Switching-off Process Research Articles

Influence of Parasitic Elements and Operating Conditions of Semiconductor Switches on Power Losses and the Junction Temperature of These Switches

This article presents the results of computer analysis of selected switching networks. In these analyses, the influence of selected parasitic components of electronic switches on the total and active power losses in these switches is considered. Analyses are performed using the SPICE software for two models of semiconductor switches: an ideal switch with RC parasitic components and the SPICE model of an IGBT. The influence of parasitic capacitances and resistances of these devices operating with the control signal of different parameters values on the total and active power dissipated in these switches is analyzed. On the basis of the obtained computations the average and peak-to-peak values of the junction temperature of electronic switches at the steady state are calculated using a compact thermal model. It is shown that parasitic elements visibly influence waveforms of the active and total power. It is proved that the simplified model using the total power in computations of the junction temperature makes it possible to obtain a high accuracy of computations only in a situation when the transistor operates with a resistive load. For an inductive load, such simplification can cause an unacceptably high computation error exceeding even 30%. Such an error is a result of big differences between the active and total powers during switching-on and switching-off processes.

Communication strategy in socialising analogue switch off in North Sulawesi

This research delves into the efficacy of the North Sulawesi Broadcasting Commission's communication strategy in facilitating the analogue switch-off programme. The study employs qualitative research methods, utilising in-depth interviews with key stakeholders, and adopts Hafied Cangara's communication strategy framework, based on Laswell's theory , to analyse the Commission's approach. The outcomes reveal that the Commission's communication plan effectively conveyed the intended message to the public. It achieved its objectives of disseminating information and educating the populace about the switch-off process. Nonetheless, the plan could have been further enhanced to better address the diverse needs and concerns of the audience. The findings offer valuable insights into the challenges and opportunities associated with implementing the analogue switch-off programme, especially concerning formulating efficient communication strategies that can effectively reach all segments of Society. By shedding light on these aspects, this research significantly contributes to the broader discourse on digital television and its profound influence on broadcasting policies in Indonesia.

Experimental validation of heat switch capability of cryogenic loop heat pipe

The nitrogen-charged cryogenic loop heat pipe (CLHP) was utilized as an effective cryogenic heat switch operating at around 100 K by thermally connecting or blocking a cryogenic heat source and a cryogenic heat sink. The switching-off function of the CLHP heat switch was achieved by eliminating heat load on the secondary evaporator without any dedicated support of additional components or mechanisms during a normal operation. The removal of heat load on the secondary evaporator leads to the dry-out of the primary evaporator, which causes the thermal switching-off ultimately. The on/off thermal conductance ratios of the CLHP heat switch were obtained in various operational conditions such as different heat loads on the primary and secondary evaporators and different initial charging-pressures of nitrogen. The switching-off process divided into the on-state, transient state, and off-state was investigated experimentally, and the characteristics in the unsteady off-state were specially analyzed in detail. The obtained on/off thermal conductance ratios of the CLHP heat switch were in the range from 400 to 3900 in the experiments which are exceedingly larger than those of the conventional heat switches. The ratio becomes larger when the initial charging-pressure of working fluid is low but the heat loads on the primary evaporator and/or the secondary evaporator are large because the effective thermal conductance in the on-state is dominantly affected by the mass flow rate of working fluid. Between the heat loads on the primary and secondary evaporators, the on/off thermal conductance ratio of the CLHP heat switch is more sensitively affected by the heat load on the PE.

Driving Waveform Optimization by Simulation and Numerical Analysis for Suppressing Oil-Splitting in Electrowetting Displays

Electrowetting display (EWD) is a new reflective display device with low power consumption and fast response speed. However, the maximum aperture ratio of EWDs is confined by oil-splitting. In order to suppress oil-splitting, a two-dimensional EWD model with a switch-on and a switch-off process was established in this paper. The process of oil-splitting was obtained by applying different voltage values in this model. Then, the relationship between the oil-splitting process and the waveforms with different slopes was analyzed. Based on this relationship, a driving waveform with a narrow falling ramp, low-voltage maintenance, and a rising ramp was proposed on the basis of square waveform. The proposed narrow falling ramp drove the oil to rupture on one side. The low-voltage maintenance stage drove the oil to shrink with a whole block. The proposed rising ramp was pushed the oil into a corner quickly. The experimental results showed that the oil splitting can be suppressed effectively by applying the proposed driving waveform. The aperture ratio of the proposed driving waveform was 2.9% higher than that of the square waveform with the same voltage.

