Flux-switching Permanent Magnet Machine Research Articles

A Vertical Flux-Switching Permanent Magnet Based Oscillating Wave Power Generator with Energy Storage

In this paper, an effective low-speed oscillating wave power generator and its energy storage system have been proposed. A vertical flux-switching permanent magnet (PM) machine is designed as the generator while supercapacitors and batteries are used to store the energy. First, the overall power generation system is established and principles of the machine are introduced. Second, three modes are proposed for the energy storage system and sliding mode control (SMC) is employed to regulate the voltage of the direct current (DC) bus, observe the mechanical input, and feedback the status of the storage system. Finally, experiments with load and sinusoidal mechanical inputs are carried out to validate the effectiveness and stability of power generation for wave energy. The results show that the proposed power generation system can be employed in low-speed environment around 1 m/s to absorb random wave power, achieving over 60% power efficiency. The power generation approach can be used to capture wave energy in the future.

Fault‐tolerant electric drive and space‐phasor modulation of flux‐switching permanent magnet machine for aerospace application

This study investigates how to improve the fault tolerance or availability of an electrical drive containing a three-phase 12 stator teeth/10 rotor poles (12/10) the flux-switching permanent magnet machine. In this respect, space-vector modulation and space-phasor modulation will be analysed in this type of machine for control scheme design under three-phase operation. While for safety critical applications, availability requires that during faults, such as loss of one inverter phase leg or open circuit of one machine phase winding, the electrical drive system remains partly operational. Therefore, initial research is given in this study on the implementation of control algorithms that drives the machine under normal condition and preserves the electromagnetic torque under phase open-circuit faults.

Dynamic performance of the novel axial flux-switching permanent magnet motor

PurposeThe purpose of this paper is to investigate a novel axial flux-switching motor with sandwiched permanent magnet for direct drive electric vehicles (EVs), in which the torque density is increased and the cogging torque is decreased. For reducing the back-electromotive force (EMF) harmonics and cogging torque, a twisted structure is employed. To improve the dynamic performance of the axial field flux-switching sandwiched permanent magnet (AFFSSPM) motor a space vector modulation-direct torque and flux control scheme is proposed.Design/methodology/approachA multi-objective optimization is performed by means of artificial neural network and non-sorting genetic algorithm II to minimize the cogging torque while preserving the average torque.FindingsA comparative study between two proposed machines and the conventional flux-switching permanent magnet (FSPM) machine is accomplished and the static electromagnetic characteristics are analyzed. It is demonstrated that the proposed model with twisted structure has significantly improved performance over the conventional FSPM machine in back-EMF and efficiency. The proposed controller has a speed loop only and contains neither the current loop nor hysteresis control. The AFFSSPM motor exhibits excellent dynamic performance with this scheme.Originality valueThe axial flux-switching permanent-magnet machine is one of the most efficient machines but the AFFSSPM with sandwiched permanent magnet has not been specially reported to date. Thus in this paper, the authors report on optimal design of an axial flux-switching sandwiched permanent magnet machine for electric vehicles and investigate its dynamic performance.

Investigation on Phase Shift Between Multiple Multiphase Windings in Flux-Switching Permanent Magnet Machines

Design rules of multiple multiphase winding configurations are investigated from the perspective of phase shift between adjacent winding sets in flux-switching permanent magnet (FSPM) machines. The relations between torque/rectified voltage and phase shift for any multiple multiphase winding topology are theoretically derived, directly showing the influence of phase shift on torque/rectified voltage harmonic components. It can be learned that the optimal phase shift for the lowest torque ripple and dc voltage oscillation depends on the winding types. Symmetrical winding is not always appropriate for any occasion. To verify the analytical results, the static characteristics of the dual three-phase, four three-phase, triplex three-phase, dual six-phase, and triplex four-phase FSPM machines with specific stator/rotor-pole combinations are studied by finite-element (FE) analysis. The FE-predicted dominant torque ripple and rectified voltage pulsation components for symmetrical and asymmetric phase shifts are in good agreement with the theoretical derivation. Prototypes are built and tested to verify the analytical and FE results.

