Influence of Stator MMF Harmonics on the Utilization of Reluctance Torque in Six-Phase PMA-SynRM with FSCW

Although fractional-slot concentrated winding (FSCW) offers many significant advantages, such as short end-turn windings, high slot filling factor, and low cogging torque, it is frequently limited by excessive stator magnetomotive force (MMF) harmonics which will induce high eddy losses in the permanent magnets (PMs). What is more, in the literature, it can be observed that the reluctance torque of the salient-pole machine with FSCW is usually much lower than that obtained with integral slot winding. To explore the underlying reason why the reluctance torque in a salient machine with FSCW significantly decreases, a new six-phase FSCW with 24 slots and 10 poles, which can significantly reduce the undesirable stator MMF harmonics, is obtained by using the concept of stator shifting. Then, two permanent-magnet-assisted synchronous reluctance machines (PMA-SynRMs) with the proposed winding layout and conventional asymmetric 12-slot/10-pole six-phase winding layout are designed and simulated by the finite-element method (FEM). The reluctance torque, total torque, and d/q-axis inductances with different current phase angles are also compared under different loaded conditions. The results show that a reduction in stator MMF harmonics can indeed lead to a significant enhancement in reluctance torque under heavy loaded conditions, while the dominance will diminish under light loaded conditions.