FSPM Machine Research Articles

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.

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.

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 and Analysis of Axial-Modular Flux-Switching Permanent Magnet Machine

This paper proposes a novel axial-modular-flux switching permanent magnet (AM-FSPM) machine, which contains two modular parts and integrated toroidal windings. After investigating the operation principle of the AM-FSPM machine, the modular PM field complementarity and integrated armature reaction field complementarity principles of two axial modular parts are revealed based on the field modulation theory. Then, a comprehensive comparison of the modulation principle between the AM-FSPM and conventional FSPM machines is conducted from perspectives of PM field, armature reaction field, cogging torque and electromagnetic torque production mechanism. It can be found that the modulation principle reveals the difference between the operation principles of two flux switching machines. In addition, the cogging torque reduction capability of AM-FSPM machine is investigated, which provides guidance on stator-slot and rotor-pole combinations in the design stage of industrial applications. Moreover, compared with conventional FSPM machines, the AM-FSPM machine exhibits high torque capability and flux weakening capability, meanwhile maintains high efficiency at high speed. Further, its characteristics are verified by the experiments.

Fault operation analysis of a novel dual-three-phase dual-rotor flux-switching permanent magnet machine

In this paper, based on the conventional flux-switching permanent magnet (PM) (FSPM) machine, a novel dual-three-phase dual-rotor FSPM machine with PMs of NS layout (NS-DRFSPM) is proposed. The stator of the proposed NS-DRFSPM machine is equipped with dual PMs and dual armature windings to operate in a variety of operating modes and to handle the case of PMs or armature windings failure. Firstly, the topological structure and eight fault operating states of the NS-DRFSPM machine are introduced, and the key design parameters of the NS-DRFSPM machine are optimized by genetic algorithm (GA) optimization and finite element analysis (FEA). Then, the operation principle of the NS-DRFSPM machine is analyzed in detail. Finally, the finite element method is used to analyze the performances of the NS-DRFSPM machine under eight fault operating states, which is mainly analyzed from two aspects: no-load performance and torque performance. The results show that the NS-DRFSPM machine has good electromagnetic performance under different fault conditions, including large back-electromotive force (EMF) amplitude, sinusoidal EMF waveform, high average torque, small torque ripple, and strong anti-saturation ability.

Analysis and Design of a Novel Doubly SalientPMMotor Based on Parallel Path Magnetic Technology

AbstractIn this paper, a novel doubly salient PM motor based on parallel path magnetic technology (PPMT) is presented. PPMT is an advanced magnetic control technology, which can be applied to linear and rotary actuators. First, the fundamental principle of the PPMT prototype is elaborated, and then a comprehensive research and analysis of PPMT motor is carried out, with particular emphasis on machine topology, operation principle and electromagnetic performance. The equivalent no‐load PM magnetic circuit model is established and equations for calculating the main PM flux are derived. Besides, a dual‐stator 6‐pole PPMT motor prototype has been developed to valid the analysis. According to the similarity of topology and operation principle, comparison between the FSPM machine and PPMT machine is conducted, which leads to the conclusion that the PPMT motor has lower cogging torque, lower torque ripple and better sine back EMF waveform, the PPMT motor is more suitable for servo applications compared to FSPM motor. Finally, to improve the power density of PPMT motor, FE parametric modeling method for designing the three coupled stator parameters, which are the PM width, the stator yoke width and the second airgap length is given out. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Iron Loss Calculation for FSPM Machine With the PWM Inverter Supply Based on General Airgap Field Modulation Theory

In this article, an iron loss for the flux switching permanent magnet machine with the pulsewidth modulation (PWM) inverter supply is calculated based on the general airgap field modulation theory (GAFMT). First, the amplitudes and rotation speeds of the main space harmonics of the airgap magnetic flux density with the supply of PWM harmonics are calculated based on the GAFMT. When calculating the source magnetizing magnetomotive force based on the GAFMT, the equivalent magnetic circuit is applied to calculate the working point of the permanent magnet. Second, each spatial harmonic in the airgap magnetic field is synthesized by an equivalent current layer in the airgap and then is substituted into the 2-D finite element analysis models to calculate the iron losses. Finally, the iron losses calculated by the proposed method with different speeds, loads, and control strategies are compared with the experimental results.

A Novel Doubly-Fed Flux-Switching Permanent Magnet Machine With Armature Windings Wound on Both Stator Poles and Rotor Teeth

In this article, a novel doubly-fed flux-switching permanent magnet (DF-FSPM) machine is proposed, whose armature windings are wound on both stator poles and rotor teeth. Different from the conventional FSPM machine in which the armature windings are only located in the stator, the rotor slot area is fully utilized in the DF-FSPM machine to improve the electrical loadings and, thus, the torque density. Moreover, it has the potential of fault-tolerant operation, since it comprises two sets of armature windings, which can work individually. The topology and the operating principle of the machine are introduced with reference to a 12-stator-pole/10-rotor-tooth DF-FSPM machine. The electromagnetic performances of the optimized DF-FSPM machine and its FSPM counterpart machine are compared, including the induced voltage, inductances, torque capability, flux weakening capability, efficiency, and power factor. It shows that the DF-FSPM machine can exhibit about 46.5% higher torque density than the FSPM machine, while its torque production per magnet volume is also improved by about 39.6%. In addition, the efficiency and power factor of the DF-FSPM machine are higher than those of the FSPM machine. Finally, experimental validation is conducted on a prototype machine.

