Electrical Engineering

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This paper presents a family of circuits for single phase diode rectifiers capable of drawing approximately sinusoidal current waveforms at unity power factor with high efficiency and minimum voltage stress across the switches. Moreover, they are suitable to work as boost and flyback converters. These topologies use coupled inductors with capacitor for resonance to achieve zero voltage switching (ZVS) of the converters. The circuits consist of a single-phase diode bridge rectifier, followed by a boost stage containing a single switch with zero current switching (ZCS) for turning on and ZVS as well as ZCS for turning off. The output voltage is regulated by employing variable frequency control. The paper explains the principle of operation and describes the analysis of each mode of operation for both boost and flyback converters. It also gives design criteria, derived from the mathematical analysis carried out, for achieving ZVS under all loading conditions from no load to full load. The simulation results obtained using PSPICE demonstrate the validity of the proposed converters. © 1998 IEEE.

World University root node

(SoE) School of Engineering

PEDES 1998 - 1998 International Conference on Power Electronic Drives and Energy Systems for Industrial Growth

Soft-switched low-cost single phase high quality rectifier circuits with minimum voltage stress across the switches

A non-contact, non-destructive technique is presented for the width profiling of modulated current carrying microconductors. Based on the Mirage Effect, experimental results on a test sample are shown to be in excellent agreement with theory. In general the technique would give a reliable estimation of the thermal behaviour of interconnect lines. Possible applications could include failure prediction studies based on the 'electromigration' phenomenon, thermal management and reliability issues in printed circuit boards and multi-chip modules, etc.

Proceedings of the 1998 4th International Workshop on Thermal Investigations of ICs and Microstructures

Mirage based profiling of current carrying microconductors

The effect of drag reducing agents (DRA) on corrosion and flow regime has been studied in a 10 cm diameter, 18 m long plexiglass flow loop in 50% oil/water mixtures with carbon dioxide gas. Superficial liquid velocities between 0.1 and 1 m/s and gas velocities between 1 and 10 m/s respectively were studied. The corrosion rate was measured for stratified, slug and annular flow. The height of liquid film, slug velocity, and slug frequency were obtained from the video image using a super-VHS camera. The DRA effectiveness was examined for DRA concentrations between 0 and 75 ppm. Flow regimes maps were determined with 25 and 75 ppm DRA. These results were compared to the flow regime map with no DRA. The results indicate that the transition from stratified to slug flow is obtained at a higher superficial liquid velocities. This resulted in much lower corrosion rates due to the elimination of the highly turbulent slugs. The corrosion rate for stratified and annular flow did not generally reduce with adding DRA concentrations. For slug flow, the slug frequency decreased with the addition of 50 ppm DRA. This led to decrease of corrosion rate by almost 50%. © 1998 by NACE International.

NACE - International Corrosion Conference Series

The effect of drag reducing agents on corrosion in multiphase flow

This paper presents some novel circuits of soft-switched quasi-resonant DC/DC boost and flyback converters. These topologies use coupled inductors with capacitor for resonating circuit to achieve zero voltage switching of the converters. The circuits have minimum voltage stress across the switches. Moreover, they have reduced commutation losses and increased switching frequency. The paper explains the principle of operation and describes the analysis of both boost as well as flyback converters. It also gives design criteria, derived from the mathematical analysis carried out, for achieving zero voltage switching under all loading conditions from no load to full load. The feasibility of the proposed circuits has been verified by PSPICE simulation.

IECON Proceedings (Industrial Electronics Conference)

Some novel topologies of soft-switched quasi-resonant DC/DC converters with minimum voltage stress across the switch

The principle of operation of the transistor-based Marx bank circuit has been examined. It was experimentally observed that stage-wise increase of reverse voltage does not occur. This cannot be explained by the principle of operation understood so far. A new explanation, consistent with the experimental observations and associating current-mode second breakdown of transistors, is proposed. A few experimental observations made by earlier workers have also been justified in light of the new current-controlled mechanism. © 1998 American Institute of Physics.

