Flux-switching Permanent Magnet Machine Research Articles

Design and Analysis of a Novel E-Core Axial Field Flux-Switching Permanent Magnet Machine

A simple analytical method is developed to design novel axial field flux-switching permanent magnet (AFFSPM) machines in terms of back electromotive force (back-EMF) and cogging torque. The machine is proposed with E-shaped laminated segments in the stator. Some major parameters are originally designed with reference to those of a 12/10-pole U-core AFFSPM machine, including the rotor tooth width, the split radio of the inner diameter to outer diameter of the stator and the stator parameters. In this paper, they are investigated and optimized for attaining essentially sinusoidal back-EMF and low cogging torque by 3-D finite element method (FEM). Compared with 12/10-pole AFFSPM machine, it is shown that the volumes of magnets are almost reduced by 30%, while the similar output torque at the rated current can be obtained, and the ratio of the mutual-to self-inductance is largely reduced, which indicates the proposed motor has better fault-tolerant capability.

Cogging Torque Analysis of Novel Dual-Rotor Axial Field Flux-Switching Permanent Magnet Machine

The cogging torque of a novel dual-rotor axial field flux-switching permanent magnet (DRAFFSPM) machine is investigated in this paper. The analytical equation of the DRAFFSPM machine is deduced. Based on 3D finite element method, the influences of the design parameters on the cogging torque are analyzed. The H-shaped stator tooth with slot chamfer is proposed and the slot opening width and chamfer thickness are optimized to reduce the cogging torque. It shows that the cogging torque is the minimum when the stator tooth width and stator magnet width equal to 8o and 7.5o mech., respectively. The cogging torque can be reduced by ~64% when the rotor pole width is 1.6 times that of the original design. The cogging torque can be reduced by ~80% when the chamfer is added in the stator slot.

Starting Performance of Linear Flux-Switching Permanent Magnet Machine Applied in Marine Direct Drive for Electric Propulsion Applications

A double-sided linear flux-switching permanent magnet machine applied in marine rudder direct drive applications is presented. The starting performances of the machine are calculated by finite element method. The simulation results of the proposed DLFSPM are verified by the experiment. The results have verified that the machine is suitability marine rudder direct drive applications.

Analysis and Optimization of Rotor-twisted Structure for 12/10 Alternate Poles Wound FSPM Machine for Electric Vehicles

Fault-tolerant capability, wide speed range and overload capability are required in electric motors used in electric vehicles. In this paper, based on the analysis of the all poles wound and alternate poles wound flux-switching permanent-magnet machines, an optimization method is studied to reduce torque ripple. The method takes account of both flux-leakage and cogging torque. The simulation result shows that the method can reduce the torque ripple effectively. This study lays the foundation for the further application of FSPM in electric vehicles.

Torque Density and Magnet Usage Efficiency Enhancement of Sandwiched Switched Flux Permanent Magnet Machines Using V-Shaped Magnets

This paper proposes a novel sandwiched switched flux permanent magnet (SSFPM) machine using V-shaped magnets for maximizing output torque and improving magnet usage efficiency. The operation principle of conventional 6/10-stator/rotor-pole SSFPM machine is firstly described. Such SSFPM machine and a novel one with V-shaped magnets are optimized and then compared with the conventional 12/10-stator/rotor-pole SFPM machine by two-dimensional (2-D) finite element analysis (FEA). It is found that the SSFPM machine with V-shaped magnets exhibits higher torque density and higher magnet usage efficiency. In addition, the influence of step-skew angle on the torque ripple suppression is investigated in the SSFPM machine with V-shaped magnets. The FEA predicted back-EMF, cogging torque, torque-current characteristic are validated by experiments on the prototype machines.

Design of Five-Phase Modular Flux-Switching Permanent-Magnet Machines for High Reliability Applications

This paper proposes and designs a new five-phase modular flux-switching permanent-magnet (M-FSPM) machine for high reliability applications. The key is the new machine topology which incorporates the concept of fault-tolerant teeth (FTT) to provide the desired decoupling among phases. The electromagnetic performances of the newly designed M-FSPM machines having 18 and 19 rotor poles are quantitatively analyzed including the flux, back-EMF, cogging torque as well as unbalanced magnetic force (UMF). The results show that the proposed M-FSPM machine not only retains the merits of stator-PM machines and multiphase machines, but also offers lower cost and higher fault-tolerant capability. Especially, the 10/19-pole one incorporates the merits of symmetric back-EMF and reduced cogging torque, while suffers from UMF. Two experimental M-FSPM machines are designed and built for exemplification. Experimental results of the prototypes are given to confirm the validity of the proposed machines.

Design and Analysis of a HTS Flux-Switching Machine for Wind Energy Conversion

This paper proposes a new high-temperature superconductor (HTS) flux-switching machine with the merit of high power density for the direct-drive wind energy conversion system. The key is to introduce HTS windings to replace permanent magnet material in the flux-switching permanent magnet machine. Also, the use of HTS field excitation windings can easily achieve constant output armature voltage under time-varying wind speeds. By using the finite element analysis, the machine performances are analyzed. Hence, the validity of the proposed machine is verified.

