2010, вып. 3 Влияние соотношения шагов скрутки различных стадий на распределение кооперативных токов … 35 УДК 621.039.6 ВЛИЯНИЕ СООТНОШЕНИЯ ШАГОВ СКРУТКИ РАЗЛИЧНЫХ СТАДИЙ НА РАСПРЕДЕЛЕНИЕ КООПЕРАТИВНЫХ ТОКОВ И ПОТЕРИ ЭНЕРГИИ В СВЕРХПРОВОДЯЩИХ КАБЕЛЯХ С.А.Егоров, М

The AC performance of the superconducting magnets of thermonuclear tokamak reactors and superconducting magnetic energy storages (SMES), made of the cable-in-conduit conductors (CICC), is greatly influenced by the deposition of the electromagnetic and mechanical energy losses in the conductor. The paper describes the electromagnetic techniques used for the measurements of these losses in the CICC short samples with and without transport current and in the International Thermonuclear Experimental Reactor (ITER) Toroidal Field Conductor Insert Coil (TFCI).

The results of AC loss and interstrand resistance measurements for the short samples of 4 kA @ 4 T NbTi cable-in-conduit conductor (CICC) are described. The effect of real orientation of the NbTi strands in regard to the magnetic field applied transversally to the cable axis on the hysteresis losses, and the magnetic field dependence, of the CICC effective time constant have been observed. No substantial effect to the interstrand resistance of the electromagnetic force, but the indications of the strand saturation and supercoupling circulation current effects have been found for a sample carrying a transport current. Mechanical hysteresis losses for this sample have been evaluated with new technique basing on the determination of the location of the conductor electric center. Dependence of these losses on the applied electromagnetic force ramp rate has been found.

An approach and formulae are given to calculate the hysteresis, coupling, eddy-current and Ohmic losses in a thin-wall tube multifilament composite superconductor carrying a transport current under low excitation by a homogeneous transverse time-varying magnetic field, taking into account possible filament saturation and current sharing effects. The technique can be applied to a single layer superconducting cable twisted around a thin-wall normal conducting tube.

Computations have shown the possibility for the non-uniformity of the applied magnetic field alteration rate profile at a superconducting cable to cause the increase of AC losses and cable coupling currents flowing along the strands. The paper presents the results of computer simulations of the effect in some cases typical for cables of tokamak-machines under operation and under the cable short sample tests.