1. PF Coils Quench Protection Design of EAST Superconducting Tokamak Oct. 5, 2005 PF power supply team Institute of Plasma Physics,Chinese Academy of Sciences Hefei Anhui 230031 P.R.China ASIPP EAST

2. ASIPP PF 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

3. ASIPP PF Coil current in EAST operation

4. ASIPP The 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.

5. ASIPP Parameter for PF Magnet and Plasma Operation Nominal cycle period2800 s PF magnetization20 s PF dwell time to keep magnetization20 s Plasma initiation0.06 s Plasma current ramp up4 s Maximum plasma flat top1000 s Plasma current ramp down4 s

6. ASIPP PF Coil Parameters and Requirements Tab. 1 EAST PF magnet parameters Rated current15kA Excited time20s Voltage (terminal to terminal)10000V Voltage (magnet to ground)10000V Limited heat condition 5.1  10 8 A 2 s Quench protection delay1s Self inductance17.6~129.5mH Mutual inductance0.33~ 21.6mH Storage energy in operation42MJ (max. 140MJ)

7. ASIPP The power supply circuit of EAST PF coil

8. ASIPP 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.

9. ASIPP QP Feature for PF Coil ★ Frequent switching off. the high current rate, and plasma disruption 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

10. ASIPP PF Coil Storage Energy

11. ASIPP PF Coil Storage Energy for Each energy

12. ASIPP 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 1，21，2 3, 45, 67,89,1011,1213,14 大拉长运行 3.84.33.42.412.13.02.6 大截面运行 3.84.33.40.733.53.91.4 大体积运行 3.84.33.41.759.15.51.03 最大能量 3.84.33.42.412.15.52.6

13. ASIPP QP System configuration The QP consists of bypass, DCCB, PB, fuse, resistor

14. ASIPP 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.

15. ASIPP DC Current Breaker Rated voltage1.5kV Rated current15kA Max. breaking current50kA Max. breaking voltage3.0kV Closing time110ms Switching time30ms Operation numbers10 4 times Weight210kg

16. ASIPP Current and voltage curve for DCCB test B– breaker current ; C– arc voltage

17. ASIPP Backup Breaker--PB Rated current20kA Max. breaking voltage2.0kV Max. voltage10kV Breaking time100µs weight110kg

18. ASIPP Discharge Resister and Fuse 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 E max stored 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

19. ASIPP 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 CurrentMelting time 400ANot melt 1000A850s 2000A80s 5000A0.8s 15000A0.01s

20. ASIPP Coil Current in Quench protection 5s /elongation

21. ASIPP Coil energy in Quench protection 5s /elongation

22. ASIPP I 2 t in Quench protection 5s /elongation

23. Control Unit for QP ASIPP 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 …

24. ASIPP Parts of PF power supply equipment (7)

25. The end Thanks ASIPP