Comparative Study Between a Novel Multi-Tooth and a V-Shaped Flux-Switching Permanent Magnet Machines

In this paper, on the basis of a conventional 12-stator-coils/17-rotor-teeth (12/17) flux-switching permanent magnet (PM) (FSPM) machine and a 6/17 V-shaped FSPM machine, a novel 6/17 multi-tooth FSPM machine with a pair of magnets located in the upper apex of stator tooth is proposed. Then, four multi-tooth topologies sharing the same 6-stator-coils but with different rotor teeth combinations, namely, 6/17, 6/10, 6/11, and 6/13, are compared by the 2-D finite element analysis (2-D-FEA). The FEA-predicted results reveal the optimal combinations of stator coils and rotor teeth should be 6/17 for high-performance multi-tooth machines. Thereafter, an optimal design criterion of multi-tooth FSPM machines for the combinations of stator coils and rotor teeth is proposed. Afterward, electromagnetic performance evaluation between the 6/17 V-shaped and 6/17 multi-tooth machines is conducted, in terms of back electromotive force (back EMF), electromagnetic torque, cogging torque, phase inductance, unbalanced magnetic force (UMF), torque/magnet ratio, and efficiency. The comparative results indicate that the proposed 6/17 multi-tooth machine is superior to the V-shaped one, since it exhibits much higher torque/magnet ratio, larger torque, lower inductance, and much lower UMF, though the cogging torque and total harmonic distribution of phase back EMF are unfavorably larger.

Investigation of Optimal Split Ratio in Brushless Dual-Rotor Flux-Switching Permanent Magnet Machine Considering Power Allocation

This paper investigates an optimal split ratio for a brushless dual-rotor flux-switching permanent magnet (BDR-FSPM) machine. Based on the design theory of conventional FSPM machine, the split ratio of the BDR-FSPM machine is deduced and redefined. And the crucial factors which have close relationship with the split ratio are determined, consisting of power split ratio, magnetic loading, PM pole width, and stator pole width. To conveniently explore the optimal split ratio, the response surface method is purposely utilized for conducting optimization, where the magnetic loading and output torque are chosen to be the objectives. In addition, considering the application requirement of hybrid electric vehicles, the concept of power allocation is proposed and integrated into the optimization process of split ratio. Then based on the optimal split ratio, the machine performances are analyzed in detail, including air gap flux density, back-electromotive force (EMF), coupled-EMF, and torque performances. Finally, a prototyped BDR-FSPM machine is manufactured and tested to verify the validity of the proposed split ratio optimization and machine design approach.

Analysis and optimization of key dimensions of co-axial dual-mechanical-port flux-switching permanent magnet machines for fuel-based extended range electric vehicles

In this paper, key dimensions of a co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machine for fuel-based extended range electric vehicles (ER-EVs), including split ratio, stator/rotor pole arcs, rotor yoke thickness, etc., are analyzed and optimized. Firstly, the topologies and operation principles of an exampled 3-phase CADMP-FSPM are introduced briefly, in which an inner-rotor FSPM machine with 12-stator-slots/10-rotor-poles for high-speed generation and an outer-rotor FSPM machine with 12-stator-slots/22-rotor-poles for low-speed motoring are assembled co-axially. Then, the relationship between the key dimensions and electromagnetic performance, particularly for electromagnetic torque (power), of the CADMP-FSPM machine is studied by 2D-finite element analysis (FEA). Further, the reasonable matches of split ratio, rotor/stator pole arcs and rotor yoke are determined and the original CADMP-FSPM machine is optimized correspondingly. Finally, the static characteristics, including no-load PM flux-linkage, electro-motive-force (EMF), winding inductances, cogging torques and electromagnetic torques, of the original and optimized machines are compared by 2D-FEA. The results verify that the optimized CADMP-FSPM machine can exhibit improved torque characteristics than the original one, i.e., the torque ripples of the inner and outer machines can be reduced by 22.7% and 4.7%, respectively, and the average torque of the inner and outer machines can be increased by 0.43Nm and 2Nm, respectively.

Design and measurements of a permanent magnet Flux-Switching-Machine for industrial applications

In this paper the design, the construction and measurements of a permanent magnet excited Flux-Switching-Machine (FSPM) are summarized. The special features of the presented 28-pole, three-phase permanent magnet Flux-Switching-Machine as variable-speed industrial drive for 400 V Y, 45 kW, 1000 … 3000 rpm are a slotted ferromagnetic rotor with no windings and no magnets, twelve stator tooth coil windings and in circumferential direction magnetized stator magnets. Special attention is paid to the manufacturing of the FSPM as it has a very simple and robust rotor, however, requires a special construction for the stator. Finally, measurement results of the designed FSPM machine are shown and compared to measurements of an already built permanent magnet synchronous machine (PMSM) of the same size and rating with segmented rotor surface mounted magnets.

