Investigation of Electromagnetic Torque Generation Mechanism in FSCW V-IPM Machines Considering Magnetic Saturation

This article investigates the generation mechanism of electromagnetic torque, particularly the reluctance torque in fractional slot concentrated winding (FSCW) V-type interior permanent magnet machine (V-IPM) machine. Based on the air-gap field modulation theory, the modulation process of the PM field and armature reaction field is elucidated by establishing a magnetomotive force (MMF) and permeance model considering the magnetic saturation of rotor magnetic bridge. Through analyzing the conditions for effective coupling of air-gap field harmonics, studying the time-domain modulation effect resulting from the magnetic saturation of rotor magnetic bridge, and establishing the mapping relationship between inductance harmonic and single-phase winding field harmonic, the generation mechanism of electromagnetic torque, including both the PM torque and reluctance torque in FSCW V-IPM machine, is first revealed. Then, a harmonic restoration method based on frozen permeability is adopted to quantitatively analyze the contribution of the armature reaction MMF harmonics to the PM torque and reluctance torque. Moreover, the reluctance torque ratio, defined as the ratio of reluctance torque to electromagnetic torque, is additionally presented from the aspect of armature reaction MMF harmonics. Finally, the analysis is verified numerically by an exist well-developed FSCW V-IPM machine.