Short Flux Path Research Articles

Introducing a 12/10 Induction Switched Reluctance Machine (ISRM) for Electric Powertrains

The induction switched reluctance machine (ISRM) is a novel electric machine that integrates the switched reluctance machine (SRM) with rotor inductive conductors to enhance performance in electric vehicle (EV) powertrain applications. In this topology, the rotor conductors act as a magnetic shield, diverting magnetic flux and preventing magnetic field lines from penetrating the rotor body. By engineering this design, short magnetic flux paths are created in both the stator and rotor of the electric machine. Since its recent introduction, the ISRM represents an emerging technology in the early stages of development. Similar to conventional SRMs, the ISRM can take on various topologies with different stator and rotor pole numbers. Minimizing rotor copper loss is a critical consideration in the ISRM design process. This paper examines two distinct ISRM topologies (12/10 and 12/8), and their characteristics are analyzed using the finite element method. Simulation results, including power density, torque density, efficiency, and copper loss, are presented and compared. Finally, the optimal ISRM topology is proposed for hybrid electric powertrains.

Electromagnetic and Thermal Analysis of a 6/4 Induction Switched Reluctance Machine for Electric Vehicle Application

In this paper, an oil-cooling induction switched reluctance machine (ISRM) is offered. The stator and rotor of the electric machine are non-segmental. However, by placing coils on the rotor, a short magnetic flux path is achieved in the rotor and stator cores. As a result, a higher torque with lower losses is generated. This configuration can be used in high-power electric motors for electric and hybrid vehicles. ISRM is a novel machine and there is a lack of access to its operation and data characteristics. ISRM can be designed in different configurations with various stator and rotor pole numbers and winding strategies. In this study, an oil-cooling three-phase ISRM with 6 stator poles and 4 rotor poles was considered. Firstly, a 2D finite element model of it is created, and its magnetic properties extracted, the flux path, torque and efficiency of the ISRM are calculated, and the results are presented. Secondly, the thermal performance of the motor is analyzed using ANSYS Motor-Cad software. Finally, a prototype of the ISRM and its appropriate drive with the oil cooling system is built and tested. The experimental results and conclusions which prove the ability of the presented machine are presented in the last parts of the paper.

Electromagnetic Characteristics of Dual-Air-Gap Surface Permanent Magnet Synchronous Motor

This paper introduces a novel dual-air-gap surface permanent magnet synchronous motor (DAG-SPMSM) and investigates its electromagnetic characteristics. The motor comprises two stators (inner and outer) and a single rotor with permanent magnets on both sides (inner and outer). The magnets are arranged in a zig-zag configuration to isolate the inner and outer stator and rotor magnets. Additionally, a magnetic shield is incorporated into the rotor to further isolate the rotor magnetic flux, which results in a localized short flux path that can reduce core loss. The insertion of the magnetic shield also affects the flux path, reducing torque ripple. The electromagnetic characteristics, such as flux path, flux density, and torque, are analyzed using finite element analysis. The effectiveness of using a magnetic screen is also evaluated, and simple experiments are conducted to validate the observed characteristics of the proposed motor.

A novel axial air‐gap transverse flux switching PM generator: Design, simulation and prototyping

AbstractWind energy as the cleanest source of renewable energy requires a highly efficient lightweight generator that provides maximum power density while having the least vibration noise and maintenance. In this study, an axial air gap transverse flux machine is presented, and all excitation sources are located in the stator. This structure provides lower core loss, weight and cost due to the full utilisation of the permanent magnets, SMC‐free structure and short magnetic flux path. In fact, by combining the features of a flux‐switching machine into a transverse flux generator with an axial air gap, it is possible to improve the performance of a direct‐drive wind turbine generator by overcoming traditional structures' challenges. To analyse the axial transverse flux switching permanent magnet generator performance characteristics, 3D finite element simulations have been performed, which have been validated by comparing them to the practical results of a single‐phase prototype. The results are in agreement with an acceptable error that is caused by manufacturing uncertainties.

Design Optimization of a Switched Reluctance Machine with an Improved Segmental Rotor for Electric Vehicle Applications

In this article, a switched reluctance machine (SRM) with six phases and a misaligned segmental rotor is proposed. The segmental rotor has an internal 15-degree misalignment, allowing the SRM structure to be a one-layer 2D structure with a short flux path structure. The proposed SRM produces a relatively low torque ripple by exciting two phases simultaneously. Additionally, an optimization method is applied, allowing for the maximum torque position of one phase to be aligned with the zero-torque position of the adjacent phase. The finite element method (FEM) is used to analyze and design the proposed SRM and to simulate the proposed liquid cooling system. The static torque waveforms are analyzed, and the dynamic torque waveforms are simulated with a drive using SiC MOSFETs. Finally, a prototype is manufactured, and the experiment is performed to validate the design and simulation results.

