Speaker
Description
REBCO superconducting coils for aircraft propulsion motors boost magnetic flux density and output power which in turn improves the power-over-weight ratio. However, self-heating which can be due to either an AC current or a short-circuited DC voltage could cause thermal quench in HTS stator coils. Therefore, it is needed to analyze the complex interactions between electromagnetic phenomena and electrothermal reactions within this configuration. Electro-thermal modelling can provide valuable insights into this aspect. Indeed, this kind of modelling is required for motor design in order to ensure the safe operation of HTS motors. In this contribution, we study by computer modelling the electro-thermal quench behavior in a racetrack coil by assuming either adiabatic conditions or heat exchange with the coolant. For the latter, we assume either liquid nitrogen immersion or a given temperature at one of the edges of the coil, ranging from 20 to 77 K. We perform coupled electro-magnetic and electro-thermal analysis using a novel and robust software that we developed, which is based on the Minimum Electro-Magnetic Entropy Production (MEMEP) and the Finite Difference Method (FDM) for the electromagnetic and thermal models, respectively. We have found that screening currents caused by AC high frequency voltages under regular motor operation could cause electro-thermal quench. In addition, relatively low DC voltages due to accidental faults are sufficient to cause electro-thermal quench. Curiously, this quench starts at one of the turns at the coil center, even for uniform properties of the superconductor and other materials in thermal contact with it. This causes the current to roughly drop to 90% of the original. In conclusion, the computer modelling method that we developed can realistically predict the electro-thermal quench behavior in coils for superconducting motors, providing useful insights for their design.
| Submitters Country | Slovakia |
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