Application of electrical and calorimetric methods to the AC loss characterization of cable conductors

Due to higher currents (and therefore higher losses) compared to individual wires and tapes, the AC loss characterization of HTS cable conductors carrying transport current can be performed using calorimetric as well as electrical methods. We discuss the main features of two calorimetric methods, one based on temperature profile determination, and one based on nitrogen boil-off rate, and of the electrical method, substantially derived from that already established for tapes, based on voltage measurement by a lock-in amplifier. Advantages and limits of each approach are analysed and compared. Tests have been carried out with the three methods on samples 1 to 1.5 m long cut from a Bi-2223 cable conductor prototype fabricated by Pirelli in a longer length. Results obtained from measurements covering a wide range of currents are compared and thoroughly discussed.