Refrigeration load calculation of a HTSC current lead under AC conditions

A 5 kA_rms/50 kV HTSC hybrid AC current lead is developed within a BRITE/EURAM cooperation between Alcatel Alsthom, Hoechst and Siemens. For the optimisation of the conductor geometry computer codes have been realised. For the evaluation of AC losses in the superconducting melt cast processed Bi-2212 part, the Bean model has not turned out to be practicable especially when the current exceeds the I_c(T) curve, This is of course related to the low n-value (n⩽10) of the superconducting transition curve in this material. A new calculation based on experimental E(J,B,T) curves allows the evaluation of AC losses in the temperature range of interest. These results are used for the calculation of the maximum stable length and the low temperature heat load which is more than three times smaller than in an all metal DC lead. Together with the 77 K heat load of the normal part of the AC lead, the overall 300 K refrigeration load is calculated