Field Excitation Flux Switching Machine Research Articles

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.

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.

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.

Outer rotor wound field flux switching machine for In‐wheel direct drive application

Nowadays the flux switching machines offer pivotal role in high speed applications. The flux sources (field excitation coil and armature winding or permanent magnet) are confined to the stator leaving rotor completely passive, and thus making the flux switching machine (FSM) more suitable for industrial applications. This paper emphasizes salient rotor pole and non-overlapping windings embedded in electrical machine design possess some pertinent features such as reduced copper losses, low-cost, and usage in high speed applications. The proposed design is analyzed for coil test analysis and flux linkage and torque. On the basis of the analysis performed, it is clear that 12-slot/13-pole has low cogging torque, high flux linkage, and maximum torque, compared with other topologies of outer rotor field excitation FSM. A deterministic optimization technique is adopted to enhance the performance of 12-slot/13-pole design. Further, finite element analysis (FEA) results are verified through Global Reluctance Network (GRN) methodology, which show close resemblance with error less than 1.2%. Hence, it validates the proposed design for outer rotor field excitation FSM direct drive application. The proposed design for hybrid electric vehicle torque characteristic is compared with existing interior permanent magnet synchronous machine (IPMSM) and 6-slot/7-pole wound field flux switching machine (WFFSM).

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.

Preliminary Design Investigation of Dual Stator HE FSM using Segmental Rotor

To drop the effect of air transportation on the atmosphere as well as to advance fuel productivity more-electric aircraft (MEA) architectures is a well-known approach. As the electrical machines are competent to deliver higher torque densities and are foremost for the viability of electrical driving force for aircraft applications. For these reasons a new category of machine has been familiar and published in last decade known as flux switching machine (FSM). FSMs comprises all excitation sources on stator side without winding robust rotor structure. Additionally, FSMs are classified into three types such as permanent magnet (PM) FSMs, field excitation (FE) FSMs and hybrid excitation (HE) FSMs. PM FSM and FE FSM use PM and FE coil for their excitation sources respectively, whereas both PM and FE coil are used in HE-FSM for excitation. Afterwards, HE FSMs have shown higher torque to weight ratios with higher efficiency during research in the last decade. Yet, in existing structures of HE FSMs, there is flux cancellation between the fluxes of PMs and FE coil which causes to reduce the performance of machines. Hence, in this paper, a novel structure of dual stator (DS) HE FSM with segmented rotor has been proposed and analyzed. The main reason of dual stator is to make the separate flow fluxes in HE machines to avoid cancellations. The proposed novel DS HE FSM has a simple structure using dual stators to endorse separate dual excitations to be used in fault conditions. The proposed structure has been analyzed using commercial 2D FEA package, JMAG-designer. Initially, this paper presents the coil test analysis of proposed DS HE FSM to confirm the working principle. Besides, performance analysis has been carried out at no load and load conditions.

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.

Torque analysis and slot regions assignment of a DC-excited flux-modulated machine with two stator windings

This paper presents a DC-excited flux-modulated (DCEFM) machine. It has one rotor with pr poles and two sets of windings on one stator. One of the windings has pf pole-pairs and is excited with DC current. The second winding has pa pole-pairs and is excited with AC sinusoidal current. The relationship between pr, pf and pa is pr = pf + pa. The purpose of this paper is to analyze the torque of the machine in order to optimize the slot regions assigned to the two stator windings for generating the highest torque at the admissible copper losses. Firstly, the torque equation of the machine is derived. The methods described in this paper are also feasible for other machine types such as variable flux reluctance machine, field excited flux-switching machine. By using the finite element analysis (FEA) the analytical results are verified. The results show that the magneto motive forces (MMFs) of the two windings need to be approximately equal to obtain optimal torque.

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.

Comparative Performance of FE-FSM, PM-FSM and HE-FSM with Segmental Rotor

Flux switching machines (FSMs), new type of electric machines with unique operating principles have been introduced and published recently. FSMs contain armature and excitation sources on the stator with robust rotor structure. According to rotor structure FSMs can be classified into two types namely salient pole rotor and segmental pole rotor. Various topologies have been studied and published using both rotor structures, however salient pole rotor has a demerit of less torque generation due to longer flux path resulting flux leakage surrounding the rotor. In this paper a new structure of hybrid excitation FSM (HEFSM) with segmental rotor is proposed and a comparative analysis with the invented field excitation FSM (FEFSM) and permanent magnet FSM (PMFSM) is presented. Initially, coil arrangement tests are examined to confirm the operating principle of HEFSM with segmental rotor. Moreover, the cogging torque, induced voltage, magnetic flux, torque at various armature current densities and power characteristics are observed based on 2D-finite element analysis (FEA).

Investigation on Flux Characteristics of Field Excitation Flux Switching Machine with Single FEC Polarity

Flux switching machines (FSMs) that consist of all flux sources in the stator have been developed in recent years due to their definite advantage of single piece robust rotor structure suitable for high speed applications. They can be categorized into three groups that are permanent magnet (PM) FSM, field excitation (FE) FSM, and hybrid excitation (HE) FSM. Both PMFSM and FEFSM has only PM and field excitation coil (FEC), respectively as their main flux sources, while HEFSM combines both PM and FECs. Among these FSMs, the FEFSM offers advantages of low cost, simple construction and variable flux control capabilities suitable for various performances. In this paper, design study and flux interaction analysis of 24S-10P FEFSM with single direction of FEC winding is presented. Initially, design procedures of the FEFSM including parts drawing, materials and conditions setting, and properties setting are explained. Then, coil arrangement tests are examined to confirm the machine operating principle and position of each armature coil phase. Finally, the flux interaction between DC FEC and armature coil, FEC flux capabilities at various current condition, and initial torque are also investigated.