Electromagnetic and mechanical AC loss of an ITER TF model coil conductor (DP4) under transverse cyclic loading

Abstract

Energising a coil results in a transverse force on the strands pushing the cable towards one side of the jacket. This load causes a transverse compressive strain in strands and in particular in strand crossover points. Besides this, contact surfaces interfere by micro-sliding resulting in friction and anomalous contact resistance behaviour versus force. Two Central Solenoid Model Coil conductors have been tested previously in a cryogenic press and now the experimental results are presented for the Toroidal Field Model Coil (TFMC) conductor (DP4). The press can transmit a variable (cyclic) force of at least 650 kN/m directly to a cable section of 400 mm at 4.2 K. The magnetisation of the conductor and the interstrand resistance (R/sub c/) between various strands inside the cable can be measured by varying pressure. The force on the cable and the displacement are monitored simultaneously in order to determine the effective cable Young's modulus and the mechanical heat generation due to friction and deformation. The mechanical heat generation, the coupling loss time constant n/spl tau/ and the R/sub c/ of the full-size ITER TFMC conductor have been studied under load up to 40 full loading cycles. The evolution of R/sub c/ is comparable to the behaviour found for the CS Model Coil type of conductors. A significant decrease of the cable coupling current time constant, n/spl tau/ and mechanical heat generation after cyclic loading is found.