Generation of Geometric Extra Phase and Accompanying Temporal Effects in Asymmetric Optically Compensated IPS-LCDs and FFS-LCDs

This paper reports the generation of an extra phase and the accompanying temporal effects in an asymmetric optically compensated in-pane-switching (IPS) liquid crystal (LC) system and a fringe-field-switching (FFS) liquid crystal display (LCD) exhibiting a twofold faster response speed in the switching-off process compared with that in single and symmetric IPS-LCDs and FFS LCDs for the first time. To explain the experimental results, we derived an approximate analytical formula for the optical output intensity that includes an extra phase advancement and conducted simulations to achieve normally black operation using a dynamic optical retarder.

Liquid-metal capillary switch for electrical power application

Liquid-metal (LM) electrical switches have been desired for decades to overcome intrinsic shortcomings of traditional mechanical switches equipped with solid contacts. Existing LM electrical switches, functioning via solid-liquid wetting or liquid droplet actuation, mostly focus on low current and small signal switches. In this Letter, a LM switch aiming at a power-level current switch has been proposed. A proof-of-concept prototype was fabricated via encapsulating Galinstan droplets into a silicone matrix. The device switches on a circuit when LM droplets are squeezed into a capillary channel to coalesce. The switch-off process with arc burning is realized by capillary breakup of the LM bridge and high-speed contact separation driven by a pressure difference contributed by Laplace pressure, electrical arc pressure, and atmospheric pressure. Switching off 0.5 A–5 A current under DC 220 V within 0.13–1.69 ms, the device demonstrates a high-speed current interruption ability compared to two kinds of commercial push-button switches. A high-speed camera is utilized to visualize the LM switch's current interruption process. In such a situation, the LM contacts exhibit a separation speed up to 3.85 m/s. Apart from the pressure difference, a slip layer between the LM and capillary wall also plays an important role in driving LM contacts. The LM switch has potential for applications in communication and control equipment acquiring a fast switch of the electrical power signal. This paper offers a framework for designing the LM switch dealing with intense electrical discharge.

Arc temperatures in a circuit breaker experiment from iterative analysis of emission spectra

A switching-off process very similar to those in real high-voltage self-blast circuit-breakers is emulated in a model chamber to study the arc properties by optical emission spectroscopy. The arc is operated in a chamber filled with SF6 between a pin-tulip contact system enclosed by a polytetrafluoroethylene nozzle. Transparent windows in the chamber wall and a slit in the nozzle enable an optical investigation of the arc cross section less than one millisecond before current zero. The side-on radiance of a fluorine atom lines has been measured with an imaging spectroscopic system. Considering rotational symmetry of the arc the corresponding radial emission coefficients have been determined by Abel inversion. The radial temperature profiles are calculated from the emission coefficients including pressure measurements and the corresponding plasma composition. In contrast to previous studies, a specific iterative approach is proposed to consider the optical thickness of the plasma. A maximum optical thickness between 0.2 and 0.4 has been observed. Temperature profiles corrected for absorption effects show increasing maximum temperature in the arc axis with decreasing current towards current zero. The effect of the plasma composition on absolute arc temperatures is discussed. The temperature profiles can be used to validate computational fluid dynamics simulations of the switching-off process in the model chamber.

Negative Conductance Modeling and Stability Analysis of High-Frequency Oscillation Based on Cascode GaN Circuits

GaN devices are developed rapidly in recent years, which makes it possible to produce power electronic converters with higher efficiency and higher power density. However, with the circuit parasitic parameters, large di/dt and dv/dt caused by the GaN devices' extremely fast switching can easily lead to voltage and current oscillations. This problem affects circuit stabilities and increases the difficulty of application with GaN devices. In this paper, oscillation problems will be explained by oscillator theory and an oscillation suppression method will be introduced. All the researches here are based on Cascode GaN devices. Considering all circuit parasitic parameters, negative conductance models of the GaN devices in the switching-on and switching-off process have been established according to oscillation mechanism analysis. And stability criteria of the GaN-based circuit have been derived which can well predict that whether the oscillations will happen and how will the oscillations last. Besides, the suppression method that placing a ferrite bead in power loop in series has been introduced based on the established model. Selection method is provided quantitively and suppression effect can be calculated. All the achievements of this research have been verified by simulations and experiments.

