Flux-switching Machine Research Articles

Design and optimization of segmented PM consequent pole hybrid excited flux switching machine for EV/HEV application

Hybrid Excited Flux Switching Machines (HEFSMs) unique feature of high torque density (T den ) of Permanent Magnet (PM) machines and flux regulation capability of wound field excitation machines. Due to aforesaid unique features, stator active HEFSMs are preferred for EV/HEV applications. In this paper a new Segmented PM Consequent Pole HE-FSM (sPMCPHEFSM) with flux bridge is proposed for EV/HEV. The developed SPMCPHEFSM exhibits improved flux modulation and flux regulation capability at reduced PM usage (suppressed PM volume by 46.52% and PM cost by 46.48%) and eliminating stator leakage flux. First, SPMCPHEFSM is geometric optimized (GO) for investigating influence of leading design with key performance indicators such as flux linkage (Φ pp ), average torque (T avg ), cogging torque (T cog ), T den , average power (P avg ) and power density (P den ) and then proceeded optimized model to structure modification for optimal stator design and position of field excitation coils (FEC). Comprehensive performance analysis reveals that the developed SPMCPHEFSM show improved Φ pp maximum up to 9.11%, improved T avg maximum up to 23.63%, truncate T cog up to 18.9% whereas T den and P den are boost up to 23.55% and 89.72% respectively.

Partitioned Stator Switched Flux Machine: Novel Winding Configurations

Torque density is one of the major limiting factors in machine design. In this paper, we propose the hybrid excited partitioned stator switched flux machine3 (HE-PSSFM3). In HE-PSSFM3, armature winding is positioned on the outer stator whereas the permanent magnet (PM) and field winding are placed at the inner stator, while the rotor is free from excitation sources and armature winding. Moreover, concentrated field winding is replaced by toroidal winding. The power splitting ratio between two stators/rotor pole combinations is analytically optimized and are validated through genetic algorithm (GA) in order to enhance average torque and flux regulation capability. The electromagnetic characteristics of the improved and initial design are evaluated and compared with existing designs, i.e., HE-PSSFM1 and HE-PSSFM2. The proposed HE-PSSFM3 has achieved high average torque, i.e., 2.0015 Nm, at same armature and field current densities of 5 A/mm. The results show that the average torques of the proposed design are 35% and 15% greater than HE-PSSFM1 and HE-PSSFM2, respectively. Furthermore, the analysis of various parameters such as flux linkage, flux regulation, electromagnetic performances, cogging torque, back EMF, electromagnetic torque, and torque ripples are investigated using two dimensional (2D) finite element analysis (FEA). Moreover, the simulation results of the proposed design are validated through GA and analytical modeling.

Development of a generic framework for lumped parameter modeling

AbstractThe purpose of this article is to present a generic reluctance network modeling tool dedicated to the modeling of electrical machines. This tool is used for the study of permanent magnet machines. The focus will be on the modeling methodology and software implementation. More precisely, the aspects related to genericity will be discussed. In order to validate the developed tool, the simulation of a 12 slot/10 pole flux-switching permanent magnet machine is conducted, and the results obtained from this generic framework are compared to the corresponding finite element analysis.

Analysis of Rotor Poles and Armature Winding Configurations Combinations of Wound Field Flux Switching Machines

The general rules of rotor pole and armature winding configurations combinations for 24-slot stator wound field flux switching machines (SWFFSMs) are investigated thoroughly in this article. Meanwhile, based on the virtual coil method, a novel general auxiliary evaluation variable, which is proportional to the fundamental amplitude of open-circuit flux-linkage of armature coil is proposed in this article. Hence, these SWFFSMs with larger open-circuit flux-linkage and back-EMF can be obtained effectively. In addition, the effect of rotor poles on the complementarity of armature windings is analyzed so that more sinusoidal and symmetrical back-EMF can be acquired. Furthermore, for these SWFFSMs with larger open-circuit back-EMF, the torque capability is restricted to a considerable extent due to the deep magnetic saturation caused by overlapping armature winding. Hence, a new method by optimizing the ratio of armature slot area and excitation slot area is proposed in this article to ensure that the higher torque density of selected SWFFSMs can be maintained. To verify the validity of analysis and methodology proposed in this article, seven representative SWFFSMs are chosen for verification at no load by the finite-element analysis (FEA) while a 24s/17p SWFFSM with the highest torque density is chosen for further verification at on-load conditions by the FEA and experiments.

