Influence of D-Q Current on No-Insulated High-Temperature Superconducting Magnets for Wound-Rotor Synchronous Motors

In this study, we analyze the impact of the armature d-q current vector on the no-insulation (NI) high-temperature superconducting (HTS) magnets utilized in wound rotor synchronous motors (WRSMs). Initially, we transform the three-phase alternating current system model into a two-phase direct current system model through direct and quadrature (
d
-
q
) transformation used to analyze the operational characteristics of motor systems. We construct a performance evaluation device based on the theoretical model to simulate the normal operating conditions of the HTS WRSM. The simulation uses an integrated model combining circuit and finite-element analysis models. Experimental testing of NI-HTS magnets uses the performance evaluation device, and the obtained results are compared with the simulation results. Our analysis reveals a direct impact of the magnetic field generated by the direct-axis armature current component on the NI-HTS magnet. The NI-HTS magnet in WRSMs is anticipated to operate stably in the second quadrant, where the direct-axis current registers a negative value on the armature current plane. Thus, for better stability of the NI HTS magnet in a WRSM, the armature current operating point must be positioned in the second quadrant of the armature current plane.