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Baral A.,Jadavpur University | Lahiri A.,Supreme Knowledge Foundation Group of Institutions
2012 1st International Conference on Power and Energy in NERIST, ICPEN 2012 - Proceedings | Year: 2012

Lightning impulse test is one of the mandatory tests that every transformer has to undergo after assembly. This is done for assessing the condition of insulation of its windings. In the case of any fault, the neutral current and/or tank current contain(s) typical signatures depending on the nature and location of the fault. Since these current signals are non-stationary in nature hence each of these faults can be classified from such a transformation technique that has the time-frequency localization property. This paper investigates the performance of Stockwell Transform, popularly known as S-transform, for identification of insulation failures of a transformer winding during impulse test. The present study is restricted only to identify failure of winding insulation due to some defects that are already present in the winding and have not been developed due to the application or during the propagation of impulse voltage applied during the test. The results presented in this paper are for simulated models of a 3 MVA and a 5 MVA transformer. From the results, the prospect of S-transform in identifying the nature and the location of winding faults in distribution transformers is reflected. © 2012 IEEE.


Ghosh M.,Supreme Knowledge Foundation Group of Institutions | Mondal M.,Supreme Knowledge Foundation Group of Institutions | Acharyya A.,University of Calcutta
Advances in OptoElectronics | Year: 2013

The authors have made an attempt to investigate the effect of electron versus hole photocurrent on the optoelectric properties of p+-p-n- n+ structured Wurtzite-GaN (Wz-GaN) reach-through avalanche photodiodes (RAPDs). The photo responsivity and optical gain of the devices are obtained within the wavelength range of 300 to 450 nm using a novel modeling and simulation technique developed by the authors. Two optical illumination configurations of the device such as Top Mounted (TM) and Flip Chip (FC) are considered for the present study to investigate the optoelectric performance of the device separately due to electron dominated and hole dominated photocurrents, respectively, in the visible-blind ultraviolet (UV) spectrum. The results show that the peak unity gain responsivity and corresponding optical gain of the device are 555.78 mA W-1 and 9.4144×103, respectively, due to hole dominated photocurrent (i.e., in FC structure); while those are 480.56 mA W-1 and 7.8800×103, respectively, due to electron dominated photocurrent (i.e., in TM structure) at the wavelength of 365 nm and for applied reverse bias of 85 V. Thus, better optoelectric performance of Wz-GaN RAPDs can be achieved when the photocurrent is made hole dominated by allowing the UV light to be shined on the n+-layer instead of p+-layer of the device. © 2013 Moumita Ghosh et al.


Varshney A.K.,Supreme Knowledge Foundation Group of Institutions | Guha R.,Supreme Knowledge Foundation Group of Institutions | Datta S.K.,Microwave Tube Research and Development Center | Basu B.N.,Supreme Knowledge Foundation Group of Institutions
Journal of Electromagnetic Waves and Applications | Year: 2016

A helix supported by a double-negative metamaterial (DNG-MMT) surrounding it, in a metal envelope, was field-analyzed to show that the shape of the dispersion is more sensitive to the value of the relative permittivity of the metamaterial (MMT) than that of its relative permeability. The field analysis was validated against equivalent circuit analysis as well as against simulation. The values of the MMT support parameters were adjusted to obtain nearly flat, rather slightly negative, dispersion characteristics together with a high value of the interaction impedance of the structure as required for a wideband traveling-wave amplifier. Unlike in a conventional traveling-wave tube, the flow of power of RF wave supported by DNG-MMT loaded helix was found to be in a direction opposite to that of the RF phase velocity of the wave supported by the structure resulting in a negative value of the interaction impedance of the structure suggesting that the device using a helix with double-negative MMT supports would operate in the backward-wave mode analogously to a reversed Cherenkov amplifier. © 2016 Informa UK Limited, trading as Taylor & Francis Group.


Acharyya A.,University of Calcutta | Chakraborty J.,Supreme Knowledge Foundation Group of Institutions | Das K.,Supreme Knowledge Foundation Group of Institutions | Datta S.,Supreme Knowledge Foundation Group of Institutions | And 3 more authors.
International Journal of Microwave and Wireless Technologies | Year: 2013

Large-signal (L-S) characterization of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on silicon designed to operate at different millimeter-wave (mm-wave) and terahertz (THz) frequencies up to 0.5 THz is carried out in this paper using an L-S simulation method developed by the authors based on non-sinusoidal voltage excitation (NSVE) model. L-S simulation results show that the device is capable of delivering peak RF power of 657.64 mW with 8.25% conversion efficiency at 94 GHz for 50% voltage modulation; whereas RF power output and efficiency reduce to 89.61 mW and 2.22% respectively at 0.5 THz for same voltage modulation. Effect of parasitic series resistance on the L-S properties of DDR Si IMPATTs is also investigated, which shows that the decrease in RF power output and conversion efficiency of the device due to series resistance is more pronounced at higher frequencies especially at the THz regime. The NSVE L-S simulation results are compared with well established double-iterative field maximum (DEFM) small-signal (S-S) simulation results and finally both are compared with the experimental results. The comparative study shows that the proposed NSVE L-S simulation results are in closer agreement with experimental results as compared to those of DEFM S-S simulation. Copyright © Cambridge University Press and the European Microwave Association 2013.