Lumped parameter magnetic equivalent circuit model for design of segmented PM consequent pole flux switching machine

PurposeThe purpose of this paper is to investigate an alternative simplified analytical approach for the design of electric machines. Numerical-based finite element method (FEM) is a powerful tool for accurate modelling and electromagnetic performance analysis of electric machines. However, computational complexity, magnetic saturation, complex stator structure and time consumption compel researchers to adopt alternate analytical model for initial design of electric machine especially flux switching machines (FSMs).Design/methodology/approachIn this paper, simplified lumped parameter magnetic equivalent circuit (LPMEC) model is presented for newly developed segmented PM consequent pole flux switching machine (SPMCPFSM). LPMEC model accounts influence of all machine parts for quarter of machine which helps to reduce computational complexity, computational time and drive storage without affecting overall accuracy. Furthermore, inductance calculation is performed in the rotor and stator frame of reference for accurate estimation of the self-inductance, mutual inductance and dq-axis inductance profile using park transformation.FindingsThe developed LPMEC model is validated with corresponding FEA using JMAG Commercial FEA Package v. 18.1 which shows good agreement with accuracy of ∼98.23%, and park transformation precisely estimates the inductance profile in rotor and stator frame of reference.Practical implicationsThe model is developed for high-speed brushless AC applications.Originality/valueThe proposed SPMCPFSM enhance electromagnetic performance owing to partitioned PMs configuration which make it different than conventional designs. Moreover, the developed LPMEC model reduces computational time by solving quarter of machine.

Effective Computational Techniques of Reducing Cogging Torque in Permanent Magnet Flux Switching Machine

In this paper various techniques are applied to decrease cogging torque of overlap winding of permanent magnet flux switching machine (PMFSM) with 24-slot/16-pole. Due to its unique design PMFSM have mechanical strength, batter torque density and high flux linkage is a suitable candidate for electrical vehicle (EV). The major disadvantage of this design are high cogging torque and torque ripple while keeping constant average torque. Four various techniques are applied to minimalize the cogging torque of PMFSM to design it more suitable for PHEV applications. The legitimacy of these techniques has been observed by 3-D and 2-D simulations. Among all techniques the optimal result of Hybrid_C2 technique which reduces the cogging torque 66.28% with 0.7% loss in average torque.

Effective Computational Techniques of Reducing Cogging Torque in Permanent Magnet Flux Switching Machine

In this paper various techniques are applied to decrease cogging torque of overlap winding of permanent magnet flux switching machine (PMFSM) with 24-slot/16-pole. Due to its unique design PMFSM have mechanical strength, batter torque density and high flux linkage is a suitable candidate for electrical vehicle (EV). The major disadvantage of this design are high cogging torque and torque ripple while keeping constant average torque. Four various techniques are applied to minimalize the cogging torque of PMFSM to design it more suitable for PHEV applications. The legitimacy of these techniques has been observed by 3-D and 2-D simulations. Among all techniques the optimal result of Hybrid_C2 technique which reduces the cogging torque 66.28% with 0.7% loss in average torque.

