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

Pulsed power technology has broad application prospects in many fields such as military weapons,civil industry,and aerospace.The pulsed power supply(PS)based on the high-temperature superconducting pulsed power transformer(HTSPPT)is beneficial to the miniaturization and light weight of the power supply device,and is one of the research hotspots in the field of pulsed power technology.Generally,superconducting coils are used as primary windings for energy storage and copper coils are used as secondary windings to generate a large current pulse in HTSPPT.The basic model of the superconductor,the classification and the calculation of AC loss were described,and the H formulation numerical method were discussed.The working process of pulsed PS based on HTSPPT was analyzed,and the current waveform of the primary energy storage winding I_p was obtained by simulation.The 2D finite element model(FEM)based on the H formulation was used to model a single YBCO tape in the finite element software Comsol Multiphysics,and the change trend of instantaneous AC loss,the distribution of current,and the distribution of the magnetic flux density were analyzed when the tape is transmitting the primary current.The 2-D axisymmetric FEM based on the H formulation was used to model the YBCO pancake coil.The distribution of the AC loss and the electromagnetic characteristics of the pancake coil were analyzed when the pancake coil is transmitting the primary current.Flux diverters are installed at the top and bottom of the pancake coil to optimize the AC loss in order to effectively reduce the AC loss of the pancake coil.The influence of the relative permeability of the flux diverter,the distance between the flux diverter and the YBCO double pancake coil,and the thickness of the flux diverter on the AC loss of the double pancake coil were analyzed.In the end,the relative permeability of the flux diverter is selected as 100,the distance between the flux diverter and the double pancake coil is selected as 0.25mm,the thickness of the flux diverter is selected as 1mm.The influence of the flux diverter on the current density,the AC loss of each turn tape and the magnetic field characteristics were analyzed.The simulation results show that the selected flux diverters can significantly reduce the radial magnetic flux density of the double pancake coil,and the AC loss of the double pancake coil is reduced by 60.89%compared with the AC loss without the flux diverter.In order to further reduce the AC loss of the YBCO double pancake coil,flux diverters are slotted,and the influence of the slot,the number of slots and the depth of the slots on the magnetic field distribution and AC loss of the double pancake coil were studied.When the number of slots is three and the depth of slots is 0.5mm,the AC loss of the YBCO double pancake coil is reduced by 10.23%compared with the AC loss without slots,and it is 64.9%lower than the AC loss without the flux diverter.The simulation results show that after the flux diverter is slotted,the radial magnetic flux density is mainly distributed at the slot,and slotting the flux diverter can reduce the AC loss of the double pancake coil.Therefore,slotting the flux diverter can not only reduce the AC loss of the YBCO double pancake coil,but also reduce the weight of the magnet,which has great significance for the design and manufacture of HTSPPT and the cooling system.