Performance investigation of odd primary pole linear switched-flux PM machine with mechanical flux adjuster

Linear switched-flux permanent-magnet machines (LSFPMMs) exhibit high thrust force density and low cost, which is especially suitable for long stroke application. They have big normal force so that the assembly becomes difficult. The mechanical flux adjuster is a suitable method to lower the big no rmal force. This paper investigates the performances of two kind odd primary pole LSFPMMs with mechanical flux adjuster based on FEA, including E- and C-core structure. The analysis results show this method can effectively lower the magnetic field in air gap. The structure parameters of mechanical flux adjuster are also optimized, and the operating curves are calculated with or without mechanical flux adjuster. With this method, not only does the assembly become easier, but also the operating range extends at small load.

Investigation of irreversible demagnetisation in switched flux permanent magnet machines under short‐circuit conditions

The irreversible magnet demagnetization phenomena are investigated in this paper , under both healthy and short - circuit conditions for a switched flux permanent magnet (SFPM) machine. The temperature effects on permanent magnet material are taken into account and the influence of short - circuit current over demagnetization is evaluated. In order to calculate the short - circuit current (mainly inter - turn short - circuit), the MATLAB/Simulink model has been employed. The aforementioned short - circuit current is then fed to the finite element model, so the demagnetization analysis can be carried out. Variou s fault scenarios are investigated, including high speeds and high fault severity. It is found that the short - circuit current has li mited effect on the magnet demagnetization due to particular features of the SFPM machines. The mechanism of demagnetization has been revealed and found out to be mainly due to temperature rise and poor PM materials utilization . Experiments have been carried out to validate the MATLAB/Simulink model for short - circuit current predictions.

Parametric Optimization and Performance Analysis of Outer Rotor Permanent Magnet Flux Switching Machine for Downhole Application

To empower safe, economical and eco-friendly sustainable solution for enhancing oil and gas productivity from deep water reservoirs, new downhole technologies are recommended. Since electric machine plays leading role in the downhole application, it is a squeezing requirement for researchers to design and develop advanced electric machine. The Recent improvement in technology and uses of high-temperature magnets, permanent magnet flux switching machine (PMFSM) has become one of the appropriate contenders for offshore drilling but fewer designed for downhole due to ambient temperature. Therefore this comprehensive study deals with the design optimization and performance analysis of outer rotor PMFSM for the downhole application. Preliminary, the basic design parameters needed for machine design are calculated mathematically. Then the design refinement technique is implemented through deterministic method. Finally, initial and optimized performance of the machine is compared and as a result the output torque is increase from 16.39 Nm to 33.57 Nm while diminishing the cogging torque and PM weight up to 1.77 Nm and 0.79 kg, respectively. Therefore, it is concluded that purposed optimized design is suitable for the downhole application.

Detent Force Reduction of a C-Core Linear Flux-Switching Permanent Magnet Machine with Multiple Additional Teeth

C-core linear flux-switching permanent magnet (PM) machines (LFSPMs) are attracting more and more attention due to their advantages of simplicity and robustness of the secondary side, high power density and high torque density, in which both PMs and armature windings are housed in the primary side. The primary salient tooth wound with a concentrated winding consists of C-shaped iron core segments between which PMs are sandwiched and the magnetization directions of these PMs are adjacent and alternant in the horizontal direction. On the other hand, the secondary side is composed of a simple iron core with salient teeth so that it is very suitable for long stroke applications. However, the detent force of the C-core LFSPM machine is relatively high and the magnetic circuit is unbalanced due to the end effect. Thus, a new multiple additional tooth which consists of an active and a traditional passive additional tooth, is employed at each end side of the primary in this paper, so that the asymmetry due to end effect can be depressed and the detent force can be reduced by adjusting the passive additional tooth position. By using the finite element method, the characteristics and performances of the proposed machine are analyzed and verified.

