STABILITY OF LARGE COMPOSITE SUPERCONDUCTORS

High current large composite conductors cooled in He II baths are planned for superconductive magnetic energy storage (SMES) systems. Such conductors have long time constant current diffusion causing high initial I2R generation when driven normal. As a result, the front of a normal zone may propagate even though the back of the normal zone is recovering as current diffuses deeper (with less I2R) into the stabilizer. Accurate knowledge of I2R heat generation in the current sharing region and the time dependent transient heat transfer to helium is determined for the stability analysis. Analytical and numerical procedures are developed to calculate the maximum non-propagating currents and propagation velocities. Round and rectangular shaped conductors are considered via the computational model. Numerical results are compared with experimental data.