Comprehensive Investigation on the Slot Leakage Inductance of Axial Flux Permanent Magnet Motor with Novel Slot Shape

The slot shape of a yokeless and segmented armature (YASA) motor differs significantly from that of traditional motors due to its dual-slot openings. An analytical method is proposed for determining the slot leakage inductance of a novel slot of the YASA axial flux permanent magnet (AFPM) motor. A general analytical formula for calculating the slot leakage inductance component within a single YASA slot is derived, and the phase-slot leakage inductance of a YASA-AFPM motor is further determined based on its unique winding distribution. This reveals that the coil-side width has a significant influence on the slot leakage inductance component, whereas the pole-slot combination has a notable influence on the number of slot leakage inductance components in the phase inductance. Additionally, the relationships between the coil-side width, pole-slot combination, and slot leakage inductance are analytically established. Finally, the slot leakage inductance of a 20-pole-24-slot AFPM-YASA motor is calculated using the proposed method, and the results are in agreement with those obtained using the finite element method (FEA), verifying the accuracy of the proposed method.