Flux-Regulation Principle and Performance Analysis of a Novel Axial Partitioned Stator Hybrid-Excitation Flux-Switching Machine Using Parallel Magnetic Circuit

This article proposes a novel hybrid-excitation flux-switching (HEFS) machine with axial partitioned stator (APS) arrangement, which can achieve the independent accommodation of armature winding and field-excitation winding, thus enhancing the field-excitation capability and improving the winding heat dissipation. More importantly, a particular parallel-magnetic-circuit hybrid-excitation pattern consisting of the axial and radial magnetic paths is innovatively developed in the HEFS machine, which is an effective solution for improving the flux-regulation ability. Consequently, the PMC-based flux-regulation principle is comprehensively illustrated. Moreover, by investigating the flux-regulation characteristics of three structural feasible APS-HEFS topologies, the bilateral complementary structure is finally determined as the preferred option. By using the multiobjective optimization method and the three-dimensional finite-element analysis (FEA), the dimensional parameter optimization design of the proposed machine is conducted, and the performance comparison with conventional HEFS counterparts is also carried out to prove the flux-regulation superiority of the proposed design. Finally, a prototype is fabricated for experimental testing, and the measured results are in good agreement with the FEA, which verifies the validity of the proposed APS-HEFS topology and its theoretical flux-regulation principle analysis.

Computationally efficient steady‐state finite element simulation of multiphase PM AC machines

In this study the authors propose a generalised procedure for computationally efficient steady-state finite element (FE) simulation of symmetrical multiphase permanent magnet (PM) AC machines with an arbitrary number of phases. The procedure is based on newly derived general equations for phase waveform reconstruction that fully exploit the phase symmetry of multiphase electrical machines. This result can be used to reconstruct the full electrical period of any phase waveform from the smallest possible number of magnetostatic FE simulations executed within the minimum angular displacement of the rotor. Reconstruction of phase waveforms is done during post-processing and does not contribute to the execution time of FE simulations. The applicability of the proposed method is demonstrated by deriving specific equations for two-phase, three-phase, five-phase and six-phase machines. Results of classical time-stepping and newly proposed computationally efficient FE simulation are presented for four rotor PM flux switching machines with the different number of phases. Obtained results show that the relative reduction of simulation time increases with the number of machine phases.

Torque characteristics of high torque density partitioned PM consequent pole flux switching machines with flux barriers

Unique double salient structure of Permanent Magnet Flux Switching Machines (PMFSM) with both Concentrated Armature Winding (CAW) and Permanent Magnet (PM) on stator attract researcher's interest for high speed brushless application when high torque density (T den ) and power density (P den ) are the primal requirements. However, despite of stator leakage flux, high rare-earth PM usage, PMFSM is subjected to slot effects due to presence of both PM and CAW in stator and partial saturation due to double salient structure which generates cogging torque (T cog ), torque ripples (T rip ) and lower average torque (T avg ). To overcome aforesaid demerits, this paper presents Partitioned PM (PPM) Consequent Pole Flux Switching Machine (PPM-CPFSM) with flux barriers to enhance flux modulation, curtail PM usage and diminish stator leakage flux which reduces slotting effects and partial saturation to ultimately reduces T cog and T rlp . In comparison with the existing state of the art, proposed PPM-CPFSM reduces 46.53% of the total PM volume and offer T avg higher up to 88.8%, suppress T rlp maximum up to 24.8%, diminish T cog up to 22.74% and offer 2.45 times T den and P den . Furthermore, torque characteristics of proposed PPM-CPFSM is investigated utilizing space harmonics injection i.e. inverse cosine, inverse cosine with 3 rd harmonics and rotor pole shaping techniques i.e., eccentric circle, chamfering and notching. Detailed electromagnetic performance analysis reveals that harmonics injection suppressed T cog maximum up to 83.5%, T rip up to 40.72% at the cost of 4.71% T avg . Finally, rotor mechanical stress analysis is utilized for rotor withstand capability and 3D-FEA based Coupled Electromagnetic-Thermal Analysis (CETA) for thermal behavior of the developed PPM-CPFSM. CETA reveals that open space along PPM act as cooling duct that improve heat dissipation.

