CERES :: Browsing by Author "Fei, Wei-Zhong"

Browsing by Author "Fei, Wei-Zhong"

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Open Access
Analytical investigation of sideband electromagnetic vibration in integral-slot PMSM drive with SVPWM technique
(Institute of Electrical and Electronics Engineers (IEEE), 2016-09-13) Liang, Wenyi; Fei, Wei-Zhong; Luk, Patrick Chi-Kwong
This paper provides a comprehensive investigation into the electromagnetic vibration associated with the sideband harmonic components introduced by space vector pulse width modulation applied in integral-slot permanent magnet synchronous machine drives. The critical permanent magnet, armature reaction, and sideband magnetic field components, which are the primary causes for sideband electromagnetic vibration in integral-slot permanent magnet synchronous machines, are identified. The analytical derivations of the magnetic field components are carried out, and amplitudes and frequencies of the resultant sideband radial electromagnetic force components are obtained. Furthermore, the proposed models of the sideband radial electromagnetic force components are incorporated into the vibration model to analytically evaluate the corresponding sideband electromagnetic vibrations of the machine. Experimental tests on an integral-slot permanent magnet synchronous machine drive are comprehensively performed to confirm the validity and accuracy of the analytical models. Not only can the validated analytical models offer insightful details in understanding the impacts of the key factors, such as operation conditions, machine geometry, electromagnetic and power converter parameters, on the sideband electromagnetic vibration, but also can be readily extended to assess and reduce noise in integral-slot permanent magnet synchronous machine drives.
Open Access
Analytical modeling of current harmonic components in PMSM drive with voltage-source inverter by SVPWM technique
(IEEE, 2014-04-22) Liang, Wenyi; Wang, Jianfeng; Luk, Patrick Chi-Kwong; Fang, Weizhong; Fei, Wei-Zhong
The sideband current harmonic components would inhere in permanent-magnet (PM) synchronous machine systems driven by a voltage-source inverter with space vector pulsewidth modulation (SVPWM). However, these harmonics could potentially deteriorate the overall performance of the drive system by increasing the resultant losses, torque ripple, and electromagnetic and acoustic noises. The main sideband harmonic voltages and currents in PM synchronous machine driven by voltage-source inverter with SVPWM technique, are analytically derived and expressed in both stator and rotor frame. The experimental results are carried out to underpin the validity of the analytical model. The analytical model could be employed to assess the influencing factors of current harmonics. In addition, it offers insightful guidance to the effective reductions of harmonic losses, torque ripples, and electromagnetic noises.
Open Access
The analytical study of stator tooth modulation on electromagnetic radial force in permanent magnet synchronous machines
(IEEE, 2020-12-02) Liang, Wenyi; Wang, Jianfeng; Luk, Patrick Chi-Kwong; Fei, Wei-Zhong
The electromagnetic radial force acting on the stator inner periphery will induce radial vibration and acoustic noise in permanent magnet machines. The radial force components are transmitted through the stator teeth to the yoke to introduce deformations. The influence of the stator tooth structure can be considered as an equivalent mechanical modulation effect on these electromagnetic radial force components. As a result, high-order electromagnetic radial force components can be modulated and potentially result in eminent stator low-mode vibration. In this paper, an analytical model is developed to offer an intuitive knowledge of stator tooth modulation effect on electromagnetic radial force. The validity of the proposed analytical method has been underpinned by both finite element analysis and experimental results. Such an effective yet simple analytical model can be of significant benefit for the stator radial vibration analysis. It can be employed to not only promptly investigate the stator radial vibration characteristics but also perform effective optimization on stator radial vibration reduction in permanent magnet machines
Open Access
Cogging torque suppression in a permanent-magnet flux-switching integrated-starter-generator
(2010-09-13T00:00:00Z) Jin, Meng-Jia; Wang, Y.; Shen, Jian-Xin; Luk, Patrick Chi-Kwong; Fei, Wei-Zhong; Wang, Can-Fei
Permanent-magnet flux-switching (PMFS) machine offers high torque density, impressive flux-weakening capability and mechanical ruggedness because of its distinctive configuration, and is potentially suitable for the application in automotive integrated-starter-generators (ISGs). However, the PMFS machine generally exhibits higher cogging torque compared with other machines commonly used in ISGs. Minimisation of the cogging torque in the PMFS machine for its utility in ISGs is therefore of particular importance. Four rotor topologies are proposed here as cost-effective means to suppress the cogging torque of a PMFS ISG. The validity of the proposed techniques has been confirmed by both two- dimensional finite-element analysis and experimental results. Moreover, the influence on the back electromagnetic force by these techniques is also investigated.
