Flux-switching Permanent Magnet Machine Research Articles

Influence of Stator/Rotor Torque Ratio on Torque Performance in External-Rotor Dual-Armature Flux-Switching PM Machines

External-rotor dual-armature flux-switching PM (ER-DA-FSPM) machines have high torque density and decent fault tolerance, making them promising candidates for in-wheel machine applications in electric vehicles. The torque output and optimal design parameters of ER-DA-FSPM machines are affected by the stator/rotor torque ratio, which is the focus of this paper. Firstly, this paper analyzes airgap flux density harmonics of ER-DA-FSPM to provide a clear insight into the torque-generation mechanism. Then, this paper investigates the influence of torque ratio on average torque under the same copper loss. It is found that the average torque decreases with torque ratio increasing due to the reduction of the positive torque component generated by the sixth airgap field harmonics and the rise in the negative torque component from the eighth harmonics. Moreover, this paper also provides the optimal parameter recommendation to guide the machine design. The split ratio should increase, and the arc of PMs should decrease for a larger torque ratio, whilst the other parameters are hardly influenced. Next, this paper makes a comparison among the ER-DA-FSPM machine, external rotor flux-switching PM (ER-FSPM) machine, and surface-mounted PM (ER-SPM) machines. It shows that the ER-DA-FSPM machine, with the torque ratio being 2, can lead to a much larger total torque. In addition, in the event of rotor winding failure, which is more possible due to the existence of slip rings than stator winding failure, the stator can still provide an average torque larger than that of ER-SPM machine and 92.0% that of the ER-FSPM machine, respectively. Finally, the theoretical analysis is verified by the experiments.

A novel double stator hybrid-excited Halbach permanent magnet flux-switching machine for EV/HEV traction applications

This research paper introduces the Double Stator (DS) Hybrid Excitation (HE) Halbach Permanent Magnet (HPM) Flux Switching (FS) machine. The machine construction and its optimization specifically designed for electric vehicle (EV)/hybrid electric vehicle (HEV) traction applications are investigated. The optimization using a multi-objective Genetic Algorithm is conducted following a sensitivity analysis-based identification of key optimization parameters and constraints. The finite element results are compared with the performance of a state-of-the-art benchmark FSPM machine having identical PM volume and winding current densities. The proposed design is shown to outperform the benchmark with 16.2% increase in back-electromotive force and 14.7% reduction in cogging torque. Furthermore, the average torque is improved at flux-enhancing operation by 20.8%, and the torque ripple is reduced by 9.9%. Notably, the proposed machine also is capable of flux regulation thereby having the ability to operate in a wide speed range. A detailed explanation of the reasons for the significant improvements in the proposed machine structure is provided to offer a comprehensive understanding of its rationale. These research findings indicate that this innovative DS-HE-HPM-FS machine can enhance the performance of EVs and HEVs.

Cogging torque reduction by utilizing the unequal rotor slot arc method for FSPM Machines

Cogging torque is a crucial and offending problem for electric machines that consist permanent magnets. Flux switching permanent magnet (FSPM) machines have magnets embedded inside the stator coils. Due to the interaction between the stator magnetic flux and the rotor steel, cogging torque occurs. To express this interaction, Magnetic Permeance Distribution Model is implemented in this study. To minimize the cogging torque, unequal rotor slot arc (URSA) technique is developed and cogging torque is calculated by using finite element method. An optimization study is performed to get the minimum value of the cogging torque under reasonable output torque. Results prove that, the proposed URSA method have promising outcomes for cogging torque reduction.

Rotor pole and stator tooth shaping in FSPM machines for torque performance optimization

Purpose This study aims to obtain the minimum torque ripple at the maximum average torque for Flux-switching permanent magnet (FSPM) machines. Design/methodology/approach This paper is about torque performance optimization of the FSPM machines. To achieve that, finite element analysis and genetic algorithm (GA) are used. Five different designs are simulated, optimized and compared on their air gap flux density, back electromotive force, cogging torque, average torque, torque density and torque ripple. Findings After the thousands of iterations, its proved that all proposed shaping techniques have potential for reducing torque ripple and cogging torque, with slightly reduced average torque. The best design is the joint stator and rotor shaping, Design V, which results in the lowest torque ripple and cogging torque. The techniques should be applicable to FSPMs with other stator slot/rotor pole number combinations. Originality/value In this paper, rotor pole shaping by notching, chamfering and generic shaping, stator tooth shaping and joint shaping techniques are investigated for 12 s/10p FSPM machines. Rotor and stator flanks are optimized separately and jointly, by using finite element analysis and GA for optimization to achieve maximum average torque and minimum torque ripple. Five different design is implemented and compared, respectively.

