An asymmetric cascaded H-Bridge inverters for generating 12-sided polygonal space vector diagrams for Motor drives

A new topology of asymmetric cascaded H-Bridge inverter is presented in this paper It consists of two cascaded H-bridge cells per phase. They are fed from isolated dc sources having a dc bus ratio of 1:0.366. Out of many space vectors possible from this circuit, only those are chosen that lie on 12-sided polygons. Thus, the overall space vector diagram produced by this circuit consists of multiple numbers of 12-sided polygons. With a proper PWM timing calculations based on these selected space vectors, it is possible to eliminate all the 6n +/- 1, (n = odd) harmonics from the phase voltage under all operating conditions. The switching frequency of individual H-Bridge cells is also substantially low. Extensive experimental results have been presented in this paper to validate the proposed concept.

Synthesis, biological studies of linear and branched arabinofuranoside-containing glycolipids and their interaction with surfactant protein A

Oligoarabinofuranoside-containing glycolipids relevant to mycobacterial cell wall components were synthesized in order to understand the functional roles of such glycolipids. A series of linear tetra-, hexa-, octa-and a branched heptasaccharide oligoarabinofuranosides, with 1 -> 2 and 1 -> 5 a-linkages between the furanoside residues, were synthesized by chemical methods from readily available monomer building blocks. Upon the synthesis of glycolipids, constituted with a double alkyl chain-substituted sn-glycerol core and oligosaccharide fragments, biological studies were performed to identify the effect of synthetic glycolipids on the biofilm formation and sliding motilities of Mycobacterium smegmatis. Synthetic glycolipids and arabinofuranosides displayed an inhibitory effect on the growth profile, but mostly on the biofilm formation and maturation. Similarly, synthetic compounds also influenced the sliding motility of the bacteria. Further, biophysical studies were undertaken, so as to identify the interactions of the glycolipids with a pulmonary surfactant protein, namely surfactant protein A (SP-A), with the aid of the surface plasmon resonance technique. Specificities of each glycolipid interacting with SP-A were thus evaluated. From this study, glycolipids were found to exhibit higher apparent association constants than the corresponding oligosaccharide portion alone, without the double alkyl group-substituted glycerol core.

A Novel VSI- and CSI-Fed Dual Stator Induction Motor Drive Topology for Medium-Voltage Drive Applications

A new configuration is proposed for high-power induction motor drives. The induction machine is provided with two three-phase stator windings with their axes in line. One winding is designed for higher voltage and is meant to handle the main (active) power. The second winding is designed for lower voltage and is meant to carry the excitation (reactive) power. The excitation winding is powered by an insulated-gate-bipolar-transistor-based voltage source inverter with an output filter. The power winding is fed by a load-commutated current source inverter. The commutation of thyristors in the load-commutated inverter (LCI) is achieved by injecting the required leading reactive power from the excitation inverter. The MMF harmonics due to the LCI current are also cancelled out by injecting a suitable compensating component from the excitation inverter, so that the electromagnetic torque of the machine is smooth. Results from a prototype drive are presented to demonstrate the concept.

A Seven-Level Inverter Topology for Induction Motor Drive Using Two-Level Inverters and Floating Capacitor Fed H-Bridges

A multilevel inverter topology for seven-level space vector generation is proposed in this paper. In this topology, the seven-level structure is realized using two conventional two-level inverters and six capacitor-fed H-bridge cells. It needs only two isolated dc-voltage sources of voltage rating V(dc)/2 where V(dc) is the dc voltage magnitude required by the conventional neutral point clamped (NPC) seven-level topology. The proposed topology is capable of maintaining the H-bridge capacitor voltages at the required level of V(dc)/6 under all operating conditions, covering the entire linear modulation and overmodulation regions, by making use of the switching state redundancies. In the event of any switch failure in H-bridges, this inverter can operate in three-level mode, a feature that enhances the reliability of the drive system. The two-level inverters, which operate at a higher voltage level of V(dc)/2, switch less compared to the H-bridges, which operate at a lower voltage level of V(dc)/6, resulting in switching loss reduction. The experimental verification of the proposed topology is carried out for the entire modulation range, under steady state as well as transient conditions.

Affinity-Chromatographic Procedure For The Purification Of The Enzyme From Mung-Bean (Phaseolus, Aureus) Seeds And Conformational-Changes On Its Interaction With Ortho-Phosphate

Flavokinase was purified, for the first time from a plant source [mung bean (Phaseolus aureus)] by affinity chromatography in the presence of orthophosphate and by using C-8 ATP-agarose (ATP linked through the C-8 position to beaded agarose), Cibacron Blue and riboflavin--Sepharoses. An altered substrates-saturation pattern was observed in the presence of K2HPO4. The conformational changes of the enzyme in the presence of K2HPO4 were monitored by fluorescence spectroscopy. These results highlight the regulatory nature of this enzyme.