A Novel Flux-Switching Permanent Magnet Machine With Overlapping Windings

In this paper, in order to enlarge its torque density, an overlapping winding (OW) is applied to the 24/16-stator/rotor-pole flux-switching permanent magnet (FSPM) machine. By adopting an OW-configuration with full-pitch coils, the pitch factor and coil-flux cross-sectional area in the 24/16-pole FSPM machine with nonoverlapping winding (NOW) can be doubled. Thus, the fundamental open-circuit phase flux-linkage and back-EMF can be effectively enhanced by 115.28%, making it comparable to the conventional 12/10-pole NOW-FSPM machine. Therefore, by injecting the same current density, the proposed OW-FSPM machine can produce 65.2% higher torque density than its NOW counterpart, and 17.6% higher torque density than the conventional 12/10-pole NOW machine despite 21.5% lower ampere turns due to a smaller slot area. However, the proposed machine suffers from high torque ripple due to high cogging torque and back-EMF harmonics. Torque ripple reduction by harmonics current injection and rotor skewing in the proposed machine are investigated. Results show that both methods can effectively reduce the torque ripple in the proposed 24/16-pole NOW-FSPM machine, albeit with the level of torque density being compromised. Experiments are performed in order to validate the analysis.

Design and Investigation of Outer Rotor Permanent Magnet Flux Switching Machine for Downhole Application

Permanent magnet flux switching machine (PMFSM) is a joint venture of switch reluctance machine (SRM) and permanent magnet synchronous machine (PMSM). It has become a prominent research topic for various applications because of robust rotor structure, high torque and power densities but few were developed for downhole applications mainly due to harsh environmental conditions. Formerly, most of developed PMFSMs for downhole applications were mainly concentrated on inner-rotor type design, and difficult to find research work on outer-rotor configuration. Therefore, this paper introduces the design and investigation of PMFSM with outer-rotor configuration for downhole application. Primarily, the geometric topology of proposed design is described in detail. Then, the no load and load analysis are implemented in order to investigate the initial performance of the proposed design.

Design and Performance of 8Slot-12Pole Permanent Magnet Flux Switching Machines for Electric Bicycle Application

This paper presents a new design and performance of single phase permanent magnet flux-switching machine (PMFSM) for electric bicycle application. 8Slot-12Pole design machine were choose by analyzing the highest power density value. All active parts such as permanent magnet and armature coil are located on the stator, while the rotor part consists of only single piece iron. PMFSM have a great advantage with robust rotor structure that make it much higher power and applicable for EV application compared to SRM and IPMSM. The design, operating principles, characteristics of torque, and power of this new topology are investigated by JMAG-Designer via a 2D-FEA. Size of motor and volume of PM is designed at 75mm and 80g, respectively. Based on the investigation, it can be concluded that the proposed topology of single phase 8Slot 12Pole PMFSM achieved the target of highest performance of power density, approximately at 0.113W/mm3 with reduced permanent magnet and size of design motor. Due to the low torque performance of this initial design, further works is ongoing to improve the torque performance. In future work, outer rotor PMFSM structure design will be presented and compared with the “Deterministic Optimization Method” to improve the initial design.

Concept of Integration of Axial-Flow Compression Into Electric Machine Design

The purpose of this paper is to propose a novel concept of a high-speed electric machine system with integrated airfoil-shaped rotor designed to perform axial-flow compression for vehicle applications. The proposed high-speed machine is both a motor for electromagnetic (EM) energy conversion and an axial flow compressor for thermodynamic energy conversion. Conventional designs usually have a separate motor and compressor that are connected through a common shaft with or without a gearbox. The proposed design simplifies the high-speed machine and compressor system by eliminating the components that connect the motor and the compressor. The integrated motor-compressor design can achieve a more compact system. The flux-switching permanent magnet (FSPM) machine is chosen out of several possible electric machine topologies with salient rotor pole features for the integrated motor design. The feasibility of this integrated motor-compressor design is discussed from both the EM and thermodynamic perspectives in this paper. The selection of slot/pole combination and EM sizing equations for the integrated FSPM motor-compressor are discussed. Mean-line design equations for the axial flow compressor are studied for the proposed integrated motor-compressor. The EM torque production capability of the proposed integrated motor-compressor is verified for one possible design in this paper by finite element analysis (FEA). The effects of two different attack angles of the rotor blades are studied compared to the conventional FSPM machine. The FEA results show that the proposed integrated motor-compressor achieves the expected output performances.

