Numerical Simulation of AC Loss in the Armature Windings of Two 50 Kw-Class All-HTS Motors with Different Pole Shapes

Achieving low AC-loss armature windings is a key challenge to enable all-HTS motors. Large AC-loss is induced in the HTS armature windings through interaction with the rotating magnetic field generated by the rotor. To reduce the AC loss in the armature windings, it is important to minimize the impact of the rotating magnetic field, especially the component perpendicular to the broad face of REBCO conductors. This work presents two different 1500 rpm, 50 kW all-HTS motor designs with different iron pole shapes: one with pole shoes on the iron core for diverting the magnetic flux around the coil windings, and one without pole shoes. REBCO coated conductors are considered for both the armature and field windings and 2D finite-element models of both designs are built using the T-A formulation and moving meshes. System-wise analysis of the motor in terms of weight and efficiency is discussed based on the simulated AC loss results. The simulation results show that, at 65 K, flux diverting pole shoes provide a 51% AC loss reduction in the HTS armature windings, without weight penalty or motor power rating reduction. Furthermore, simulation results at 20 K show that the AC loss decreases with decreasing operating temperature due to a decrease in the penetrated field in the HTS windings, which reduces the magnetization loss component.New Zealand Ministry of Business, Innovation and Employment (MBIE); Strategic Science Investment Fund "Advanced Energy Technology Platform"; Engineering and Physical Sciences Research Council (EPSRC) Early Career Fellowship, EP/P020313/1