A New Method for Getting Rational Approximation for Fractional Order Differintegrals

In this paper a new algorithm is presented to calculate the poles and zeros to approximate a fractional order (FO) differintegral (s^±α,α∈(0,1)) by a rational function on a finite frequency band ω∈(ω_l,ω_h). The constant phase property of the FO differintegral is the basis for development of the algorithm. Interlacing of real poles and zeros is used to achieve the constant phase. The calculations are done using the asymptotic Bode phase plot. A brief investigation is made to get a good approximation for the Bode phase plot. Two design parameters are introduced to keep the average phase close to the desired phase angle and to keep the error within the allowed bounds. A study is done to empirically understand the relationship between the error and the design parameters. The results thus obtained help in the further calculations. The algorithm is computationally simple and inexpensive, and gives a fairly good approximation of fractance frequency response on the specified frequency band.     

Fuzzy Logic-based Electrothermal Life Model for Inverter-fed Induction Motor Insulation

Pulse width modulated adjustable speed drives used in industries lead to significant advantages in terms of performance, size, and efficiency. But, the output voltage and the current waveforms become non-sinusoidal leading to an increase in voltage and thermal stresses. This results into accelerated insulation aging and premature failure of the motors. With multiple stresses, the life models for insulating materials become complex and ambiguous. This article presents the fuzzy logic application to derive an electrothermal life model to investigate the synergic effects of voltage and thermal stresses on intrinsic aging of inverter-fed induction motor insulation. Three parameters, viz. voltage stress factor, waveform slope stress factor, and spike frequency factor, are proposed to describe the insulation stresses for pulse width modulated voltages. These parameters are computed from the experimental results at different switching frequencies and are used in fuzzy logic-based life estimation algorithms. The results of the fuzzy logic life model are verified by performing the accelerated aging test with the same pulse width modulated voltages on paper insulation. An electrothermal life model is derived from the fuzzy logic results, which can be directly used for the life estimation of any general purpose low-voltage inverter-fed induction motor insulation.     

Improved controller for power conditioner using high-temperature superconducting magnetic energy storage (HTS-SMES)

One of the most important functions in a superconducting magnetic energy storage (SMES) system when used for power conditioning, is the ability to charge the super-conducting coil as fast as possible to ensure that it is ready when it is next required. This paper describes a novel controller for a high-temperature SMES (HTS-SMES) that can ensure: 1) fast return of energy to the superconducting coil under constant-current mode and 2) a constant and sinusoidal input supply current irrespective of the varying load demand with and without harmonics. In the new HTS-SMES proposed, two hysteresis controllers are used, one to control the magnitude, phase and the waveform of the ac supply current, and the other is to control a dc chopper to regulate the SMES coil current. The first hysteresis controller ensures that as far as the power utility is concerned, the load appears to the utility system as a constant sinusoidal load with unity power factor irrespective whether the load is distorted or varying in nature. The second hysteresis controller has been designed to regulate the energy in and out of the superconducting coil. A special feature of this controller is its ability to smoothly charge the superconducting coil using constant current charging so that it can be ready for the next discharging operation as soon as possible. Analysis of the circuit operation under hysteresis control is presented in details. Simulation and experimental results are presented demonstrating the feasibility of the proposed power conditioning system.     

Manually powered manufacture of keyed bricks

The production of bricks, one of the main components in conventional construction technology, has been carried out by either a hand moulding process or by a fully mechanized process. Both processes have limitations in developing countries. An alternative solution is the use of decentralized non-power-consuming brick making units, utilizing unconventional raw materials which do not require baking to develop strength. A manually energized brick making machine (MEBM) has proven the feasibility of extruding various mixes including a lime-fly ash-sand mixture. The production of bricks with a keyed cross-section is investigated using the MEBM to establish the functional and economic viabilities of the technology to create a construction technology which relies on abundant resources, unskilled labour and zero energy input. La production de briques, l'un des elements essentiels de la construction traditionnelle, est assuree soit par moulage manuel, soit par des procedes entierement mecanises. Les deux procedes montrent leurs limites dans les pays en voie de developpement. Une solution alternative consiste a utiliser des machines decentralisees ne consommant pas d'energie, faisant appel a des matieres premieres non conventionnelles qui n'exigent pas de cuisson pour donner la resistance a la brique. Une machine a fabriquer les briques mue par la force manuelle (manually energized brick making machine - MEBM) a prouve sa capacite a extruder differents melanges comportant un melange de chaux et de sable cendre. La production de briques a section creuse au moyen de la MEBM est a l'etude, afin d'etablir la faisabilite economique et fonctionnelle de cette technique propre a creer une technologie de construction basee sur des ressources abondantes, une main-d'oeuvre non qualifiee et une depense energetique nulle.     

Life Model for PWM Controlled Induction Motor Insulation using Design of Experiments Method

According to numerous industrial surveys, the failure rate of stator insulation is much higher for Pulse Width Modulated (PWM) controlled induction motors than for the motors with sinusoidal voltage supply. Voltage spikes, high slew rate of spikes, and repetition and harmonics of PWM voltages generate higher electrical and thermal stresses in motor insulation that result into premature failure. In this paper, the Design of Experiments (DoE) method has been proposed to estimate the life of PWM controlled induction motor insulation. The insulation stress under PWM voltages is quantified by three factors viz. spike magnitude, spike frequency and voltage harmonics factor. These stress factors are experimentally computed for PWM controlled induction motor at different switching frequencies. Keeping these stress factors as input, a fuzzy logic model for insulation life is subsequently developed. This model is fine tuned to match the results obtained through insulation aging test with PWM voltages. The fuzzy logic data is analyzed by statistical techniques such as, ANOVA and Standardized Pareto Chart. A full factorial Design of Experiments technique is then applied to the fuzzy logic results to get the first order model relating the insulation life of induction motor with the stress factors. This model can be directly used for insulation life estimation of PWM controlled induction motors.     

