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Venado Tuerto, Argentina

Milardovich N.,Laboratorio Of Electricidad | Prevosto L.,Grupo de Descargas Electricas | Lara M.A.,UNR
Advanced Electromagnetics | Year: 2014

A numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commerciallyavailable LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral) of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current) were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severe harmonic emission limits should be defined for LED lamps. © 2014, Tarbiat Modares University. All rights reserved.

Prevosto L.,Grupo de Descargas Electricas | Kelly H.,Grupo de Descargas Electricas | Kelly H.,CONICET | Mancinelli B.,Grupo de Descargas Electricas
Plasma Chemistry and Plasma Processing | Year: 2016

A model of an atmospheric pressure nitrogen glow discharge in high-gas temperature regimes is developed. The model considers a fairly complete set of chemical reactions, including several processes with the participation of electronically exited nitrogen atoms describing the energy balance and charged particles kinetic processes in the discharge. It is shown that the thermal dissociation of vibrationally excited molecules plays an essential role in the production of N(4S) atoms. The dominant ion within the investigated current range (52–187 mA) is the molecular N2 + with an increasing proportion of atomic N+ towards high-current values. The process of production of electrons within the almost whole current range is controlled predominantly by associative ionization in atomic collisions N(2P) + N(2P) → N2 + + e; being the N(2P) atoms mainly produced via quenching of N2(A3∑u +) electronically excited molecules by N(4S) atoms. The results of calculations are compared with the available experimental data and a good agreement is found. © 2016, Springer Science+Business Media New York.

Prevosto L.,Grupo de Descargas Electricas | Kelly H.,Grupo de Descargas Electricas | Kelly H.,CONICET | Mancinelli B.R.,Grupo de Descargas Electricas
Review of Scientific Instruments | Year: 2014

Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N2 gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 10 22 m-3 were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW. © 2014 AIP Publishing LLC.

Prevosto L.,Grupo de Descargas Electricas | Mancinelli B.,Grupo de Descargas Electricas | Kelly H.,Grupo de Descargas Electricas | Kelly H.,CONICET
Advanced Electromagnetics | Year: 2012

The power sources used in cutting arc torches are usually poorly stabilized and have a large ripple factor. The strong oscillatory components in the voltage and arc current produce in turn, large fluctuations in the plasma quantities. Experimental observations on the dynamics of the nonequilibrium plasma inside the nozzle of a 30 A oxygen cutting torch with a 7 % ripple level of its power source are reported in this work. The observed electron temperature (mean value ≈ 5400 K) shows a rms deviation ≈ 5 % (± 300 K), which is of the order of the arc voltage ripple level. A considerable different situation occurs with the plasma density (mean value ≈ 3 × 10 19 m -3). In this case the rms deviation was ≈ 75 %, much greater than that of the electron temperature. © 2012, Advanced Electromagnetics. All rights reserved.

Prevosto L.,Grupo de Descargas Electricas | Kelly H.,Grupo de Descargas Electricas | Kelly H.,CONICET | Mancinelli B.,Grupo de Descargas Electricas | Chamorro J.C.,Grupo de Descargas Electricas
Plasma Chemistry and Plasma Processing | Year: 2015

The present work provides a detailed kinetic analysis of the time-resolved dynamics of the gas heating during the arc reattachment in nitrogen gas in order to understand the main processes leading to such a fast reattachment. The model includes gas heating due to the relaxation of the energy stored in the vibrational as well as the electronic modes of the molecules. The results show that the anode arc reattachment is essentiality a threshold process, corresponding to a reduced electric field value of E/N ~ 40 Td for the plasma discharge conditions considered in this work. The arc reattachment is triggered by a vibrational instability whose development requires a time of the order of 100 µs. For E/N < 80–100 Td, most of the electron energy is transferred to gas heating through the mechanism of vibrational–translational relaxation. For larger values of E/N the electronic–translational energy relaxation mechanism produces a further intensification of the gas heating. The sharp increase of the gas heating rate during the last few µs of the vibrational instability give rises to a sudden transition from a diffuse (glow-like) discharge to a constricted arc with a high current density (~107 A/m2). This sudden increase in the current density gives rise to a new anode attachment closer to the cathode (where the voltage drop between the original arc and the anode is the largest) thus causing the decay of the old arc spot. © 2015 Springer Science+Business Media New York

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