1,721,150 research outputs found
Switching network units for high currents and voltages or plasma applications
No full textOCEM and ENEA gained a wide experience in the design and experimental characterization of fast and accurate switching systems for high DC currents, as required to control magnets and superconductors. The exploited idea consists in inserting an electronic switch in parallel to a fast electromechanical switch in air, to combine the benefits of both devices. The electronic switch is turned on and off to support the electromechanical commutations, reducing the jitter to tens microseconds and limiting the arcs that would reduce the system lifetime. During the performed tests, DC currents up to 20 kA were diverted in less than 100 Âμs with good repeatability. In case of emergency, the current can be interrupted in few tens of milliseconds. If necessary, a resistor can be inserted in parallel to the switch to dissipate the energy trapped in inductive loads or to produce desired overvoltages (a voltage up to 5 kV was reached in this configuration). Specific circuits were designed to preserve the components from transient voltage overshoots. This switching system is expected to work for 10000 operations without major maintenance. The developed solutions may be extended to many relevant applications as particle accelerators and HVDC networks. Copyright © 2017 CC-BY-3.0 and by the respective author
Granelli di senapa all'Indice. Tessere di storia editoriale (1585-1700). Seconda edizione rivista e ampliata
No full textOra alla seconda edizione, il volume ripercorre la vicenda di settantacinque titoli di carattere mistico-devozionale, colpiti dal divieto censorio dopo il 1687, anno che segna, con l’abiura e la condanna al carcere perpetuo del Molinos, l’inizio di una vera e propria caccia ai testi contaminati dal veleno della Quiete. Nel fuoco dell’indagine genesi testuale, spesso stratificata e complessa, diffusione sul piano peninsulare e oltralpe, sopravvivenza e stato di conservazione degli esemplari. I molteplici percorsi della ricerca consentono di individuare il profilo di pressoché altrettanti bestseller, farmaci dell’anima oggetto di lettura intensiva, radicati nell’immaginario di più generazioni in tutta l’Europa occidentale
Design and implementation of four 20 kA, 5 kV hybrid switching networks for plasma ignition in the international tokamak JT-60SA
No full textThis paper describes the design and implementation of the Switching Network Unit (SNU) for the superconducting Central Solenoid coils of the international nuclear fusion experiment JT-60SA to be built in Naka, Japan. Fusion experiments require an overvoltage in the poloidal coils inducing an overvoltage in the plasma chamber in order to produce the plasma breakdown. In the modern fusion devices, as JT-60SA, this is achieved by a SNU. The designed SNU can interrupt a DC current up to 20 kA in less than 1 ms to create a voltage up to 5 kV. It is realized with a hybrid switch integrating an electro-mechanical device and a solid state static circuit breaker, parallel connected. The SNU resistance can be prearranged and dynamically reduced by a solid state making switch to comply with the experimental requests. Preliminary test results confirmed the current balance of the multiple parallel branches constituting the solid state switch and proper behavior of the devices, confirming simulations results. The developed technical solutions may be employed in many other fields where is required a DC high current interruption, as medium and high voltage DC networks (HVDC systems). © 2014 IEEE
Overview of the new Magnet Power Supply Systems of JT-60SA procured by EU
No full textJT-60SA, the superconducting tokamak under construction in Japan, will be equipped with a mix of new and reused Power Supply Systems. Most of the new Power Supply Systems are procured by European Voluntary Contributors under the framework of Broader Approach agreement between Europe and Japan. For the toroidal circuit, the 25.7 kA steady state ac/dc converter is procured by CEA. For the poloidal circuits, the procurement of 10 ac/dc converters, almost all rated ±20 kA and about ±1 kV is shared between CEA and ENEA. The two in-vessel coils for fast control of plasma position are supplied with two independent thyristor converters procured by ENEA, each one rated ±5 kA and ±1 kV. The operation of four Switching Network Units procured by ENEA inserts settable resistors in series to each Central Solenoid module, producing up to 5 kV at the nominal current of 20 kA and allowing stable plasma initiation. The protection of toroidal and poloidal superconducting magnets is assured by thirteen Quench Protection Circuits procured by Consorzio RFX, rated ±20 kA and ±3.8 kV for poloidal coils and 25.7 kA and 2.8 kV for toroidal ones, inserting a discharge resistor in the related circuit for fast dissipation of the magnetic energy stored in the coil. Finally, the suppression of Resistive Wall Modes is actively performed by 18 in-vessel coils, independently supplied by a corresponding number of fast inverters procured by Consorzio RFX, each one rated for 300 A and 240 V. The key aspects of the design of the aforementioned Power Supply Systems are described in the paper, informing also about the present status of the procurement: their design was completed and some systems were already manufactured, tested and delivered to Japan. © 2015 Elsevier B.V. All rights reserved
