Flux-switching Permanent Magnet Machine Research Articles

Analysis of partitioned stator flux-switching permanent magnet machine by magnetic equivalent circuit

This paper presents a novel technique for modeling Partitioned Stator Flux-Switching Permanent Magnet (PS-FSPM) machine by Magnetic Equivalent Circuit (MEC) method which provides adjustable accuracy for the modeling of the machine. The machine geometry is divided into 13 zones, where the number of flux tubes in the core and air parts can be selected. Considering multiple flux tubes in the teeth and slots regions, the flux distribution can be accurately obtained. The saturation effect of the core elements are also taken into account by nonlinear reluctances. A novel method for saturation effect is proposed, where the B-H curve can be tuned by selectable parameters. The proposed model is capable of modeling PS-FSPMs with various poles-teeth combination. Finally, the results of the proposed method are compared with finite element method (FEM) in terms of accuracy and processing time.

Performance comparison and optimisation of dual mover linear permanent magnet flux switching machine

Short moving primary and rigid low-cost secondary are important requirements of linear machines designed for long stroke applications. In the race, linear permanent magnet flux switching machine (LPMFSM) is a competitive candidate by confining excitation sources to short mover, thus making stator robust and low cost (made of only iron). However, single-sided LPMFSM exhibit a demerit of high normal (attraction) force due to its topology. In order to rectify the problem and enhance thrust force profile, two novel double-sided LPMFSMs are proposed with dual stator and dual mover topologies. After stator pole study, both topologies with same design dimensions are analysed and compared by 2-D finite element method here. Detailed analysis revealed that 12/14 DMLPMFSM exhibit low numerical values of thrust force ripples and detent force while maintaining average thrust force value. Hence, 12/14 DMLPMFSM is selected and optimised by structure-based deterministic optimisation (SBDO) approach to further enhance thrust force profile. Finally, comparison of initial and optimised design of 12/14 DMLPMFSM is presented to validate optimisation procedure.

Reliability Analysis and Evaluation for Flux-Switching Permanent Magnet Machine

In this paper, a quantitative evaluation of the flux-switching permanent magnet (FSPM) machine system reliability is carried out based on the Markov model. The evaluation model of the permanent magnet machine system consists of six main functional components and their dominant failure modes are counted. The performance of the FSPM machine system under each fault is simulated and compared with the reliability criteria to judge the reliability state of the machine system. The Markov model is used to calculate the FSPM machine system reliability. The influence of machine phase number, stator core topology, and hybrid excitation method on the machine system reliability is investigated. The experiments are presented to validate the accuracy of fault simulation. The reliability analysis results lay the foundation for the reliability design of an FSPM machine.

Electromagnetic Characteristic of a Novel Linear Flux Switching Machine With Three-Dimensional Magnetic Circuit

The novel linear flux switching permanent magnet machine with a three-dimensional magnetic circuit is proposed in this paper, which is suitable for aerospace, missile launch, and other fields, benefiting from high thrust force and low cost. First, the basic structure and working principle of the machine are introduced. Second, the equivalent magnetic circuit model considering the variable reluctance is established and the equations are put forward for magnetic analysis. Third, the simplified finite element model is performed to calculate the field distribution, the air-gap flux density, the flux linkage of winding, and the back electromotive force. Finally, a prototype is constructed and experiments show a good agreement with analysis.

Influence of Rotor Tooth Shaping on Cogging Torque of Axial Flux-Switching Permanent Magnet Machine

This paper proposes a rotor tooth shaping method to reduce the cogging torque of an axial flux-switching permanent magnet machine. The rotor tooth is shaped in different configurations, including constant, trapezoidal, asymmetrical, extended, and square shapes to evaluate the effects on cogging torque ripple minimization. A three-dimensional (3-D) finite-element analysis (FEA) is performed to compare the proposed shapes of the rotor tooth. Peak-to-peak cogging torque, fundamental flux linkage, loaded torque, and the total weight of teeth are compared using various rotor tooth angles. The simulation results show that overall minimum cogging torque is achieved by the extended shape of the rotor tooth. 3-D FEA results are also verified with experimental results.