Fulltext

Review of Scientific Instruments

The principle of operation of the avalanche transistor-based Marx bank circuit: A new perspective

This paper presents a new quasi-resonant DC-link (QRDCL) PWM inverter with zero voltage switching (ZVS) capability. The proposed quasi-resonant circuit creates zero voltage intervals in the DC-link to facilitate ZVS of the inverter switches under all operating conditions. This is achieved with the DC-link voltage being clamped at the source voltage V, using minimum additional components. It requires only two additional switches compared to the conventional PWM converter. Moreover, the control circuit is not called upon to control the inductor current, as it is the case with other circuits of the same family. Hence, it doesn't require any current sensing device, thereby, making the control circuit simple and cheap. The operating principle of the circuit is explained and detailed analysis of each operating mode is given. A design criterion for achieving ZVS is obtained from the mathematical analysis. The feasibility of the proposed circuit operation has been verified by PSPICE simulation. The simulation results show full ZVS for both the proposed circuit and the PWM inverter. © 1998 IEEE.

PESC Record - IEEE Annual Power Electronics Specialists Conference

A novel ZVS quasi-resonant DC-link PWM inverter with minimum voltage stress across the switches

The use of a self-organising neural network as a feedforward compensator for robot tracking control applications is proposed. The topology of the input space is adaptively mapped onto a set of neurons where each neuron represents a discrete cell in the input domain. Within each cell, a linear mapping is established between the input and output space. The training of such a network involves training of a weight vector that represents the topology of the input space and weight vectors (action space weights) that linearly code an input pattern to action space. In the first phase of network training, a 'neural-gas' algorithm is employed for learning the topology of the input space while weight vectors representing control action space is learned by backpropagating feedback control action. During this phase of learning, the weights associated with neurons in the neighbourhood of winning neurons are also updated. In the second stage, a recursive least squares based estimation scheme is applied to fine tune the action space weights associated with winning neurons only, without disturbing the input topology map learned in the first phase. The proposed scheme has been compared with multilayered network (MLN) and radial basis function network (RBFN) based inverse dynamics learning schemes. Simulation results show that the proposed scheme has better generalisation capability than both MLN and RBFN. © lEE, 1998.

IEE Proceedings: Control Theory and Applications

Application of self-organising neural networks in robot tracking control

A definition is given for a Froude number in the liquid film ahead of the slug and it is seen that slug characteristics are strongly influenced by the Froude number. The mechanisms in the mixing zone of the slug are described in detail and are shown to be a function of the film Froude number. It is shown that the Hubbard and Dukler model for mixing length is inadequate. A new expression is proposed for the slug mixing length as a function of the film Froude number. © 1998 by ASME.

Journal of Energy Resources Technology, Transactions of the ASME

The study of dynamic slug flow characteristics using digital image analysis-Part II: Modeling results

This paper reports the application of novel, digital image analysis techniques in the study of slug flow characteristics, under dynamic conditions in two-phase gas-liquid mixtures. Water and anoil of viscosity 18 cP were used for the liquid phase and carbon dioxide was used for the gas phase. Flow in a 75-mm i.d., lO-m long acrylic pipeline system was studied. Images of slugs were recorded onvideo by S-VHS cameras, using an audio-visual mixer. Each image was then digitized frame-by-frame andanalyzed on a SGIࡊ workstation. Detailed slug characteristics, including liquid film heights, slug translational velocity, mixing length, and, slug length, were obtained. © 1998 by ASME.

The study of dynamic slug flow characteristics using digital image analysis-part I: Flow visualization

A mechanistic model has been developed to predict corrosion rates in multiphase (water/oil/CO2) flow conditions. The model takes into account electrochemistry, reaction kinetics, and, mass transport effects. This paper describes the equations used to determine pH and bulk concentrations of various ions, which are then used to calculate the mass transfer rates to the corrosion surface. The result includes the determination of the mass transfer coefficients of various ionic species and corrosion rates. Details of relations used for determination of mass transfer coefficients for multiphase flows, and rates of electrochemical reaction kinetics are discussed and predicted results are compared with experimental observations. Agreement between model results and experimental data is good. © 1997 by NACE International.