Magnetic Conduction Structure Design and Charging Test of a Linear-Motor Type Flux Pump for Through-Dewar Excitation of High Temperature Superconducting Motors

High temperature superconductivity (HTS) flux pump can be used as the exciter to inject direct current into the superconducting excitation coil of a synchronous motor, without current lead and with low thermal efficiency, which will reduce the cryogenic volume and improve the efficiency of HTS synchronous motor. However, the flux pump has non-negligible thermal impact when it is running continuously for a long time within the cryogenic Dewar, which will cause a heavy heat burden to the cryogenic system. Therefore, based on the linear-motor type flux pump previously invented in our laboratory, this paper improved its magnetic circuit, so that it can introduce the travelling magnetic wave into the Dewar from outside. Firstly, we have used COMSOL Multiphysics to simulate and optimize the waveform of this flux pump. Secondly, we have manufactured the flux pump and magnetic conduction structure, and have tested its performance in liquid nitrogen at 77 K, a pumped DC current of 216 A was measured with a single 12 mm wide YBCO stator. These work have further optimized the linear-motor type flux pump, which provide a contactless static excitation device (CSED) for the 16.9 kW HTS synchronous motor built in our laboratory.