Due to the growing demand for eco-friendly and energy-efficient technology, superconducting generators and motors are gaining more and more popularity. In particular, the use of a superconducting racetrack coil in either the rotor or stator of electric motors for air transport is a significant advancement in electrical engineering, being the most promising technology that could reach the high power-over-weight requirements for zero-emission hydrogen-electric airliners, which is around 25 kW/kg. In addition, REBCO high-temperature superconductors (HTSs) are very promising for power and magnet applications due to their relatively high operation temperatures and good performance under high magnetic fields, compared to other superconductors.
However, HTS motors face the danger of a thermal quench due to self-heating effects when subjected to alternating or short-circuit onset DC voltage and in addition, screening currents cause thermal events when motors operate at high frequencies. Therefore, for the safe operation of HTS motors, quench research is crucial. To accurately simulate and analyze quench events in different scenarios, it is imperative to employ fast and precise software to numerically model the electrothermal behavior in racetrack coils. Such computational model was developed by Arif Hussain and his colleagues in programing language C++ and presented in this article. The novel and efficient model couples together electromagnetic and electrothermal analyses using variational methods and also accounts for screening currents.
The model incorporates both Minimum Electro-Magnetic Entropy Production method and the Finite Difference Method (FDM). The phenomenon of a temperature rise within a racetrack coil subjected to either alternating or DC voltages of magnitudes ranging from 0.1 V to 1000 V was explored (Fig. 1). The study encompasses conditions of an adiabatic operation and a heat exchange with liquid nitrogen (LN2). Among other results, we found that in moderate DC voltages like 10 V, non-uniformity in the AC loss causes highly localized quench at the central turns (Fig. 2), meaning screening currents play a key role also for DC voltages. The developed model exhibits the potential to comprehensively and swiftly analyze the electromagnetic and electro-thermal characteristics of real-world superconducting applications, including high-field rotating machines, such as motors for aviation. The computational models and further results are presented in detail in the linked article.
Authors: Arif Hussain, Anang Dadhich, Enric Pardo
Link: https://iopscience.iop.org/article/10.1088/1361-6668/ad7644