A new fault-tolerant switched flux machine with hybrid permanent magnets

This paper put forward a new fault-tolerant hybrid switched-flux PM (HSFPM) machine design employing the synergy of NdFeB and Ferrite Magnet. The key of the proposed HSFPM designed machine is the unique design E-core laminated stator with the hybrid magnet to ensure a drastic reduction of NdFeB magnet without compromising the output performances and efficiency in the conventional SFPM machine design to avert the huge demand of NdFeB and its associated volatile high price increase. Additionally, the fault-tolerant stator teeth designed principle implemented in the proposed HSFPM machine provides enhanced segregation among the various phases and ensures continuity of operation with acceptable operating performance under fault-condition. For fair evaluation and comparison, both the proposed HSFPM and the conventional SFPM (CSFPM) machine have the same slot-pole combination, winding arrangements, and stator/rotor dimensions except for the unique outer-stator of the proposed design. Meanwhile, compared to the CSFPM machine, the proposed HSFPM machine design makes use of only 60% of the PM (NdFeB) length. Finally, the evaluation of the no-load in conjunction with the load condition performances was carefully investigated by the Finite Element Method (FEM) of the ANSYS Maxwell software. The results depicted that the proposed HSFPM exhibits similar sinusoidal back electromotive force, comparable output torque, and slightly higher efficiency compared to that of the CSFPM machine.

Development of single phase 12S‐6P FEFSM and field‐oriented control algorithm based on the effect of rotor position on stator flux pair linkage

Field excited flux-switching machines (FEFSMs) falls into advance category of synchronous machine. However, most FEFSM structures are comprised of overlapped stator windings, which ends up in taking more space, more copper losses and material costs. Moreover, FSM works on flux-switching principle which made the implementation of field-oriented control (FOC) significantly complex. This study proposes a new structure of single phase FEFSM having segmented rotor and non-overlapped windings for the elimination of above-mentioned drawbacks. Additionally, this study also presents a mechanism to implement FOC without the need of magnetomotive force (MMF) in the rotor. Design of this new topology and its performance characteristics have been analysed through two-dimensional finite element analysis. FOC algorithm has been designed on the basis of sinusoidal variation of stator flux linkage due to rotor position. Experimental results show staggering performance efficiency of about 96% in terms of torque generation when compared to simulation results. Thus, verified the successful implementation of the proposed algorithm on the designed prototype.

A Novel Analysis on a New DC-Excited Flux-Switching Machine Using Modified MEC Method for Ground Power Unit Application

This article presents a novel analysis on a new DC-Excited Flux-Switching Machine (DC-FSM) for Ground Power Unit (GPU) application. The performance of machine under different structures can be studied by a flexible Magnetic Equivalent Circuit (MEC), where the core non-linearity can be fixed on the material B-H curve. The model accuracy can also be adjusted arbitrary by determining the number of proposed MEC elements (flux tubes) for a given structure. The performance analysis of two sample DC-FSMs as two high-frequency 120 V generators is performed by the proposed MEC and validated by 2D and 3D FEM based simulations. The obtained results show a very good improvement in processing time with valuable accuracy. In general, introducing a new DC-FSM for the GPU application and analyzing its performance by proposing a modified MEC approach are the paper novelties which are studied in this work. Since the suggested MEC is more flexible than FEM, it is recommended for designing, modeling, and optimization purposes.