Performance Improvement of Torque and Suspension Force for a Novel Five-Phase BFSPM Machine for Flywheel Energy Storage Systems

To improve the electromagnetic performance of the machine for a flywheel energy storage system, in this paper, a five-phase bearingless flux-switching permanent magnet machine with an E-core stator is presented. The topology and structure are introduced and the operation principle of the generation of torque and suspension force is also explained. Based on the simple variable method and overall trial and error method, the influence of the machine parameters on machine performance is investigated by using a finite element analysis. Then, the parameters are optimized. The results show the improvement of the torque and suspension force with increased amplitude and smaller fluctuation.

Performance Analysis of a Novel Three-phase Axial Flux Switching Permanent Magnet Generator with Overlapping Concentrated Winding

This paper proposes a novel axial flux switching permanent magnet generator for small wind turbine applications. Surface mounted axial flux switching permanent magnet (SMAFSPM) machine is a new type of these machines that is introduced in this paper. One of the most important challenges in optimal designing of this kind of machines, is ease of construction and maintenance. One of the main features of this machine is putting the magnets on the surface, which makes the construction of the machine easier. The overlapped three-phase winding improves the quality of voltages and power of the machine.To reach the optimum dimensions of machine, centeral composite design (CCD) and response surface methodology (RSM) combined with 3D finite element methods have been used.

Tubular unified magnetic‐field flux‐switching PMLM for free‐piston energy converter

A tubular flux-switching permanent-magnet linear machine (PMLM), which features unified magnetic field between the mover and two stators, is investigated for free-piston energy converter. The topology evolution, topology, operating principle and design considerations of the machine are thoroughly analysed. With the sinusoidal speed characteristic of free-piston Stirling engine considered, a tubular unified magnetic-field flux-switching PMLM is designed by finite-element analysis. Several main structural parameters, which include the outer and inner radius of the mover, the mover tooth width, the magnet thickness, the tooth widths of both the outer and inner stators and the widths of both the outer and inner stator yokes are studied to achieve high-force and mass-power density. Finally, the proposed machine is compared with two typical flux-switching PMLMs. The comparison results show that the unified magnetic-field flux-switching PMLM is suitable for applications which require high-power density, light mover structure and fast dynamic.

Analytical Calculation of Electromagnetic Performances of Bearingless Flux-Switching Permanent-Magnet Machine Considering Iron Saturation Based on Exact Subdomain Model

In this paper, an accurate analytical subdomain model to calculate electromagnetic performances of bearingless flux-switching permanent magnet (BFSPM) machines is developed. The entire region of the machine is divided into six subdomains, including slots, air gap, magnets, and so on. According to the Neumann boundary conditions between the subdomains and the iron and the continuity conditions at the interface between the adjacent subdomains, the magnetic field distributions of subdomains are obtained by solving the Maxwell equations. In addition, a method to compensate the saturation effect is proposed, and the magnetic saturation of the stator and rotor is considered by the actual B-H characteristics. Based on the proposed analytical method, the air-gap flux density distributions of the machine with different iron material under linear and nonlinear conditions are predicted. Further, the electromagnetic performances including the cogging torque, electromagnetic torque, flux linkage, back-EMF, inductance, and suspension force are calculated. These analytical results are compared with those obtained by the Finite Element Analysis (FEA) to verify the accuracy of the proposed analytical method.

