Optimisation of Rotor Skewing of a Yokeless And Segmented Armature Axial Flux Machine

This paper presents an optimization of rotor skewing of an Axial Flux Machine (AFM) in a Yokeless And Segmented Armature (YASA) design in the torque-speed characteristics diagram. AFM have advantages regarding a compact design and high torque density compared to other variants of permanent magnet machines. The drive train Noise, Vibration and Harshness (NVH) performance is influenced by cogging torque, magnetic torque ripple and tooth forces. While the axial skewing of rotors in radial flux machines (RFM) has already been extensively studied to minimize these magnetic excitations, this represents a target value for optimizations in AFM. Optimizations are carried out and validated using 2D and 3D finite-element (FE) models. The 2D model combines multiple 2D slices but lacks accuracy because an insufficient inclusion of 3D effects. The 3D model allows to obtain a noticeable reduction by more than 30% of the dominant torque harmonic amplitudes over the whole torque-speed range in combination with a constant peak torque after optimization.