A novel flux-switching permanent magnet machine with v-shaped magnets

In this paper, firstly a novel 6-stator-coil/17-rotor-pole (6/17) flux-switching permanent magnet (FSPM) machine with V-shaped magnets, deduced from conventional 12/17 FSPM machines is proposed to achieve more symmetrical phase back-electromotive force (back-EMF), and smaller torque ripple by comparing with an existing 6/10 V-shaped FSPM machine. Then, to obtain larger electromagnetic torque, less torque ripple, and easier mechanical processing, two improved variants based on the original 6/17 V-shaped topology are proposed. For the first variant, the separate stator-core segments located on the stator yoke are connected into a united stator yoke, while for the second variant the stator core is a whole entity by adding magnetic bridges at the ends of permanent magnets (PMs). Consequently, the performances of the three 6/17 V-shaped FSPM machines, namely, the original one and the two variants, are conducted by finite element analysis (FEA). The results reveal that the first variant exhibits significantly larger torque and considerably improved torque per magnet volume, i.e., the magnet utilization ratio than the original one, and the second variant exhibits the smallest torque ripple, least total harmonic distribution (THD) of phase back-EMF, and easiest mechanical processing for manufacturing.

Fabrication and Experimental Analysis of an Axially Laminated Flux-Switching Permanent-Magnet Machine

The traditional flux-switching permanent-magnet machines (FSPMMs) with radial lamination have serious partial magnetic saturation for their nonlinear magnetic path, where the maximal flux density is usually more than 2.0 T occurring at the edges/tips of stator teeth or rotor poles. In this case, the core loss of FSPMMs becomes evident especially beyond the rated speed, which leads to decrease of output power, torque/power density, and efficiency. To overcome these problems, an axially laminated flux-switching permanent-magnet machine (ALFSPMM) with high grain-oriented silicon steel stator and rotor cores is proposed. The detailed fabrication procedures are presented in this paper. The theoretical characteristics of the ALFSPMM, such as back electromotive force, self-/mutual inductance, and cogging torque are calculated by the two-dimensional finite-element method (FEM). The influence of misalignment between the stator core and the rotor shaft (a common issue in motor manufacturing) is investigated by the FEM. Experimental measurements of the prototype machine are presented to validate the FEM calculation. In addition, a simple low-cost method to measure the cogging torque is also presented in this paper.

Comparison of switched‐flux permanent magnet machines with non‐overlapping concentrated winding for open‐winding generator system

The open-winding permanent magnet generator (OWPMG) systems, having the advantages such as high power density, relatively few power switches, high degree of integration and easy to realise power distribution, are suitable for applications like renewable energy power generation systems with multiple power sources. The non-overlapping concentrated winding switched-flux permanent magnet (NOWSFPM) machines, having relatively high torque density and big flux-weakening inductance, are good choices when used in OWPMG systems. The electromagnetic performance of the 6/10 NOWSFPM machine, the 6/7 E-core NOWSFPM machine, the 6/7 E-core NOWSFPM machine with pole shoe and the 6/19 multi-tooth NOWSFPM machine are compared and analysed. Based on the results and according to two defined factors, namely the proportion factor of the power distribution and the speed range, this study mainly focuses on the influence of the flux-weakening coefficient ( ρ ) on the capability of the power distribution control. The analysis conclusions are verified by experimental results, indicating that the 6/19 multi-tooth NOWSFPM machine ( ρ ≃ 1) has relatively strong power distribution capability.

