This paper proposes a novel multistep design and optimization strategy to minimize torque pulsations in a spoke-type permanent magnet motor with phase-group concentrated-coil windings. Different from the conventional techniques that work on the motor itself, in the first step, an auxiliary inner stator is designed to suppress torque pulsations with the aid of a finite-element method (FEM). In the second step, the optimization by using the Kriging method and genetic algorithm, is then applied to the auxiliary inner stator to further reduce torque pulsations. In the third step, the harmonic injected current is utilized to suppress torque ripple by maintaining the required power, while the optimal input current waveform is optimized by the aforementioned algorithms based on the harmonic analysis of back electromotive force. Through the analysis results by the FEM, it shows that the cogging torque and torque ripple of the final model are significantly reduced by 95.7% and 70.0%, respectively, when compared with those of the initial model.

This paper presents an investigative study on a dual-stator spoke-type vernier machine (DSSTVM) suitable for direct-drive electric vehicle (EV) propulsion systems. DSSTVM was a superior choice as a direct-drive motor because of its high torque density per volume, wide speed range operation, and high power factor, which are critical features for the direct-drive EV propulsion system. However, previous research on DSSTVMs was restricted to conventional 12 slots and 20 poles (12S20P) with distributed windings. Thus, the 12S22P combination, which has a higher gear ratio, was presented to enhance the torque performance. Different winding configurations were also considered to further improve the performance, as concentrated and distributed windings in vernier machines show different performances due to their different vernier effects and different end windings. A total of four models, 12S20P and 12S22P models with concentrated and distributed windings, were suggested and compared. The finite-element method analysis was performed to confirm the characteristics of each model. Consequently, the 12S22P model with a distributed winding was chosen for EV applications due to its good overall performance.

We herein propose a novel high-torque-density flux-switching permanent magnet machine (FSPMM) which adopted phase-group concentrated-coil (PGCC) winding and a cogging torque reduction technique. The PGCC winding was applied to increase the torque density. In order to maximize the torque of the FSPMM that utilizes the PGCC windings, the performance according to stator slots/rotor poles combinations were compared. A machine which had 12 stator slots and 13 rotor poles (12S13P) was selected for its top average torque value. However, the 12S13P PGCC FSPMM contains high cogging torque that must be reduced. The cogging torque reduction technique is applied, and the parameters used in the technique are further optimized to achieve the target average torque, while suppressing the cogging torque as much as possible. The optimization process was performed with a collaboration of the genetic algorithm and Kriging method. The analysis results of the optimized design exhibited huge reductions in the cogging torque and eventually in the torque ripple from the initial machine, with reasonable average torque reduction. The entire work was evaluated experimentally using a manufactured prototype.

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 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.

This paper proposes the novel topology of a high-efficiency dual output stator-permanent magnet (PM) machine (DOSPMM) for two different washing machine operating speeds. The proposed machine consists of two machines integrated into a single machine: Machine I is an outer rotor type Vernier machine with low speed and high torque for washing mode operations. Machine II is an inner rotor type flux-reversal PM (FRPM) machine with high speed and low torque for dehydrating mode operations. Each machine was designed to be highly efficient for the assigned operating mode. Both machines also possess robust rotors due to stator positioned PMs. To demonstrate the superiority of the proposed machine, performance comparisons with conventional machines for general washing machine applications were performed via finite-element method (FEM) analysis. A prototype of the proposed machine was built and experimental results of the prototype machine were presented for a validation of the work.