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Dive into the research topics where L. M. Redondo is active.

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Featured researches published by L. M. Redondo.


IEEE Transactions on Dielectrics and Electrical Insulation | 2009

Generalized solid-state marx modulator topology

L. M. Redondo; Hiren Canacsinh; José Fernando Silva

A generalized circuit topology for bipolar or unipolar high voltage repetitive pulse power applications is proposed. This circuit merges the negative and positive solid state Marx modulator concepts, which take advantage of the intensive use of semiconductor devices to increase the performance of the original dissipative Marx modulators. The flexibility of the proposed modular circuit enables the operation with negative and/or positive pulses, selectable duty cycles, frequencies and relaxation times between the positive and negative pulse. Additionally, the switching topology enables the discharge of the parasitic capacitances after each pulse, allowing the use of capacitive loads, and the clamping of inductive loads, recovering the reset energy back to the main capacitors. Analysis of efficiency and power loss will be addressed, as well as experimental details for different conditions based on laboratory prototype, with 1200 volt Insulated Gate Bipolar Transistors (IGBT), diodes, and 4.5 muF capacitors.


IEEE Transactions on Plasma Science | 2009

Repetitive High-Voltage Solid-State Marx Modulator Design for Various Load Conditions

L. M. Redondo; José Fernando Silva

The analysis of a solid-state Marx modulator (S2M2) topology, which have been developed for repetitive high-voltage (in kilovolts) applications, needing positive or negative rectangular pulses, is presented. The proposed topology benefits from the intensive use of semiconductors, allowing kilohertz operation with different load conditions. In addition to resistive loads, capacitive loads can be discharged to ground after each pulse and inductive loads can be clamped and the energy recovered to the main capacitors. Furthermore, the presented topology and proposed switching sequence enables the use of typical half-bridge semiconductor structures currently integrated in modular packages, which is advantageous for circuit assembling and triggering the semiconductors. Discussion on the advantages and limitation will be given. Finally, experimental results of some modulator features will be presented.


IEEE Transactions on Plasma Science | 2012

Marx-Type Solid-State Bipolar Modulator Topologies: Performance Comparison

Hiren Canacsinh; L. M. Redondo; José Fernando Silva

The operation of generalized Marx-type solid-state bipolar modulators is discussed and compared with simplified Marx-derived circuits, to evaluate their capability to deal with various load conditions. A comparative analysis on the number of switches per cell, fiber optic trigger count, losses, and switch hold-off voltages has been made. A circuit topology is obtained as a compromise in terms of operating performance, trigger simplicity, and switching losses. A five-stage laboratory prototype of this circuit has been assembled using 1200 V insulated gate bipolar transistors (IGBTs) and diodes, operating with 1000 V dc input voltage and 1 kHz frequency, giving 5 kV bipolar pulses, with 2.5 μs pulse width and 5 μs relaxation time into resistive, capacitive, and inductive loads.


IEEE Transactions on Plasma Science | 2010

A DC Voltage-Multiplier Circuit Working as a High-Voltage Pulse Generator

L. M. Redondo

The intensive use of semiconductor devices enabled the development of a repetitive high-voltage pulse-generator topology from the dc voltage-multiplier (VM) concept. The proposed circuit is based on an odd VM-type circuit, where a number of dc capacitors share a common connection with different voltage ratings in each one, and the output voltage comes from a single capacitor. Standard VM rectifier and coupling diodes are used for charging the energy-storing capacitors, from an ac power supply, and two additional on/off semiconductors in each stage, to switch from the typical charging VM mode to a pulse mode with the dc energy-storing capacitors connected in series with the load. Results from a 2-kV experimental prototype with three stages, delivering a 10- s pulse with a 5-kHz repetition rate into a resistive load, are discussed. Additionally, the proposed circuit is compared against the solid-state Marx generator topology for the same peak input and output voltages.


IEEE Transactions on Power Electronics | 2002

Rise time reduction in high-voltage pulse transformers using auxiliary windings

L. M. Redondo; Elmano Margato; José Fernando Silva

Today high-voltage pulses are reaching more fields of application. High-voltage pulse transformers are often used in association with high-voltage pulse generating circuits to further increase the pulse output voltage level. However, because of the transformer parasitic elements involved, the transformer is the critical device in shaping the rising characteristics of the output pulse. One of the techniques usually adopted to decrease the leakage inductance of the transformer adds two auxiliary windings to the transformer. If properly used, these auxiliary windings reduce the leakage flux and, therefore, the leakage inductance. As a result the pulse rise time is reduced. In this paper, a mathematical model is used to describe the observed behavior of a transformer operating with auxiliary windings, based on the theory of electromagnetic coupled circuits. The model is discussed regarding the experimental results obtained from a high-voltage test transformer associated with a high-voltage pulse generating circuit, and the simulation results obtained from the numerical evaluation of the developed differential equations implemented in Matlab/Simulink with the measured transformer parameters.


