Field Excitation Flux Switching Research Articles

Design and comparative analysis of dual rotor wound field excited flux switching generator for household DC microgrid system with rooftop wind turbine

In this paper, two variants of the magnetless dual rotor wound field excited flux switching generator (DRWFEFSG) are comparatively analyzed for single rotor wind turbine (termed as machine I (MI)) and counter rotating wind turbine applications (termed as machine II (MII)) for household direct current (DC) microgrid system. First, design concept and integration to wind turbine system are discussed. Secondly, comprehensively performance analysis i.e., static analysis, dynamic load/speed analysis and electromagnetic performance analysis are executed. Finite element analysis (FEA) based static analysis evident that MI offers 7.6% higher torque in inner rotor whereas MII exhibits 18% higher torque in outer rotor. Dynamic respond unveils that in comparison to MII, MI suffers from the issue of voltage regulation. Additionally, electromagnetic analysis reveals that both MI and MII exhibits excellent response under variable field Magneto-motive force (MMF). Comparative analysis unveils that MII requires lower field MMF to achieve same response to counterpart MI. Quantitative analysis divulge efficiency of 88.49% and power factor of 0.93 in MI whereas MII at rated operating point demonstrates 85.9% efficiency and 0.96 power factor. Finally, effectiveness of the study and validity of DRWFEFSG for wind turbine applications are tested with hardware prototypes of both MI and MII that fairly matched with FEA results.

Performance Analysis and Optimization of a Novel Outer Rotor Field-Excited Flux-Switching Machine with Combined Semi-Closed and Open Slots Stator

Slotting effect in electric machines reduces flux per pole that effect magnetic flux density distribution in the air gap which induces harmonics in magnetic flux density causing flux pulsation, that in turn generates dominant torque pulsation in the form of cogging torque and torque ripples. To overcome the abovesaid demerits, a novel outer rotor field-excited flux-switching machine (OR-FSFSM) with a combined semi-closed and open slots stator is proposed in this study. The developed OR-FEFSM offers a high-power factor, due to the utilization of the semi-closed slot for armature coils. The open slot stator structure was chosen for the field excitation coil, which effectively suppresses leakage reluctance that causes flux pulsation. Thus, the influence of torque ripples is reduced, and the average torque is improved. In order to investigate the effectiveness of the proposed OR-FEFSM, a detailed study of stator slot and rotor pole combinations are performed. Based on simplified mathematical formulation, 12S/7P (stator slot/rotor poles), 12S/11P, 12S/13P, and 12S/17P are the most feasible combinations. Finite Element Analysis (FEA) based on comprehensive electromagnetic performance is performed on each combination, and found that 12S/13P offers the highest average torque of 4.62 Nm, whereas 3.72 Nm, 2.72Nm, and 1.68 Nm average torque is offered by 12S/17P, 12S/7P, and 12S/11P, respectively. Based on the initial analysis, 12S/13P was considered for further analysis and optimized using JMAG built-in Genetic Algorithm (GA). Moreover, thermal analysis was performed, and the proposed design was compared with the conventional design.

Investigation of low‐cost dual port co‐rotating dual rotor field excited flux switching generator for low‐power rooftop wind turbine integrated with multi‐port DC micro grid

In this paper, a novel low-cost dual port dual rotor-field excited flux switching generator (DPDR-FEFSG) is proposed for low power rooftop wind turbine integrated with DC-micro-grids. The proposed DPDR-FEFSG incorporated inner/outer machine to design a dual rotor structure with dual output port. Due to the existence of field excitation in DPDR-FEFSG, overall machine cost is reduced and offered excellent flux regulation capabilities. Furthermore, single tooth non-overlapped armature winding and toroidally wounded field winding significantly shorten end winding that reduces copper losses. Additionally, compared with the existing single-bus DC-micro grids system, the proposed DPDR-FEFSG exhibits two-port output which makes it feasible for low-voltage (12–24 V) and high-voltage (48 V) applications connected to the DC micro-grids without the requirements of extra power electronics circuitry. The proposed DPDR-FEFSG is investigated under variable field excitation and variable rotor speed. In order to achieve the desired voltage level at low and high port without frequency variation, AC–DC rectification is employed. Analysis reveals that proposed DPDR-FEFSG offers dual output port from inner and outer machines. This dual port makes it feasible for wind turbine integrated to multi-port DC micro-grids. Due to availability of different voltages at various ports, different load classes are incorporated without the requirements of extra power electronics circuitry and thus reduce overall cost. Finally, a prototype is built and tested to confirm the validity of the proposed concept and finite element analysis (FEA) results.

