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Wyświetlanie 1-10 z 10
Tytuł:
Modeling and optimization of the YAG:Yb microchip laser passively Q-switched by YAG:Cr absorber
Autorzy:
Buryy, O
Ubizskii, S
Powiązania:
https://bibliotekanauki.pl/articles/175041.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Yb:YAG crystal
microlaser
Q-switching
numerical simulation
Opis:
Based on analytical and numerical solutions of the rate equations system and the heat conductivity equation, the model of the quasi-three-level passively Q-switched YAG:Yb/YAG:Cr microchip laser is developed. The obtained results are used for its optimization, i.e., for the determination of the output mirror reflectivity, the pumping beam radius, the thickness of the absorber and the phototropic centers concentration maximizing the energy in the laser pulse. The influence of the thermal load on the spatial parameters of the laser beam is also determined.
Źródło:
Optica Applicata; 2014, 44, 4; 621-636
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Development of energy-efficient IBC with IGBT module for photovoltaic applications
Autorzy:
Kumar, C. Prasanna
Rao, Anand
Powiązania:
https://bibliotekanauki.pl/articles/1193903.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
interleaved boost converter
efficiency
stability
power converter
switching frequency
Opis:
The proposed study is improvised value-engineered modifications for the basic interleaved boost converter (IBC) by including relevant modifications in circuits, which is expected for a better performance in switching with reduction in losses. The newly modified IBC circuit with insulated gate bipolar transistor (IGBT) along with converter has been experimented by simulations and the results are tabulated to modified IBC with metal oxide silicon field effect transistors. Further experimental analysis and validations of the proposed simulation with hardware developed adopting model SKM195GB066D consisting of IGBTs is presented. This study further enhances and summarises the optimum utilisation and the performance of IBC with the proposed IGBT modules that synchronises power diode. Enhancing the simulation outcomes, the hardware is proposed and developed to be tested for a load up to 1.5 kW with the evaluation of key parameters such as efficiency of the converter.
Źródło:
Power Electronics and Drives; 2020, 5, 40; 73-81
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reliability analysis of N-policy vacation-based FTC system subject to standby switching failures
Autorzy:
Kumar, Sudeep
Gupta, Ritu
Powiązania:
https://bibliotekanauki.pl/articles/27315336.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
reliability
standby switching failure
N-policy
server breakdown
optional service
Opis:
The paper is aimed to investigate the reliability metrics of a multi-unit fault-tolerant control (FTC) system wherein the units are subject to failure and those are repairable by two heterogeneous servers. Server 1 remains permanently available for essential service of failed units, whereas server 2 goes on vacation and renders service based on the N-policy threshold, which may also provide optional and essential services. Server 1 may break down at a steady rate during its servicing period but immediately gets repaired and resume servicing the failed units. When the working unit fails, the available warm standby unit holds responsibility for the smooth operation of the system. The transition of standby units to operational mode may be unsuccessful with switching failure probability. We develop a Markovian model to obtain the steady-state probabilities. We explore computational and sensitivity analysis of different performance measures for various variability of the parameters.
Źródło:
Operations Research and Decisions; 2023, 33, 2; 53--80
2081-8858
2391-6060
Pojawia się w:
Operations Research and Decisions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Power-induced lasing state switching and bistability in a two-state quantum dot laser subject to optical injection
Autorzy:
Jiang, Zaifu
Wu, Zhengmao
Jayaprasath, Elumalai
Yang, Wenyan
Hu, Chunxia
Cui, Bing
Xia, Guangqiong
Powiązania:
https://bibliotekanauki.pl/articles/173329.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
two-state quantum dot laser
lasing state switching
bistability
optical injection
Opis:
We theoretically investigate power-induced lasing state switching and bistability in a two-state quantum dot laser subject to optical injection. The simulated results show that, for a free-running two-state quantum dot laser operating at the ground state under low current, a power-induced lasing state switching between the ground state and the excited state can be achieved through introducing optical injection with a frequency (winj) close to the lasing frequency of excited state (wES). The injection power required for the state switching depends on the scanning route of injection power, i.e. there may exist state bistability for the injection power within a certain region. For forward scanning injection power, with the increase of frequency detuning (ΔΩ = winj – wES), the injection power required for the state switching shows a decreasing trend accompanied by slight fluctuations. However, for backward scanning injection power, the injection power required for the state switching exhibits obvious fluctuations with the increase of ΔΩ. The width of the hysteresis loop fluctuates with ΔΩ, and the fluctuation amplitude is increased with the increase of the injection current. Additionally, the influences of the inhomogeneous broadening factor and the electron escape rate on the bistability performances are analyzed.
Źródło:
Optica Applicata; 2020, 50, 2; 257-269
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The desctiption of turn-off process and evaluation of switching power losses in the ultra fast power MOSFET
Autorzy:
Grzejszczak, P.
Barlik, R.
Powiązania:
https://bibliotekanauki.pl/articles/1193214.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
power MOSFET
turn-off transient
parasitic capacitance
switching losses
thermovision measurement
Opis:
The article presents an analytical description of the turn-off process of the power MOSFET suitable for use in high-frequency converters. The purpose of this description is to explain the dynamic phenomena occurring inside the transistor and contributing to the switching power losses. The detailed description uses the results of simulation studies carried out using a very precise model of the CoolMOS transistor manufactured by Infineon (IPW60R070C6). The theoretical analysis has been verified in experimental measurements of power dissipated during turn-off transient of MOSFET operating in a full bridge converter with switching frequency of 100 kHz. To estimate these switching losses an original thermovision method based on the measurement of heat dissipated in the power semiconductor switches has been used. The obtained results confirm the correctness of the conclusions drawn from the theoretical analysis presented in this paper.
