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

Abstract

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.

Dynamic resistance and total loss in small REBCO pancake and racetrack coils carrying DC currents under an AC magnetic field

“…The 3D numerical model based on the T-A formulation is used to calculate magnetization loss, dynamic resistance and total loss in the DPC. The details of the T-A formulation can be found in previous studies [24][25][26][27]. Figure 5(a) shows the 3D geometry for the DPC, which is simplified as a vertical stack of two ten-turn pancake coils.…”

“…The air gap between these two pancake coils is 0.2 mm, and the height of each pancake coil is 4 mm. Only the superconducting layer of the REBCO CC is considered and approximated as a sheet, while the nonsuperconducting layers are assumed to be air [24][25][26][27]. A cylinder air domain was built, whose diameter and height are three and six times the diameter and height of the DPC.…”

Numerical modelling of HTS tapes under arbitrary external field and transport current via integral method: review and application to electrical machines *

“…Later, instead of the two-stage method, fully coupled models were developed in which the full machine with superconductor tapes was simulated in one model, e.g. by the H-A formulation [31,32] and the T-A formulation [33][34][35][36][37][38][39][40][41]. The H-A and the T-A formulations have been compared [39,41,42].…”

Measurement of AC loss down to 25 K in a REBCO racetrack coil for electrical aircraft motor

“…Superconducting machines (motors and generators) could be built with superconducting windings on the rotor, in the stator, or in both stator and rotor 1 – 9 . For superconducting stators, heat generation due to AC loss could be an issue in order to be able to keep the required low temperature for operation.…”