PF Coils Quench Protection Design of EAST Superconducting Tokamak

Oct. 5, 2005

PF power supply teamPF power supply teamInstitute of Plasma Physics,Chinese Academy of SciencesInstitute of Plasma Physics,Chinese Academy of Sciences

Hefei Anhui 230031Hefei Anhui 230031P.R.ChinaP.R.China

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EAST

ASIPPPF Coil Distribution

The whole EAST PF

magnet system consists

of 14 coils, among them

PF1 to PF6 are the CS

coils, PF7 to PF10 are the

diverter coils, and PF11

to PF14 are the PF big

coils. They located

symmetrically around the

equatorial plane

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PF Coil current in EAST operation

I (KA)

t (s)

ASIPPThe connection between PF coils

and PFPS

The PF system consists of 14 upper and lower SC coils around the plasma in the EAST tokamak, due to the series connection in diverter, 12 set of PFPS is essential.

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Parameter for PF Magnet and Plasma Operation

Nominal cycle period 2800 s

PF magnetization 20 s

PF dwell time to keep magnetization 20 s

Plasma initiation 0.06 s

Plasma current ramp up 4 s

Maximum plasma flat top 1000 s

Plasma current ramp down 4 s

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PF Coil Parameters and Requirements

 Tab. 1 EAST PF magnet parameters

Rated current 15kA

Excited time 20s

Voltage (terminal to terminal) 10000V

Voltage (magnet to ground) 10000V

Limited heat condition 5.1108 A2s

Quench protection delay 1s

Self inductance 17.6~129.5mH

Mutual inductance 0.33~ 21.6mH

Storage energy in operation 42MJ (max. 140MJ)

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The power supply circuit of EAST PF coil

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The requirements of quench protection

★ to discharge the magnets in such a way that is less than a prescribed limit under all conditions;

★ to limit the maximum instantaneous voltages imposed on the magnet (terminal to terminal, and terminal to ground);

★ to ensure successful discharge with a prescribed reliability for a given number of events over the design lifetime.

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QP Feature for PF Coil

★ Frequent switching off. the high current rate, and plasma disrup

tion in operation, The PF coil has possibly more quench,

★ strong coupling. The 12 pairs of coil have strong decoupling in each other, in QP the coil energy dissipation will be different from single coil.

★ Positive and negative current. in PF coil,it is important for QP design to use artificial current zero technology

★High power in input power supply. In PF magnet system, the primary power supply usually is quite high voltage, therefore it is necessary to suppress the input power supply in QP

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PF Coil Storage Energy

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PF Coil Storage Energy for Each energy

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不同运行方式下各线圈最大储能 （ MJ ）

托卡马克运行方式 \ 线圈号

1 ， 2 3, 4 5, 6 7,8 9,10 11,12 13,14

大拉长运行 3.8 4.3 3.4 2.4 12.1 3.0 2.6

大截面运行 3.8 4.3 3.4 0.73 3.5 3.9 1.4

大体积运行 3.8 4.3 3.4 1.75 9.1 5.5 1.03

最大能量 3.8 4.3 3.4 2.4 12.1 5.5 2.6

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QP System configuration

The QP consists of bypass, DCCB, PB, fuse, resistor

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QP Operation Scenario

★ Bypass primary PS. Upon command, the quench protection system will suppress the power supply, close the bypass CU3.

★ Open DCCB. open the DCCB1, after 100ms, and open DCB2.

★ Open PB. If the current detected by sensor DCCT after 200ms is not zero, the pyrobreaker PB will open.

★ Fuse melt, and Energy is dissipated in R . The current flowing through the magnet then follows the circuit through CU3, R and L, and the majority of the energy is deposited in R.

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DC Current Breaker

Rated voltage 1.5kV

Rated current 15kA

Max. breaking current 50kA

Max. breaking voltage 3.0kV

Closing time 110ms

Switching time 30ms

Operation numbers 104 times

Weight 210kg

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Current and voltage curve for DCCB test

B– breaker current ; C– arc voltage

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Backup Breaker--PB

Rated current 20kA

Max. breaking voltage 2.0kV

Max. voltage 10kV

Breaking time 100µs

weight 110kg

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Discharge Resister and Fuse

0]][[][

][ iRdt

idL

][|][ 00 ii t

max00 ]][][[2

1EiLi T

......,12) 2, 1,(j 2 mj Adti

) 12 ........, 2, , 1(j mjj uRi

The QP in each power supply will work during the quench of any PF coil. Therefore the PF QP system consists of 12 R-L branches that have magnetic coupling, the total maximum energy Emax store

d in all coils should be dissipated in these resistor R of each QP. In R design it is necessary to consider whole energy transfer and max. energy storage in each PF coil and different operation time

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Fuse

Pay attention:

★ at high current, melt rapidly

★ at low current, melt longer

★ shunt current from parallel switch

★ Suitable fuse parameter match with SC magnet heat condition.

★ two diodes in opposite parallel are in series with fuse

Current Melting time

400A Not melt

1000A 850s

2000A 80s

5000A 0.8s

15000A 0.01s

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Coil Current in Quench protection

5s /elongation

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Coil energy in Quench protection

5s /elongation

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I2t in Quench protection

5s /elongation

Control Unit for QP

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QP controllers consist of two parts: one is hardware controller realized by electronic circuit and relay; others is software controller realized by realtime operation system and industrial computers.

Up commands …

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Parts of PF power supply equipment (7)

The end

Thanks

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