No-Insulation High-Temperature Superconductor Winding Technique for Electrical Aircraft Propulsion

Abstract

High temperature superconductor (HTS) machine is promising candidate for the electrical aircraft propulsion, due to its great advantage on high power density. However, the HTS machine always suffers the problem of low thermal stability during quench. In this study, we apply a no-insulation (NI) coil technique on the rotor windings of HTS machines to enhance the stability and safety of the electrical aircraft. The NI HTS rotor windings experience ripple magnetic fields, which leads to induced eddy currents through the turn-to-turn contacts. This induced current and accompanying losses will considerably affect the practicality of this technique. To study this issue, an equivalent circuit network model is developed, and it is validated by experiments. Then analysis using this model show that most of induced current flows in the outer turns of the NI HTS coil because of skin effect, and lower turn-to-turn resistivity leads to higher transport current induced and more significant accumulation of turn-to-turn loss. A grading turn-to-turn resistivity is proposed to reduce the transport current induced and AC loss accumulation and meanwhile keep the high thermal stability of the NI HTS coil. Optimization of turn-to-turn resistivity is required when the NI HTS coil is applied in the machines environments.

Experimental and Simulation Study of Resistive Helical HTS Fault Current Limiters: Quench and Recovery Characteristics

“…When the SFCL coil operates in normal operation, nearly zero resistivity exists in superconducting layer and all the curent passes through this layer. When a fault happens, fault current is higher than the critical current of the SFCL coil, leading to increase of the resistivity of superconducting layer [30,31].…”

Machine learning the lattice constant of cubic pyrochlore compounds

“…But there are still a lot of potential pyrochlores that have not been synthesized, and without validated source of lattice constants, the explorations of new compositions are greatly limited. 23,27,28 Nonetheless, pyrochlores A 2 B 2 O 7 retain cubic structures, where the lattice constant, a, is the only parameter that is variable among the six lattice constants. Ionic radii of constituting elements affects the interatomic separation greatly, while the electronegativity and valence state affect the chemical bonding at the same time.…”

“…To study the electronic structure, lattice constants obtained through experimental approaches, including synthesis and X‐ray diffraction, are commonly used if available. But there are still a lot of potential pyrochlores that have not been synthesized, and without validated source of lattice constants, the explorations of new compositions are greatly limited 23,27,28 . Nonetheless, pyrochlores A 2 B 2 O 7 retain cubic structures, where the lattice constant, a, is the only parameter that is variable among the six lattice constants.…”

Investigations on Quench Recovery Characteristics of High-Temperature Superconducting Coated Conductors for Superconducting Fault Current Limiters

“…From the macroscopic point of view, the topology of SFCLs was discussed qualitatively, mainly for determining the current-limiting efficiency [23][24][25]. For more precise descriptions of quench recovery processes, measurement and calculation of HTS tapes were carried out, which clarified the physical nature of the process [26][27][28][29][30][31][32][33]. However, when a practical SFCL is designed and built for operation, how the quench recovery time changes with a different fault current or energy needs to be known.…”