Letteratura scientifica selezionata sul tema "Solid-State closing switch"

We propose a Si -based delayed breakdown diode (DBD) with an improved three-step gradual changing doping structure for picosecond semiconductor closing switch and discuss the physical process, which underlies the operation principle of high-power closing switch. From the results of two-dimensional mixed device-circuit simulations and theoretical analysis, several parameters of utmost important on the optimal design of picosecond switch are discussed in detail. Performance comparisons of traditional and improved DBDs are given systematically.

The results of studies of a solid-state closing switch for a high-current pulse switching are presented. The experiments were carried out on a laboratory facility with a capacitive energy storage run down a discharge circuit with electrical-explosive opening switch (EEOS) by a current pulse with an amplitude ~450 kA. The discharge circuit consists of two sections separated by a branch with a solid-state closing switch. A metal foil of the EEOS can be located in an interelectrode gap of the closing switch. The operation of the EEOS leads to a breakdown of the insulation of the closing switch, as a result of which an effective shunting of the section of the discharge circuit containing the EEOS occurs. The developed combined solid-state closing switch in the future is capable of providing multi-channel switching of a high-current pulse to the load synchronously with the EEOS operation.

Abstract Solid-state compact Marx generator using saturable pulse transformer (SPT) and fast recovery diodes has been proposed. The primary circuit is switched by three MOSFETs connected in parallel. The SPT functions as a step-up transformer to increase the voltage amplitude and as a closing switch for the secondary circuit. Meanwhile, all the SPTs share the same magnetic core to achieve a compact structure and ensure good synchronization. The energy storage capacitors on the secondary sides are charged through the unsaturated SPT. When the SPT saturates, the capacitors firstly transfer a little energy to the saturated inductors through the diodes reversely during their reverse recovery process. Currents rise quickly in these inductors until diodes totally recover to reverse blocking state. Then capacitors discharge in series to the load and high-voltage pulses are generated over the load. With the currents in the saturated inductors, the front edges of pulses are no longer affected by them but are dominated the turn-off speed of the diodes, which makes high-voltage and high-current pulses with short front edges possible. The regular and cheap fast recovery diodes in the generator act as semiconductor opening switch to sharpen the pulse front edges. Experiments were carried out with a 4-stage Marx generator prototype, 10.8-kV high-voltage pulses with a front edge of 11 ns, a pulse width of 190 ns, were obtained over a 100-Ω resistive load. The total energy efficiency is 49.8%. The proposed Marx generator using regular fast recovery diodes is compact, cheap, and efficient to generate high-voltage pulses with short front edges.

Diamond holds promise to reshape ultrafast and high-power electronics. One such solid-state device is the diode avalanche shaper (DAS), which functions as an ultrafast closing switch where closing is caused by the formation of the streamer traversing the diode much faster than 107 cm/s. One of the most prominent applications of DAS devices is in ultrawideband (UWB) radio/radar. Here, we simulate a diamond-based DAS and compare the results to a silicon-based DAS. All DASs were simulated in mixed mode as ideal devices using the drift-diffusion model. The simulations show that a diamond DAS promises to outperform an Si DAS when sharpening the kV nanosecond input pulse. The breakdown field and streamer velocity (∼10 times larger in diamond than Si) are likely to be the major reasons enabling kV sub-50 ps switching using a diamond DAS.