Open Access
Design and analysis of a new outer-rotor permanent-magnet flux-switching machine for electric vehicle propulsion
(2011-01-31T00:00:00Z) Fei, Wei-Zhong; Shen, Jian-Xin; Wang, Can-Fei; Luk, Patrick Chi-Kwong
Purpose − The purpose of this paper is to propose a new outer-rotor permanent- magnet flux-switching machine for in-wheel electric vehicle propulsion. The paper documents both the design procedure and performance investigation of this novel machine. Design/methodology/approach − The topology and preliminary sizing equations of the outer-rotor permanent-magnet flux-switching machine are introduced. Both the number and width of rotor poles are then optimized using comprehensive two-dimensional FEA. The machine losses are particularly investigated by transient FEA for the optimal design. Findings − A outer-rotor permanent-magnet flux-switching machine, with 12 stator poles and 22 rotor poles, is most suitable for the proposed application. The analytical sizing equations are quite efficient with a suitable level of accuracy for preliminary design. The optimal rotor pole width from the FEA results is nearly 1.3 times of the original one. The efficiency of the proposed machine under rated load is relatively low, nearly 85%, as a result of significant eddy current losses in the permanent magnets, which can be effectively suppressed by implementing segmentation. The predicted outstanding performance implies that by adopting magnet segmentation the proposed machine is a leading contender for direct electric vehicle drives. Research limitations/implications − The end effects, which could be considerable in the machine with relatively short axial length, are neglected during the study. In addition, due to the high current density and deep slot, proximity losses in the winding which is not issued in this research could be significant. All the limitations mentioned above could bring corresponding errors to the results. Although the research is concentrated on the application of electric vehicle drive, the techniques can be potentially employed for other applications. Practical implications − The practical implementation of such a machine is confronted with several mechanical hurdles, especially the thermal issues which can be addressed by implementing innovative cooling system. Originality/value − The outer-rotor permanent-magnet flux- switching machines so far have not been addressed yet. This research provides designers with the technical background and another alternative for electric vehicle
Open Access
Design and analysis of high-speed coreless axial flux permanent magnet generator with circular magnets and coils
(2010-11-29T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Jinupun, Ken
A high-speed coreless surface mounted axial flux permanent magnet generator with circular magnets and coils is proposed and studied. The performances of the machine are estimated and optimised by approximate theoretical analysis and comprehensive three-dimensional (3D) electromagnetic finite element analysis (FEA). Mechanical stresses in the rotor disc developed at high rotational speed are analysed and evaluated by 3D mechanical FEA to ensure the rotor's integrity. Finally, a prototype machine is constructed and tested. Both the experimental and predicted results have shown that the proposed generator possesses distinct advantages such as simple structure and high efficiency. The prototype also demonstrates its utility as a very low-cost generator.
