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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.


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.


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.


Banerjee P.,Techno India | Acharyya A.,Supreme Knowledge Foundation Group of Institutions | Biswas A.,NFET | Bhattacharjee A.K.,National Institute of Technology Durgapur
Journal of Computational Electronics | Year: 2016

In this paper, a two-dimensional (2-D) large-signal model has been presented to study the effect of steady magnetic field on the RF performance of millimeter-wave (mm-wave) double-drift region impact avalanche transit time device. Magnetic field sensitivities of various static and large-signal parameters of the device designed to operate at W-band have been calculated and discussed in detail. Results show that the frequency tuning of the source of around 3.64 GHz is achievable with maximum sensitivity of about (Formula presented.) 1.59 GHz (Formula presented.) for the application of transverse magnetic field varying from 4.0 to 5.0 T. The nature of both frequency and power tuning of the device due to application of transverse magnetic field is in good agreement with the experimental results carried out earlier. © 2015, Springer Science+Business Media New York.


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.

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