Des impulsions de courant d'amplitude élevée (plusieurs centaines de kA) dans la gamme des microsecondes peuvent être appliquées pour générer des champs magnétiques de l'ordre du mégagauss. Cette technologie relative au domaine des haute puissances pulsées a été utilisée pour des travaux de recherche sur la fusion par confinement inertiel, le X-pinch ou la physique des hautes densités d'énergie. De plus, un certain nombre d'applications industrielles telles que le soudage par impulsion magnétique et la fracturation des roches nécessitent une puissance moyenne élevée, une répétabilité et un générateur d'impulsions de forts courants fiable avec une longue durée de vie. Par conséquent, le développement d'un interrupteur à semi-conducteurs rapide fonctionnant dans la gamme de plusieurs centaines de kA est d'une importance considérable.Un interrupteur rapide à courant élevé est l'un des composants les plus complexes d'un générateur de hautes puissances pulsées. Historiquement, seuls les interrupteurs remplis de gaz pouvaient fonctionner dans de telles conditions extrêmes. Cependant, les interrupteurs remplis de gaz présentent plusieurs inconvénients bien connus, notamment une faible fréquence de répétition des impulsions, une durée de vie courte et une instabilité lors du déclenchement. Ils sont également coûteux à utiliser, nécessitant souvent des systèmes de flux de gaz et des chambres de recirculation de gaz pour une opération répétitive. Ces inconvénients ont freiné l'adoption généralisée des technologies de hautes puissances pulsées.Les récents progrès en physique et technologie des semi-conducteurs ont introduit les interrupteurs à semi-conducteurs dans le domaine des hautes puissances pulsées. En particulier, les structures en silicium à haute tension déclenchées en mode onde d'ionisation par impact représentent une solution prometteuse pour les interrupteurs à semi-conducteurs rapides à très fort courant (dizaines à centaines de kA et gradient de courant de plusieurs dizaines de kA/μs).L'objectif principal de cette thèse est de démontrer expérimentalement la capacité des thyristors à haute tension à commuter rapidement des impulsions de courant d'amplitude élevée. Pour atteindre cet objectif, des études expérimentales et théoriques sont entreprises. Dans les travaux expérimentaux, l'accent principal est porté sur une limitation critique mise en évidence dans la littérature, à savoir la surface de section transversale du thyristor. Pour s'affranchir de cette limitation, plusieurs solutions ont été étudiées dans cette thèse, notamment (i) le déclenchement du plus grand thyristor disponible dans le commerce, d'un diamètre de 100 mm avec une tension de claquage statique de 5,2 kV, (ii) le déclenchement en parallèle d'un ensemble de deux et quatre thyristors à haute tension, (iii) la configuration série-parallèle afin d'augmenter simultanément la tension de blocage et la capacité de courant de l'interrupteur. En termes d'étude théorique, la simulation numérique est réalisée pour apporter une meilleure compréhension des phénomènes de claquage par avalanche en mode de commutation par ionisation d'impact
Micro-second range high-current pulses (100s kA) are applied to generate megagauss-range magnetic fields. This high pulsed power technology has been employed in inertial fusion research, X-pinch, and high-energy-density physics. Moreover, a number of industrial applications such as magnetic pulse welding and rock fracturing require high average power, repeatability, and a reliable high-current pulse generator with a long lifespan. Hence, a fast solid-state switch development operating in the range of several hundred kA is of considerable importance.A fast high-current switch is one of the most complex components in a pulsed power generator. Historically, only gas-filled switches could operate under such extreme conditions. However, gas-filled switches have several well-known disadvantages, including low pulse repetition frequency, short lifetimes, and instability in triggering. They are also expensive to use, often requiring gas flow systems, costly gases, and recirculating chambers of gas for repetitive operation. These disadvantages have hindered the widespread adoption of pulsed power technologies.Recent advancements in semiconductor physics and technology have introduced solid-state switches into the pulsed power domain. In particular, silicon high-voltage structures triggered in impact-ionization wave mode present a promising solution for fast high-current solid-state switches (10s-100s kA and 10s kA/μs).The main goal of this thesis is to experimentally demonstrate the capability of high-voltage thyristors to switch fast-high current pulses. to accomplish this goal, two major axes of study are defined as the experimental and theoretical studies. In the experimental work, the main focus is determined based on a key limitation highlighted in the literature, i.e., the cross-sectional area of the thyristor. To eliminate this limitation several solutions have been investigated in this thesis including (i) triggering the largest commercially available thyristor, 100 mm wafer diameter with 5.2 kV static voltage breakdown. (ii) Parallel triggering of an assembly of two and four high-voltage thyristors. (iii) Series-parallel configuration in order to further increase blocking voltage and current capability of the switch simultaneously. In terms of theoretical study, the numerical simulation is conducted to shed light on the avalanche breakdown phenomena in impact-ionization switching mode

RF MEMS switches have many advantages over solid-state switches but their main disadvantage is poor reliability. The reliability problem stems from the impact forces generated at the time of closing of the switch and subsequent bouncing. This paper proposes a feedback control strategy to rapidly close the switch without bouncing. The stiffness of the system is switched between a positive value and a negative value to achieve small rise and setting times with no overshoot. Simulation results are presented to demonstrate the feasibility of the proposed control strategy.

The Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 96-06 [1] which required utilities to evaluate the potential for waterhammers in cooling water systems serving containment following a Loss of Offsite Power (LOOP) concurrent with a Loss of Coolant Accident (LOCA) or Main Steam Line Break (MSLB). At Duke’s Oconee Nuclear Station, analysis and system testing in response to GL 96-06 concluded that waterhammers occur in the Low Pressure Service Water (LPSW) system during all LOOP events. Column Closure Waterhammers (CCWH) occur when the LPSW pumps restart following a LOOP and rapidly close vapor voids within the system, specifically, in the Reactor Building Cooling Unit (RBCU) and Reactor Coolant Pump (RCP) motor piping. Condensation Induced Waterhammers (CIWH) occur when heated steam voids interact with sub-cooled water in long horizontal piping sections, specifically in the RBCU and Reactor Building Auxiliary Coolers (RBAC) piping. These waterhammers were not expected to result in pipe failure, but resulted in piping code allowable stresses being exceeded. Piping code compliance was achieved by installing modifications that prevent all GL 96-06 related waterhammers inside containment. Two modifications were designed and implemented. These modifications were designed to isolate the piping inside containment, the high point in the open loop system, in order to maintain it in a water solid state. This was accomplished by a valve closure scheme that is actuated by low LPSW supply header pressure. Additionally, “controllable vacuum breakers” (pneumatic valves) open on low LPSW supply header pressure to eliminate void formation and collapse while the isolation valves are closing. The pneumatic isolation valve arrangement is single failure proof to open and to close. The Waterhammer Prevention System (WPS) circuitry closes the valves by one of two digital channels consisting of relays, which are triggered by two of four analog channels consisting of a pressure transmitter/current switch. The valves re-open on increasing supply header pressure. A “leakage accumulator” was provided in the supply header to make-up any boundary valve leakage that may occur when the system is isolated. This provides for a larger allowable aggregate boundary valve leakage rate. The system response was predicted by a model using the thermal-hydraulic code GOTHIC. Following installation, an integrated test was successfully conducted by inducing a LOOP into the LPSW system.

This paper presents a novel latchable phase-change actuator that can potentially be used for flow valving and gating in portable lab-on-a-chip systems, where minimal energy consumption is required. The actuator exploits a low melting-point paraffin wax, whose solid-liquid phase changes allow the closing and opening of fluid flow through deformable microchannels. Flow switching is initiated by melting of paraffin, with an additional pneumatic pressure required for flow switching from open to closed state. After paraffin solidifies the switched state is subsequently maintained passively without further consumption of energy. The actuator can be fabricated from PDMS through the multilayer soft lithography technique. Testing results demonstrate that the actuator has a response time about 60-100 sec for flow switching, and can passively hold a microvalve closed under pressures up to 35 kPa.