Surface & Coatings Technology | 2001

A new method to build a high-voltage pulse supply using only semiconductor switches for plasma-immersion ion implantation

L. M. Redondo; Elmano Margato; J. Fernando Silva

Abstract A new method to obtain high voltage (kV) pulses suitable for a plasma immersion ion implantation (PIII) facility is presented. The circuit proposed is based on a step-up transformer with a constant flux reset clamp circuit that takes advantage of the low duty ratio required to reduce the voltage stress on all semiconductor switches. An initial prototype was assembled with 800-V semiconductor switches for an output pulse of −5 kV, 5-μs pulse width and 10-kHz pulse frequency. Theoretical and experimental results are presented and discussed.


power electronics specialists conference | 2008

New solid-state Marx topology for bipolar repetitive high-voltage pulses

Hiren Canacsinh; L. M. Redondo; José Fernando Silva

A novel bipolar high-voltage modulator topology, based on the Marx generator concept, is proposed for high-voltage repetitive pulsed power applications. The proposed topology is a generalized version of the negative and positive all-solid-state Marx modulator concepts, which takes advantage of the intensive use of power semiconductor switches to increase the performance of the classical circuit, strongly reducing losses and increasing the pulse repetition frequency. Additionally, the proposed topology enables the use of typical half-bridge semiconductor structures while ensuring that the maximum voltage blocked by the semiconductors is the voltage of the capacitor in each stage. Due to semiconductor topology used the output voltage is very flexible. Hence, it is possible to change from negative to positive unipolar to bipolar pulse, with different duty cycles and different switching patterns. Experimental results are presented and discussed. A laboratory prototype with 10 kW peak power, of this bipolar solid-state modulator circuit, was assembled 1200 V IGBTs and diodes, operating with 1000 V d-c input voltage and 10 kHz frequency, giving 2 kV bipolar pulses, 5 A, with 5 mus into a resistive load.


IEEE Transactions on Magnetics | 2007

Pulse Shape Improvement in Core-Type High-Voltage Pulse Transformers With Auxiliary Windings

L. M. Redondo; José Fernando Silva; Elmano Margato

High-voltage pulsed power technologies are rapidly emerging as a key to efficient and flexible use of electrical power for many industrial applications. One of the most important elements in high-voltage pulse-generating circuit technology is the transformer, generally used to further increase the pulse output voltage level. However, its nonideal behavior has significant influence on the output pulse shape. The most attractive winding configuration for high-voltage, the core-type transformer with primary and secondary on different core legs, is seldom used in pulsed applications, because of its weak magnetic coupling between windings, which would result in a slow-rising output voltage pulse. This paper shows that auxiliary windings, suitably positioned and connected, provide a dramatic improvement in the pulse rise time in core-type high-voltage pulse transformers. The paper derives a mathematical model and uses it to describe the observed behavior of the transformer with auxiliary windings. It discusses experimental results, obtained from a high-voltage test transformer associated with a high-voltage pulse generating circuit, and the simulation results obtained from the numerical evaluation of the developed differential equations implemented in Matlab and taking into account the measured transformer parameters


IEEE Transactions on Plasma Science | 2009

Flyback Versus Forward Switching Power Supply Topologies For Unipolar Pulsed-Power Applications

L. M. Redondo; José Fernando Silva

We discuss and compare modified flyback and forward switching power converter topologies in applications needing repetitive high-voltage (HV) low duty-cycle rectangular unipolar pulses. The output filters of these two converter topologies are removed, and the needed low duty-cycle operation is used advantageously to generate several kilovolts of pulses using only low-voltage seriesless semiconductors. The two circuits proposed are based on step-up transformers with a constant flux reset clamp that uses the low duty cycle required to reduce the voltage stress on all semiconductor switches. Prototypes were assembled using < 1-kV semiconductor switches to obtain -5-kV output pulses with 5-mus pulsewidth and 10-kHz pulse frequency. Experimental results are presented and discussed. The forward topology was found to be a better choice to deliver HV low duty-cycle unipolar rectangular pulses, and it was tested in a plasma load.


Bioelectrochemistry | 2015

Control of predators in industrial scale microalgae cultures with Pulsed Electric Fields.

D. Rego; L. M. Redondo; V. Geraldes; Luiz Costa; J. Navalho; Marcos Teotónio Pereira

This work describes the utilization of Pulsed Electric Fields to control the protozoan contamination of a microalgae culture, in an industrial 2.7 m(3) microalgae photobioreactor. The contaminated culture was treated with Pulsed Electric Fields, PEF, for 6h with an average of 900 V/cm, 65 μs pulses of 50 Hz. Working with recirculation, all the culture was uniformly exposed to the PEF throughout the assay. The development of the microalgae and protozoan populations was followed and the results showed that PEF is effective on the selective elimination of protozoa from microalgae cultures, inflicting on the protozoa growth halt, death or cell rupture, without affecting microalgae productivity. Specifically, the results show a reduction of the active protozoan population of 87% after 6h treatment and 100% after few days of normal cultivation regime. At the same time, microalgae growth rate remained unaffected.

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Hiren Canacsinh

Instituto Superior de Engenharia de Lisboa

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J. Fernando Silva

Instituto Superior Técnico

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J. Rocha

Instituto Superior Técnico

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Elmano Margato

Instituto Superior de Engenharia de Lisboa

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J. Lopes

Instituto Superior de Engenharia de Lisboa

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João Paulo Mendes

Universidade Nova de Lisboa

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M.F. da Silva

Instituto Nacional de Engenharia

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E. Alves

Instituto Superior Técnico

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