22P167-P
Overview of JT-60SA Magnet Power Supply System
JT-60SA磁場コイル電源システムの概要
Kunihito Yamauchi (山内邦仁) 1, Oliver Baulaigue 2, Alberto Coletti 3,Roberto Coletti 4, Alberto Ferro 5, Elena Gaio 5, Alessandro Lampasi 4,Makoto Matsukawa (松川 誠) 1, Luca Novello 3, Katsuhiro Shimada (島田勝弘) 1,Fabio Starace 4 and Tsunehisa Terakado (寺門恒久) 1
1

Japan Atomic Energy Agency
801-1 Mukoyama, Naka, Ibaraki 311-0193, Japan1
日本原子力研究開発機構 〒311-0193 茨城県那珂市向山801-1
2
CEA, IRFM, Cadarache, Saint-Paul-lez-Durance, France
3
Fusion for Energy, Garching, Bavaria, Germany
4ENEA, Frascati, Rome, Italy
5Consorzio RFX, Euratom-ENEA Association, Padova, Veneto, Italy
The JT-60SA tokamak device consists of superconducting toroidal and poloidal field coils, and somein-vessel coils. This paper describes the key features and the expected performances of the main power
supply system for the superconducting magnets in JT-60SA.

1. Introduction
JT-60SA magnets consist of superconducting
Toroidal Field (TF) and Poloidal Field (PF) coils,
some in-vessel coils. In the following sections,the key features and the expected performances
including the protection for the superconducting
magnets in JT-60SA are described.
2. TF Coil Power Supply
The TF coil circuit is shown in Fig. 1. A single
thyristor converter provides a unidirectional DC
current to 18 series-connected TF coils
continuously.
The nominal DC voltage isdetermined to be sufficient to charge/discharge thefull current of 25.7 kA within ~20 min. In order toreduce the voltage to ground in the case of Quench
Protection
Circuit(QPC;after-mentioned)
operation to < 2 kV, TF coils are divided into threeblocks, and three QPCs are interleaved among them.
As a typical operation of TF coil PS, TF coils areThyristor
Converter~ ±80V / +25.7kA
2.2MVA
11kV/60V%X: TBC

1 k(TBC)

energized every day in the morning before thestarting of the plasma experiments, anddemagnetized after the end of the dailyexperimental period.
3. PF Coil Power Supply
There are ten superconducting PF coils, i.e. fourCentral Solenoids (CS1–4) and six Equilibrium
Field (EF1–6) coils. Each PF coil circuit isindependent from the others although mutualcouplings exist. Every PF coil PS provides abidirectional DC current adequate to achieve therequired plasma scenarios within the commonratings of 5 kVdc and 20 kAdc. The typical DC
circuits of them are shown in Figs. 2 and 3,respectively. Their basic PS components areseries-connected Base PS, Switching Network Unit
(SNU) or Booster PS, and QPC (after-mentioned).
Each grounding resistor is connected to themidpoint of the Crowbar Switch unit in Base PS in

160 0.0375  0.0375 CBPS
QPC1160 

TF1-TF6Current Reversing Link1 k1 k(TBC)

C Crowbar
SwitchCurrent Reversing Link

TF13-TF180.0375  0.0375 BPS
QPC2CurrentReversing
Link

QPC3BPS
0.0375  0.0375 160 

Fig.1. Schematic DC circuit diagram of TF coil PS

TF7TF12order to fix the potential from the viewpoint of thewithstand voltages for PS components.
0°

3.1 Base PS
Base PS is based on low-voltage back-to-backfour-quadrant thyristor converters (±~1 kVdc, ±20
or +10/–20 kAdc) with long-time rating. Because
SNU or Booster PS can be operated only in shortduration, PF coils are driven by Base PSs for wholeoperation period including pre-magnetization,plasma current flat-top and demagnetization phases.
From the viewpoints of harmonic current andreactive power, Base PSs are planned to be poweredby a motor-generator (H-MG reused from JT-60).
3.2 Switching Network Unit (SNU)
SNU consists of a fast unidirectional DC current
interrupter and discretely variable discharge
resistors, and is used to produce a negative highvoltage (–5 kVdc) necessary for stable breakdown
and fast plasma current ramp-up. Since SNU isworkable with using the magnetic energy stored in
the coil, it is adopted for the inner PF (CS1–4 andEF3, 4) coils through which a highpre-magnetization current flows.

4. Quench Protection Circuit (QPC)In the case of superconducting coil quench or
failure inside the PS system, fast extraction of themagnetic energy stored in the superconducting coilis necessary to protect the conductor. For thispurpose, QPC consisting of a DC current interrupter,a dump resistor and a Pyrobreaker (pyrotechniccircuit interrupter) for backup protection isprovided for each superconducting coil. The DC
current interrupter is a hybrid circuit breakercomposed of a mechanical ByPass Switch (BPS)
for conducting the continuous current and a staticcircuit breaker for the current interruption inparallel.
The Pyrobreaker also provides theremarkable performance of continuous conduction.
The final design of QPCs is referred to [2].

-30°

+30°

Base PS
939V/±10kA×2units

CB
1.25kVCC

1 k
CrowBar

CrowBar Switch

Swit

Switching Network Unit
~ -5kV
0.19 BPSC

0.19 O/CBPS

Quench Protection Circuit(Hybrid type)±3.8kV/±20kA

R1R2Quench Protection C(Hybrid type)±3.8kV/±20kA

Current Reversing
LinkCurrent RLin+Superconducting
Coil
CS1 Circuit Configuration

SuperconCo
CS2 Circuit C

Fig.2. Schematic DC circuit diagram of typical PF coil(CS1) PS with SNU+15°

3.3 Booster PS
Because a low pre-magnetization current isrequired and then the current polarity reverses
immediately for the case of the outer PF (EF1, 2, 5and 6) coils, high-voltage thyristor converters (±5kVdc, +4/–14.5 kAdc) with short-time rating, which
are reused from JT-60, are utilized as Booster PS
for the same purpose as SNU. As in the case ofBase PSs, Booster PSs are also planned to be
powered by a motor-generator (H-MG reused fromJT-60) from the viewpoints of harmonic current andreactive power.

T3G
30.1MVA×2units
18kV/803.5V%Z: 23.12% at 77.6Hz

T2G
30.1MVA×2units
18kV/803.5V%Z: 23.12% at
77.6Hz

-15°

0°

-30

Base PS
939V/-10kA

Base PS
939V/±10kA

CBase
939V/±C
1 k

Booster PS±5kV/+4kA(full load)
+7.5°

C
1

CrowBar Switch
C

CrowBar Sw+37.5°0.19 

0.19 +7.5°

BPS

Quench Protection Circuit(Hybrid type)±3.8kV/±20kA+37.5°
Booster PS±5kV/-14.5kA(full load)

BPS

Quench Protection Circ(Hybrid type)±3.8kV/±20kA

Current Reversing
Link

Current Rev
Link

Superconducting
Coil
EF1 Circuit Configuration

Supercondu
Coil
EF6 Circuit Co+Fig.3. Schematic DC circuit diagram of typical PF(EF1) coil PS with Booster PS

Acknowledgments
This work was supported within the frameworkof the “Broader Approach Internationals
Agreement”.
References[1] S. Ishida et al.: Fusion Eng. Des., 85 (2010) 2070.
[2] E. Gaio et al.: IEEE T. Plasma Sci., to be published.
[3] A. Coletti et al.: Fusion Eng. Des., 86 (2011) 1373.