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Recent 37

Vol. 14 (2013), No. 1 (37), March 2013

 

This issue of the RECENT® journal was edited and multiplied with support of:

  • Transilvania University of Brasov, Romania

  • Romanian Association for Nonconventional Technologies


CONTENTS



  • Obbu CHANDRA SEKHAR, Dr. Koritala CHANDRA SEKHAR

Torque Ripple Reduction in Direct Torque Control Induction Motor Drive Using SVM and FLDRC

» Abstract

Direct Torque Control (DTC) is a control technique used in AC drive systems to obtain high performance torque control. The conventional DTC drive contains a pair of hysteresis comparators, a flux and torque estimator and a voltage vector selection table. The torque and flux are controlled simultaneously by applying suitable voltage vectors, and by limiting these quantities within their hysteresis bands, de-coupled control of torque and flux can be achieved. However, DTC drives utilizing hysteresis comparators suffer from high torque ripple and variable switching frequency. This work aims at developing a DTC scheme for induction motor, with reduced toque ripple, using fuzzy logic duty ratio control (FLDRC) and Space Vector Modulation (SVM) techniques. From the simulation results shows that feeding electrical drive with proposed system greatly improves the drive performance. The performance of this control method has been demonstrated by simulations performed using a versatile simulation package, MATLAB/SIMULINK.

» Keywords

DTC, Fuzzy logic, Duty ratio control, SVM, Induction motor, MATLAB/SIMULINK

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  • Ioan DAN, Romeo CIOARĂ

A Study on the Pre-Stressed C-Frames of the Presses

» Abstract

The authors of the paper herein are preoccupied with the connection between the elastic deformation of a power press with open frame and the operation energetic consumption of such a machine. Following previous studies, the authors focused on three identified lines of action that should not require additional metal consumption for manufacturing the frame: ribbing of the frame side walls, shortening of the frame, in fact of the distance between the press mass and the main shaft axis, and pre-stressing of the frame. These preoccupations motivated and called for an extended study on other researchers’ interest and achievements in the field. By patenting research, a few groups of solutions for the pre-stressed frames were identified. The present article synthesizes this information, fitting into context the solutions resulted from our research.

» Keywords

C-frame, elastic deformation, rigidity, pre-stressing, patent

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  • Florina-Cristina FILIP

Improvement Production Process by Inspections CMMI

» Abstract

Peer reviews are important instances of verification and quality assurance activities and they shall be conducted early in the development life cycle to identify defects and problems as early as possible in order to prevent them from being delivered to the customers. An inspection is a formal variant of conducting peer reviews on work products. Inspections are conducted on work products by the author’s peers to identify defects for removal and to recommend other changes that are needed. These can be conducted via "formal inspection", "lean inspection" or "pass-around-review", which are all collegial review methods. Alternatively, it is possible to conduct peer reviews in a less formal way as “walk-through” process.

» Keywords

inspection, process, review, decision, method

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  • Cristian-Ioan LEAHU, Horia ABĂITĂNCEI, Sebastian RADU

Drive with Rotative Speed Independent from the Engine of the Pressure Wave Compressors

» Abstract

With a view to achieving internal combustion engines as economical and less polluting as possible, in this paper a new configuration for the driving system of the pressure wave supercharging compressors is submitted. A new driving system is absolutely necessary, as the currently used system, which requires a rotative speed of the compressor in direct proportion with the one of the crankshaft, constitutes a major impediment in the reach of maximum efficiency by the compressor. This probable performance level may exceed even the one of the turbocharger, the latter being nowadays the most widely used supercharging compressor.

» Keywords

internal combustion engine, compressor, supercharging, driving system

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  • Nikolay NIKOLOV

General Mathematical Model for Type-Dimensional Synthesis of Function-Generating Mechanisms with Four-Bar Topological Structure, Rotation of the Input and Translation of the Output

» Abstract

The present work is devoted to the developing of a general mathematical model for type-dimensional synthesis of function-generating mechanisms with four-bar topological structure, rotation of the input and translation of the output. The known cases of particular belt mechanisms and cam mechanisms can be obtained as corollary from the mathematical model.

» Keywords

mathematical model, function-generating mechanism, synthesis

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  • Gudapati Sambasiva Rao, Koritala CHANDRA Sekhar

Space Vector PWM Signal Generation for Twelve-Level Inverter Using Reference Signals

» Abstract

A refined space vector modulation scheme for a twelve-level inverter system for dual-fed induction motor drive, using only the instantaneous sampled reference signals is presented in this paper. The dual-fed structure is realized by opening the neutral-point of the conventional squirrel cage induction motor. The twelve-level inversion is obtained by feeding the dual-fed induction motor with symmetrical four-level inverter from one end and symmetrical three-level inverter from other end. The proposed space vector pulse width modulation technique does not require the sector information and look-up tables to select the appropriate switching vectors. The inverter leg switching times are directly obtained from the instantaneous sampled reference signal amplitudes and centers the switching times for the middle space vectors in a sampling time interval, as in the case of conventional space vector pulse width modulation.

» Keywords

dual-fed induction motor, middle space vectors, space vector PWM, twelve-level inverter

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