Research On AC Loss Of Winding Of High-Temperature Superconducting Pulsed Transformer

AC losses are unavoidable in the operation of superconducting power equipment and directly affect the efficiency,size,and weight of superconducting equipment.In the superconducting pulse power technology field,the high-temperature superconducting pulse transformer,as a critical component in pulse power technology,directly impacts the miniaturization and lightweight of the pulse power supply.Previous research on high-temperature superconducting pulse transformers has focused on the topology of the pulse power supply and the optimization of the parameters of the electromagnetic structure of the pulse transformer,with less research on the AC losses of superconducting pulse transformers.The calculation of the AC losses of high-temperature superconducting coils is based on the perfect winding,ignoring the effect of misalignment between the ring turns.In this paper,systematic numerical modeling of superconducting strips,superconducting coils,and superconducting pulse transformers has been carried out to analyze the AC loss characteristics and electromagnetic properties of superconductors.The AC loss characteristics of superconducting tapes under self-field,external field,and full-field conditions are studied,respectively.The correctness of the model is verified by comparing the simulation results with the analytical calculation results,which provides theoretical support and essential data for the modeling and analysis of superconducting coils and transformers.The effects of tilted and disorderly misalignment on the AC losses are investigated for superconducting coils.The electromagnetic properties differences between the axially misaligned and perfectly wound coils are compared and analyzed.For high-temperature superconducting pulse transformers,the influence of three critical parameters on the accuracy and speed of AC loss calculations is first investigated based on the homogenization method,including the number of homogenized cells,the calculation step size of the model solution and the partial differential equation(PDE)discretization settings.An optimized scheme for the fast and accurate calculation of AC losses in superconducting pulse transformer windings is proposed.A model of the superconducting pulse transformer was developed after realizing a simplified winding coil.The AC losses under the action of the primary and secondary coupling were analyzed and calculated,and adding the flux diverter reduced the AC losses.In order to improve the effectiveness of the flux diverter and further reduce the AC loss of the superconducting pulse transformer winding,the influence of the installation position,number,and structural parameters of the flux diverter on the AC loss of the superconducting pulse transformer is explored.The simulation results show that the influence of the axial misalignment of the coil on the AC loss can be eliminated by applying the excitation in the range of 0.7 to 0.8 times the critical current of the strip.This result provides a guiding significance for the strip selection of the primary and secondary windings of the superconducting pulse transformer and the adjustment of the peak charge and discharge current.It is beneficial to reduce the AC loss of the primary and secondary windings of the superconducting pulse transformer by using the disc coil stacking structure.The AC loss calculation is done for various superconducting pulse transformer model schemes equipped with the flux diverter.Finally,the optimal strategy is obtained.The AC loss is 70.2 % lower than that of the transformer without the magnetic ring,which provides a solution to reduce the AC loss of the superconducting pulse transformer.It provides an essential reference for designing and manufacturing the high-temperature superconducting pulse transformer and the cooling system.