Źródło:
Power Electronics and Drives; 2016, 1, 36/1; 55-67
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method of reducing switching losses in three-level NPC inverter
Autorzy:
Beniak, R.
Rogowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1193262.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
reduction of switching losses
three-level NPC inverter
space vector modulation
Opis:
The aim of the paper is to present a concept of implementation of a space vector modulation (SVM) algorithm, which is used to create alternating current waveforms of changing amplitude and frequency in power inverters. The main goal of the method is to decrease the number of state changes in power transistors. It is realized by utilizing a prediction algorithm and sequences of transistors, which are not common in use. The method requires measurement of inverter output current flow. The prediction algorithm analyzes possible sequences of transistors’ states and choose those which offers smaller switch count. A decrease of about 20% was obtained for the cases tested. This paper presents simulation result for selected driving scenario. The described method decreases the number of state changes in power transistors and therefore it is a potentially good method to considerably decrease energy losses of multilevel inverter-powered drive.
Źródło:
Power Electronics and Drives; 2016, 1, 36/2; 55-63
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Price patterns in an oligopoly with switching cost and uncertain demand
Autorzy:
Zawisza, M.
Kamiński, B.
Powiązania:
https://bibliotekanauki.pl/articles/406324.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
price competition
switching cost
agent-based modeling
uncertain demand
price volatility
Opis:
Characteristics of price patterns have been investigated in an oligopoly market with costs for switching a provider. Two regimes of a company’s access to information have been considered. In the benchmark scenario, firms make decisions based on perfect information about demand. In the other – more realistic scenario – they conduct market research to estimate an unknown demand curve and therefore face uncertainty regarding their profit function, which in turn leads to suboptimal decision making. The authors inspected how a company’s access to information on demand, costs for switching a provider and the rate of market renewal influence price patterns on the market. It has been shown that positive switching cost is a sufficient condition for price dispersion, as well as imperfect information about the company's profit function, e.g. from market research. The average price under the perfect information regime is lower than under market research based price setting, a higher switching cost makes it easier for companies to coordinate their prices and a higher rate of market renewal softens the influence of the switching cost on market price.
Źródło:
Operations Research and Decisions; 2013, 23, 3; 71-89
2081-8858
2391-6060
Pojawia się w:
Operations Research and Decisions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Arc to Glow Transition for Using DC Low Power Switches in Low Voltage Electric Grids
Autorzy:
Wisniewski, G.
Powiązania:
https://bibliotekanauki.pl/articles/1202499.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
switching arc DC
low voltage
low power installation
arc-to-glow transition
Opis:
This paper presents and discusses results of analysis and investigations of arc to glow transformation phenomenon at contact opening, under DC inductive loads of low power (≤10 J) and low voltage (≤250 V). The proportion in duration of arcing and glowing is investigated in dependence on current and voltage value, contact material properties. The transition phenomenon is analyzed by means of fast photography and emission spectroscopy to complete the study. On the basis of investigated results the conclusions about the possibility of control of the arc to glow transformation for practical use in DC low voltage and low power electrical grids are formulated.
Źródło:
Present Problems of Power System Control; 2017, 8; 31-40
2084-2201
Pojawia się w:
Present Problems of Power System Control
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sliding mode speed control of an induction motor drive using time-varying switching line
Autorzy:
Tarchała, G.
Powiązania:
https://bibliotekanauki.pl/articles/1193307.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
sliding mode control
equivalent control
induction motor
speed controller
time-varying switching line
Opis:
An equivalent sliding mode control method of an induction motor speed has been discussed. The control signal consists of two parts: a continuous and discontinuous one. Very good dynamical response of the drive system has been obtained, which however changes influenced by external and parametric disturbances occurring under various operation conditions. In order to ensure identical dynamic performance of the speed transients and system robustness during the switching line reaching phase, regardless of external and parametric disturbances, the time-varying switching line is proposed. The simulation results have been validated by experimental tests of the induction motor drive system.
Źródło:
Power Electronics and Drives; 2017, 2, 37/1; 105-120
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Bidirectional Buck-Boost Converter-Based Switching Ripple Communication Strategy for Intelligent Street Lighting Systems
Autorzy:
Zhang, Yixuan
Hu, Yihua
Tse, Zion
Liu, Yuwei
Deng, Jiamei
Xu, Hui
Wang, Yangang
Li, Wei
Powiązania:
https://bibliotekanauki.pl/articles/1955998.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
bidirectional switching ripple communication
buck-boost converter
intelligent street lighting system
pulse width modulation
smart city
Opis:
The light-emitting diode (LED) is an essential component of intelligent street lighting (ISL) systems. An efficient ISL system can not only reduce power consumption by planning LED illuminating time but also reduce maintenance costs through a high degree of automation. In this paper, a buck-boost converter is used to realise composite transmission of power and signals for an ISL system. The power is modulated by the pulse width modulation (PWM) approach, and the switching ripple generated in the PWM process is utilised as the carrier of the signals transmitted between the remote-control centre and the slave nodes. Moreover, the proposed model involves a ‘request to send (RTS)/confirm to send (CTS)’ mechanism to avoid signal conflicts. Compared with the conventional power line communication (PLC) approach, the proposed transmission scheme has the advantages of simple circuit structure and simple system wiring. Additionally, a simulation model built in MATLAB/Simulink proves the designed transmission method has strong anti-noise ability.
Źródło:
Power Electronics and Drives; 2021, 6, 41; 260-275
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-10 z 10

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