Power distribution of a co-axial dual-mechanical-port flux-switching permanent magnet machine for fuel-based extended range electric vehicles

In this paper, power distribution between the inner and outer machines of a co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machine is investigated for fuel-based extended range electric vehicle (ER-EV). Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced, which consist of an inner FSPM machine used for high-speed, an outer FSPM machine for low-speed, and a magnetic isolation ring between them. Then, the magnetic field coupling of the inner and outer FSPM machines is analyzed with more attention paid to the optimization of the isolation ring thickness. Thirdly, the power-dimension (PD) equations of the inner and outer FSPM machines are derived, respectively, and thereafter, the PD equation of the whole CADMP-FSPM machine can be given. Finally, the PD equations are validated by finite element analysis, which supplies the guidance on the design of this type of machines.

Analysis and Design of a Double-Stator Flux-Switching Permanent Magnet Machine Using Ferrite Magnet in Hybrid Electric Vehicles

A double-stator flux-switching permanent magnet (DS-FSPM) machine using ferrite is proposed to replace an interior permanent magnet synchronous motor (IPMSM) on hybrid electric vehicles. A conventional FSPM machine is designed, and its torque characteristic is analyzed by a frozen permeability method. It is verified that magnetic saturation causes the reduction of flux linkage generated by PM and leads to the deterioration of electromagnetic torque. A DS-FSPM machine is effective for magnetic saturation because of its unique structure and makes the improvement of efficiency and power density. The proposed DS-FSPM machine achieves distinct performance enhancement compared with an IPMSM, even by utilizing ferrite PM.

Investigation of a Co-Axial Dual-Mechanical Ports Flux-Switching Permanent Magnet Machine for Hybrid Electric Vehicles

In this paper, a co-axial dual-mechanical ports flux-switching permanent magnet (CADMP-FSPM) machine for hybrid electric vehicles (HEVs) is proposed and investigated, which is comprised of two conventional co-axial FSPM machines, namely one high-speed inner rotor machine and one low-speed outer rotor machine and a non-magnetic ring sandwiched in between. Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced; secondly, the control system of the proposed electronically-controlled continuously-variable transmission (E-CVT) system is given; thirdly, the key design specifications of the CADMP-FSPM machine are determined based on a conventional dual-mechanical ports (DMP) machine with a wound inner rotor. Fourthly, the performances of the CADMP-FSPM machine and the normal DMP machine under the same overall volume are compared, and the results indicate that the CADMP-FSPM machine has advantages over the conventional DMP machine in the elimination of brushes and slip rings, improved thermal dissipation conditions for the inner rotor, direct-driven operation, more flexible modes, lower cogging torque and torque ripple, lower total harmonic distortion (THD) values of phase PM flux linkage and phase electro-motive force (EMF), higher torque output capability and is suitable for the E-CVT systems. Finally, the pros and cons of the CADMP-FSPM machine are highlighted. This paper lays a theoretical foundation for further research on CADMP-FSPM machines used for HEVs.

Analysis and Optimization of Rotor-twisted Structure for 12/10 Alternate Poles Wound FSPM Machine for Electric Vehicles

Fault-tolerant capability, wide speed range and overload capability are required in electric motors used in electric vehicles. In this paper, based on the analysis of the all poles wound and alternate poles wound flux-switching permanent-magnet machines, an optimization method is studied to reduce torque ripple. The method takes account of both flux-leakage and cogging torque. The simulation result shows that the method can reduce the torque ripple effectively. This study lays the foundation for the further application of FSPM in electric vehicles.

Back-EMF Harmonic Analysis and Fault-Tolerant Control of Flux-Switching Permanent-Magnet Machine With Redundancy

A flux-switching permanent-magnet (PM) (FSPM) machine is a new class of stator-PM brushless machines, which offers the advantages of high reliability, high power density, and high efficiency. In this paper, by employing redundant winding in the existing FSPM machine topology, a new redundant FSPM (R-FSPM) machine is proposed for a fault-tolerant operation of critical applications. The redundant winding configuration is analyzed, and the corresponding suitable control strategy for the postfault operation is proposed. The electromagnetic performance of the R-FSPM motor drive under normal and fault conditions is analyzed by using a cosimulation method coupling magnetic and electrical circuit solvers. Finally, a 12-stator-tooth/10-rotor-pole R-FSPM machine is prototyped for verification. Both simulation and experimental results are presented, verifying the fault-tolerant characteristic of the proposed motor drive.

Advanced Flux-Switching Permanent Magnet Brushless Machines

This paper overviews the recent development and new topologies of flux-switching (FS) machines, with particularly emphasis on the permanent magnet (PM) type. Specific design issues, including winding configurations, combinations of stator and rotor pole numbers, rotor pole width, split ratio, etc., are investigated, while the torque capability of selected FSPM machines is also compared.