Flux-switching Permanent Magnet Research Articles

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.

Electromagnetic Performance Analysis of Dual-Three-Phase Dual-Rotor Flux-Switching Permanent Magnet Machines

In this paper, a novel dual-three-phase dual-rotor flux-switching permanent magnet (PM) (DRFSPM) machine, building upon conventional FSPM machines, is proposed, where the stator is equipped with dual PMs and dual armature windings, enabling it to operate in various working modes and provide fault tolerance in the event of PM or armature winding faults. Depending on the magnetization directions of the PMs, the proposed DRFSPM machine’s structure can be categorized as 6N-DRFSPM or NS-DRFSPM. In order to assess the electromagnetic performance of the proposed DRFSPM machines with two different magnetizing modes, the topology and operating principle of the two DRFSPM machines are introduced first. Then, the no-load air-gap flux density of the two proposed machines is investigated for a more optimized and purposeful design. Finally, a comparison of the electromagnetic performance between the two proposed DRFSPM machines is conducted by finite-element analysis (FEA), and the FEA-predicted results indicate that the proposed 6N-DRFSPM machine outperforms the NS-DRFSPM machine, as it exhibits a larger back-EMF and average torque and a smaller cogging torque and torque ripple.

Sürekli mıknatıslı akı anahtarlamalı motorda mıknatıs, stator ve rotor geometrilerinin tork ve tork dalgalanmasına etkisinin incelenmesi

Bu çalışmada, referans alınan bir sürekli mıknatıslı akı anahtarlamalı motora (SMAAM) ait mıknatıs geometrisi ve konumu ile stator ve rotor çıkıntılarında değişiklikler yapılarak yeni tasarımlar gerçekleştirilmiştir. Referans tasarım olarak daha önce literatüre sunulmuş olan üç fazlı bir SMAAM temel alınmış ve tüm motor yapılarına ait benzetim çalışmaları yapılmıştır. Adil bir kıyaslama yapılabilmesi için benzetim çalışmalarında tüm SMAAM tasarımlarında temel parametre ve kullanılan malzemeler korunmuştur. Yapılan tasarımsal değişiklikler ile kabul edilebilir tork değeri beraberinde düşük tork dalgalanması, üretim kolaylığı ve geniş hız aralığında çalışma yeterliliği elde edilmeye çalışılmıştır. Analiz çalışmaları, elektrik makinalarının analizinde yaygın bir şekilde kullanılmakta olan ve oldukça doğru sonuçlar verebilen sonlu elemanlar yöntemi (SEY) temel alınarak gerçekleştirilmiştir. Referans alınmış olan ve tasarlanan yeni SMAAM yapılarına ait elde edilen sonuçlar kapsamlı bir şekilde karşılaştırılmıştır. Bu karşılaştırmlar da tork değerinde kabul edilebilir azalmalar görülürken tork dalgalanma değerinde ciddi azalmalar olduğu sonucuna varılmıştır.

Design synthesis of hybrid stator type flux-switching bearingless permanent magnet memory machines

A magnetic flux-switching type bearingless permanent magnet memory motor is proposed, which not only solves the problem of friction in high-speed rotating mechanical bearings, but also achieves the true effect of “variable flux” operation with almost no excitation loss through permanent magnets with low coercivity such as aluminum nickel cobalt that can be adjusted online by applying only instantaneous pulse current. Ultimately, the goal of efficient magnetic flux regulation, high torque density, and high stable suspension force can be achieved. A hybrid stator type flux-switching bearingless permanent magnet memory motor (HSTFBPMM) is a special type of motor that combines magnetic levitation technology, a flux-switching permanent magnet motor, and the adjustable magnetic flux principle. It integrates the advantages of the former without mechanical wear and lubrication, and the latter with simple structure, high power density, and adjustable air gap magnetic field. This article first provides a detailed introduction to the structural characteristics of an HSTFBPMM. Secondly, based on the principles of torque generation, suspension, and magnetic flux regulation, the magnetic field distribution, no-load permanent magnet flux, back electromotive force, inductance, positioning torque, and static torque were analyzed in detail. The results lay the foundation for establishing an accurate mathematical model for an HSTFBPMM incorporating the aforementioned physical quantities in the future.

