AC transport loss analysis of HTS stack busbars for all-electric aircraft with harmonics and DC offset considerations

This paper presents a study of the current carrying capacity and AC loss of high-temperature superconducting (HTS) stacks to be used in busbar applications for all-electric aircraft. A 2D model was developed using COMSOL Multiphysics with a T-A formulation for detailed analysis. The study began by applying a stable 20 kA DC offset current to the HTS stacks to simulate practical operating conditions. Firstly, the behaviour of the critical current was studied under self-field conditions for stacks with different numbers of HTS tapes and spacing. Secondly, AC ripple currents were introduced with DC offsets, and the effects of 3rd and 5th harmonic distortions (HD) were studied. The results show that configurations with 40 tapes and gaps of more than 2 mm are considered suitable for safe current transport under DC conditions. On the other hand, increasing the tape spacing leads to an increase in the safe transport current ripple due to the reduced magnetic field interaction within the stack. In addition, the transport loss decreases as the air gap increases due to the reduction in the self-field, whereas it increases as the number of strips increases. The influence of the 3rd HD on the transport loss is minimal at a ripple current of 1% and slightly noticeable at 2%. However, it becomes more obvious as the ripple current approaches the critical value. Remarkably, even cases with equivalent total HD show significantly higher transport losses when characterised by higher 5th HD than their counterparts with 3rd HD. This comprehensive analysis provides valuable information on the performance characteristics of HTS stacks in all-electric aircraft busbar applications and offers important insights for the development and optimisation of these systems in practical aerospace applications.