29th Symposium on Fusion Technology (SOFT 2016)

P3.086 Energy dissipating resistors for the ITER switching network units

7 Sep 2016, 11:00

1h 20m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 86

Poster E. Magnets and Power Supplies P3 Poster session

Speaker

Rustam Enikeev (Efremov Institute)

Description

The superconductive coils of ITER magnet system will be energized by ac/dc converters. Before each plasma pulse the magnet system will be pre-charged with energy (8GJ) to be used for generating the toroidal loop voltage required for the gas mixture breakdown and plasma formation. This will be realized by inserting energy dissipating resistors in series with the central solenoid (CS) modules and two poloidal field (PF) coils, PF1 and PF6, with the help of circuit breakers of switching network units (SNU). The dissipating resistors will be located in a stand-alone building with the required cooling conditions and connected with the circuit breakers by cables. The compact design of the switching network resistors (SNR) is provided by modular approach, effective system of forced ventilation and the ability to withstand high-thermal loads at the temperatures up to 350˚C. The resistive element is made from stainless steel plates in a zigzag pattern to minimize self-inductance, thus decreasing the switching overvoltages during transients. Selection of material with a low-temperature resistance coefficient restricts SNR resistance variation, which is necessary to ensure the required plasma ignition conditions. The main ratings of the resistors correspond to the following operational parameters: maximum current and voltage at breakdown are 45 kA and 8.5 kV, respectively, dissipated energy per coil system in normal operation is up to 1 GJ. This paper describes the resistor design based on the relevant analysis and the detailed investigation carried out during R&D phase, as well as the procedure and results of type tests on a full-scale prototype. In particular, considerable attention is paid to thermal and pulsed current tests with the aim to prevent steel plates deformation caused by heating and high currents. The successful results of the tests confirmed the suitability of the resistor design and compliance with ITER requirements.