Study on a Long Primary Flux-Switching Permanent Magnet Linear Motor for Electromagnetic Launch Systems

Based on the principle of rotational flux-switching permanent magnet machines, a novel double-sided long primary flux-switching permanent magnet linear motor (FSPMLM) is proposed for electromagnetic launch systems (EMLS). Compared with traditional induction and synchronous linear machines used in EMLS, the proposed motor is more suitable for EMLS because of its high thrust density and simple structure of the secondary. First, the structure and operation principle of the proposed FSPMLM are given and analyzed. Second, considering the longitudinal end effect, the thrust components are analyzed and derived. According to the generation principle of the thrust components, the optimal methods, implemented to reduce the thrust ripple, are obtained and analyzed. In addition, a 2-D transient finite element method is used to investigate the dynamic electromagnetic characteristics of the FSPMLM and the process of electromagnetic launch. Finally, a prototype of single-sided FSPMLM is employed to validate the thrust performance of the proposed machine.

Cogging Force Reduction of Double-Sided Linear Flux-Switching Permanent Magnet Machine for Direct Drives

This study proposes a double-sided linear flux-switching permanent magnet machine for direct drives in precision servo applications. The method of asymmetry distribution of stator teeth (ADST) is introduced to reduce the cogging force. Moreover, cogging force, back-EMFs, and thrust force are calculated by using finite element analysis. In addition, the performance comparison is carried out to verify the accuracy and effectiveness of the method of cogging force reduction. Finally, the experiment confirms the reasonability and feasibility of the ADST method.

Permanent Magnet Flux-Switching Machine, Optimal Design and Performance Analysis

In this paper an analytical sizing-design procedure for a typical permanent magnet flux-switching machine (PMFSM) with 12 stator and respectively 10 rotor poles is presented. An optimal design, based on Hooke-Jeeves method with the objective functions of maximum torque density, is performed. The results were validated via two dimensions finite element analysis (2D-FEA) applied on the optimized structure. The influence of the permanent magnet (PM) dimensions and type, respectively of the rotor poles' shape on the machine performance were also studied via 2D-FEA.

Thrust Optimization of a Flux-Switching Linear Synchronous Machine With Yokeless Translator

Linear permanent magnet machines have been increasingly used in several applications that require high reliability and good dynamic characteristics. In this paper, a novel double-sided design of a 3φ permanent magnet flux-switching linear synchronous machine (FSLSM) with a yokeless translator is proposed. It is found that the proposed design can achieve more than 50% higher thrust than a conventional FSLSM and excellent linearity even under high excitation currents. Optimization of the proposed machine is performed using individual parameter optimization and is compared with results from global optimization using genetic algorithm (GA). Force analysis of the proposed design is performed to establish the mechanical integrity of the design. The proposed FSLSM is most suitable for long-stroke applications and intermittent oscillatory type applications.

Preliminary study on a 3D field permanent magnet flux switching machine - from tubular to rotary configurations

A permanent magnet flux switching (PMFS) machine has a simple rotor, whilst both magnets and coils are set in the stator, resulting in easy removal of heat due to both copper loss and eddy current loss in magnets. However, the volume of magnets used in PMFS machines is usually larger than in conventional PM machines, and leakage flux does exist at the non-airgap side. To make full use of the magnets and gain higher power density, a novel 3-dimensional (3D) field PMFS machine is developed. It combines merits of the tubular linear machine, external-rotor rotary machine and axial-flux rotary machine, hence, offers high power density and peak torque capability, as well as efficient utility of magnets owing to the unique configuration of triple airgap fields.

Reduction on Cogging Torque in Flux-Switching Permanent Magnet Machine by Teeth Notching Schemes

The cogging torque in flux-switching permanent magnet machines (FSPMs) is high due to its unique structure and high air-gap flux density. The cogging torque principle in FSPM is different from that in traditional PM machines, which can not be correctly predicted by analytical consideration. The aim of paper is to present the investigation on cogging torque principle in FSPM by analyzing the flux density distribution and a simple cogging torque reduction technique, i.e., teeth notching. Various kinds of notching schemes and their influence on cogging torque are examined along with instantaneous torque and average output torque at different load conditions. Numerical optimization process combined with finite-element analysis, which gives more preciseness to calculations, is performed to minimize cogging torque. The results show that the cogging torque circle depends on the real flux density distribution in the machine rather than the number of stator/rotor poles and the presented method can greatly reduce the torque ripple at only slight cost of average output torque.

