Investigation of the Slotting Effect on the Magnetization of Trapped Field Stacks in a Superconducting Machine

Stacked high-temperature superconducting (HTS) coated conductors (CCs) are preferred for trapped field magnets over HTS bulk due to their improved mechanical strength and shape flexibility. In superconducting machines, the demagnetisation phenomenon in HTS CCs is crucial as it affects the machine's magnetic field loading, affecting power and torque output. The stator slotting effect, common in conventional machines, can also influence TFMs made from HTS CCs in superconducting machines, leading to magnetic flux distortion and additional losses. To gain a comprehensive understanding of these influences, numerical analyses based on the finite element method have been conducted for different variants of a superconducting machine. Findings indicate that in the machine model: (1) a slotted stator yields higher trapped field values compared to a slotless stator, and (2) closed slots prove effectively in eliminating air gap harmonics. A final design with distributed winding and closed slots is recommended for reference in HTS motor development.