Open Access
Design issues of an IPM motor for EPS
(Emerald Group Publishing Limited, 2011-12-31T00:00:00Z) Wang, Can-Fei; Shen, Jian-Xin; Luk, Patrick Chi-Kwong; Fei, Wei-Zhong; Jin, Meng-Jia
In electric power steering (EPS), permanent magnet (PM) brushless ac (BLAC) motors offer distinct advantages over other electric motor types in terms torque smoothness, reliability and efficiency. The design procedure of an interior permanent magnet (IPM) motor used in EPS is presented in this paper. The requirements of the steering system are first introduced, and the machine's specifications are then derived. Critical issues which have considerable impacts on the machine's performance, such as operation mode, rotor structure and slot/ pole combination, are analyzed. Subsequently, a 12-slot/10-pole sinusoidally excited IPM machine with concentrated windings is proposed and optimized based on finite element analysis (FEA) modelling. The losses and efficiency are then computed. Performance predictions from the FEA results confirm all the requirements are met or exceeded. A prototype motor has been built for validation.
Open Access
Design of a multi-layer interior ferrite permanent magnet synchronous machine for traction applications
(IET, 2014-04-10) Xia, Bing; Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Wu, D
A novel design of interior ferrite permanent magnet synchronous machine with multi-layer configuration is proposed for traction applications. Although the ferrite magnet can be disadvantaged by its low residual flux density and energy product, it is proposed that flux-focusing and multi-layer configurations can be utilized to harness both permanent magnet (PM) torque and reluctance torque to recoup the loss of the PM torque due to its intrinsic property. The machines with up to three-layer magnets are presented and evaluated comprehensively. The results suggest that the two-layer machine provides the best performance among the three configurations. Furthermore, compared against a commercial rare-earth equivalent, the proposed ferrite machine is shown to have nearly the same torque with 32% less electromagnetic losses. The findings underpin interior ferrite permanent magnet synchronous machine as an attractive alternative for traction applications
Open Access
Development of a magnetic-geared permanent-magnet brushless motor
(IEEE; 1999, 2009-09-22T00:00:00Z) Wang, L. L.; Shen, Jian-Xin; Luk, Patrick Chi-Kwong; Fei, Wei-Zhong; Wang, Can-Fei; Hao, He
High-torque and low-speed electrical drives are often employed for applications where mechanical gearing cannot be accommodated. On the other hand, permanent-magnet (PM) gear has drawn significant attention from both academies and industries due to the conspicuous merits, such as reduced acoustic noise, maintenance free, improved reliability, precise peak torque transmission capability, and inherent overload protection. In this paper, a magnetic-geared PM brushless motor is presented. It is a novel low-speed and high-torque motor which merges the advantages of conventional PM brushless motor and PM gear. Its topology and operation principle are introduced. Some techniques are employed to optimize and improve the motor performance, while the validity of the proposed techniques is verified with finite-element analysis. Moreover, an alternative operation condition, which can further reduce the motor speed and increase its output torque, is proposed and analyzed.
Open Access
A high-performance line-start permanent magnet synchronous motor amended from a small industrial three-phase induction motor
(2009-09-22T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Ma, J.; Shen, Jian-Xin; Yang, G.
Small industrial three-phase induction motors (IMs) normally suffer from poor operational efficiency and power factor. This paper presents a high-performance line-start permanent magnet synchronous motor (LSPMSM) which is developed by simple modifications of an off-the-shelf small industrial three-phase IM with minimized additional costs. Two-dimensional (2-D) dynamic finite element analysis (FEA) models are employed to assess the machine performances, which are validated by comprehensive experimental results. The experimental comparisons between the amended LSPMSM and the original IM have indicated that significant improvements in efficiency and power factor can be achieved by the proposed LSPMSM.
Open Access
An improved model for the back-EMF and cogging torque characteristics of a novel axial flux permanent magnet synchronous machine with a segmental laminated stator
(IEEE; 1999, 2009-10-31T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong
An improved model for the back-electromagnetic-force (back-EMF) and cogging torque characteristics of a novel axial flux permanent magnet (AFPM) synchronous machine with a segmental laminated stator is presented. Based on a 3-D finite-element analysis (FEA) modeling approach that takes into the anisotropic properties of the machine's laminated cores, the proposed model provides superior performance prediction to existing isotropic models, in which lamination effects are not considered. An anisotropic model has been developed to predict the back-EMF and cogging torque of an existing prototype AFPM machine with optimized rotor magnets. Experimental results of the AFPM machine are compared against the results from the FEA models based on anisotropic and isotropic modeling, respectively. The results show that anisotropic modeling provides more accurate performance prediction of the AFPM machine with laminated cores.