Demagnetization investigation of a partitioned rotor flux switching machine with hybrid permanent magnet

In this paper, the partitioned rotor flux switching permanent magnet machine with ferrite permanent magnet is proposed. By the adoption of the partitioned rotor configuration, the stator flux leakage is eliminated and the permanent magnet utilization is improved. The ferrite permanent magnet machine often suffers from irreversible demagnetization due to the inherent relatively low coercivity of ferrite permanent magnet. To mitigate the machine irreversible demagnetization risk, an improved partitioned rotor flux switching permanent magnet machine with hybrid permanent magnet topology is also proposed. Two little pieces of rare-earth permanent magnet are installed at the corners of ferrite permanent magnet, thus forming the hybrid permanent magnet topology. And the demagnetization mechanisms of both machines are clarified by the magnetic equivalent circuit method, which prove that the rare-earth permanent magnet offer magnetic protection function for the ferrite permanent magnet. Furthermore, by the 2-D finite element analysis, the demagnetization characteristics and the electromagnetic performances of the two machines are quantitively assessed, revealing that the demagnetization risk is reduced significantly. Both theoretical analysis and simulation results verify that the improved machine can not only maintain low-cost design, but also possess enhanced demagnetization withstand capability and competitive electromagnetic performances as expected.

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.

Design and analysis of a 3D-flux flux-switching permanent magnet machine with SMC cores and ferrite magnets

Since permanent magnets (PM) are stacked between the adjacent stator teeth and there are no windings or PMs on the rotor, flux-switching permanent magnet machine (FSPMM) owns the merits of good flux concentrating and robust rotor structure. Compared with the traditional PM machines, FSPMM can provide higher torque density and better thermal dissipation ability. Combined with the soft magnetic composite (SMC) material and ferrite magnets, this paper proposes a new 3D-flux FSPMM (3DFFSPMM). The topology and operation principle are introduced. It can be found that the designed new 3DFFSPMM has many merits over than the traditional FSPMM for it can utilize the advantages of SMC material. Moreover, the PM flux of this new motor can be regulated by using the mechanical method. 3D finite element method (FEM) is used to calculate the magnetic field and parameters of the motor, such as flux density, inductance, PM flux linkage and efficiency map. The demagnetization analysis of the ferrite magnet is also addressed to ensure the safety operation of the proposed motor.

Evaluation of parameter sensitivities for flux-switching permanent magnet machines based on simplified equivalent magnetic circuit

Most of the published papers regarding the design of flux-switching permanent magnet machines are focused on the analysis and optimization of electromagnetic or mechanical behaviors, however, the evaluate of the parameter sensitivities have not been covered, which contrarily, is the main contribution of this paper. Based on the finite element analysis (FEA) and simplified equivalent magnetic circuit, the method proposed in this paper enables the influences of parameters on the electromagnetic performances, i.e. the parameter sensitivities, to be given by equations. The FEA results are also validated by experimental measurements.

Vibration prediction in fault‐tolerant flux‐switching permanent‐magnet machine under healthy and faulty conditions

This study investigates the vibration behaviour of a fault-tolerant flux-switching permanent-magnet (FT-FSPM) machine due to electromagnetic origins. The FT-FSPM machine adopts fault-tolerant teeth and odd rotor pole to obtain more symmetric back electromotive force and reduced cogging torque. However, this topology suffers from high local magnetic force and unbalanced radial force, thus producing significant vibration and noise. In order to predict the vibration characteristic generated by the structure, electromagnetic and structural models are developed. First, the air-gap field is qualitatively analysed by using the rotor permeance to modulate the magnetomotive force. Second, the radial forces during healthy and faulty operations are compared by using finite element method. Then, the most significant vibration modes are calculated to determine how the machine is excited. Furthermore, the vibration behaviour of the FT-FSPM machine under healthy and faulty conditions is predicted by structural analysis. Finally, the experimental measurements are given for verification.