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.

SSO-DRSS Axial Flux sensing in Switching Permanent Magnet Motor for cogging torque mitigation

This paper addresses the imperative requirements of high efficiency, power density, and speed in Axial Flux-Switching Permanent Magnet Motors (AxFSPM) for electric vehicles. Recognizing the limitations of conventional motor designs, especially their weight and size, hindering their universal applicability, this study proposes a novel approach. A Double Rotor Single Stator (DRSS) configuration is introduced, and its parameters are systematically optimized using the Shark Smell Optimization (SSO) algorithm. The SSO algorithm refines critical motor parameters, including axial length, turns per phase, and stator and rotor dimensions, resulting in a more compact AxFSPM motor with enhanced torque. Geometrical constraints are similarly optimized with SSO, and magnet skewing angles are employed for cogging torque reduction. The optimization process, implemented in MATLAB and ANSYS Maxwell, yields an average torque below 1.4 N m and cogging torque below 0.8 N m, demonstrating the effectiveness of the proposed approach. Comparative analyses against various motor models underscore the superiority of the SSO-optimized DRSS motor in terms of efficiency and compactness.

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.

Multiple-Mode Current Control for a Hybrid-Excitation Axial Flux Switching Permanent Magnet Motor Considering Driving Cycles

This paper proposes a multiple mode current (MMC) control for hybrid-excitation axial flux switching permanent magnet (HE-AFSPM) motors considering driving cycles. To satisfy the diverse and compound control demands in multiple operating condition of EVs, the model predictive control is adopted, and multiple current vector prediction method including <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current, and DC excitation current is proposed to optimize current assignment ratio, enhance the dynamic performance, and improve motor efficiency. An online optimization method considering four operating conditions in two speed domains is demonstrated, where the different current assignment function and constraint is applied in each operating condition, and the optimal assignment currents are obtained effectively by the Lagrange multiplier method online in real time. Finally, to verify the feasibility of the multiple-mode control method, a prototype motor is built and tested. And, the motor performances in the different driving modes are investigated in detail. The experimental results reveal that the proposed control method can offer an effective control for the HE-AFSPM motor, where multi-mode operations are indispensable.

Design and Optimization of the Dual-Stator Axial-Field Flux-Switching Permanent Magnet Motor with High-Torque Density and Low-cost

Design and Optimization of the Dual-Stator Axial-Field Flux-Switching Permanent Magnet Motor with High-Torque Density and Low-cost

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

Characteristics Analysis and Optimization of Secondary Permanent Magnet Flux-Switching Linear Machines

Characteristics Analysis and Optimization of Secondary Permanent Magnet Flux-Switching Linear Machines

A modified approach for efficient cogging torque suppression in a flux switching permanent magnet generator used in micro‐scale wind turbines

AbstractIn recent years, Flux Switching Permanent Magnet (FSPM) machines have attracted notable attention in direct drive, low speed, and high torque density applications such as wind turbines. However, their relatively high cogging torque has been identified as a significant challenge for such applications primarily because of its effects on both starting and running performance of the wind turbines. The authors, therefore, aim to present a modified approach that can improve the cogging torque issue and eliminate the weaknesses of the previously introduced designs. To reach this goal, first, an operating point is chosen for the studied machine regarding the available small‐scale turbines in the market. Then, the potential benefits of combining different cogging torque reduction schemes are investigated thorough the proposed method. This is intended to be done on the rotor teeth without imposing any complications or extra costs. The results show that a simultaneous improvement in the cogging torque and the energy conversion capability of the machine could be achieved through this cost‐effective approach. To end with, the sensitivity of the best cases to the expected manufacturing tolerances is investigated. All analyses are performed via two‐dimensional finite‐element (2D‐FE) models, the accuracy of which has been pre‐certified through experimental measurement.

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.