Analysis of Linear Hybrid Excited Flux Switching Machines with Low-Cost Ferrite Magnets

Linear hybrid excited flux switching machines (LHEFSM) combine the features of permanent magnet flux switching machines (PMFSM) and field excited flux switching machines (FEFSM). Because of the widespread usage of rare-earth PM materials, their costs are steadily rising. This study proposes an LHEFSM, a dual stator LHEFSM (DSLHEFSM), and a dual mover LHEFSM (DMLHEFSM) to solve this issue. The employment of ferrite magnets rather than rare-earth PM in these suggested designs is significant. Compared to traditional designs, the proposed designs feature greater thrust force, power density, reduced normal force, and a 25% decrease in PM volume. A yokeless primary structure was used in a DSLHEFSM to minimize the volume of the mover, increasing the thrust force density. In DMLHELFSM, on the other hand, a yokeless secondary structure was used to lower the secondary volume and the machine’s total cost. Single variable optimization was used to optimize all of the proposed designs. By completing a 3D study, the electromagnetic performances acquired from the 2D analysis were confirmed. Compared to conventional designs, the average thrust force in LHEFSM, DSLHEFSM, and DMLHEFSM was enhanced by 15%, 16.8%, and 15.6%, respectively. Overall, the presented machines had a high thrust force density, a high-power density, a high no-load electromotive force, and a low normal force, allowing them to be used in long-stroke applications.

Stress and coupled electromagnetic-thermal analysis of field excited flux switching machine

Purpose Field excited flux switching machines (FEFSM) are preferred over induction and synchronous machines due to the confinement of all excitation sources on the stator leaving a robust rotor. This paper aims to perform coupled electromagnetic thermal analysis and stress analysis for single phase FEFSM as, prolonged high-speed operational time with core and copper losses makes it prone to stress and thermal constraints as temperature rise in machine lead to degraded electromagnetic performance whereas the violation of the principle stress limit may result in mechanical deformation of the rotor. Design/methodology/approach This paper presents the implementation of coupled electromagnetic-thermal and rotor stress analysis on single-phase FEFSM with non-overlap winding configurations using finite element analysis (FEA) methodology in JMAG V. 18.1. three-dimensional (3D) magnetic loss analysis is performed and extended to 3D thermal analysis to predict temperature distribution on various parts of the machine whereas Stress analysis predicts mechanical stress acting upon edges and faces of the rotor. Findings Analysis reveals that temperature distribution and rotor stress on the machine is within acceptable limits. A maximum temperature rise of 37.7°C was noticed at armature and field windings, temperature distribution in stator near pole proximity was 35°C whereas no significant change in rotor temperature was noticed. Furthermore, principal stress at the speed of 3,000 rpm and 30,000 rpm was found out to be 0.0305 MPa 3.045 MPa, respectively. Research limitations/implications The designed machine will be optimized for improvement of electromagnetic performance followed by hardware implementation and experimental testing in the future. Practical implications The model is developed for axial fan applications. Originality/value Thermal analysis is not being implemented on FEFSM for axial fan applications which is an important analysis to ensure the electromagnetic performance of the machine.

Electromagnetic Performances and Main Parameter Sensitivity Effect on Unbalance Magnetic Flux in a New Single-Phase FEFSM with Segmental Rotor

Three-phase field excitation flux switching motor (FEFSM) with salient rotor structure has been introduced with their advantages of rotor easy temperature elimination and controllable FEC magnetic flux. Yet, the salient rotor structure is found to lead a longer magnetic flux path between stator and rotor parts, producing a weak flux linkage along with low torque performances. Hence, a new structure of single-phase FEFSM using segmental rotor with non-overlap windings is proposed with advantages of shorter magnetic flux path, light weight and robust rotor structure. Analysis on fundamental magnetic flux characteristics, armature and FEC magnetic flux linkages, cogging torque, back-Emf, various torque capabilities, refinement of unbalance magnetic flux, and torque-power versus speed characteristics are conducted using 2D FEA through JMAG Designer version 15. The results show that magnetic flux amplitude ratio has been improved by 41.2% while the highest torque and power achieved are 1.45 Nm and 343.8 W, respectively.