Open Access
An improved sideband current harmonic model of interior PMSM drive by considering magnetic saturation and cross-coupling effects
(Institute of Electrical and Electronics Engineers, 2016-03-10) Liang, Wenyi; Fei, Wei-Zhong; Luk, Patrick Chi-Kwong
The sideband current harmonics, as parasitic characteristics in permanent-magnet synchronous machine (PMSM) drives with space vector pulsewidth modulation technique, will increase the corresponding electromagnetic loss, torque ripple, vibration, and acoustic noises. Therefore, fast yet accurate evaluation of the resultant sideband current harmonic components is of particular importance during the design stage of the drive system. However, the inevitable magnetic saturation and cross-coupling effects in interior PMSM drives would have a significant impact on the current components, while the existing analytical sideband current harmonic model neglects those effects. This paper introduces a significant improvement on the analytical model by taking into account these effects with corresponding nonlinear factors. Experimental results are carried out to underpin the accuracy improvements of the predictions from the proposed model over the existing analytical one. The proposed model can offer a very detailed and insightful revelation of impacts of the magnetic saturation and cross-coupling effects on the corresponding sideband current harmonics.
Open Access
Investigation of magnetic field inter-harmonics and sideband vibration in FSCW IPMSM drive with SPWM technique
(IEEE, 2017-06-01) Wenyi, Liang; Luk, Patrick Chi-Kwong; Fei, Wei-Zhong
The high-frequency sideband current harmonics are the inherent concomitants of applying sinusoidal pulse width modulation (SPWM) in permanent magnet synchronous machine drives. Abundant spatial interharmonic magnetic field components in fractional-slot concentrated-winding (FSCW) interior permanent magnet synchronous machine (IPMSM) render it very susceptible to electromagnetic radial vibration (ERV). In this paper, a universal analytical interharmonic model of magnetic field in FSCWIPMSMs is proposed, and further it is employed to develop the sideband radial force density model of SPWM. Both comprehensive finite element analysis (FEA) simulations and experimental tests are carried out to underpin the validity of the analytical models. The close agreements between the analytical, FEA, and experimental results have revealed that the proposed analytical approaches can deliver accurate sideband current and vibration predictions with minimum computational efforts and suffice for fast preliminary assessments. In addition, the validated analytical models can offer detailed and insightful revelations of various factors that affect the corresponding sideband vibration components.
Open Access
Investigation of torque characteristics in a novel permanent magnet flux switching machine with an outer-rotor configuration
(IEEE; 1999, 2014-04-01T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Miao, Dong-Min; Shen, Jian-Xin
This paper comprehensively investigates the torque characteristics of a novel permanent magnet flux switching machine with outer-rotor configuration. Due to the nature of severe magnetic saturations in the machine, it is of particular interest to ascertain the extent of impact of the load conditions on the overall torque output as well as its component parts. The frozen permeability techniques are implemented in finite element analysis to segregate the output torque of the outer-rotor permanent magnet flux switching machine into three parts: cogging torque, reluctance torque and permanent magnet torque. Two dimensional finite element analysis is first employed to reveal the effects of phase current amplitudes and angles on those three torque components as well as the overall torque, while the three dimensional finite element analysis is carried out to further uncover the influences of end effects on the torque characteristics of the machine. Finally, experimental tests on a prototype machine are performed to validate the torque characteristic predictions by finite element analysis.
