Speaker
Miguel Pretelli
(Power Electronics)
Description
Switching Network Units (SNUs) are inserted in the power supply circuits of modern tokamaks for plasma initiation. In the framework of the “Broader Approach” agreement, the four SNUs for the superconducting modules of the JT-60SA Central Solenoid will be procured by European Union through the Italian Agency ENEA.
The design is based on the synchronized operations of a light electromechanical contactor and of a static switch to combine the benefits of both devices. The adopted solutions could be extended to many fusion and industrial applications.
Exhaustive tests were performed in last years both on critical components and on the complete SNUs. In particular:
The first SNU was tested in the ENEA FTU facilities, even in conditions more demanding than expected during JT-60SA operations.
The four SNUs, consisting of 24 cubicles, were assembled for operational tests in a configuration similar to the final installation and controlled by their Local Control Cubicle and by an emulator of the JT-60SA Supervising Computer.
A SNU was able to divert to a breakdown resistance (from 0.25 Ω to 3.75 Ω) currents up to 20 kA, producing a nominal breakdown voltage of 5 kV in less than 100 µs with a small overshooting voltage limited to about 200 V. Due to the obtained short duration of the arc in the contactor, the erosion is reduced with advantageous effect on the system lifecycle. A further electronic making switch allows a fast (less than 150 µs) resistance reduction to support the plasma ramp-up.
The tests showed good performance repeatability for all the SNUs. The accuracy of all the breakdown resistors was well within ±2%. Specific tests showed that they could dissipate much more than 360 MJ.
Since all the tests on the CS SNUs were successfully, the SNUs will be delivered to Japan in Spring 2016.
Co-authors
Alessandro Lampasi
(Dipartimento Fusione e Tecnologie per la Sicurezza Nucleare (FSN), Enea, Via Enrico Fermi, 45 00044 Frascati (Roma), Italy)
Filippo Burini
(Power Electronics, OCEM Energy Technology, Via della Solidarietà 2/1 - 40056 Valsamoggia (BO), Italy)
Giuseppe Taddia
(Power Electronics, OCEM Energy Technology, Via della Solidarietà 2/1 - 40056 Valsamoggia (BO), Italy)
Katsuhiro Shimada
(JT-60 Power Supply and Control Group, Japan Atomic Energy Agency (JAEA), Naka, Japan)
Luca Novello
(Broader Fusion Development Department,, Fusion for Energy (F4E), Garching, Germany;Broader Fusion Development Department,, Fusion for Energy (F4E), Garching, Germany)
Makoto Matsukawa
(JT-60 Power Supply and Control Group, Japan Atomic Energy Agency (JAEA), Naka, Japan)
Miguel Pretelli
(Power Electronics, OCEM Energy Technology, Via della Solidarietà 2/1 - 40056 Valsamoggia (BO), Italy)
Pietro Zito
(Dipartimento Fusione e Tecnologie per la Sicurezza Nucleare (FSN), Enea, Via Enrico Fermi, 45 00044 Frascati (Roma), Italy)
Sandro Maria Tenconi
(Power Electronics, OCEM Energy Technology, Via della Solidarietà 2/1 - 40056 Valsamoggia (BO), Italy)