Quasi-Three-Dimensional Computations of the Microscopic Thermal and Dielectric Characteristics of an SF6 Rotating Switching Arc.

Pure sulfur hexafluoride (SF6) is chemically inert, non-flammable, non-toxic and thermally stable, and it has excellent dielectric strength and arc-quenching and control properties. The switching-off process of SF6 arc discharges occurs at the region between the contacts during the opening sequence to interrupt the flow of excessive current in a faulty network. The arc is tolerated in a controlled manner until a natural current zero when the arc discharge is rapidly quenched to restrict the thermal and dielectric reignition to the interruption. An SF6 self-blast switching chamber combines two advantages of blowing by heat expansion of the SF6 and arc rotation by electromagnetic effect of coil to improve the switching performance on thermal and dielectric reignition. The thermal and aerodynamic behaviors of an SF6 rotating switching arc in the chamber physically are complex and difficult to understand only by measurement due to their three-dimensional effects. Since the late nineteen-eighties, significant progress has been made in the method of computational fluid dynamics describing the physical processes occurring in the switching arc. The final goal of computer simulation technology on the arc switching is to predict the switching phenomena on the thermal and dielectric reignition from an engineering point of view. In this paper, we have conducted quasi-three dimensional computations to predict the thermal and dielectric reignition of SF6 rotating arcs occurring after a current zero in the self-blast switching chamber. Through the complete work, the microscopic thermal and aerodynamic behaviors of the remnant arc column after a current zero should be good criteria to predict the thermal and dielectric reignition of the rotating switching arc in the chamber.

Dual-frequency liquid crystal-polymer grating for fast response optical beam steering

In this study, we propose a liquid crystal (LC) beam deflector by combining dual frequency nematic LCs with optical micro structures. The total efficiency of up to 81% and 97%, are obtained for the beam steering state and the non-steering state, respectively. Optical micro gratings with fixed spacers are successfully fabricated using laser ablation and soft embossing. A dual frequency driving method is applied to the LC beam steering device for both the switching-on and the switching-off processes. The non-steering state is switched to the beam steering state rapidly with a duration as short as 3.8 ms, and the response time from the beam steering state to the non-steering state is achieved to be 20.5 ms, even when a thick LC layer with thickness of about 10 micron is required. The response behavior of this LC beam deflector can be further improved with the increase of the driving voltage or/and decrease of the LC thickness, which is very promising in quick response LC applications, such as dynamic lightings, autostereoscopic displays, optical communications etc.

Petrological, geochemical, isotopic, and geochronological constraints for the Late Devonian–Early Carboniferous magmatism in SW Gondwana (27–32°LS): an example of geodynamic switching

We report a study integrating 13 new U–Pb LA-MC-ICP-MS zircon ages and Hf-isotope data from dated magmatic zircons together with complete petrological and whole-rock geochemistry data for the dated granitic rocks. Sample selection was strongly based on knowledge reported in previous investigations. Latest Devonian–Early Carboniferous granite samples were collected along a transect of ~ 900 km, from the inner continental region (present-day Eastern Sierras Pampeanas) to the magmatic arc (now Western Sierras Pampeanas and Frontal Cordillera). Based on these data together with ca. 100 published whole-rock geochemical analyses we conclude that Late Devonian–Early Carboniferous magmatism at this latitude represents continuous activity (ranging from 322 to 379 Ma) on the pre-Andean margin of SW Gondwana, although important whole-rock and isotopic compositional variations occurred through time and space. Combined whole-rock chemistry and isotope data reveal that peraluminous A-type magmatism started in the intracontinental region during the Late Devonian, with subsequent development of synchronous Carboniferous peraluminous and metaluminous A-type magmatism in the retro-arc region and calc-alkaline magmatism in the western paleomargin. We envisage that magmatic evolution was mainly controlled by episodic fluctuations in the angle of subduction of the oceanic plate (between flat-slab and normal subduction), supporting a geodynamic switching model. Subduction fluctuations were relatively fast (ca. 7 Ma) during the Late Devonian and Early Carboniferous, and the complete magmatic switch-off and switch-on process lasted for ~ 57 Ma. Hf TDM values of zircon (igneous and inherited) from some Carboniferous peraluminous A-type granites in the retro-arc suggest that Gondwana continental lithosphere formed during previous orogenies was partly the source of the Devonian–Carboniferous granitic magmas, thus precluding the generation of the parental magmas from exotic terranes.

