Cogging torque reduction of axial field flux-switching permanent magnet machine by rotor tooth notching

Axial field flux-switching permanent magnet machine (AFFSPMM) is a novel permanent magnet (PM) machine which incorporates the merits of flux-switching PM (FSPM) machine and axial field PM machine. AFFSPMM exhibits many advantages, such as sinusoidal back-EMF waveform, good flux weakening capability, favorable for cooling, high torque/power density and high efficiency [1]. However, compared to the traditional PM machines, the cogging torque of AFFSPMM is high due to the doubly salient structure and the extremely high flux density caused by the flux focusing effects. The cogging torque reduction of AFFSPMM by rotor tooth notching is investigated in this paper. Three different rotor tooth notching schemes are presented and the influence of the dummy slot parameters on the cogging torque for different rotor tooth notching is investigated based on 3-D finite element method (FEM). The dummy slot width, slot depth, and slot shape are optimized by response surface method (RSM), the cogging torque and output torque under different optimal combinations are calculated and compared.