Investigation on influence of Wurster coating process parameters for the development of delayed release minitablets of Naproxen

The present work aims at studying process parameters affecting coating of minitablets (3?mm in diameter) through Wurster coating process. Minitablets of Naproxen with high drug loading were manufactured using 3?mm multi-tip punches. The release profile of core pellets (published) and minitablets was compared with that of marketed formulation. The core formulation of minitablets was found to show similarity in dissolution profile with marketed formulation and hence was further carried forward for functional coating over it. Wurster processing was implemented to pursue functional coating over core formulation. Different process parameters were screened and control strategy was applied for factors significantly affecting the process. Modified Plackett Burman Design was applied for studying important factors. Based on the significant factors and minimum level of coating required for functionalization, optimized process was executed. Final coated batch was evaluated for coating thickness, surface morphology, and drug release study.     

Torque ripple reduction in direct torque controlled five-phase induction motor using modified five-level torque comparator

The five-phase induction motor inherently has the minimal torque ripple. However, when it is controlled by direct torque control (DTC) technique, the torque ripple increases due to the presence of a hysteresis torque comparator. The classical five-level torque comparator is presented in the previous literatures to control the torque ripple. However, this comparator has the drawback of wrong selection of zero voltage vectors inside the inner band on the positive side of the comparator, which enables the torque ripple to increase and dc-link utilization to decrease. In this paper, in order to reduce the torque ripple and to increase the dc-link utilization, a modified five-level torque comparator is proposed, which selects either medium or small voltage vectors instead of zero voltage vectors inside the inner band on the positive side of the comparator. In addition to torque ripple reduction and improvement in dc-link utilization, the proposed comparator significantly improves the quality of phase current. All the available 32 voltage vectors are selected through the proposed five-level torque comparator based on the location of x–y stator flux in order to eliminate the x–y stator flux so as to obtain reduced distortion in the phase current. By employing all the available voltage vectors, the freedom of utilization of all voltage vectors in the five-phase induction motor DTC drive is availed. The proposed five-level torque comparator is compared to its classical five-level counterpart through simulation and experimental results in order to validate the proposed DTC strategy.     

Design and Realization of Stand-Alone Digital Fractional Order PID Controller for Buck Converter Fed DC Motor

The aim of paper is to employ digital fractional order proportional integral derivative (FO-PID) controller for speed control of buck converter fed DC motor. Optimal pole-zero approximation method in discrete form is proposed for realization of digital fractional order controller. The stand-alone controller is implemented on embedded platform using digital signal processor TMS320F28027. The five tuning parameters of controller enhance the performance of control scheme. For tuning of the controller parameters, dynamic particle swarm optimization technique is employed. The proposed control scheme is simulated on MATLAB and verified by experimental results. Performance comparison shows better speed control of separately excited DC motor with the realized digital FO-PID controller than that of the integer order PID controller.     

Reactions of ketene dithioacetal for a new versatile synthesis of 4,5-substituted 3-aminothiophene-2-carboxylate derivatives

Poly substituted 3-aminothiophenes were successfully synthesized in good yields by using a one-pot protocol via ketene S,S-acetal as an intermediate in basic medium (K₂CO₃/N,N-dimethylformamide) followed by Dieckmann condensation with ethyl bromoacetate. Further, chemistry of thiophenes was explored using active functional groups such as C₃–NH₂, C₄–CN and C₅–SCH₃ on the thiophene nucleus.

Synthesis of ethyl 3-acetamido-4-cyano-5-(methylthio)thiophene-2-carboxylate derivatives and ethyl 3-amino-4-carbamoyl-5-(methylthio)thiophene-2-carboxylate derivatives.     

Manually powered manufacture of keyed bricks

The production of bricks, one of the main components in conventional construction technology, has been carried out by either a hand moulding process or by a fully mechanized process. Both processes have limitations in developing countries. An alternative solution is the use of decentralized non-power-consuming brick making units, utilizing unconventional raw materials which do not require baking to develop strength. A manually energized brick making machine (MEBM) has proven the feasibility of extruding various mixes including a lime-fly ash-sand mixture. The production of bricks with a keyed cross-section is investigated using the MEBM to establish the functional and economic viabilities of the technology to create a construction technology which relies on abundant resources, unskilled labour and zero energy input. La production de briques, l'un des éléments essentiels de la construction traditionnelle, est assurée soit par moulage manuel, soit par des procédés entièrement mécanisés. Les deux procédes montrent leurs limites dans les pays en voie de développement. Une solution alternative consiste à utiliser des machines décentralis´ees ne consommant pas d'énergie, faisant appel à des matières premières non conventionnelles qui n'exigent pas de cuisson pour donner la résistance à la brique. Une machine à fabriquer les briques mue par la force manuelle (manually energized brick making machine - MEBM) a prouvé sa capacité á extruder différents mélanges comportant un mélange de chaux et de sable cendré. La production de briques à section creuse au moyen de la MEBM est à l'étude, afin d'établir la faisabilité économique et fonctionnelle de cette technique propre à créer une technologie de construction basée sur des ressources abondantes, une main-d'oeuvre non qualifiée et une dépense énergétique nulle.