Some Physical and Computational Features of Unloaded Power Transmission Lines' Switching-off Process

The paper presents results of research some physical and computational features of unloaded power transmission lines switching-offs. It was stated that there are not monotonous dependence between magnitudes of transitional voltages at switching-off high voltage aerial lines and their lengths. There was studied influence of the circuit-breaker type (SF6 or vacuum ones) on transitional voltages. Features of use the ordinary differential equations' solvers at computer simulation from the point of view stability of solutions and simulation time consuming were investigated in the presented research.

Asymmetric noise sensitivity of pulse trains in an excitable microlaser with delayed optical feedback

A semiconductor micropillar laser with delayed optical feedback is considered. In the excitable regime, we show that a single optical perturbation can trigger a train of pulses that is sustained for a finite duration. The distribution of the pulse train duration exhibits an exponential behavior characteristic of a noise-induced process driven by uncorrelated white noise present in the system. The comparison of experimental observations with theoretical and numerical analysis of a minimal model yields excellent agreement. Importantly, the random switch-off process takes place between two attractors of different nature: an equilibrium and a periodic orbit. Our analysis shows that there is a small time window during which the pulsations are very sensitive to noise, and this explains the observed strong bias toward switch-off. These results raise the possibility of all optical control of the pulse train duration that may have an impact for practical applications in photonics and may also apply to the dynamics of other noise-driven excitable systems with delayed feedback.

Modelling and Simulation of SF6 High-Voltage Circuit-Breakers - an Overview on Basics and Application of CFD Arc Simulation Tools

The paper gives an overview on the basics of CFD arc simulation tools with respect to the simulation of the fluid mechanical processes in the interrupter unit of SF<sub>6</sub> high-voltage circuit-breakers at no-load and short-circuit switching-off processes. On the example of SF<sub>6</sub> self-blast circuit-breakers the complete process from the analysis of the switching-off process to the creation of a modular simulation model consisting of several sub models is illustrated. Details to the modelling in the particular sub modules and to the implementation are given. The capability of a CFD arc simulation tool based on the program package ANSYS/FLUENT is demonstrated on the basis of selected simulation results. Furthermore case examples for the application of the presented CFD arc simulation tool in the development process of high-voltage circuit-breakers are given.

Roles of conducting filament and non-filament regions in the Ta2O5 and HfO2 resistive switching memory for switching reliability.

The endurance of switching cycles, which is a critical measure of device reliability, in an ultra-thin (1.5 nm) Ta2O5 and HfO2 resistive random access (ReRAM) memory cell with a 28 nm lateral dimension was studied using current-voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. The two devices showed the typical oxygen-deficient conducting-filament (CF)-mediated bipolar resistance switching behaviour, which was induced by the asymmetric electrode configuration: Ta as the oxygen vacancy (VO) source/reservoir and TiN as the inert electrode. In these device geometries, the CF is supposed to initiate at the oxide/TiN interface and to grow towards the Ta electrode during the switch-on process, while the switch-off process was induced by the contraction of the CF from the Ta/oxide interface. Both devices, however, showed inversion (anomalous SET; switching from the off- to on-state) behaviour in the RESET (switching from the on- to off-state) process, which can be explained by the authors' previous model of the hourglass-shaped CF. In this model, once the CF is ruptured, the RESET polarity bias makes the lower portion of the CF regrow to slightly reconnect such a CF through the accelerated migration of VO from the upper-portion CF to the lower-portion CF, which induces switching performance degradation. In the I-V sweeps, the on- and off-states of the devices showed an overall conductance difference approximately corresponding to the integer multiple values of quantum point contact (G0), but there were arbitrary 0.25 and 0.125G0 differences in the conductance values of the on-state for the Ta2O5 and HfO2 devices, respectively. This suggests that these are the minimal units of conductance variation even for a given CF with a standard G0. Although the precise reason for the emergence of such an abnormal conductance unit is not yet understood, its implication for the reliability is critical. Reliable resistive switching was achieved only for the cases where the minimum point conductance was retained even in the off-state; in the other cases, over-SET and over-RESET were induced, which eventually degraded the device reliability. The detailed quantitative analysis of the device failure revealed that the increasing concentration of VO within the non-CF region in the cell decreased the resistance values of that region, which eventually resulted in the over-SET and over-RESET behaviours during the CLPS tests.