Modular Rotor Single Phase Field Excited Flux Switching Machine with Non-Overlapped Windings

This paper aims to propose and compare three new structures of single-phase field excited flux switching machine for pedestal fan application. Conventional six-slot/three-pole salient rotor design has better performance in terms of torque, whilst also having a higher back-EMF and unbalanced electromagnetic forces. Due to the alignment position of the rotor pole with stator teeth, the salient rotor design could not generate torque (called dead zone torque). A new structure having sub-part rotor design has the capability to eliminate dead zone torque. Both the conventional eight-slot/four-pole sub-part rotor design and six-slot/three-pole salient rotor design have an overlapped winding arrangement between armature coil and field excitation coil that depicts high copper losses as well as results in increased size of motor. Additionally, a field excited flux switching machine with a salient structure of the rotor has high flux strength in the stator-core that has considerable impact on high iron losses. Therefore, a novel topology in terms of modular rotor of single-phase field excited flux switching machine with eight-slot/six-pole configuration is proposed, which enable non-overlap arrangement between armature coil and FEC winding that facilitates reduction in the copper losses. The proposed modular rotor design acquires reduced iron losses as well as reduced active rotor mass comparatively to conventional rotor design. It is very persuasive to analyze the range of speed for these rotors to avoid cracks and deformation, the maximum tensile strength (can be measured with principal stress in research) of the rotor analysis is conducted using JMAG. A deterministic optimization technique is implemented to enhance the electromagnetic performance of eight-slot/six-pole modular rotor design. The electromagnetic performance of the conventional sub-part rotor design, doubly salient rotor design, and proposed novel-modular rotor design is analyzed by 3D-finite element analysis (3D-FEA), including flux linkage, flux distribution, flux strength, back-EMF, cogging torque, torque characteristics, iron losses, and efficiency.

Design and Optimization of Complementary Field Excited Linear Flux Switching Machine With Unequal Primary Tooth Width and Segmented Secondary

Linear flux switching machines (LFSMs) are one of the recently emerging and competitive candidates for long stroke applications due to high thrust force density, low cost and robust secondary, and high reliability. In the past decade, permanent magnet linear flux switching machines (PMLFSMs) with continuous secondary is researched by numerous researchers. However, cost of rare earth permanent magnet and iron material for continuous secondary in case of long stroke application makes PMLFSMs not an economical choice. In order to incorporate advantages of segmented secondary, such as: less use of stator iron, high power factor, and less critical saturation, a novel complementary dual mover field excited linear flux switching machine (FELFSMs) with segmented secondary and parallel magnetic structure is proposed and investigated in this paper. Furthermore, geometry-based deterministic optimization approach based on finite element analysis (FEA) is adopted to uplift overall thrust force profile, reduce secondary iron volume, and balance magnetic circuit of the machine. During optimization process, magnitude difference of flux flow between ac winding tooth and dc winding tooth is observed, that compel designers to go for unequal primary teeth design. Finally, optimal ac and dc current densities of geometrically optimized model and without any cooling arrangements are investigated for maximum average thrust force and minimum thrust force ripple ratio.

Performance Comparison between Salient and Segmental Rotors Single-Phase FEFSM Using Non-Overlap Windings for Home Appliances

Field excitation flux switching machines (FEFSMs) in which their torque performance produced by interaction between armature and field excitation (FE) coils have been widely designed for various applications. In this regard, three-phase salient rotor FEFSM with overlap windings is considered the most suitable candidate for high speed applications because of their advantages of flux controllability, and robust due to single piece of rotor structure. However, the overlap windings cause a high copper loss, hence efficiency of the motor becomes low and higher stack length. Besides, the salient rotor structure is found to produce low torque performance due to the longer flux path in stator and rotor yielding weak flux linkage. In this paper, a new single-phase FEFSM using non-overlap windings between armature coils and FE coils is proposed. Both non-overlap windings FEFSMs with salient and segmental rotors have been designed using JMAG Designer version 15 and the investigation process is conducted via 2D finite element analysis. The proposed motor performances verification has been done by comparing the results of flux linkage, flux line and distribution, flux strengthening, various torque capability, and torque-power versus speed characteristics. As a conclusion, single-phase non-overlap windings FEFSM using segmental rotor with power, torque and speed capabilities of 277.5 W, 0.91 Nm and 2,899 rpm, respectively considered as the best candidate for low torque high speed applications.