Theoretical Research on New Laminated Structure Flux Switching Permanent Magnet Machine for Novel Topologic Plug-In Hybrid Electrical Vehicle

In this paper, a novel configuration for University of Technology Sydney (UTS) plug-in hybrid electric vehicle (PHEV) is introduced which has only one electric machine functioning as either a motor or generator at a time. For continuous working, more strict requests are made to the drive machine, mainly including good thermal dissipation capability, high torque density, great flux weakening ability, etc. One new laminated structure flux switching permanent magnet machine (LSFSPMM) is proposed in this paper, which stator and rotor are laminated in parallel to the axis. It can make full use of PM flux linkage and reduce the core loss particularly in the high excitation frequency. Based on the 2D model prediction by finite element algorithm (FEA), LSFSPMM has lower cogging torque, higher torque density, greater flux weakening ability, higher efficiency, etc., and hence it can be regarded as one ideal candidate for the UTS PHEV drive system.

Static Characteristics Analysis and Experimental Study of a Novel Axial Field Flux-Switching Permanent Magnet Generator

A novel axial field flux-switching permanent magnet (AFFSPM) machine with a doubly-salient structure is developed as a wind power generator. The electromagnetic characteristics of a 0.6 kW, 3-phase 12/10-pole AFFSPM machine, including the air-gap flux density distribution, open-circuit flux linkage, EMF, and winding inductances, etc., are investigated based on 3-D finite element (FE) analysis. A prototype is built to test the characteristics under both open-circuit and load conditions. The theoretical analysis is validated experimentally. It shows that the phase EMF is essentially sinusoidal, and the machine can not only be used as a wind power generator, but also as a permanent magnet brushless AC motor.

Novel Dual-Rotor Axial Field Flux-Switching Permanent Magnet Machine

A dual-rotor axial field flux-switching permanent magnet (DRAFFSPM) machine is proposed. A 3-phase 12/10-pole DRAFFSPM machine is designed. The topology and operation principle of the machine are described in detail. The power equation is deduced and the dimensions of the DRAFFSPM machine are determined. The electromagnetic characteristics including the air-gap field distribution, the PM flux-linkage, the back-EMF, and the cogging torque, are investigated based on the 3-D finite element (FE) analysis. The influences of the rotor pole width and the stator slot chamfer on the back-EMF and cogging torque are investigated. It shows that the sinusoidal back-EMF can be gained and the cogging torque can be greatly reduced.

Flux-Switching Machine With DC Excitation

This paper proposes a topology of flux-switching machine with dc excitation to improve the field-weakening capability of flux-switching machines. This dc-excited flux-switching machine preserves the structure of typical flux-switching permanent-magnet machines while replacing the permanent magnets with dc field windings. The combined advantages of this type of machine in torque production and field weakening are exhibited and validated by finite element analysis.

Energy Conversion Loops for Flux-Switching PM Machine Analysis

Induction and synchronous machines have traditionally been the first choice of automotive manufacturers for electric/hybrid vehicles. However, these conventional machines are not able anymore to meet the increasing demands for a higher energy density due to space limitation in cars. Flux-switching PM (FSPM) machines with their high energy density are very suitable to answer this demand. In this paper, the energy conversion loop technique is implemented on FSPM for the first time. The energy conversion technique is a powerful tool for the visualization of machine characteristics, both linear and nonlinear. Further, the technique provides insight into the torque production mechanism. A stepwise explanation is given on how to create these loops for FSPM along with the machine operation.

A Multi-Tooth Fault-Tolerant Flux-Switching Permanent-Magnet Machine With Twisted-Rotor

Flux-switching permanent-magnet (FSPM) machines have high torque density, high efficiency, and robust rotor structure. In order to achieve a high level of fault-tolerant capability and torque capability simultaneously, a multi-tooth 6-stator pole, 19-rotor pole fault-tolerant FSPM machine with twisted-rotor (MTFTFSPM-TR) is investigated and its design specifications including rotor pole numbers and gap width between the stator tooth and the fault-tolerant tooth are analyzed in this paper. Compared with a 12-stator pole, 14-rotor pole alternate poles wound fault-tolerant FSPM (FTFSPM) machine, the MTFTFSPM-TR shows higher torque density, better capability to inhibit short-circuit current, and lower cogging torque. Moreover, the twisted-rotor structure can achieve a symmetric and high sinusoidal back-electromotive force in each armature coil without the value reduction. Electromagnetic performance of the MTFTFSPM-TR has been verified experimentally on a prototype machine.

Torque Analysis of Permanent-Magnet Flux Switching Machines With Rotor Step Skewing

This paper investigates the torque characteristics of permanent-magnet flux switching (PMFS) machines with rotor step skewing. The cogging torque, torque ripple, and average output torque of a PMFS machine with a common stator and different rotor pole widths and rotor pole numbers are first established using two-dimensional (2-D) finite element analysis (FEA). A cost-effective rotor step skewing technique is then proposed to reduce the cogging torque and torque ripple of the machine with two different rotors. The results have revealed that the least step number and angle for optimal torque ripple mitigation of the PMFS machine are determined by the harmonic contents of the torque pulsation and the rotor pole number. The influences of load conditions on the machine torque characteristics are carried out by varying current excitations. The corresponding three-dimensional (3-D) FEA models are constructed and experimental prototypes are built for validations.