Modelling of the deformation of PTFE-nozzles in a high voltage circuit breaker due to multiple interruptions

This paper deals with the utilization of an improved model for the PTFE-nozzle deformation caused by the ablation process in the simulation of on-load switching-off processes in high-voltage circuit breakers. In order to describe the plasma’s behaviour, a transient axisymmetric model is used, which is based on the @Fluent software. The presented arc model uses mixed formulations for the calculation of the self-induced magnetic field and the radiative heat transfer. The proposed ablation model is based on PTFE evaporation including the nozzle wall deformation. The newly developed approach is used to simulate test series taking into account the accumulated PTFE wall degradation of previous interruptions. The simulation model is validated by the comparison of the simulation results with the measurements. We show the necessity of considering the accumulated nozzle wall degeneration and PTFE evaporation enthalpy in dependence on pressure to yield a good agreement between experiment and simulation.

Dynamics of Helfrich-Hurault deformations in smectic-A liquid crystals

A dynamics of the Helfrich-Hurault deformations in the SmA sample in the case of a rigid homeotropic anchoring has been theoretically investigated. It has been found that, unlike the Freedericksz transition, in the nematic liquid crystals, both the switching-on and switching-off characteristic times for this phenomenon are linearly proportional to the SmA sample thickness, and the switching-off process is much faster than the switching-on one.

3D electrohydrodynamic simulation of electrowetting displays

The fluid dynamic behavior within a pixel of an electrowetting display (EWD) is thoroughly investigated through a 3D simulation. By coupling the electrohydrodynamic (EHD) force deduced from the Maxwell stress tensor with the laminar phase field of the oil–water dual phase, the complete switch processes of an EWD, including the break-up and the electrowetting stages in the switch-on process (with voltage) and the oil spreading in the switch-off process (without voltage), are successfully simulated. By considering the factor of the change in the apparent contact angle at the contact line, the electro–optic performance obtained from the simulation is found to agree well with its corresponding experiment. The proposed model is used to parametrically predict the effect of interfacial (e.g. contact angle of grid) and geometric (e.g. oil thickness and pixel size) properties on the defects of an EWD, such as oil dewetting patterns, oil overflow, and oil non-recovery. With the help of the defect analysis, a highly stable EWD is both experimentally realized and numerically analyzed.

Experimental study on temperature variation in a porous inert media burner for premixed methane air combustion

The detailed axial temperature variations of the porous media burner during startup and switch-off processes were experimentally measured and analyzed for the premixed methane air combustion. A tubular burner filled by alumina pellets with diameters of 10 mm and 4.3 mm, respectively, was used as the porous media burner to study the effect of the burner inlet gas flow rate, equivalence ratio, and diameter of alumina pellets on the combustion temperature distribution along the burner axis and the combustion wave velocity. The results showed that the superadiabatic combustion could be achieved for the combustion wave velocity greater than zero, and the critical equivalence ratio corresponding to the superadiabatic combustion was bigger for the smaller pellet diameter or higher inlet air flow rate. This study can provide the useful information for the design and operation of the porous media burner, and is significant to understand the combustion phenomena in the porous media burner.

Switching performances of static induction thyristor with buried-gate structure

The switching characteristics of SITh are not only determined by the conductance modulation in channel between the gate regions, but also affected by the external gate driving circuit. The physical mechanism and behavior of switching process are studied deeply based on the fabrication practice of SITh. The dependence of switching performances of SITh on material, geometric structure and technological parameters are analytically discussed by using two-dimensional dynamical model firstly proposed in this paper. A series of optimum matching technological approaches have been developed for improving the switching characteristics of SITh. A versatile testing circuit is designed to get more accurate switching parameters and more stable switching-off process with lower power consumptions. The switching times t on and t off are reduced from 0.2 μs and 1.2 μs to 0.08 μs and 1.0 μs, respectively, and the dynamic dv/dt value of more than 1000 V/μs at switching-off is obtained.