Improved design-oriented analytical modelling of flux switching PM machines

Purpose This paper aims at the analytical formulation of the electromagnetic features of flux switching permanent magnet (PM) machines with emphasis on the PM air gap flux density and armature magnetic reaction. Design/methodology/approach The PM air gap flux density is formulated considering three different analytical models. These differ by the incorporation of the air gap magnetic saliency level from the stator side. In addition, the armature magnetic reaction is investigated based on a simplified magnetic reluctance circuit that considers the flux switching permanent magnet machines magnetic circuit geometry specification. Then, the no- and on-load torque is predicted based on the two air gap flux densities. Findings It has been found that the PM air gap flux density considering the stator saliencies with trapezoidal magnetomotive force waveform presents the highest accuracy. Despite the simplicity of the magnetic equivalent circuit-based approach, the predicted air gap armature magnetic reaction is in good agreement with the finite element analysis (FEA) one. These lead to the analytical predictions of the no- and on-load torque which is characterized by an acceptable accuracy. Research limitations/implications This work should be extended to experimental validation of the FEA results regarding the torque production generation. Originality/value The paper proposes an improved design-oriented analytical approach with emphasis on the PM air gap flux density and the armature magnetic reaction of flux switching PM machines.

Torque Capacity Improvement of Flux-Switching PM Machines Based on Directional Stator Permeance Design

As one type of flux modulation machines, flux-switching permanent magnet (FSPM) machines present high sensitivity to airgap structures. Therefore, both stator/rotor teeth and slot/pole combinations have significant influences on machine performance. However, the relationships between the optimal stator structure and maximum torque capability of the FSPM machine are barely investigated. Therefore, this paper is devoted to proposing a directional stator permeance design approach to achieve the maximum torque of the FSPM machines under a given rotor, and reveal the corresponding stator structure. First, the relations between torque and air-gap permeance are presented based on a constructed torque contribution equation, where amplitudes and phase angles of the stator permeance harmonics are determined. Then, main permeance harmonics are directionally optimized to enlarge positive torque, while negative contributions are inversed to be positive. Especially, two FSPMs with 6-slot/19-pole and 6-slot/13-pole are chosen as design examples, and their optimal design processes and torque performances have been deeply analyzed, which verifies the effectiveness of the proposed design approach.

Cogging Torque Reduction of Axial-Modular Flux Switching Permanent Magnet Machine by Module Combination Technique

Flux switching permanent magnet machine exhibits high cogging torque due to the doubly salient topology and high air gap flux density. This paper proposes a new axial-modular flux switching permanent magnet (AM-FSPM) machine, which has an improved torque capability and the potential of cogging torque suppression by module combination technique. The cogging torque analytical expression of the machine with axial-modular topology is derived based on a magnetomotive force-permeance model. Then, the AM-FSPM machines are divided into two types by the combinations of stator-slot and rotor-pole, named fundamental harmonic offset naturally and fundamental harmonic offset manually. In addition, four approaches are investigated to reduce cogging torque by changing modular magnetomotive force and changing modular permeance. It can be concluded that the modular rotor tooth combination method has the most attractive torque performances among the four methods. Finally, the effectiveness of the proposed approaches is verified by the 3D finite element analysis and experimental results.

Cogging torque and torque ripple analysis of permanent magnet flux-switching machine having two stators

Cogging torque and torque ripple analysis of permanent magnet flux-switching machine having two stators

The effect of winding topologies on the performance of flux-switching permanent magnet machine having different number of rotor poles

The effect of winding topologies on the performance of flux-switching permanent magnet machine having different number of rotor poles

Core Loss Analysis of Flux Switching PM Machines with Toroidal Winding and Concentrated Winding by Field Modulation Theory

Core Loss Analysis of Flux Switching PM Machines with Toroidal Winding and Concentrated Winding by Field Modulation Theory

Investigation of Five-Phase Flux-Switching Permanent Magnet Machines for EV and HEV Applications

As a member of stator permanent magnet (PM) brushless machines, flux-switching (FS) PM machine features outstanding advantages, e.g., robust rotor structure, easy temperature management, high torque density, etc. In this paper, the five-phase FSPM machines for electric vehicle (EV) and hybrid electric vehicle (HEV) applications are investigated. Firstly, the working principle of such machine is analyzed by air-gap field modulation theory. Then, the feasible slot/pole combination is discussed, considering flux leakage, back electro-magnetic force (EMF) quality and unbalanced magnetic force (UMF). Besides, in order to further choose the recommendable slot/pole combination, the torque performances are studied and compared by taking the 20-stators-slot FSPM machines as examples, such as rated torque, overload capability, flux weakening capability and fault tolerance capability. Further, in order to optimize the slot/pole combination which suffers from severe UMF, two different techniques for UMF reduction are proposed, including chamfering both in stator and rotor side. Finally, finite element analysis is employed to verify the analytical analyses. Meanwhile, a 20/18 prototyped machine is manufactured and tested. It is found that the experimental results verify the effectiveness of the analytical analyses.