Design and Optimization of a Pole Changing Flux Switching Permanent Magnet Motor

A flux switching permanent magnet (FSPM) motor is designed and optimized in this paper to achieve high torque density and expanded speed regulation range from a design viewpoint of pole-changing (PC). Based on the field modulation theory, the PM field in the FSPM motor is modulated by the stator and rotor teeth, generating rich harmonics with different pole-pair numbers in the air-gap flux density. By adopting an appropriate slot pole combination, working harmonics with different slot pitch angles are obtained to establish a basis of the PC-FSPM motor. Then, different working harmonics can be used to achieve different energy conversions with different winding configurations, so the PC operation can be performed to realize the high torque and wide speed regulation range by switching the working modes. Based on the field modulation theory, the operation principle of conventional and PC-FSPM motors are analyzed and compared. Then, according to the design principle of the PC-FSPM motor, a 24/22-pole PC-FSPM motor with the E-core is designed and optimized by a multi-level optimization method. Finally, the electromagnetic performances are analyzed by finite element analysis and the test results of the prototype have verified the feasibility of the motor.

Design of 6 slots/10 poles modular rotor sandwich switched flux switching permanent magnet motor

Conventional flux-switching permanent magnet brushless machines (PMFSM) gained a lot of attraction due to their high torque densities, simple and robust rotor structure, and the permanent magnets and coils on the stator. The sandwich PMFSM machine has been proposed to improve the torque density of the machine in which two PM pieces are sandwiched in one stator pole to enhance the PMs usage efficiency. 2D finite element analysis (2DFEA) method is employed to compare the performance of sandwich PMFSM with salient rotor topology with that of sandwich PMFSM with modular rotor, in terms of flux linkage, flux distribution, flux strengthening, induced back EMF, cogging torque and average torque. From the results it is shown that the salient sandwich PMFSM and sandwich PMFSM modular rotor produces 9.28Nm and 6.7Nm, respectively.

Magnetic Coupling Effect and Performance Analysis of Dual Rotor Permanent Magnet Flux Switching Generator for Counter Rotating Wind Power Generation

To eliminate slip rings, brushes, and terminate gear-box mechanism, ferrite permanent magnet (PM) based counter rotating dual rotor PM flux switching generator (CRDRPMFSG) for direct drive counter rotating wind turbine (D <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CRWT) application is proposed in this paper. Initially, the mechanism of gearless and brushless counter rotating wind power generation is discussed, and a simplified formulation opted for the slot/pole combinations. The proposed CRDRPMFSG encapsulate inner and outer machines with circumferentially magnetized PM enclosed by non-overlapped armature windings; thus, offering reduced overhang with compact design. However, co-axially linking the inner and outer machines through a shared stator yoke results in serious issues of magnetic coupling due to dual air-gap fields. To this end, eight topologies with various slot/pole combinations are comprehensively investigated using finite element analysis (FEA) for magnetic coupling effects and its influence on electromagnetic performance. From the analysis, it is shown that magnetic coupling level influence electromagnetic performance i.e., average torque, ripple rate, power factor, efficiency, losses, and output power. Moreover, it is noted that coupling level can be reduced by adopting same stator teeth in inner and outer machines or same stator teeth with different rotor poles. Finally, the predicted FEA calculations are verified experimentally with four benchmarked CRDRPMFSG prototypes.

Performance analysis of sandwich switched flux switching permanent magnet motor using modular rotor

Conventional flux-switching permanent magnet brushless machines (PMFSM) gained a lot of attraction due to their high torque densities, simple and robust rotor structure, and the permanent magnets and coils on the stator. The sandwich PMFSM machine has been proposed to improve the torque density of the machine in which two PM pieces are sandwiched in one stator pole to enhance the PMs usage efficiency. 2D finite element analysis (2DFEA) method is employed to compare the performance of sandwich PMFSM with salient rotor topology with that of sandwich PMFSM with modular rotor, in terms of flux linkage, flux distribution, flux strengthening, induced back EMF, cogging torque and average torque. From the results it is shown that the salient sandwich PMFSM and sandwich PMFSM modular rotor produces 9.28Nm and 6.7Nm, respectively.

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.