Analytical validation of novel consequent pole E‐core stator permanent magnet flux switching machine

Flux switching machines (FSMs) encompass unique features of conventional direct current machine, permanent magnet (PM) synchronous machine and switch reluctance machine. Permanent magnet FSM (PMFSM) is capable of high torque density and applicable for high-speed application, however conventional PMFSM exhibits demerits of high PM volume, high torque ripples and significant stator flux leakage. In this paper, a novel consequent pole E-core stator PMFSM is proposed and compared with conventional topology utilising 2D finite-element analysis (2D-FEA). Finite-element analysis revealed that proposed design enhanced flux modulation effects by introducing flux bridges and flux barriers as a result reduced cogging torque by reducing 46.53% of the total PM volume, reduce torque ripples by reducing PM slot effects and reduce flux leakage utilising flux bridges in the stator. Furthermore, analytical model for flux linkages, cogging torque, mechanical torque, no load and on-load magnetic flux density (MFD) is developed for initial design of conventional and proposed model. 2D analytical methodologies resolve equivalent magnetic circuits for open-circuit flux linkages, Fourier analysis for cogging torque, Laplace equations for MFD and Maxwell stress tensor for mechanical torque. Finally, results obtained from 2D-FEA and analytical methodologies are validated and compared.

A Flux-Controllable NI HTS Flux-Switching Machine for Electric Vehicle Applications

This paper deals with a flux-controllable NI HTS flux-switching machine (FSM) for electric vehicle (EV) applications. In a variable-speed rotating machine for EVs, such as electric buses, electric aircraft and electric ships, an electric motor capable of regulating the flux offers the advantage of constant output operation. In general, conventional HTS rotating machines have excellent flux-regulation performance, because they excite an HTS field coil. However, it is difficult to ensure any flux-regulation capabilities in HTS rotating machines using HTS field coils that apply the no-insulation (NI) winding technique, due to the inherent charge and discharge delays in these machines. Nevertheless, the NI winding technique is being actively researched as a key technology for the successful development of HTS rotating machines, because it can dramatically improve the operational stability of HTS field coils. Therefore, research to implement an HTS rotating machine with flux-regulation capabilities, while improving the operating stability of the HTS field coil using the NI winding technique, is required for EV applications. In this paper, we propose an HTS rotating machine with a flux switching structure, a type of topology of a rotating machine that is being actively studied for application to the electric motors used in EVs. The proposed HTS flux-switching machine (FSM) uses NI field coils, but additional field windings are applied for flux regulation, which enables flux control. In this study, an NI HTS field coil was also fabricated and tested because the characteristic resistance value should be used for the design and characteristic analyses of machines which utilize an NI coil. The simulation model used to analyze the flux-regulation performance capabilities of the NI HTS FSM were devised based on the characteristic resistance values obtained from a charging test of the fabricated NI HTS field coil. This study can provide a good reference for further research, including work on the manufacturing of a prototype NI HTS FSM for EV applications, and it can be used as a reference for the development of other HTS rotating machines, such as those used in large-scale wind power generation, where flux-regulation capabilities are required.

A New Outer Rotor Permanent Magnet Flux Switching Machine using Segmental Rotor for Electric Scooter

The use of brushes electric motors for propulsion of electric vehicles have come to stay not because of its impressive innovation but mainly due to economic and environmental imperatives. Internal Permanent Magnet Synchronous Motors (IPMSMs) and Flux Switching Machines are being employed in electric vehicles to improve vehicles torque and speed and their performances have proved excellent for gas emission reduction or no fuel usage at all. This paper presents a new outer rotor permanent magnet flux switching machine enveloped by eternal non-ferromagnetic segmental rotor to secure the structure while rotating at very high speed. The segmental rotor is simple and easy to manufacture at low cost employing less material. The geometric topology of this outer rotor is introduced using Eclimo electric scooter parameters. Two dimensional finite element analysis (2D-FEA) models is used to investigate four machine performances namely flux distribution, cogging torque, induced back-EMF, torque and speed versus power characteristics. Results proved high torque and high power sustainability for long distance travel.