Design and realization of JT-60SA Fast Plasma Position Control Coils power supplies
No full textFast Plasma Position Control Coils (FPPCC) PSs control the vertical position of the plasma during a plasma shot, to prevent Vertical Displacement Event (VDE), using FPPC coils installed in vacuum vessel for JT-60SA. For this task, the FPPCC PSs have to be very fast for reacting to plasma movements. Further, an open loop feed forward voltage control is adopted in order to achieve a fast control of FPPCC PSs. The main characteristics are: 4-quadrant AC/DC converter 12-pulse with circulating current, DC load voltage ±1000 V and DC load current ±5 kA. The overvoltage induced by FPPC coil during a plasma disruption can reach 10 kV and it is protected by a nonlinear resistor in parallel to the crowbar up to its intervention. All these technical characteristics have strongly influenced the design of the FPPCC converter and transformers which have been validated by simulation model of FPPCC PS. The outcomes of the simulation allowed to finalize the performances and dynamic behavior of voltage response. © 2015 Elsevier B.V. All rights reserved
First Switching Network Unit for the JT-60SA superconducting Central Solenoid
No full textThis paper presents the main characteristics and test results of the first Switching Network Unit (SNU) of the Central Solenoid for plasma initiation in the international experiment JT-60SA. The SNU can interrupt a direct current up to 20 kA producing at its terminals a voltage up to 5 kV with a rise time shorter than 100 μs. This is obtained by synchronizing the operation of a light electromechanical contactor with a static switch in order to combine the benefits of both devices. Even though the design was based on the JT-60SA specifications, the adopted solutions can be extended to many fusion and industrial applications. Due to the novelty of the developed solutions, an exhaustive set of tests were performed both on relevant single devices and on the complete SNU, even at full current, full voltage and full energy. The most relevant tests were performed using the Frascati Tokamak Upgrade (FTU) facilities reproducing the JT-60SA operating conditions. As the presented tests demonstrated the capabilities of the SNU to comply with the requirements, the manufacturing of the remaining three Central Solenoid SNUs can proceed and is expected to be completed by 2015. © 2015 Elsevier B.V. All rights reserved
Type tests of JT-60SA fast plasma position control coil (FPPCC) power supplies
No full textIn JT-60SA, Fast Plasma Position Control Coils (FPPCC) PSs allow controlling the vertical position of the plasma during a plasma shot, to prevent a Vertical Displacements Event (VDE). The FPPCC PSs have to react very fast to plasma movements. For this reason, an open loop feed forward voltage control is adopted in order to achieve a fast control of FPPCC PSs. The characteristics of the PS are: 4-quadrant AC/DC converter 12-pulse, DC load voltage ±1000 V and DC load current ±5 kA. The design of the FPPCC converters has been validated by a simulation model, finalizing the performances and dynamic behavior of voltage response. After the completion of the realization phase, the testing phase has been carried out in accordance to the IEC60146 Standards and this is the focus of the paper. The tests performed have pointed out a good dynamic behavior of the FPPCC converter in open loop feed forward voltage control, for a reference voltage step of 1kV, the rise time of output voltage is 2.88 ms, confirming outcomes achieved by simulations. © 2015 IEEE
Installation, commissioning and tests of four fast switching units of up to 20 ka for the JT-60SA nuclear fusion experiment
No full textThe nuclear fusion project JT-60SA is presently under construction in Naka (Japan) as a joint collaboration between Europe and Japan, within the framework of the Broader Approach Agreement. According to such agreement, the various JT-60SA systems are supplied by European and Japanese institutions. In particular, the Italian Agency ENEA was in charge for the procurement of the four Switching Network Units (SNUs) for the JT-60SA Central Solenoid (CS). The main SNU function is to interrupt a DC current up to 20 kA in a short time (less than 1 ms) in order to produce an overvoltage of up to 5 kV, crucial to generate and sustain the fusion plasma. The SNU design, manufacturing and factory test activities have been completed in 2016. After the delivery in Naka, the four SNUs have been installed and successfully commissioned in 2017. After an overview on the main technical characteristics of the SNUs and the key aspects of their design, this paper describes the activities performed on-site, highlighting the results obtained during the final acceptance tests and comparing them with the design simulation and the factory test results. © 2018 by the authors
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