Multiobjective Optimization Design of a Double-Rotor Flux-Switching Permanent Magnet Machine Considering Multimode Operation

The multimechanical-port double-rotor machine, as a core component in hybrid electric vehicles, has attracted considerable attention due to the merits of compact structure, control flexibility, and diverse performances. However, since there often exist two electric or mechanical ports in one compound machine frame, traditional design theory cannot be applied to it directly. Besides, because of the relatively complex machine structure and multiple design parameters, design objectives often influence even conflict with each other. In this paper, a new multiobjective optimization design approach is proposed to design and optimize a flux-modulated double-rotor flux-switching permanent magnet machine, where multiple driving modes are considered. To verify the feasibility of the double-rotor machine and the effectiveness of an optimization design method, the electromagnetic characteristics of the machine are investigated in detail. Finally, a prototype machine is built and tested. Both theoretical analysis and experimental results verify the validity of the proposed machine and multiobjective optimization design approach.

Analysis of a Novel Consequent-Pole Flux Switching Permanent Magnet Machine With Flux Bridges in Stator Core

In this paper, a novel flux switching permanent- magnet machine (FSPM) with consequent-pole magnets and flux bridges in the stator core is proposed to improve the torque capability of FSPMs with high pole ratios. The stator yoke and flux bridges adjacent to the magnets can provide magnetic paths for the main working harmonic field, thus the magnetic reluctance of the working harmonic field is reduced, and the flux modulation effect, winding back-electromotive force (EMF), and output torque of the proposed FSPM can be significantly improved compared to the regular FSPM with high pole ratios. The operation principles and stator–slot/rotor–slot combinations of the proposed FSPM are introduced. Then, the influences of pole ratio, split ratio, slot opening ratio, and PM width on the torque density of the proposed FSPM is investigated using finite element analysis. Moreover, after the investigations, a proposed FSPM is compared to a regular FSPM in terms of back-EMF, rated torque, power factor, etc. Finally, to verify the theoretical analysis, a 12-stator–slot/14-rotor–slot FSPM is built and tested.

Development of a new flux switching transverse flux machine with the ability of linear motion

This paper proposes a new rotary flux switching transverse flux machine with the ability of linear motion (FSTFMaLM), in which both the stator and the rotor cores are made by using soft magnetic composite (SMC) materials. With the special design pattern, for the rotary motion model, the proposed machine can combine both the advantages of the flux switching permanent magnet machine (FSPMM) and the transverse flux machine (TFM). It can output with relatively high torque density, and as there is no windings or the magnets on the rotor cores, the proposed machine can operate in the high speed region to improve the output power. With the adoption of the SMC materials, the manufacturing of this machine can be quite easy. By stacking the rotor core together and prolong it with the determined length in the axial direction, in addition with the special control algorithm, the proposed machine can have the ability of the linear motion. In this paper, the operation principle of this machine has been explained and the design methods are also presented. To seek the better performance, the main dimension of the machine is optimized, and for the performance evaluation, the finite element method (FEM) is adopted. The proposed machine can be used for the electric driving systems, robotic systems or other applications where the linear motion ability is required.

Loss Calculation and Thermal Analysis for Nine-Phase Flux Switching Permanent Magnet Machine

This paper investigates the accurate loss calculation and thermal analysis for a nine-phase flux switching permanent magnet (FSPM) machine. First, the 3 D finite element method (FEM) model is developed to calculate the PM eddy current loss, in which magnet axial segmentation is taken into account. In order to calculate the iron loss quickly and precisely, the magnetic flux leakage coefficient is proposed in this paper to modify the 2 D calculation model of iron loss. Both the dc-biased magnetic induction and the rotational magnetization are taken into account. Then, the key parameters for thermal modeling, such as the convective heat-transfer coefficient between external frame and ambient, and the coefficient of convection heat transfer in the end region, are derived, based on which a dissymmetric 3 D FEM are used for thermal calculation of nine-phase FSPM machine. Finally, experiments on a prototype machine at the rated generation operation condition are carried out to verify the effectiveness of the developed model.