Ghosh M.,Supreme Knowledge Foundation Group of Institutions | Ghosh S.,Supreme Knowledge Foundation Group of Institutions | Acharyya A.,Cooch Behar Government Engineering College
Journal of Computational Electronics | Year: 2016

In this paper, the authors have presented a self-consistent quantum drift-diffusion model for multiple quantum well (MQW) impact avalanche transit time (IMPATT) diodes. The bound states in MQWs have been taken into account by self-consistent solutions of the coupled classical drift-diffusion (CLDD) equations and time-independent Schrödinger equations associated with both the conduction and valence bands. The static and high-frequency properties of MQW DDR IMPATTs based on Si(Formula presented.)3C-SiC material system designed to operate near 94-GHz atmospheric window have been studied by means of the above-mentioned self-consistent solutions of coupled CLDD equations and Schrödinger equations followed by a well-established double-iterative field maximum computational technique. A symmetric and two complementary asymmetric doping profiles for the proposed structures have been taken into account for the present study. The RF power outputs of Si(Formula presented.)3C-SiC MQW DDR IMPATTs near 94 GHz obtained from the simulation are compared with the experimentally obtained power outputs of flat DDR IMPATT diodes based on Si, GaAs, and InP at the same frequency band. It is observed that Si(Formula presented.)3C-SiC MQW DDR IMPATTs are capable of delivering significantly higher RF power compared with IMPATTs based on the above-mentioned materials especially when the doping concentrations of 3C-SiC layers are kept higher than those of the Si layers. © 2016 Springer Science+Business Media New York


Day R.R.,Supreme Knowledge Foundation Group of Institutions | Majumder A.,Society for Applied Microwave Electronics Engineering and Research | Chatterjee S.,Jadavpur University
2015 IEEE Applied Electromagnetics Conference, AEMC 2015 | Year: 2015

Present paper exhibits the computer aided design and simulation of a low loss, broadband, rectangular micro-coaxial line to coplanar waveguide (cpw) transition for measurement of two port network parameters for any devices built in micro coaxial transmission line. The transition is designed and optimized around 20 GHz and exhibits a maximum insertion loss of 0.15dB, and a return loss of 18dB. © 2015 IEEE.


Acharyya A.,Supreme Knowledge Foundation Group of Institutions | Banerjee J.P.,University of Calcutta
Journal of Computational Electronics | Year: 2014

A generalized analytical model based on multistage scattering phenomena has been developed in this paper for estimating the impact ionization rate of charge carriers in semiconductors. The probabilities of impact ionization initiated by electrons and holes have been calculated separately by taking into account all possible combinations of optical phonon scattering and carrier-carrier collisions prior to the impact ionization. Finally the analytical expressions of impact ionization rate of electrons and holes have been developed by using the aforementioned impact ionization probabilities. The impact ionization rates of electrons and holes in 4H-SiC have been calculated within the field range of (formula presented) by using the analytical expressions of those developed in the present paper. Those are also calculated by using the analytical expressions developed by some other researchers earlier without considering the multistage scattering phenomena. Finally the theoretical results obtained from the analytical model proposed in this paper and the analytical model developed by earlier researchers within the field range under consideration have been compared with the ionization rate values calculated by using the empirical relations fitted from the experimentally measured data. Closer agreement with the experimental data has been achieved when the impact ionization rate of charge carriers in 4H-SiC are calculated from the proposed model as compared to the earlier one. © 2014, Springer Science+Business Media New York.


Biswas B.N.,Supreme Knowledge Foundation Group of Institutions | Varshney A.K.,Supreme Knowledge Foundation Group of Institutions
Proceedings of the 2015 International Conference on Microwave and Photonics, ICMAP 2015 | Year: 2015

Reflex Klystron Oscillator has been studied again to explore the effects of considering bunching parameter X greater than one. It is observed that as X exceeds unity, the relation between the departure time and the arrival time of the bunched electrons becomes as multivalued function and the Fourier component of the beam current comprises not only the in phase term but also quadrature terms and the equivalent circuit consists of linear negative conductance as well as a non linear reactive part. © 2015 IEEE.


Ghosh B.K.,Supreme Knowledge Foundation Group of Institutions
Asian Journal of Agricultural Research | Year: 2011

This study deals with the study of the diversification of agricultural activities of the West Bengal, one of the leading agricultural state in India. Using the Minhas and Parikh substitution and expansion effects methodology this study revealed that the cropping pattern in West Bengal in terms of allocation of acreage had been skewed towards food grain. However, during the last fifteen to twenty years some important crops (boro rice, potato, oilseeds, especially mustard) emerged as the main crop for the farmers. The cropping pattern turned against pulses, coarse cereals and sugarcane. It was also found that in the cropping pattern changes the expansion effect could explain 54.69% of the gross cropped area and the remaining 45.31% of the gross cropped area was due to the substitution effect. © 2011 Knowledgia Review, Malaysia.


Acharyya A.,University of Calcutta | Chatterjee S.,Supreme Knowledge Foundation Group of Institutions | Goswami J.,Banipur College Road | Banerjee S.,Maulana Abul Kalam Azad University of Technology | Banerjee J.P.,University of Calcutta
Journal of Computational Electronics | Year: 2014

Quantum correction is necessary on the classical drift-diffusion (CLDD) model to predict the accurate behavior of high frequency performance of ATT devices at frequencies greater than 200 GHz when the active layer of the device shrinks in the range of 150-350 nm. In the present work, a quantum drift-diffusion model for impact avalanche transit time (IMPATT) devices has been developed by incorporating appropriate quantum mechanical corrections based on density-gradient theory which macroscopically takes into account important quantum mechanical effects such as quantum confinement, quantum tunneling, etc. into the CLDD model. Quantum potentials (synonymous as Bohm potentials) have been incorporated in the current density equations as necessary quantum mechanical corrections for the analysis of millimeter-wave (mm-wave) and Terahertz (THz) IMPATT devices. It is observed that the large-signal (L-S) performance of the device is degraded due to the incorporation of quantum corrections into the model when the frequency of operation increases above 200 GHz; while the effect of quantum corrections are negligible for the devices operating at lower mm-wave frequencies. © 2014 Springer Science+Business Media New York.

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