Slot Pole Study of Field Excitation Flux Switching Machines Using Segmental Rotor and Non-Overlap Windings

Field excitation flux switching machines (FEFSMs) in which their torque performance generated by interaction between armature and field excitation (FE) coils have been widely designed and developed for various applications. In this regard, FEFSM with salient rotor is considered the most suitable candidate for high speed applications because of their advantages of flux controllability, and robust due to single piece of rotor structure. However, the existing FEFSM with overlapped armature and FEC windings lead to increment of copper loss, motor size and material cost. In addition, the declination of torque and power densities due to high rotor weight needs to be improved. In this paper, performance comparisons of four FEFSM topologies particularly emphasis on non-overlap armature coil and FEC windings placed on the stator with segmental rotor are investigated. The performances, including flux linkage, back-emf, flux strengthening, flux line, flux distribution, cogging torque, torque and power of the proposed motor are analysed and compared using 2D finite element analysis (FEA) thru JMAG Designer version 15. As a result, segmental rotor has produced shorter flux paths, while non-overlapping windings has reduced the copper consumption. Finally, the best combination of stator slot-pole configurations is 12S-6P which provide high flux linkage, high torque and power of 0.0412 Wb, 0.77 Nm and 0.26 kW, respectively.

Magnetic Flux Analysis of a New Field-Excitation Flux Switching Motor Using Segmental Rotor

Recently, a three-phase field-excitation flux switching motor (FEFSM) with salient rotor structure has been introduced with their advantages of easy rotor temperature removal and controllable field excitation coil (FEC) magnetic flux particularly suitable for high torque, high power, and high-speed diverse performances. Nevertheless, the salient rotor structure is found to lead a longer magnetic flux path between stator and rotor producing weak flux linkage along with low torque performances. Besides, the overlap armature coil and FEC windings yield high coil end length, producing much high copper loss and large motor size. In this paper, a new FEFSM using segmental rotor with non-overlap armature coil and FEC windings is proposed. The shorter magnetic flux path of the proposed segmental rotor is noticeably more focused to produce much higher torque while the non-overlap armature and FEC will reduce the copper loss and motor weight. Both FEFSMs with salient and segmental rotors are designed using 2-D-FEA JMAG Designer version 14.1 for comparison. As a result, magnetic flux of the segmental rotor design is 11 times higher than the salient rotor structure mainly due to shorter magnetic flux linkage between two stator teeth and single rotor segment. The torque and power of 0.91 Nm and 293 W, respectively, are obtained from the new FEFSM which are much higher than salient rotor design. In addition, the simulation and experimental results show a good agreement in back-electromotive force amplitude and waveform at various speeds, as well as similar increment of torque versus FEC current characteristics. As the conclusion, the proposed FEFSM with non-overlap and segmental rotor structure has produced much higher flux, with significant improvement of torque and power performances compared with existing FEFSM with salient rotor.

Design Improvement of Three Phase 12Slot-14Pole Outer Rotor Field Excitation Flux Switching Motor

This paper present with design improvement of 12Slot-14Pole outer rotor field excitation flux switching motor (ORFEFSM) from the initial design by implement Deterministic Optimization Method (DOM) which involve 2-dimensional Finite-Element Analysis (FEA). The design improvement starts with the non-active part, rotor and followed with active part, stator which involve the armature coil slot and field excitation coil (FEC) slot. Since it is one of local optimization method, this method involves more than one cycle of improvement depends on the design structure and slot-pole configuration until achieve optimum performance. However, the initial torque and power output of 12Slot-14Pole is 112.95 Nm and 50.46 kW. The main objective is to improve the structure in order to obtain optimum torque and power output. Besides, it is necessary to reduce flux saturation and optimize the flux flow between the rotor teeth and stator arc width. The target torque and power output performance is expected higher than 210 Nm and 123 kW. With the deterministic optimization method technique, the final torque and power output achived are 221.83 Nm and 189kW.