Design and Performances of Multi-Tooth Stator Permanent Magnet Flux Switching Machine for Light Weight Applications

Permanent magnet flux switching machines (PMFSMs) in which their torque performance produced by interaction between armature coils and permanent magnet (PM) have been widely designed for various applications. In this regard, single-phase 8Slots-12Poles PMFSM with single tooth stator is considered the most suitable candidate for light weight applications because of their advantages of lower copper loss, high efficiency and robust rotor. However, issues of low torque performance due to weak flux linkage, high of PM volume, and high distortion in back-emf that need to be improved. In this paper, a new design of single-phase PMFSM using multi-tooth stator is proposed. Both PMFSMs have been designed using JMAG Designer version 15 and analysed through 2D-FEA. Parameters of stator outer radius, rotor outer radius, air gap, and stack length are set to 37.5mm, 22mm, 0.25mm, and 20.3mm, respectively. Based on the 2D-FEA, PM flux linkage and torque performances of the PMFSM using multi-tooth are 5 times and 38% higher than PMFSM using single-tooth. As a conclusion, single-phase 4Slot-12Poles PMFSM using multi-tooth stator considered as the best candidate for light weight applications due to the less PM volume, and good performances of toque, power and based speed of 1.44Nm, 219W, 1,062rpm, respectively.

A Comparative Study of Single-tooth and Multi-tooth Stator of 4S-8P Permanent Magnet FSM for Electric Bicycle Application

This paper present a comparative study of single-tooth and multi-tooth stator of 4S-8P permanent magnet Flux Switching Machine (FSM) for electric bicycle application. Detailed comparison of the performance characteristics of the machines are presented that include important issues such as average torque, volume of PM, back-EMF and speed performance. For a fair comparison, the valid stator slot and rotor combinations is same dimension and analyzed using finite element analysis, and the one among of the design has the best electromagnetic performance is selected. On the basis of the investigation, it can be concluded that the single-tooth design of proposed permanent magnet FSM for a single phase 4S-8P topology has presented higher torque performance compared to multi-tooth design. However, since design of single-tooth exhibits a higher back-EMF, Design optimization and improvement structural is ongoing to achieve the best performance.

Reducing cogging torque of 6/4 pole FSPM machine by optimising parameters of chamfering and flange rotor pole shape without skewing teeth

Due to the doubly salient structure, high magnetic flux density in the air gap and low pole number, cogging torque of 6/4 pole flux-switching permanent magnet (FSPM) machine is seriously high. In some cases, it may cause this machine hard to start up and serious torque ripple. So, reducing the cogging torque of 6/4 pole FSPM machine to a certain low extent is important to keep it work properly. To reduce cogging torque, a chamfering and flange rotor pole shape is proposed to reduce the cogging torque of 6/4 pole FSPM machine without skewing teeth. The key dimensions of the proposed rotor pole shape have been optimised by analytical methods and simulation based on finite-element analysis. The effectiveness of the proposed method has been verified by experimental results. The effect of the proposed rotor pole shape method on back-electromagnetic force and average electromagnetic torque has also been investigated.

Quantitative Evaluation of the Topologies and Electromagnetic Performances of Dual-Three-Phase Flux-Switching Machines

Hybrid-excited flux-switching machines based on permanent magnet (PM) flux-switching machines were proposed to achieve improved torque–speed characteristics. However, due to the reduction of PM volume, decreases in torque density and efficiency are usually inevitable. Thus, it is necessary to make a comprehensive comparison between the dual-three-phase hybrid-excited flux-switching machines and their PM flux-switching counterparts. To obtain a full understanding of flux-switching machines, PM flux-switching machines with U-shaped stator cores and alternate-pole magnets or C-shaped stator cores are considered. From the perspective of the frequency domain, this paper not only gives a comprehensive evaluation and comparison of the above-mentioned six flux-switching machines, but also reveals the theoretical mechanism that results in their different electromagnetic behavior in a unified way by the general field modulation theory, which is the main contribution of this paper.