Design and performance analysis of various high torque segmented rotor HE‐FSM topologies for aircraft applications

Electrical machines for aircraft applications require basic characteristics such as lightweight, high reliability, fault tolerance ability, and torque power and higher densities. Correspondingly, hybrid excitation flux switching machines (HE-FSMs) are capable of producing significant characteristics of high torque and power by improving flux strengthening in the iron core. However, magnetic flux cancellation and leakage in HE-FSMs cause the reduction of flux linkage created by permanent magnet (PM) and field excitation (FE), which leads to deterioration of electromagnetic torque. This study presents magnetic flux performance and comparison of various topologies of HE-FSMs by employing different positions of PMs and FE coils on the stator core. The purpose of a segmented rotor is to deliver a well-defined electromagnetic flux pathway for carrying magnetic flux to nearby armature coil on stator with rotor rotation to improve the flux strengthening. Moreover, magnetic performances of various proposed HE-FSMs at different positions of PMs are investigated and compared based on 2D finite element analysis. Subsequently, the enhanced HE-FSM III has successfully achieved flux strengthening of 22%, torque of 54% and power of 61% more than initial design of HE FSM I, respectively. In conclusion, the proposed HE-FSM structures show the capability to match high torque and power for aircraft applications.

Linear Machines for Long Stroke Applications—A Review

This document reviews the current state of the art in the linear machine technology. First, the recent advancements in linear induction, switched reluctance and permanent magnet machines are presented. The ladder slit secondary configuration is identified as an interesting configuration for linear induction machines. In the case of switched reluctance machines, the mutually-coupled configuration has been found to equate the thrust capability of conventional permanent magnet machines. The capabilities of the so called linear primary permanent magnet, viz. switched-flux, flux-reversal, doubly-salient and vernier machines are presented afterwards. A guide of different options to enhance several characteristics of linear machines is also listed. A qualitative comparison of the capabilities of linear primary permanent magnet machines is given later, where linear vernier and switched-flux machines are identified as the most interesting configurations for long stroke applications. In order to demonstrate the validity of the presented comparison, three machines are selected from the literature, and their capabilities are compared under the same conditions to a conventional linear permanent magnet machine. It is found that the flux-reversal machines suffer from a very poor power factor, whereas the thrust capability of both vernier and switched-flux machines is confirmed. However, the overload capability of these machines is found to be substantially lower than the one from the conventional machine. Finally, some different research topics are identified and suggested for each type of machine.

Control System for a Single-Phase DC-Excited Flux-Switching Machine With a Torque Ripple Reduction Scheme

Single-phase dc-excited flux-switching machines (DCFSMs) are suitable for operations in harsh environments and cost-sensitive applications due to their rugged structure. However, the practical application of DCFSMs is limited because significant torque ripple is generated in them as the armature current commutates. However, with a marginal modification to the rotor structure, the single-phase DCFSM exhibits a unique property that its reluctance torque is complementary to its electromagnetic torque. A significant reluctance torque can be generated by the field current near the commutation positions. To explore the characteristics of the complementary torque, this paper presents a speed control system with a torque ripple reduction scheme for single-phase DCFSMs. In this scheme, the armature and field currents are controlled with precalculated profiles such that the reluctance torque compensates for the loss of the electromagnetic torque near the commutation positions. The experimental results indicated that with the proposed control scheme, the maximum torque ripple reduced to 56% near the commutation positions when the machine provided the rated torque. Moreover, because the studied DCFSM generated highly linear torque, satisfactory speed control performance was achieved.

Performance modifications and design aspects of rotating flux switching permanent magnet machines: a review

Permanent magnet flux switching machines (FSPMs) have attracted considerable attention in recent years, due to their outstanding characteristics to operate as brushless AC drives. Since they are relatively new, there are particular challenges not only for their design procedure but also for their operating principle comprehension. This study highlights several issues on FSPMs from the basic operation description to their key design points. After a comprehensive description of FSPMs working principles, a detailed discussion is presented on their armature winding design. In addition, this study reviews various methods for their performance modification, including torque profile, electromotive force, and loss characteristics. This study also surveys field regulation technologies, modelling and design optimisation methods applied to FSPMs along with their fabrication and cost issues.