Speaker
Description
It is well known that screening currents induced in REBCO coils are an annoying phenomenon. Due to the thin tape shape of REBCO coated conductors, the large amount of screening currents are induced, and unexpected magnetic fields are generated. It worsens the magnetic field quality of REBCO magnets by which homogeneous fields are required as applications of NMR and MRI. Recent years, it was pointed out that screening currents cause local overstresses. Hence, the screening current estimation by simulation is very important.
A few screening currents modeling of REBCO pancake coils have been proposed, and these characteristics are different. Our team have also proposed three different modelings: 1) FEM based, 2) network circuit based, and 3) simple circuit based. Accurate modelings need long time, and a fast modeling has less accuracy. To overcome such properties, we have newly developed a fast screening current modeling with sufficient accuracy. In this presentation, we have compared the simulated screening current induced field (SCIF) and the simulation time. The proposed method can accelerate the speed by approximately 6 times by reducing the degree-of-freedom, comparting the FEM based one. When the screening current of 12 single pancake coils, whose turns are insulated, was simulated, the simulate time decreased to 17.5 hours from 105 hours, but the simulated SCIF results are very close. We will show and discuss the hysteresis curve of SCIF when the 12 single pancake REBCO coils are charged and uncharged.
In addition, this proposed model can simulate the screening current of no-insulation (NI) REBCO pancake coils. So far, the FEM based model cannot simulate the screening current without any special technique. By making it circuit-based, it is easy to consider the no-insulation winding structure. Moreover, we pay the attention to the coil voltage during charging.
Acknowledgement: This work was supported by the JSPS KAKENI under Grant 20H02125 and Grant-in-Aid for Scientific Research(S) under Grant 18H05244.