Computation of Cogging Force of a Linear Tubular Flux-Switching Permanent Magnet Machine Using a Hybrid Analytical Modeling

Permanent magnet flux switching machines are gaining more and more interest due to their relatively good characteristics. Indeed, the presence of all magnetic field sources in the stator (armature windings, permanent magnets and/or field windings), which implies a completely passive rotor, makes it suitable for a large variety of applications [1] [2]. Different flux switching machines topologies have been studied in scientific literature. In this contribution, a relatively new modeling approach [3] based on the coupling of mesh based generated reluctance networks (MBGRN) and analytical models (AM), based on the formal solution of Maxwell’s equations, is used for the accurate prediction of cogging force of a linear tubular flux switching machine. This type of machines could be favorably used in oceanic renewable energy conversion. Figure 1(a) illustrates how the two approaches are combined for the case of a tubular linear flux switching structure. In this example the analytical solution is used for modeling the mechanical air-gap, and inner and outer airs, and the RN method is used to model the moving and static armatures. In order to have a more generic approach, the stator and moving armatures are modeled using mesh based generated reluctance network (MBGRN) technique [3]. This technique, as classical RN method, can be used with a minimum number of reluctances for regions where flux tubes are not highly affected by topology changes. As for finite elements analyses (FEA), the studied domain in MBGRN should be finely meshed in some regions (air-gap for example) and coarsely meshed in other regions. However, in contrast to FEA, the mesh relaxation in MBGRN can be done more easily conducting to reduced system matrix dimensions, and consequently reduced computation time. Indeed, while in FEA two adjacent elements should share an edge, it is no more necessary for RN method, as illustrated in Fig. 1(b). This new modeling approach has been used to analyze the performance of different electromagnetics devices (2D and 3D) [3]–[7]. In this contribution, this technique is used for the computation of cogging force of a linear tubular flux switching permanent magnet structure, something which has never been reported yet, to the best of our knowledge, in scientific literature. The goal is to further extend the investigation of this technique for the computation of relatively sensitive quantities, such as the cogging force, in more complex structures. Another goal is to highlight advantages of HAM as compared to other modeling techniques, and more particularly FEA, in order to obtain reduced order equations system [8] [9].

Investigation of Direct & Quadrature Current Effects on Demagnetization of Flux Switching Permanent Magnet Motors

In recent years flux-switching permanent magnet machines have become popular for industrial applications and research, due to advantages such as robustness, high torque, and power density. However, as permanent magnet motors, their performance is affected by demagnetization. It is known, for example, that armature reactions and temperature increases cause permanent magnet demagnetization that leads to power and torque density reduction in motors. In this paper, partially irreversible demagnetization in an flux-switching permanent magnet motor will be investigated using the time stepping finite element method. In addition, the effects of the d and q - axis currents on this type of demagnetization are evaluated by considering several points on the magnets and comparing the flux density of these points with the flux density of the knee point. It is shown that an increase of the q-axis current component increases the machine’s demagnetization tolerance.

Fault-Tolerant Control of Hybrid Excitation Axial Field Flux-Switching Permanent Magnet Machines

With the development of electric vehicles (EVs), the reliability and security of the motor drive system have been in high demand in recent years. EVs can still work reliably even when the motor drive system encounters some failures. Therefore, fault-tolerant motors have become the focus of research all over the world. The hybrid excitation axial field flux-switching permanent magnet machine (HEAFFSPMM) is a novel stator excitation brushless PM machine. It combines the advantages of AFFSPMM and hybrid excitation PM machine. Based on a 600 W prototype of three-phase 12/10 stator/rotor pole AFFSPMM, these parameters of HEAFFSPMM are optimized by 3-D finite element method in order to obtain the high self-inductance and low ratio of mutual and self-inductances, including the number of rotor poles, the split ratio, the width of permanent magnet, and the width of stator middle teeth. Then, the fault-tolerant control method of the space vector pulse width modulation based on minimum copper loss is proposed in this paper with the combination of adjusting the field current. The control methods of the HEAFFSPMM are simulated and investigated at healthy and one-phase open-circuit operation. Finally, the experiments are done to validate the proposed fault-tolerant control method. The results indicate that the HEAFFSPMM has good fault tolerance under the proposed control method.