The ITER toroidal field model coil project

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224 A. Ulbricht et al. / Fusion Engineering and Design 73 (2005) 189–327 Fig. 4.24. Measured and calculated temperature profiles of (+)-terminal (top) and (−)-terminal (bottom) for 0, 40 and 80 kA. 4.4.6. Summary The 80 kA current leads including the water-cooled flexible jumper cables were operated successfully during both test phases of the TFMC in 2001 and 2002. Various optimisation runs were performed at zero current as well as at 40 and 80 kA, respectively. It could be demonstrated that the current leads were operated with the design mass flow rates through the heat exchanger. The slightly different mass flow rates of both terminals can be explained by different RRR of the copper of the heat exchanger. The water-cooled flexible jumper cables were operated reliably up to 80 kA in steady state with a copper current density of up to 43 A/mm 2 . Maximum outlet temperatures of the cooling water of about 60 ◦ C were obtained resulting in a total cooling power of up to 240 kW for both legs.
Table 4.5 Main operation parameters of the 80 kA current leads Current [kA] A. Ulbricht et al. / Fusion Engineering and Design 73 (2005) 189–327 225 0 40 80 THe,in [K] 5.62 4.83 4.79 TCu,cold [K] 10.64 7.1 7.03 TCu,SC [K] 102 51.3 6.86 TCu,warm [K] 287 290 299 mW [g/s] 0.8 2.15 4.5 mC [g/s] 0 5.78 6.24 �pheat exchanger [mbar] 75 165 420 Qsum [W] 112 166 168 Cu, copper conductor; He, helium; SC, superconductor. The steady state heat load of the current lead superconducting bus bar system at the 4.5 K level was very high even at zero current (110 W per terminal). Detailed investigations showed that the heat exchangers could not be responsible for this high heat load because changes in the heat exchanger helium mass flow rate did not change the heat load significantly. Up to now, there is no final conclusion. 4.5. Power supply system and safety discharge performance For the test of the ITER TFMC, the electrical power supply system has been extended in the following way [59]: (1) The existing 50 and 30 kA thyristor AC/DC converters were switched in parallel by means of a new Fig. 4.25. Total heat load vs. coil current for (+) and (−)-terminals. control unit in order to obtain a maximum output current of 80 kA. (2) An 80 kA safety discharge switching circuit of about 100 MJ energy capacity at a voltage level of 1 kV was installed. (3) A new 20 kA thyristor AC/DC converter had to be installed and connected with the existing 20 kA safety discharge circuit of about 300 MJ energy capacity at a voltage level of 2.5 kV for the operation of the LCT coil. For the 80 kA supply system the main problem, that had to be solved, was the nearly simultaneous current commutation of both power supplies on the short circuit path also under fault conditions. Besides this, a sufficient low resistance and inductance of the short circuit path had to be achieved in order to have a voltage drop across it was remarkably lower than the nominal voltage of the rectifiers in inverter mode of operation. The 20 kA thyristor rectifier had some specific problems in the balance control of the two 10 kA rectifiers. They were mastered in a way that there was practically no impact on the progress of the test procedure. The POLO switching circuit was applied for the fast high voltage discharge of the TFMC (Section 9). Early testing of the 30 and 50 kA power supplies with the POLO and a copper coil, steamed out the need of detailed analysis of current sharing during the safety discharge sequence and the optimisation of the feedback loop. This has been achieved with the help of computer models built using SIMULINK and Power System Blockset (PSB) developed both for MATLAB ® . Several models of different complexity have been built for the two power systems to perform separate circuit analysis and predictions after validation with experimental data [60]. The first problem of the 80 kA power supply system, that had to be solved at the beginning of Phase 1, was the simultaneous commutation of the power supply currents into the short circuit path during a safety discharge. For this purpose, a sufficiently low resistance and inductance of the short circuit path was necessary in order to have a voltage drop across the short circuit lower than the voltage of the rectifiers in inverter mode of operation. This has been achieved connecting in parallel a second short circuit path (i.e., made of a make switch S1.2 and circuit breaker S2.2 connected
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Page 3 and 4: The application and continuation of
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surement with voltage taps located
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Table 7.3 TFMC pancake (joint) resi
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Table 7.8 Values of TFMC and FSJS j
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Fig. 7.7. The insulated bus bar typ
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Rneg, 1[nΩ] = 1.77 [n�] + 3.75
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law actually is good (better than
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Fig. 7.16. Current in the petals re
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ence may exceed the inaccuracy of t
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provided support to the coil and th
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(c) The best fit in relation to the
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8.5. Comparison to ITER TF coil str
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Fig. 9.7. Partial discharge activit
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circular cross-section and central
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two different sets of Hall probe ar
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equation: dx = Ax + Bu dt y = Cx +
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[34] E. Salpietro, R. Maix, G. Bevi
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[86] R. Heller, D. Ciazynski, J.L.
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ple for ITER, IEEE Trans. Appl. Sup
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PSB: Power System Blockset is a MAT
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The ITER toroidal field model coil project

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