Open Access
A new technique of cogging torque suppression in direct-drive permanent-magnet brushless machines
(IEEE Institute of Electrical and Electronics, 2010-07-21T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong
In direct-drive electric propulsion systems, where there is no reduction gear to minimize and absorb the adverse effects of cogging torque generated by the permanent-magnet (PM) machine, minimization of cogging torque generation is of particular importance. In this paper, a novel axial pole-pairing method is proposed to minimize cogging torque generation in a special three-phase outer-rotor PMbrushless machine, which uses uneven stator poles to enhance back electromotive force (EMF). Analytical formulas of the machine’s cogging torque are first derived. The new technique is compared with conventional cogging torque suppression methods by means of analytical models and comprehensive finite-element analysis (FEA). The FEA results show that the new method not only achieves effective cogging torque reduction, but also results in improved harmonic content of the back EMF. The validity of the FEA model is verified by experimental results from the prototype machines. Finally, the significance of optimizing both the load-independent machine design techniques and load-dependent driving techniques to achieve overall torque ripple minimization is discussed.
Open Access
A novel permanent magnet flux switching machine with an outer-rotor configuration for in-wheel light traction applications
(IEEE Institute of Electrical and Electronics, 2012-09-30T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Shen, Jian-Xin; Wang, Yu; Jin, Meng-Jia
This paper proposes a novel permanent magnet flux switching (PMFS) machine with an outer-rotor configuration for in-wheel light traction applications. The geometric topology of the outer-rotor PMFS machine is introduced and the analytical sizing equations are derived to determine the main design parameters of the machine. Two-dimensional (2-D) Finite element analysis (FEA) models are developed to investigate and optimize the machine performance. Furthermore, the flux weakening capability of the machine is analyzed and further improved by segmental permanent magnets with iron bridges. The machine performance predictions by 2-D FEA models are validated by experimental tests on the prototype machine. The suitability of the proposed outer-rotor PMFS machine for in-wheel light traction application is demonstrated.
Open Access
Particle swarm optimization of air-cored axial flux permanent magnet generator for small-scale wind power systems
(IET, 2014-04-10) Xia, Bing; Luk, Patrick Chi-Kwong; Fei, Wei-Zhong; Yu, L.
Axial flux permanent magnet synchronous machines with aircored configuration is particular suitable for small scale wind power system due to their advantages of low synchronous reactance, cogging torque free, high efficiency and high power factor. However, due to the number of machine parameters, with some tightly `coupled' with each other, optimisation of the design could become extremely challenging by conventional analytical means. Here, the particle swarm optimization method is used in the design of an axial flux permanent magnet generator for small-scale wind power system. Five inter-dependent design parameters are adjusted simultaneously to achieve an optimal solution for the application. Three-dimensional finite element analysis is employed to evaluate the electromagnetic performance for the optimization. The results show the proposed optimization method is efficient and with fast convergence.
Open Access
Permanent magnet synchronous machines with fractional slot and concentrated winding configurations
(2011-09-08) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong
The permanent magnet synchronous machines with fractional slot and concentrated winding configuration have been steadily gaining traction in various applications in recent times. This is mainly driven by several advantages offered by this configuration such as high-torque density, outstanding efficiency, and easy and low-cost fabrication. The main focus of this thesis is dedicated to the investigation of three main topologies of fractional-slot and concentratedwinding permanent magnet synchronous machines specifically suited for particular applications. Additionally, the cogging torque and torque ripple reduction technique based on a novel axial pole pairing scheme in two different radial-flux permanent magnet synchronous machines with fractional-slot and concentratedwinding configuration are investigated. First, an axial flux permanent magnet segmented-armature-torus machine with laminated stator is proposed for in-wheel direct drive application. Both simplified analytical method and three-dimensional finite element analysis model accounting for anisotropic property of lamination are developed to analyze the machine performance. The predicted and experimental results are in good agreement and indicate that the proposed machine could deliver exciting and excellent performance. The impact of magnet segmentation on magnet eddy current losses in the prototype is carried out by the proposed three-dimensional