Fault‐Tolerant Characteristics Analysis of U‐Shaped Rotor Stator Excitation Generator for Vehicle Applications

In order to improve the reliability of the traditional doubly salient electro‐magnetic generators (DSEG) and realize the isolation of interphase magnetic circuit, a U‐shaped rotor stator excitation generator (UR‐SEG) for vehicle applications is proposed in this paper. The machine has the interphase physical isolation and short flux path structure because of the U‐shaped rotors. According to the theoretical analysis of the fault‐tolerant characteristics of this UR‐SEG, the characteristic of the phase electromotive force (EMF) of the UR‐SEG completely overlaps with the EMF of front and rear phase in the entire power generation stage is revealed. Then the flux linkage, EMF, output voltage of both normal and faulty states are comparative investigated using the two‐dimensional finite element method (FEM). The output characteristics of the normal state and four faulty states of the machine with different exciting currents are researched, and the influence rules of fault on output characteristics are obtained. Finally, the outstanding fault‐tolerant characteristics of the UR‐SEG were verified by the experimental results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Preliminary Evaluation of Induction Switched Reluctance Machine (ISRM) for Electric Vehicle Application

In this paper, a novel electric machine, Induction Switched Reluctance Machine (US patent-US20170370296A1) is introduced, and its preliminary performance is evaluated. The innovation is based on placing windings on the rotor, in order to create short magnetic flux paths in the rotor and stator core of the electric machine. As a result, a higher torque with lower copper and iron losses is generated. Like other ideas, there are unknown aspects of this electric machine, such as thermal and mechanical properties, that should be studied. A comprehensive research program is required to analyze and design an Induction Switched Reluctance Machine with an optimized configuration. This electric machine could be designed with different pole numbers and various winding strategies, and it is not possible to consider all configurations and aspects of it in this paper. Moreover, the size and the rated power of the machine can affect its properties. The purpose of this paper is to introduce, simulate and prototype a simple Induction Switched Reluctance Machine. This electric machine has an excellent potential to be implemented in the propulsion system of electric vehicles.

Experimental Validations of Hybrid Excited Linear Flux Switching Machine

Linear Flux Switching Machines (LFSMs) possess the capability to generate adhesive thrust force, thus problems associated with conventional rotatory electric machines and mechanical conversion assemblies can be eliminated. Additionally, the unique features of high force/power density, efficiency, and a robust secondary structure make LFSMs a suitable candidate for linear motion applications. However, deficiency of controllable air-gap flux, risk of PM demagnetization, and increasing cost of rare earth PM materials in case of PMLFSMs, and inherent low thrust force capability of Field Excited LFSMs compels researchers to investigate new hybrid topologies. In this paper, a novel Double-Sided Hybrid Excited LFSM (DSHELFSM) with all three excitation sources, i.e., PMs, DC, and AC windings confined to short moving primary and segmented secondary providing short flux paths is designed, investigated, and optimized. Secondly, unequal primary tooth width optimization and additional end-teeth at all four corners of the primary equip proposed design with balanced magnetic circuit and reduced end-effect and thrust force ripples. Thirdly, the measured experimental results of the manufactured proposed machine prototype are compared with corresponding simulated model results and shows good agreements, thus validating the theoretical study.

Performance investigation of doubly salient outer rotor switched reluctance motor using finite element analysis

PurposeThe automotive industry extensively uses switched reluctance motors (SRM) because of their excellent performance. The main purpose of this article is to investigate the design of a particular type of SRM called doubly salient outer rotor switched reluctance motor (DSORSRM) for electric vehicle application in this paper.Design/methodology/approachDifferent configurations of DSORSRM motor such as long flux path SRM, reduced flux path mutually coupled SRM and short flux path SRM (SF-SRM) are considered for investigation. The best configuration based on average torque is selected for further investigation by conducting an electromagnetic analysis. Also, in the proposed design, laminating material with low iron loss and superior performance characteristics is selected by doing electromagnetic analysis for SRM with M19, M660-50D, M-19 and M800-100A non-oriented laminating core material. Because vibrations are produced in DSORSRM devices as a result of changing induction, a mechanical analysis was performed to estimate the natural frequencies of vibration and the amplitudes that may lead to acoustic noises.FindingsSF-SRM configuration with three-phase, 12/10, 250 W, 48 V, 1,000 rpm is selected with the impact in the elimination of flux reversals and also has various salient features such as singly excited, no rotor windings, no permanent magnet, pure in construction and high starting torque. Still, this SRM suffers from vibration owing to changing induction. In lamination material selection, M19 is chosen as optimized material to obtain vibration reduction. Vibration analysis was performed for the optimized 12/10 SF-SRM with M19 lamination material, and the corresponding modes for the machine to operate with reduced vibration are analyzed. The current and speed characteristics of the prototype model for the DSORSRM motor are obtained and validated with finite element analysis (FEA) results.Originality/valueThe performed FEA result shows that the proposed DSORSRM with short flux path configuration produces a high average torque of 1.915 N m. The M19 lamination material gives a minimum iron loss of 9.056 W. The modal frequencies are estimated and validated with numerical equations.

