This article investigates the application of star-delta hybrid concentrated-winding (CW) in permanent magnet vernier machines (PMVMs), with main focus on power factor and field-weakening capability. The analysis results show that the hybrid CW exhibits low-coupling property, namely both the mutual inductances between the comprising coils of each single phase and that among three-phase windings are eliminated. As a result, the q-axis flux linkage and required terminal voltage are reduced substantially, which contributes to improving power factor and field-weakening property. When operating below base speed, higher voltage margins are obtained, thus the proposed PMVM exhibits a higher power factor and wider constant torque region. With speed over base speed, the field-weakening control strategy is adopted, allowing the proposed PMVM to employ a higher q-axis current to generate torque. As a consequence, the output capability and power factor under high-speed field-weakening region are improved. In particular, the maximum achievable output power is improved by 19%, and the constant power speed range (CPSR) ratio is improved from 2 to almost 10.

This article presents the analysis of a vernier machine with spoke-V (SV) array permanent magnet (PM), termed SV-PMV. By combining the spoke- and V-array PMs, the topology of SV-PMV is obtained. Based on the general air-gap flux modulation theory, the operating principle of the SV-PMV is investigated. It is found that the main working harmonics can be effectively enhanced by the SV array PM. To provide general design guidelines, the parametric analysis of the SV-PMV is conducted. The electromagnetic performances of three vernier machines are compared by using finite element method (FEM). It is found that the SV-PMV exhibits the highest torque density, the highest power factor, the best overloading capability, and the highest efficiency among three vernier machines.

This paper presents a high power-factor permanent magnet vernier machine (PMVM) employing hybrid concentrated-winding (CW). The hybrid winding, carrying both delta- and star-winding sets, allows for low harmonic tooth-wound coil and satisfied winding factor for PMVM with high gear ratio. Therefore, the torque density of the PMVM can be enhanced with reduced end-winding length and more compact structure. More importantly, the mutual inductances between the three phases and the coils that comprise each phase are reduced to a large extent in the hybrid winding, without deteriorating the output torque capability. As a result, the presented PMVM possesses a lower ratio of inductance to PM flux linkage due to the low-harmonic and low-coupling winding, and hence, improved power factor. Two benchmark PMVMs with identical gear ratio have been optimized for comparison. Further finite element results verify that the proposed CW PMVM presents superior performance in terms of end-winding length, torque density, power factor, and efficiency. It is revealed the proposed hybrid CW PMVM can improve the torque density to 23Nm/L from 21Nm/L and 14Nm/L, with the consideration of end-winding volume, and power factor to 0.86 from 0.72.

This paper presents a new vernier permanent magnet machine (VPMM) with stator-V-shaped permanent-magnet arrangement, termed as (SV-VPMM). The key is to adopt unevenly distributed V-shaped PMs in the stator, which exhibits flux concentration effect and generates abundant working harmonics, thus improving the torque density and PM utilization ratio. Based on the air-gap field modulation theory, the working mechanism of the proposed SV-VPMM is investigated from two perspectives including stator-PM and rotor-PM fields. Then, the electromagnetic performance comparison between the proposed SV-VPMM and an existing VPMM is conducted by using finite element analysis (FEA).

This paper proposes a novel flux switching memory machine (FSMM) in which low coercive force (LCF) magnets are alternatively arranged between adjacent U-shape stator cores. The proposed machine exhibits superiority in flexible online flux regulation capability, large flux regulation range, robust structure and inherent advantage for avoiding uncontrolled generator fault (UGF). Meanwhile, the excitation losses can be almost eliminated since the LCF magnets can be remagnetized or demagnetized by a current pulse of a few milliseconds. The demagnetization risk is avoided due to the parallel pattern between PM flux and armature reaction flux. In addition, the FSMM benefits from a simple and robust salient rotor and easy thermal management as a result. Subsequently, the machine structure and operation principle are illustrated. The stator slot-rotor pole combinations are analyzed. The comprehensive electromagnetic performances are evaluated.