To shorten the cooling time of the superconducting rotor, reduce the thermal leakage of the cold mass, enhance the working stability of high-temperature superconducting (HTS) magnets, and reduce the amount of HTS wires, a novel warm rotor for a 200 kW HTS generator (HTSG) with radial support rods, tangential racetrack rings, and modular HTS magnets was successfully developed. There are 12 HTS magnets in 6 poles of the HTSG, all of which can work stably without quench, and the performance of the magnets meets the expectation. The vacuum, thermal insulation, and cryogenic systems of the generator run stably, which meet the needs of continuous operation at full load. The manufactured warm rotor and the original iron-core stator of the existing 200 kW HTSG were assembled into a new 200 kW HTSG, the assembly process was completed at Wuhan, and then finished the performance test. The test results show that the output power of the HTSG reaches 203.4 kW and the torque reaches 3885 N.m when the field current reaches 24 A and the speed is 500 r/min, which achieved the target power.

High-temperature superconducting (HTS) technology enables the realization of compact and efficient designs, with the potential to break through the bottleneck of high-power-density motors. In HTS motors, field windings are crucial components that significantly influence overall performance. The motor’s power capacity is generally proportional to the air gap magnetic field (B _g), which is further limited by the critical current of the HTS coils. In this paper, we designed and tested a single pole magnet for the HTS rotor that generated B _g of 3.39 T for an air gap of 3.5 mm and 3.04 T for an air gap of 15 mm at 30 K. These results are promising for high-energy-density motors, especially for HTS motors intended for aircraft. In addition, we established a 2D axisymmetric numerical model accommodating the J _c ( B , θ ) dependence of the critical current of HTS tapes to yield a more accurate estimation of the critical current of the racetrack coils. This methodology has been validated with various HTS tapes possessing different intrinsic flux pinning properties, demonstrating high accuracy and effective capability in simulating HTS coil performance. This work provided valuable guidance for the design and optimization of future high-power-density superconducting motors, while also validating a universal numerical simulation method.

This study introduces the results of preparing and testing a persistent current system including persistent current switch (PCS), large-scale HTS magnet, and joints. The transition state of PCS between superconductivity and normal was controlled by changing its temperature. The magnet with inductance of 2.5 H was excited to 136 A at 37 K and worked in persistent current mode. The joint resistance and magnetic field attenuation rate of the PCS system were calculated to be 1×10 ^-6 Ω and 1.24 mT/h, respectively. If HTS magnets in machine are in persistent current mode, slip-ring just works at charging the magnet period. In the long run, by reducing working hours of the slip-ring, the HTS machine can be saved from frequent maintenance.

REBCO coil is a promising technology for superconducting magnetic energy storage system (SMES). Although degradation has been discovered in epoxy impregnated coil, it is essential to fill the coil with epoxy in such occasion. This paper describes preparation of large scale epoxy impregnated REBCO coil for SMES. The coil with inner diameter 320 mm and 268 turns was tested at 77 K both before and after epoxy impregnation. Consistency of Ic value and high n-value suggest that there was no degradation in the coil. Conduction cooled test was also carried out. Transport current was run up to 223 A at 50 K.

A high-temperature superconducting (HTS) motor was designed, which employs the HTS wires in the rotor field windings. To reduce the welding joint resistance of the wires, a simple and efficient welding method is developed, and the welding process suitable for 2G and 1G HTS wires is summarized as follows. First, the welding process was obtained by the tests, the results show that the welding temperature is chosen to be 220°C, the lap length is chosen to be 160mm, and the resistance of the joint can reach 10 ^-9 Ω. Second, the resistance influenced by the radius was analyzed by the finite element method. The results show that there might be little decrease in the critical current of the joints. Last, a 2G HTS magnet was manufactured to verify whether the joints made by the method can meet the requirements of bending deformation in the HTS magnet winding process. The results show that the welding process can satisfy the requirements, and provide an important reference for subsequent work.

Since the epoxy-impregnated REBCO superconducting coil is a multi-layer structure, the internal stress generated during cooling cannot be directly observed. Therefore, we measure the radial strain of the coil to indirectly assess the degree of radial delamination damage of the coil. In this paper, we establish a homogenization model for small-sized coils to calculate stress and strain. A superconducting coil was wound and tested for critical current and strain at a temperature of liquid nitrogen, using a copper sheet and a straight stack structure as standard references. Compared with the strain simulation results, the experimental data indicate that the thermal strain and elastic strain data of the coil are in good agreement, with a relative error within 7%, which verifies the applicability and accuracy of the model and experimental method. It is helpful for the equivalent observation of the delamination behavior of the superconducting tape inside the coil.