A comparative study of switched reluctance motors with a single‐phase and a novel Synchronous double‐phase excitation mode

To obtain a short flux path and improve the torque performance, a double-phase excitation (DE) was generally used for switched reluctance motor (SRM). But the torque ripple of the SRM working under DE with traditional winding distribution increases because of the inconsistent electromagnetic field. To deal with this problem, an 8/6 SRM working under DE with novel winding distribution (DESRM) is proposed here. In order to comprehensively analyse the electromagnetic performance of DESRM, it is compared with a traditional single-excitation SRM and double-excitation SRM with traditional winding, in terms of air flux density, radial and tangential force components, inductance, torque, and losses. The theoretical and finite element analysis results reveal the cause of differences on torque and vibration of the motor as well as the mechanism of generating different motor performance. In addition, the analysis shows that the proposed DESRM generates a higher torque with a reduced torque ripple. Finally, a pair of prototypes with different winding configurations is designed and used to verify the theoretical analysis.

Modelling of High Torque Density Switched Reluctance Motors with Mutual Coupling

In this paper a method is introduced which models the resulting motor torque and current dynamics directly from the flux linkages. With the introduced method to process the flux linkage characteristics it is sufficient to calculate half of an electrical period to receive all information for modelling the system’s behaviour, even for both long and short flux path mutual coupling. The model is validated by 2D finite

Permanent magnet flux switching motor technology as a solution for high torque clean electric vehicle drive

<span lang="EN-US">A breakthrough in this century has been the development of electric vehicle which is propelled by electric motor powered by electricity. Already, many electric motors have been used for electric vehicle application but performances are low. In this paper, a permanent magnet motor technology using unconventional segmented rotor for high torque application is presented. Unlike conventional motors, this design, flux switching motor (FSM) is an advance form of synchronous machine with double rotating frequency. It accommodates both armature winding and flux source on the stator while the rotor is a simple passive laminated sheet steel. Conventionally, rotor of the maiden FSM and many emerging designs have focused on the salient pole, this design employs segmented rotor. Segmented rotor has advantages of short flux path more than salient rotor pole resulting in high flux linkage. Geometric topology of the proposed motor is introduced. It consists of 24Stator-14Pole using PM flux source with alternate stator tooth armature winding. The 2D-FEA model utilized JMAG Tool Solver to design and analyze motor’s performance in terms of torque with average torque output of 470Nm. The suitability of segmented outer-rotor FS motor as a high torque machine, using permanent magnet technology is a reliable candidate for electric vehicle.</span>

Characteristics Analysis and Comparison of Conventional and Segmental Rotor Type 12/8 Switched Reluctance Motors

This paper proposes a novel 12/8 switched reluctance motor (SRM) with segmental rotor for vehicle cooling fan application. Unlike conventional SRMs, the proposed motor adopts one body stator with hybrid stator poles and segmental rotor structures, thereby making the motor operate in short flux paths and parts of the flux paths magnetically isolated between the phases. Therefore, compared with conventional SRMs, the proposed structure not only improves the output torque density and reduces the magneto-motive force requirement and core losses of the motor, but also inherits the advantages of conventional SRMs like flexible control as well as the adaptability in harsh environment. To verify the proposed structure, a finite element method is employed to get characteristics of the proposed SRM. Meanwhile, a conventional 12/8 SRM, which has been used for vehicle cooling fan application, is also analyzed for comparison. Furthermore, the prototypes for the conventional and proposed 12/8 SRMs are manufactured and tested. Finally, the simulation and experimental results are presented and analyzed to verify the effectiveness of the proposed SRM.

A Non-segmental Outer Rotor Switched Reluctance Machine for In-Wheel Electric Vehicle Application

In this paper, an outer rotor switched reluctance machine with a non-segmental rotor and short flux path is studied. In this topology, the rotor cage could be eliminated and just an external housing is required to keep the rotor. This configuration can alleviate the motor assembly for in-wheel electric vehicle application. As a result, a smaller air gap between rotor and stator could be achieved in mass production. In this research, for the first time, the effect of implementing a non-segmental rotor on the flux path and the torque capability of segmental outer rotor switched reluctance machine is investigated. Using finite element method, the machine is analyzed and the torque profile and the flux path of the machine are compared with the segmental outer rotor switched reluctance machine. Finally, a motor prototype is implemented and tested.