finite element analysis model. The results show that the eddy current losses in the magnet could be effectively reduced by either circumferentially or radially segmenting the magnets. Furthermore, a magnet shaping scheme is employed and investigated to reduce the cogging torque and torque ripple of the prototype. This is validated using the three-dimensional finite element analysis model as well. Second, a coreless axial flux permanent magnet machine with circular magnets and coils is proposed as a generator for man-portable power platform. Approximate analytical and three-dimensional finite element analysis models are developed to analyze and optimize the electromagnetic performance of the machine. Comprehensive mechanical stress analysis has been carried out by threedimensional structural finite element analysis, which would ensure the rotor integrity at expected high rotational speed. The results from both three-dimensional finite element analysis and experiments have validated that the proposed prototype is a compact and efficient high speed generator with very simple and robust structure. Additionally, this structure offers simplified assembly and manufacturing processes utilizing off-the-shelf magnets. Third, a novel radial flux outer rotor permanent magnet flux switching machine is proposed for urban electric vehicle propulsion. Initial design based on the analytical sizing equations would lead to severe saturation and excessive magnet volumes in the machine and subsequently poor efficiency. An improved design is accomplished by optimizing the geometric parameters, which can significantly improve the machine efficiency and effectively reduce the overall magnet volumes. Magnet segmentations can be employed to further improve the machine performance. Finally, a novel axial pole pairing technique is proposed to reduce the cogging torque and torque ripple in radial flux fractional-slot and concentrated-winding permanent magnet synchronous machines. The implementation of the technique in outer rotor surface mounted permanent magnet synchronous machine shows that the cogging torque and torque ripple can be reduced very effectively with different magnet pairs. However, careful pair selection is of particular importance for compromise between cogging torque and torque ripple minimizations during the machine design stage. This technique is also employed to minimize the cogging torque in a permanent magnet flux switching integrated-stator-generator and it is compared with rotor step skewed technique. The estimated and experimental results show that the axial pole pairing technique can not mitigate the torque ripple of the machine as effectively as rotor step skewed approach although both the techniques could reduce the cogging torque to the same level.
Open Access
Permanent-magnet flux-switching integrated starter generator with different rotor configurations for cogging torque and torque ripple mitigations
(IEEE Institute of Electrical and Electronics, 2011-05-18T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Shen, Jian-Xin; Xia, Bin; Wang, Yu
This paper investigates the cogging torque and torque ripple features of a permanent-magnet flux-switching integrated starter generator. The effects of the rotor pole arc width on the cogging torque, torque ripple, and output torque are first established using finite-element analysis (FEA). Three torque ripple reduction techniques based on the optimization of three different rotor pole configurations, namely, uniform, step skewed, and axial pairing, are then proposed. The torque characteristics of each rotor configuration at varying load currents and phase angles are studied in detail. A prototype machine with a common stator and the three optimized rotor configurations are built for experimental validation. Both the FEA results and the experimental tests show that the step skewed and axial pairing techniques can alleviate the cogging torque significantly, but the latter is less effective than the former in reducing the overall torque ripple.
Open Access
Rotor integrity design for a high-speed modular air-cored axial-flux permanent-magnet generator
(IEEE Institute of Electrical and Electronics, 2011-09-30T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; El-Hasan, T. S.
The rotor integrity design for a high-speed modular air-cored axial-flux permanent-magnet (AFPM) generator is presented. The main focus is on the mechanical parametric optimization of the rotor, which becomes a more dominating design issue over electromagnetic optimization at high operational speeds. Approximate analytical formulas are employed for preliminary sizing of the mechanical parameters of the rotor, which consists of the permanent magnets, retainment ring, and back iron. Twodimensional (2-D) finite-element analysis (FEA) models are used to optimize the values of the parameters. Then, 3-D FEA models are developed to verify the final design. Finally, based on the final design, an AFPM prototype is built for experimental validation, and mechanical integrity tests for the rotor are undertaken. The results confirm the validity of the analytical and FEA models, as well as the overall design approach.