Design Consideration for E-Core Outer-Rotor Flux-Switching Permanent Magnet Machines From the Perspective of the Stator-Poles and Rotor-Teeth Combinations

Design Consideration for E-Core Outer-Rotor Flux-Switching Permanent Magnet Machines From the Perspective of the Stator-Poles and Rotor-Teeth Combinations

Fault-Tolerant Operation for Single-Phase Open Circuit of Dual-Armature Flux-Switching Permanent Magnet Machine by Connecting Neutral Points

Fault-Tolerant Operation for Single-Phase Open Circuit of Dual-Armature Flux-Switching Permanent Magnet Machine by Connecting Neutral Points

Multi-objective Optimization of a Multi-tooth Flux-switching Permanent Magnet Machine with HTS Bulks

Multi-objective Optimization of a Multi-tooth Flux-switching Permanent Magnet Machine with HTS Bulks

Influence of Rotor Pole Number on the Output of Double Stator Flux-Switching Machine

Influence of rotor pole numbers on the output performance of a double stator flux-switching permanent magnet machine is investigated and compared in this study. A description of the analyzed machine is first given. Maxwell-2D time-stepping finite element analysis is adopted in estimating the results. The no-load and load characteristics of the investigated machine is considered and quantitatively compared amongst four different rotor pole configurations. The compared machine categories are designated as: 6S/10P, 6S/11P, 6S/13P and 6S/14P, where P stands for rotor pole and S stands for stator slot. It is revealed that the compared 6S/11P machine topology has a lot of good qualities amongst all the compared machine types, since it exhibits the largest electromotive force (EMF), power, torque and greatest overload sustainability feature, etc. Though, the 6S/14P has excellent flux-weakening capability. Moreover, the 6S/13P machine configuration would produce the largest torque if all the compared machines are equipped with same amount of permanent magnet volume/material. The compared machine topologies have reasonably good anti-demagnetization potentials; particularly, the 6S/13P topology.

The Effects of the Unequal Rotor Slot Arc on Cogging Torque for Flux Switching Permanent Magnet Machines

Many of the electric machine researchers are studying the Flux switching permanent magnet (FSPM) machines. The cogging torque is one of the most unwanted parameter for highly sensitive electric machine applications. In this study, the configuration of the unequal rotor slot arc (URSA) to see the effects of the asymmetry for three phase FSPM machine has been studied. The proposed asymmetry contains of presenting different arc angled rotor poles and analyzing the torque performance of them by using 2D finite element analysis (2D-FEA). 12-stator pole/ 10-rotor pole (12s/10p) FSPM machine topology has been chosen for the design. Results proved that unequal rotor slot arc proposition demonstrate good performance in comparison to the symmetric design. Inequality on the rotor slots were simulated by using parametric analysis to minimize the cogging torque. The suggested design indicates a substantial reduction in cogging torque, achieving a conspicuous minimization. Consequently, the suggested using unequal rotor slot arc for FSPM machine has reasonable outcomes.

Design and Analysis of a Novel Six-Phase Axial Switched-Flux Permanent Magnet Machine With Different Winding Configuration

In this paper, a novel six-phase axial switched-flux permanent magnet (PM) machine with stator-PM is proposed and designed. The topology and operating principle are analyzed in detail. Two different winding configurations, which are called the symmetric double-three-phase and asymmetric double-three-phase, are presented and studied. The electromagnetic performance of the machine with two winding configurations, including flux-linkage, back electromotive force, inductance, torque characteristics, and so on, is investigated. The behavior of the machine under the healthy and faulty conditions is analyzed and the fault-tolerant performance is researched. The prototype is manufactured and the experimental results are consistent with that of the finite element analysis. The results demonstrate that the performance of the machine with two winding configurations is excellent. The machine with asymmetric double-three-phase winding configuration has high quality PM flux-linkage and back-EMF, low cogging torque and torque ripple, and strong fault-tolerant capability. The machine with symmetric double-three-phase winding configuration has large torque capacity.

Effects of Undesirable Features of A Double Stator Switched-Flux Permanent Magnet Machine

Effects of Undesirable Features of A Double Stator Switched-Flux Permanent Magnet Machine

Comparative Analysis of Consequent-Pole Flux-Switching Machines with Different Permanent Magnet Arrangements for Outer-Rotor In-Wheel Direct-Drive Applications

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.

A Flux-Switching Permanent Magnet Machine with HTS Bulks and Radially Magnetized PMs Arranged

In order to improve the torque density of flux switching permanent magnet machine (FSPMM), a novel multi-tooth fault-tolerant FSPMM with high temperature superconducting (HTS) bulks is proposed in this paper. The HTS bulks and radially magnetized PMs are arranged inside in the stator. And due to the flux bridges at both ends of the permanent magnet, 6 stator teeth are connected as a whole. Then the optimized machine parameters are obtained based on multi-objective genetic algorithm (MOGA). Finally, the topology performance is assessed and verified by finite element method (FEM) Compared with the conventional model, the torque density of the proposed model is increased by 30.39%, and the coupling coefficient ratio are reduced by 14.62%.