Design and Analysis of a Novel Bearingless Segmented Switched Reluctance Motor

A novel bearingless segmented switched reluctance motor (BSSRM) is proposed in this paper to solve the coupling problem of the traditional bearingless switched reluctance motor (BSRM). Different from traditional BSRMs, the proposed BSSRM adopts the double stator and segmented rotor structure, thereby making the motor operate in short flux paths and the magnetic flux path isolated between torque and suspension system. On the basis of introducing the structure and working principle of the BSSRM, the mathematical model of torque and suspension force is deduced. The 2D finite element simulation model is established by the Ansoft software. The influence of structural parameters on torque and suspension system is analyzed, and its electromagnetic characteristic and decoupling characteristic are analyzed. Compared with the double stator bearingless switched reluctance motor (DSBSRM), the BSSRM not only improves the torque and suspension output but also weakens the coupling between torque and suspension system. Finally, the simulation results verify the effectiveness of the BSSRM.

Principle and design of a novel axial flux-switched reluctance motor with short flux path

Principle and design of a novel axial flux-switched reluctance motor with short flux path

Preliminary Design Analysis of a New Field Excitation Flux Switching Machine with Segmental Rotor and Non-overlap Winding

Recently, a three-phase Field Excitation Flux Switching Motor (FEFSM) with salient rotor structure has been introduced with their advantages of easy rotor temperature elimination and controllable FEC magnetic flux particularly meet for high torque, high power as well as 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. Therefore, a new structure of a single-phase FEFSM using segmental rotor with non-overlap windings is proposed. Segmental rotor and non-overlap windings are the clear advantages of these topologies as the copper losses gets reduce and rotor becomes less weight as well as more robust. Detailed analysis on winding arrangement test analysis, armature and FEC flux linkage, back-EMF and average torque characteristics have been performed by using 2D Finite Element Analysis (FEA) through JMAG version 15 software. The results show that the proposed motor with segmental rotor and non-overlap windings produce short flux path, high flux linkage and the highest torque capability achieved is 0.91 Nm.

A High Torque Segmented Outer Rotor Permanent Magnet Flux Switching Motor for Motorcycle Propulsion

Electric scooters also known as electric motorcycle are viable and personal means of road transportation have been making their ways into the world markets now because in them, combustion engine with the use of fuel oil for propulsion have been completely eliminated for economic and environmental imperatives. Electric motor which converts electrical energy into mechanical energy is used to overcome the complication of combustion engine. As it is, everyone is opting for combustion engine free and fuel-less type of vehicle. For this reason, manufacturers have exhibited interest, making research on electric motor very attractive. Meanwhile, surface permanent magnet synchronous motor (SPMSM) has been successfully developed having output torque of 110 Nm, the assembly of motor lacked mechanical strength between the rotor yoke and the mounted permanent magnet (PM) which heats up during speed operation, resulting to poor performance. To overcome the challenges laced with SPMSM, this paper presents a novel design of 24 stator 14 pole outer rotor-permanent magnet flux switching motor (SOR-PMFSM) capable of high torque and high performance. It employs an unconventional segmented rotor which has short flux path flow. It also embraces alternate stator tooth windings to reduce material cost. Design specifications and restriction with input DC current are the same with SPMSM. The 2D-FEA by JMAG, version 14 is used to examine the performance of the proposed motor in terms of cogging torque, back-emf, average torque, power and efficiency. Preliminary results showed that torque, power output and efficiency of the proposed motor are 1.9Nm times, 5.8kW times more than SPMSM and efficiency of 84% thus, can sustain acceleration for long distance travel.

Introductory assessment of a novel high‐torque density axial flux switched reluctance machine

A novel structure of switched reluctance machines (SRMs) is proposed in this study. The proposed structure uses the advantages of the axial flux path, short flux path, segmental rotor, and flux reversal free stator machines all together to improve the torque density of the SRMs. The main geometrical, electrical and physical specifications are presented. In addition, some features of the proposed structure are compared with those of a state-of-the-art radial flux SRM, considered as a reference machine. Achieved results reveal that, compared with the reference machine, the proposed machine delivers about the same torque, albeit employing considerably lower volume and active material mass. These make the proposed structures a potentially proper candidate for traction and propulsion applications demanding high-torque density machines.

Electromagnetic evaluation of an in-wheel double rotor axial-flux switched reluctance motor for electric traction

In this paper, a novel in-wheel double rotor axialflux switched reluctance motor for electric traction is presented. The proposed double rotor axial-flux switched reluctance motor has a particular disposition of the stator and rotor poles that provides short flux path without flux reversal. The ferromagnetic pieces of the stator and the rotor are built using soft magnetic composites. Electromagnetic analysis is performed using three dimensional finite element analyses, 3D FEA. Matlab-Simulink simulation coupled with the results of finite element analysis proves that the proposed motor drive is suitable for the propulsion of a given E-scooter.