Browsing by Author "Shen, Jian-Xin"

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    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.
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    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
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    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.
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    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.
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    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.
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    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.
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    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.
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    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.
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    Sensorless high-speed BLDC machine using hardware-RFO
    (2011-12-31T00:00:00Z) Shen, Jian-Xin; Hao, He; Jin, Meng-Jia; Fei, Wei-Zhong
    High-speed permanent magnet (PM) brushless dc (BLDC) motor often needs a continuous rotor position signal for dynamic phase-advancing control, whist such kind of position signal cannot be directly obtained from the conventional Hall effect sensors or via the traditional back-EMF-based sensorless control strategy. Furthermore, during high-speed operation, the inverter free-wheeling diodes may conduct for more than 30 elec-deg, obscuring the back-EMF zero- crossings. Hence, the traditional back-EMF-based sensorless control strategy becomes unworkable. To overcome these problems, a new sensorless control method is proposed in this paper. It uses full hardware to observe the flux vector which is excited by rotor magnets. Thus, it can provide the rotor position which is the same as the phase angle of the observed flux vector. The proposed sensorless control method is validated with a 2Kw, 85000rpm PM BLDC motor system.
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    Torque analysis of permanent magnet flux switching machines with rotor step skewing
    (IEEE; 1999, 2012-10-01T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Shen, Jian-Xin
    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.