3D Modeling of Coils for Pulsed Field Magnetization of HTS Bulk Pellets Placed on an Inductor of a Superconducting Electrical Machine
Résumé
The development of cryo-magnets based on REBaCuO type superconductors that can generate up to 17 T requires the implementation of a magnetization system, and therefore one or more coils around massive superconducting materials. However, the most convenient way to magnetize a High Temperature Superconducting bulk is to use a pulsed magnetic field. This method is called PFM for Pulsed Field Magnetization. It can generate strong magnetic fields while using a relatively compact and simple coil. Thus, HTS bulks can be directly magnetized into the final application.
Here, we propose to study and design different coils in order to magnetize, using PFM, an inductor of a radial flux superconducting machine with one pair of poles. Each pole contains 4 HTS bulks of 30 mm in diameter that can be placed in a square or rectangular pattern. The cryostat already exists for this application and the temperature of the HTS bulks can vary from 4.2 K to their critical temperature in transient state.
For a given primary source of energy, here a capacitor bank of 10 kJ (5 mF, 2 kV), the PFM process strongly depends of the inductance value of the coil used to magnetize because it defines the waveform of the current: the peak value and the time constant. Thus, 3D modeling of the coil is required in order to be sure that its inductance value and magnetic field produced will allow us to fully magnetize the HTS bulks. From the practical point of view, we would like to achieve an average magnetization of each pole around 4 T.
In this paper, different numerical modeling approaches and different geometries of poles will be studied. Results will be the maximal magnetic field that can be applied on the HTS bulks, and the estimated magnetization of the poles of the inductor.