Pulsed Magnetization on Jointless Loops Coil Using Multi-Toroidal Auxiliary Winding

Jointless persistent current coils, known as the crossed loops, have been developed and studied by our group since 2018 and could be an interesting solution for challenges concerning current leads for HTS field coils in electric machine applications. To trap flux in such coils, pulsed field magnetization (PFM) through the armature coils is often employed. In this work, a different PFM is proposed, by taking advantage of the jointless loops geometry. This approach uses a low-current secondary winding magnetically coupled to the coil heads, wound in a toroidal shape, forcing the pulsed magnetic field around the HTS tapes and inducing persistent currents. The main advantage of this idea is that such auxiliary winding could be used as a flux pump for its main coils without the need to reroute the stator source for a re-magnetization process. A prototype of the proposed application is presented in this work. It was verified using finite element simulations then built and tested as a proof of concept. Its behavior is observed and a special attention is given to how the coupling of multiple loops affect the global persistent current of a coil, due to the dependence of the critical current to the magnetic field. The data show the feasibility of the proposed idea and opens another path for improving the HTS crossed-loops machine topology.