Conceptual design and optimization study of a 3 MW fully superconducting synchronous electrical machine for the electric aircraft based on the magnetic vector potential boundary method

Abstract Future electrical propulsion systems for electric aircraft need lightweight and compact electrical machines with high power density, high efficiency, and high power-to-weight ratio (PWR). High temperature superconducting (HTS) electrical machine is expected to be a promising technology to meet these challenging demands due to the ultrahigh current density, near-zero DC resistance, light weight, and compact volume of the 2 G HTS REBCO coated conductors. However, in traditional superconducting machine design processes, the unique properties of the HTS machine windings are often oversimplified. These oversimplifications make it challenging to accurately estimate the critical current and loss of the HTS machine windings under the complex background magnetic fields inside the electrical machines. This paper proposes a magnetic vector potential boundary (MVPB) method to design and optimize a 3 MW fully HTS synchronous electrical machine (FHTS-SM). The results show that the MVPB method can consider the superconducting properties in the design and optimization of the electrical machine, and it has highly accurate results. Meanwhile, the MVPB method significantly reduces the quantity and complexity of computations, and the computation time is reduced by 96%. Through a joint simulation (modelFRONTIER & MATLAB & COMSOL), multi-objective optimization was conducted on the 3 MW FHTS-SM design to obtain the optimal design. Moreover, the HTS armature winding is optimized by the multifilamentary method to reduce AC loss. The results show that the optimal design can increase the PWR (machine only) by approximately 25% and improve the efficiency by about 8% simultaneously. This work provides a powerful tool to effectively and accurately estimate the loss of the HTS machine windings at a stable operation state. Meanwhile, it offers a good understanding of designing high power-to-weight and high efficiency superconducting electrical machines. Additionally, the simulation results can provide a basis for the R&D of the superconducting electrical machine prototype for future electric aircraft.