ahmadi Someh, Saeed (Author) ; Kaboli, Shahryar (Supervisor)
    Abstract
    Mostly, the high voltage DC power supplies have output voltage ripple. In such an applications like power supply of microwave lamps in radar systems, low output voltage ripple is an important point of operational characteristics. On the other hand, measuring the low voltage ripple will be a challenge that can lead to recognize of its reasons and reduce its amplitude. In this thesis, different ways of ripple measurement constraints is described, then a method based on high pass filters for output voltage ripple measurement is implemented. The impact of components tolerance and their parasitic components like shunt parasitic resistance of a capacitor in filter operational characteristics is... 

    Electronic features of rippled graphene

    , Article ICEE 2012 - 20th Iranian Conference on Electrical Engineering ; 2012 , Pages 170-172 ; 9781467311489 (ISBN) Haji Nasiri, S ; Moravvej Farshi, M. K ; Faez, R ; Bajelan, A ; Sharif University of Technology
    2012
    Abstract
    Using tight binding theory the effect of topological ripples on the electronic band structure, density of states (DOS), and Fermi velocity of graphene are studied. The results show that by an increase in the ripple height the graphene Fermi velocity decreases and its DOS increases.- Moreover, we show that an increase in the ripple period causes the graphene band gap and DOS to decrease and its Fermi velocity to increase  

    Performance of phase-modulated microwave photonics in the presence of group delay and reflection amplitude ripples of the dispersive device

    , Article Conference Proceedings - 11th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2011, 4 September 2011 through 8 September 2011, Kharkov ; 2011 ; 9781612848136 (ISBN) Mokhtari, A ; Akbari, M ; Sharif University of Technology
    Abstract
    We develop an analytic approach to investigate the effect of reflection amplitude and group delay ripples of the dispersive device on the performance of phase-modulated microwave-photonic filters. Experimental results conform to our proposed analytical approach  

    A new configuration of switched reluctance motor for reducing the torque ripple

    , Article 2009 International Conference on Electric Power and Energy Conversion Systems, 10 November 2009 through 12 November 2009 ; 2009 ; 9789948427155 (ISBN) Sheikhi, A ; Oraee, H ; Kaboli, S ; Dorkhah, M. R ; Sharif University of Technology
    Abstract
    Switched reluctance motors (SRM) are one of the most reliable and cost effective motors and their applications are increasing in industry. However, it suffers from high level of torque ripple. In this paper, a new configuration for stator and rotor of SRM is presented. In the proposed method, a new saliency is developed to remove negative torque and therefore decrease torque ripple and acoustic noise, increase efficiency and as a result, expand speed range. The simulation results demonstrate that the new motor structure has a smooth torque profile with possibility to work at higher speed lower acoustic noise  

    Wideband and polarisation-independent antireflection coating using metamaterials

    , Article IET Optoelectronics ; Volume 14, Issue 5 , 2020 , Pages 266-273 Sepehripour, F ; Karimi, P ; Khavasi, A ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    Abstract
    Here, the authors propose a new approach for realising wideband and polarisation-independent antireflection coating, based on a metamaterial composed of a subwavelength array of metallic pillars with a square cross-section. The effective impedance of the array can be duly adjusted by the size and distance of the pillars. As such, the authors design the effective impedance of the antireflection coating to be the geometrical mean of the impedance of upper and lower media and choose its height to be quarter of operating wavelength. Doing so, the reflection vanishes at the desired frequency and fractional bandwidth of 56% is achieved with a criterion of 10% reflectance (the refractive index of... 

    Axiomatic control of Buck converter for high efficiency over wide load range

    , Article 2008 IEEE International Conference on Industrial Technology, IEEE ICIT 2008, Chengdu, 21 April 2008 through 24 April 2008 ; 2008 ; 9781424417063 (ISBN) Kaboli, S ; Haddadi, A ; Khaligh, A ; Sharif University of Technology
    2008
    Abstract
    In this paper, the axiomatic design is introduced for controlling a power electronic converter. The main idea of axiomatic design is to introduce variables affecting the desired performances of the system most independently possible. The control process is presented for a Buck converter to achieve constant efficiency and output voltage ripple. ©2008 IEEE  

    Operation and design analysis of an interleaved high step-up DC–DC converter with improved harnessing of magnetic energy

    , Article International Journal of Circuit Theory and Applications ; Volume 49, Issue 2 , 2021 , Pages 221-243 ; 00989886 (ISSN) Sabahi, M ; Tarzamni, H ; Kolahian, P ; Sharif University of Technology
    John Wiley and Sons Ltd  2021
    Abstract
    In this paper, a new interleaved DC–DC converter based on a coupled and a single input inductor is proposed. The suggested high step-up converter utilizes various inductive and capacitive methods to transfer magnetic energy more efficiently. The output voltage is regulated with the switches' duty cycle and the coupled inductor (CI) turns ratio, which provide a wide output voltage range. Interleaving improves the converter reliability, employs both the first and third areas of CI's B-H plane, cancels DC component of the CI, and reduces the input current ripple of the proposed converter with twice switching frequency. Utilization of two output ports for voltage stress and ripple reduction in... 

    Two building blocks of microwave photonics filters in the presence of group delay ripple: A comparative survey

    , Article Optical and Quantum Electronics ; Volume 44, Issue 8-9 , 2012 , Pages 403-414 ; 03068919 (ISSN) Mokhtari, A ; Akbari, M ; Sharif University of Technology
    Springer  2012
    Abstract
    We have developed an analytic approach to investigate the effect of group delay ripple of the dispersive devices on the performance of two major building blocks of microwave- photonic filters. Firstly, performance of PM-based block in the presence of an arbitrary group delay ripple (GDR) is analyzed and compared with the ripple-free case to reveal the destructive effects of added group delay ripple. In the next step, we repeat the proposed approach for the AM-based one; again, the performance is compared with the ripple-free case. Two distortion metrics are also introduced to quantify this distortion. Comparison of the performance of two building blocks in the presence of group delay ripple...