Hybrid LCI/VSI Power Circuit-A Universal High-Power Converter Solution for Wound Field Synchronous Motor Drives

Load commutated inverter (LCI)-fed wound field synchronous motor drives are used for medium-voltage high-power drive applications. This drive suffers from drawbacks such as complex starting procedure, sixth harmonic torque pulsations, quasi square wave motor current, notches in the terminal voltages, etc. In this paper, a hybrid converter circuit, consisting of an LCI and a voltage source inverter (VSI), is proposed, which can be a universal high-power converter solution for wound field synchronous motor drives. The proposed circuit, with the addition of a current-controlled VSI, overcomes nearly all of the shortcomings present in the conventional LCI-based system besides providing many additional advantages. In the proposed drive, the motor voltage and current are always sinusoidal even with the LCI switching at the fundamental frequency. The performance of the drive is demonstrated with detailed experimental waveforms from a 15.8-hp salient pole wound field synchronous machine. Finally, a brief description of the control scheme used for the proposed circuit is given.

Dynamics of pulled desorption with effects of excluded-volume interaction: The p-Laplacian diffusion equation and its exact solution

We analyze the dynamics of desorption of a polymer molecule which is pulled at one of its ends with force f, trying to desorb it. We assume a monomer to desorb when the pulling force on it exceeds a critical value f(c). We formulate an equation for the average position of the n-th monomer, which takes into account excluded-volume interaction through the blob-picture of a polymer under external constraints. The approach leads to a diffusion equation with a p-Laplacian for the propagation of the stretching along the chain. This has to be solved subject to a moving boundary condition. Interestingly, within this approach, the problem can be solved exactly in the trumpet, stem-flower and stem regimes. In the trumpet regime, we get tau = tau(0)n(d)(2), where n(d) is the number of monomers that have desorbed at the time tau. tau(0) is known only numerically, but for f close to f(c), it is found to be tau(0) similar to f(c)/(f(2/3) - f(c)(2/3)) If one used simple Rouse dynamics, this result would change to tau similar to f(c)n(d)(2)/(f - f(c)). In the other regimes too, one can find exact solution, and interestingly, in all regimes tau similar to n(d)(2). Copyright (C) EPLA, 2011

Micro stepping of Shape Memory Alloy based Poly Phase motor

In literature we find broadly two types of shape memory alloy based motors namely limited rotation motor and unlimited rotation motor. The unlimited rotation type SMA based motor reported in literature uses SMA springs for actuation. An attempt has been made in this paper to develop an unlimited rotation type balanced poly phase motor based on SMA wire in series with a spring in each phase. By isolating SMA actuation and spring action we are able achieve a constant force by the SMA wire through out its range of operation. The Poly phase motor can be used in stepping mode for generating incremental motion and servo mode for generating continuous motion. A method of achieving servo motion by micro stepping is presented. Micro stepping consists of controlling single-phase temperature with a position feedback. The motor has been modeled with a new approach to the SMA wire Hysterysis model. Motor is simulated for different responses and the results are compared with the experimental data.

Shape memory alloy based motor

Design and characterization of a new shape memory alloy wire based Poly Phase Motor has been reported in this paper. The motor can be used either in stepping mode or in servo mode of operation. Each phase of the motor consists of an SMA wire with a spring in series. The principle of operation of the poly phase motor is presented. The motor resembles a stepper motor in its functioning though the actuation principles are different and hence has been characterized similar to a stepper motor. The motor can be actuated in either direction with different phase sequencing methods, which are presented in this work. The motor is modelled and simulated and the results of simulations and experiments are presented. The experimental model of the motor is of dimension 150mm square, 20mm thick and uses SMA wire of 0·4mm diameter and 125mm of length in each phase.

Energy-insensitive Guidance of Solid Motor Propelled Long Range Flight Vehicles Using MPSP and Dynamic Inversion

A energy-insensitive explicit guidance design is proposed in this paper by appending newlydeveloped nonlinear model predictive static programming technique with dynamic inversion, which render a closed form solution of the necessary guidance command update. The closed form nature of the proposed optimal guidance scheme suppressed the computational difficulties, and facilitate realtime solution. The guidance law is successfully verified in a solid motor propelled long range flight vehicle, for which developing an effective guidance law is more difficult as compared to a liquid engine propelled vehicle, mainly because of the absence of thrust cutoff facility. The scheme guides the vehicle appropriately so that it completes the mission within a tight error bound assuming that the starting point of the second stage to be a deterministic point beyond the atmosphere. The simulation results demonstrate its ability to intercept the target, even with an uncertainty of greater than 10% in the burnout time

A five level inverter scheme with common mode volatge elimination by cascading conventional two level and three level NPC inverters for an induction motor drive

Common-mode voltage generated by the PWM inverter causes shaft voltage, bearing current and ground leakage current in induction motor drive system, resulting in an early motor failure. This paper presents a common-mode elimination scheme for a five-level inverter with reduced power circuit complexity. The proposed scheme is realised by cascading conventional two-level and conventional NPC three-level inverters in conjunction with an open-end winding three-phase induction motor drive and the common-mode voltage (CMV) elimination is achieved by using only switching states that result in zero CMV, for the entire modulation range.