Performance Comparison of 12S-14P Inner and Outer Rotor Field Excitation Flux Switching Motor

Hybrid excitation flux switching machines (HEFSMs) have a several advantages such as robust rotor structure, high torque and power capabilities, and high efficiency suitable for light load and heavy industry applications. However, the general structure of HEFSMs employed with three main flux sources namely permanent magnet (PM), field excitation coil (FEC) and armature coil located on the stator body causes high manufacturing cost. Therefore, a new non-PM field excitation flux switching machine (FEFSM) consists of rugged rotor structure suitable for high-speed operation with capability to keep similar torque and power density of HEFSM is proposed and examined. In this paper, performances of both outer and inner rotor 12S-14P FEFSMs are analyzed and compared. As conclusion, the inner-rotor topology provides much higher torque and power when compared with outer rotor configuration.

Design Studies and Analysis of Single Phase 8S-12P Field Excitation Flux Switching Motor

This paper presents a new structure of field excitation flux switching motor (FEFSM) as an alternative candidate of non-permanent magnet (PM) machine. The rotor is consisted of only stack of iron and hence, it is reliable and appropriate for high speed operation. Initially, the coil arrangement tests are examined to validate the operating principle of the motor and to identify the zero rotor position. Furthermore, the profile of flux linkage, induced voltage, cogging torque, torque and power characteristics are observed based on 2D finite element analysis (FEA). Initial performances show that 8S-12P FEFSM produce torque and power of 8.79Nm and 1.5kW, respectively with low cogging torque and sinusoidal flux waveform. Further design refinement and optimization will be conducted to improve the performances of the motor.

Uni- and Bidirectional Flux Variation Loci Method for Analytical Prediction of Iron Losses in Doubly-Salient Field-Excited Switched-Flux Machines

Field-Excited Flux-Switching machines are doubly-salient machines with complex flux-density waveforms in the core. Hence, prediction of iron losses is difficult. In this article, we propose a method to determine flux loci in iron parts in an analytical manner, accounting for bidirectional field in back-irons of stator and rotor. The analytical model for flux-density prediction in the core at no-load was first validated with 2D FE simulations. Then measured iron losses on a prototype machine were used to calibrate an iron loss model. It was shown that in FE-SF machines rotor iron losses are not negligible and represent 28% of total iron losses. This model could be advantageously used in a design optimization procedure.

Analytical Armature Reaction Field Prediction in Field-Excited Flux-Switching Machines Using an Exact Relative Permeance Function

In this paper, an analytical approach for the prediction of the armature reaction field of field-excited flux-switching (FE-FS) machines is presented. The analytical method is based on the magnetomotive force (MMF)-permeance theory. The doubly-salient air-gap permeance, developed here, is derived from an exact solution of the slot permeance. Indeed, the relative slot permeance is obtained by solving Maxwell's equations in a subdomain model and applying boundary and continuity conditions. In addition, during a no-load study, we found that, regarding the stator-rotor teeth combination, phase distributions were modified. Hence, in this paper, phase MMF distributions, for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> phases, several stator-rotor combinations and also phase winding distribution (single- or double-layers) are proposed. We compare extensively magnetic field distributions calculated by the analytical model with those obtained from finite-element analyses. Futhermore, the model is used to predict the machine inductances. Once again, FE results validate the analytical prediction, showing that the developed model can be advantageously used as a design tool of FE-FS machine.

Analytical Approach for Air-Gap Modeling of Field-Excited Flux-Switching Machine: No-Load Operation

This paper presents a general and accurate approach to determine the no-load flux of field-excited flux-switching (FE-FS) machines. These structures are inherently difficult to model due to their doubly-slotted air gap. This analytical approach is based on magnetomotive force-permeance theory. The analytical model developed is extensively compared to field distribution obtained with 2-D finite element (2-D FE) simulations. The good agreement observed between analytical model and 2-D FE results emphasizes the interest of this general approach regarding the computation time. Hence, this analytical approach is suitable for optimization process in pre-sizing loop. Furthermore, based on the field model, classical electromagnetic performances can be derived, such as flux linkage and back-electromotive force (back-EMF) and also, unbalanced magnetic force. Once again, FE results validate the analytical prediction, allowing investigations on several stator-rotor combinations, or optimization of the back-EMF.