Superconducting rectifier flux pumps have been gaining attention as potential high current supplies for REBCO magnets, due to their small footprint and thermal efficiency. Separately, HTS dynamos have recently been demonstrated to output kA currents, and can be introduced into rotating machine designs without penetrating the cryogenic environment. Here, we present a novel mechanically-rectified flux pump topology that combines the advantages of both types of device. We report the design, build and 1st experimental validation of this hybrid concept.

This new class of high-Tc superconducting flux pump employs permanent magnets mounted on a simple rotor to induce an ac emf in an HTS stator coil, which is then rectified by periodic variation of the resistance of a parallel bridge tape. The focus of the device design are the steel rotor and stator which direct magnetic flux through both the induction coil and the separate switching bridge. The relative timing of flux through the coil and bridge is determined by the stator geometry, and can be adjusted to maximise the rectified DC output. An experimental prototype device has been demonstrated by charging a 77.6 µH superconducting magnet to 12.8 A in 73 s. Results from experiments with one and two rotor magnets are presented, which show evidence of two different modes of operation: (i) self-rectification and (ii) field-switched Jc(B) rectification. The maximum load current is found to increase non-linearly as rotor speed increases, plateauing near 450 RPM. This flux pump design has the potential to be operated atr very low heat load in future machine designs, by placing the magnets outside of the cryostat.

Acknowledgments
This work was supported by the Ministry of Business, Innovation and Employment, New Zealand under the Advanced Energy Technology Platform program “High power electric motors for large scale transport” contract number RTVU2004. 

Keywords: HTS flux pump, HTS magnet, Efficiency