Abstract
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.
Highlights
Nowadays, owing to its high torque density and high efficiency, the rare-earth permanent-magnet (PM) synchronous machine (PMSM) is widely used for industrial applications, such as electric vehicle (EV) traction application [1,2,3]
NdFeB after 2011 as well as a limited flux-weakening capacity have immensely limited their further development for EV applications, which require a low cost and a wide speed range [4]
PMA-SynRMs with NdFeB were designed for EV applications in References [9,10]
Summary
Nowadays, owing to its high torque density and high efficiency, the rare-earth permanent-magnet (PM) (such as NdFeB) synchronous machine (PMSM) is widely used for industrial applications, such as electric vehicle (EV) traction application [1,2,3]. NdFeB after 2011 as well as a limited flux-weakening capacity have immensely limited their further development for EV applications, which require a low cost and a wide speed range [4]. For this reason, owing to their advantages such as mature technology, robust structure, relatively low cost, and excellent flux-weakening performance, induction machines (IMs) are often more competitive for EV applications [1]. To balance the performance and cost, permanent-magnet-assisted synchronous reluctance machines (PMA-SynRMs) are employed, which can reduce the amount of PMs by increasing the reluctance torque with a high saliency ratio, and keep a relatively high efficiency due to the added PMs [5,6,7,8]. PMA-SynRMs with NdFeB were designed for EV applications in References [9,10]
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