In this paper, a novel E-core dual-permanent magnet flux-switching (DPM-FS) machine is proposed for traction applications in electrified transportation. The key is that an extra set of permanent magnet (PM) source is artfully inserted into stator slot openings, which has a parallel main flux path with spoke-type PMs, significantly improving the utilization ratio of the stator core as well as alleviating the magnetic saturation in the iron core. As a result, the proposed machine exhibits a bidirectional flux improvement ability of multiple working harmonics. The working harmonics of air-gap flux density with positive contributions to torque production are greatly enhanced, and those with negative influences are effectively suppressed. Compared with a conventional E-core FSPM machine with the same PM volume, the proposed machine exhibits a 42.8% higher open-circuit back electromotive force (EMF) and a 38.5% higher average output torque. A magnetomotive force (MMF)-permeance model is established to investigate the working principle of the proposed machine. Furthermore, the effectiveness of the proposed design is verified by using finite element analysis (FEA) and experimental results.

In this paper, a novel dual-set permanent magnet (PM) flux-switching (DSPM-FS) machine is proposed for the improvement of torque density and fault-tolerance capability. Originating from a flux-switching permanent magnet (FSPM) machine with a U-shaped PM array, fault-tolerance stator teeth are first introduced in the stator slots to prevent the risk of short-circuit faults between coils of different phases. Subsequently, aiming to enhance the torque generation, a set of surface-mounted PM is added to the fault-tolerance teeth. Due to a parallel flux circuit, the phase flux linkage is greatly increased, further improving the no-load back electromotive force (EMF). Meanwhile, a magnetomotive force (MMF)-permeance model is established, which reveals that the amplitudes of the main working harmonics of the DSPM-FS machine are significantly elevated. Moreover, the proposed and conventional machines are comprehensively compared regarding various electromagnetic performances. Consequently, the no-load back EMF and output torque of the proposed machine are increased by 43.89% and 31.47%, respectively. Additionally, the proposed machine showcases a comparable overload performance compared to the conventional machine. Furthermore, the fault-tolerance ability and power efficiency of the proposed DSPM-FS machine also exhibit notable improvement. Finally, a prototype is fabricated and tested to verify the performance of the proposed machine.

In this work, a novel general pattern of assisted flux barriers in an asymmetric V-shape interior permanent magnet (AVIPM) machine is presented. The AVIPM machine has a symmetric permanent magnet (PM) structure and an asymmetric rotor core structure to realize the magnetic-field-shifting (MFS) effect. The general pattern can represent four possible types of assisted flux barriers at different positions on the rotor core and the final structure can be automatically determined by using optimization method. The advantage of the proposed optimization pattern is that the optimal design of assisted flux barriers in V-shape interior permanent magnet (VIPM) machines with high torque and low torque ripple can be generated within a short computing time. The proposed optimization method is applied to improve the structure of a conventional 8-pole 48-slot VIPM machine, which is commonly used for driving electric vehicles (EVs). A non-dominated sorting genetic algorithm II (NSGA-II) is used for the global optimization of both a VIPM machine and an AVIPM machine. The electromagnetic performance is computed using a finite element analysis (FEA). Moreover, a frozen permeability (FP) method is applied to perform an accurate separation of PM torque and reluctance torque. The results exhibit that the peak output torque of the AVIPM machine is increased by 8.7% compared to a conventional VIPM machine with the same PM volume due to the notable MFS effect. In the meantime, the AVIPM machine has a better overload capability due to the larger contribution of reluctance torque. Moreover, the proposed machine has high efficiency of over 97%.

Recently, the interest in consequent-pole flux-switching permanent magnet (CP-FSPM) machines has been increasing because of the flux-focusing PM arrangements and the removal of the flux-barrier effect. A simple and rigid outer-rotor salient pole rotor structure can be adopted in CP-FSPM machines, making them applicable for in-wheel direct-drive applications. In this study, three CP-FSPM machines with II-shaped (II-PM), V-shaped (V-PM), and straight U-shaped PM (SU-PM) arrays are analyzed and compared. Moreover, a CP-FSPM machine with inclined U-shaped PM (IU-PM) arrays is proposed to improve the flux-focusing effect and stator slot utilization. The working principles of CP-FSPM machines are analyzed by adopting a semi-analytical model. Combining the finite element analysis (FEA) results of air gap flux density and the analytical model of phase back electromotive force (EMF), the contributions of multiple working harmonics to the back EMF are quantitatively analyzed. Additionally, 6/16 and 6/17 CP-FSPM machines with different PM arrangements are globally optimized. Both the no-load and on-load performance of the optimized machines are included in the performance comparison. The results illustrate that the 6/16 and 6/17 machines exhibit their respective merits, and the IU-PM machine shows the best torque production ability in these CP-FSPM machines with the same design criteria.

Torque density is a crucial performance metric for flux-switching permanent magnet (FSPM) machines. However, the emergence of flux barriers tends to impede the magnetic field modulation effect, especially in machines with high pole ratios, ultimately impacting overall performance. To solve this issue, this paper proposed a consequent-pole FSPM machine with a flux-concentrated magnet design. The proposed machine adopts a 12-slot/13-pole configuration with a pole ratio of 13. To optimize the magnetic field concentration, the design integrates shortened clockwise tangentially magnetized PMs under an “h” core, positions radially magnetized PMs at the core's shoulders, and inserts counterclockwise tangential PMs into the slot openings. This arrangement effectively addresses the magnetic barrier issue, enhancing the magnetic field compactness within the machine. The operating principle of the proposed FSPM machine is analyzed using analytical computations and finite element analysis (FEA). The structural parameters are optimized for maximum average torque and efficiency. The proposed machine offers a 14.96% higher average torque and 2.1% higher efficiency than the existing FSPM machine with flux bridges at the same stator copper loss. A 640 W-rated prototype of the proposed machine was fabricated and tested, validating the simulation results and design accuracy through experiments.

A novel asymmetric spoke-type interior permanent magnet (AS-IPM) machine is proposed in this paper. It utilizes the magnetic-field-shifting (MFS) effect to improve the torque performance, which achieves a high utilization ratio of both permanent magnet (PM) torque and reluctance torque. In addition, a general pattern of rotor topologies is proposed to represent all possible machine structures. Various rotor structures can be obtained by changing the design parameters of the general pattern. A non-dominated sorting genetic algorithm II (NSGA-II) is adopted to automatically search for optimal rotor configurations. With the aid of the optimization program, an asymmetric spoke-type rotor structure with improved performance is obtained. To showcase the advantages of the proposed machine, the electromagnetic performance is compared between a conventional spoke-type interior permanent magnet (S-IPM) machine and a proposed AS-IPM machine. The finite-element simulation results show that the optimal design of the AS-IPM performs a 7.7% higher output torque ripple due to the MFS effect while the total PM volume remains the same. Meanwhile, the torque ripple of the proposed structure is significantly reduced by 82.1%.