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This paper proposes a dual-mode brushless wound rotor synchronous machine (DBL-WRSM) for high starting torque. The proposed DBL-WRSM consists of two modes: induction and brushless (BL)-synchronous modes. First, the induction mode operates as a wound rotor induction machine (WRIM) to achieve a high starting torque. Second, the BL-synchronous mode operates as a brushless wound rotor synchronous machine (BL-WRSM) using the subharmonic of the stator magnetomotive force (MMF) in the steady state. To realize the dual-mode topology of the proposed machine, the stator is composed of two divided armature windings and two inverters that can produce subharmonics. The rotor has five switches that convert the rotor winding configuration between the two modes. To verify the proposed topology of DBL-WRSM, finite element analysis (FEA) was performed. Through the FEA results of the transient electromagnetic torque for the voltage source, it was confirmed that the proposed DBL-WRSM not only operates as a BL-WRSM in a steady state but also has a sufficiently high starting torque even under a full-load condition.

This paper proposes a rotary-linear surface-mounted permanent magnet (PM) voice coil motor (RL-SVCM) with PM flux bridges in place of the iron flux bridges in a traditional RL-SVCM for enhancing average torque and force ripple but slight damage of torque ripple and average linear force. The iron flux bridges in a basic RL-SVCM cannot participate in the generation of rotary torque. In contrast, the PM flux bridges in the proposed RL-SVCM can participate in the generation of rotary torque. The magnetic equivalent circuit (MEC) is used to analyze the magnetic circuits of the basic and proposed models. The results explain the reasons for the performance improvements achieved by the proposed motor. The finite element method (FEM) is used to derive the precise output performance of the basic and proposed motors. Additionally, a prototype of the proposed RL-SVCM with PM flux bridges was manufactured for experimental verification. Close agreement between the experimental results and FEM results validates the feasibility of the proposed RL-SVCM.

This study proposes an analytical method (AM) for V-type consequent-pole permanent magnet (V-CPM) machines to quickly determine the suitable permanent magnet (PM) volume while reducing the PM volume compared to that of the V-type interior PM (V-IPM) machine. Special air-gap magnetic flux density modeling is adopted in the AM, which consists of 4 asymmetric regions under one PM and the iron pole of the V-CPM. This specific modeling is utilized for the V-CPM topology, which has a different magnetic saturation trend from the conventional surface-mounted CPM (S-CPM). Hence, additional consideration of rotor saturation by novel method has been done compared to the previous works. To achieve average torque similar to that of the V-IPM machine, a V-CPM machine is designed by the proposed AM to have the same fundamental harmonic value of air-gap flux density. Furthermore, two conditions are considered for the V-CPM machine design to prevent unnecessary saturation and to minimize torque ripple. All the performance metrics of the designed V-CPM machine are compared with those of the other machines to demonstrate its superiority.

A high gear ratio flux switching permanent magnet machine (HFSPM) was proposed to improve the torque performance in flux switching permanent magnet machine (FSPM). Conventional FSPMs address flux bypass issue when designed with a high gear ratio. The HFSPM adopts a dual rotor structure to overcome this flux bypass issue. First, the cause and effect of flux bypass issue was discussed using a magnetic equivalent circuit (MEC). Further, the process of overcoming the flux bypass issue using dual rotor structure was discussed. An alternative HFSPM, consequent pole HFSPM (CP-HFSPM), was proposed to enhance torque performance. The CP-HFSPM was optimized for high torque performance and proper power factor.

This paper proposed a novel hybrid-excited wound field synchronous machine (HE-WFSM) to efficiently use the field torque and reluctance torque. Meanwhile, an analytical method is utilized to achieve the torque-angle consistency principle, which allows the field torque and the reluctance torque to reach their maximum values at the same phase current angle. First, a novel HE-WFSM with two different rotor excitations is proposed. Second, the PMs and the field windings in the rotor are designed by an analytical method based on the magnetic equivalent circuit (MEC) to produce the same magnetic flux in the air gap to obtain the torque-angle consistency. Third, one practical HE-WFSM applied for a small power fan is designed by the analytical method as an example. Finally, all the performances of the proposed HE-WFSM are predicted by the finite element method (FEM), thereby verifying the improved torque characteristics.

This article proposes a novel low-cost consequent-pole permanent magnet (CPM) synchronous machine structure, considering the reluctance torque utilization. First, a novel CPM machine with doubled salient ferromagnetic iron poles (ICP-PMSM) is proposed, featuring an N pole - iron - S pole - iron sequence to maximize the reluctance torque utilization and reduce cost. Flux barriers are integrated into the rotor structure to maintain the same magnetic rotor pole number as the conventional CPM synchronous machine (CP-PMSM). Second, for a low torque ripple, soft ferrite is used to replace part of the iron pole in the ICP-PMSM (ISCP-PMSM) to improve the air-gap flux density distribution. Furthermore, the CP-PMSM, ICP-SPMSM, and ISCP-PMSM rotors are optimized for a fair comparison. The electromagnetic performances of all the optimized machines are compared with those of a conventional surface permanent magnet synchronous machine (SPMSM). It is demonstrated that the ISCP-PMSM can obtain an almost equivalent torque and torque ripple, but with reduced PM (NdFeB) usage and cost when compared to the SPMSM.

This paper proposes a low-cost dual-mechanical-port dual-excitation machine for washing machine application. The proposed machine artfully combines two machines (vernier and permanent magnet synchronous machine (PMSM)). An outer vernier rotor is used for the low-speed washing operations, and an inner PMSM rotor is used for the high-speed drying operations of the washing machine. The proposed machine is compared with a similar recently presented machine to verify its cost-effectiveness. Comparison using the finite element analysis (FEA) shows that the ferrite magnets used in the proposed topology are more cost-effective. Furthermore, compared to the existing machine, the power factor of the proposed machine is high during the drying operation; hence, a lower rating inverter is sufficient to drive the machine, which further reduces the overall cost. In addition, the proposed machine provides similar efficiencies as the existing machine for both washing and drying operations.

This paper proposes a two-phase dual-stator axial-flux permanent magnet brushless dc motor with an ironless rotor for higher torque per magnet volume using the only-pull drive technique. The advantage of the ironless rotor is that it reduces magnet volume by providing an effective flux linkage, while the only-pull drive technique, which involves only the pull process, benefits from the use of thin magnets that do not experience the irreversible demagnetization. The axial-flux configuration of the proposed dual-stator motor was adopted because of its capability of achieving the desired trapezoidal back electromotive force that maximizes the advantages of the only-pull drive technique. The thin magnets were fixed on the ironless rotor using a non-magnetic structure, and the stator was particularly designed to implement the only-pull drive technique. The performance of the motor was analyzed in terms of torque per magnet volume using the finite element analysis and validated by the experimental results.