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This paper proposes an optimal design for a surface-mounted permanent magnet motor (SPMM) to reduce torque pulsations, including cogging torque and torque ripple, by using multi-grade ferrite magnets. Based on a conventional SPMM with single-grade ferrite magnets, the proposed SPMM is designed with four-grade ferrite magnets and then optimized to minimize torque pulsations by maintaining the required torque, utilizing the Kriging method and a genetic algorithm. The results obtained by the finite element analysis show that the optimized SPMM with multi-grade ferrite magnets exhibits improved airgap flux density distribution with highly reduced cogging torque and torque ripple by maintaining the same average torque, as compared to the conventional SPMM. Furthermore, the analysis of the working points for the multi-grade ferrite magnets reveals that the optimized SPMM has good durability against the irreversible demagnetization. [ABSTRACT FROM AUTHOR]

The paper proposes a hybrid-excited wound field synchronous machine (HE-WFSM), which can achieve high reluctance torque utilization. The key of the proposed HE-WFSM is that two permanent magnets (PMs) assist each rotor pole in forming an additional magnetic flux circle. It is opposite to the magnetic flux circle along the q-axis in the WFSM. The reduction of the q-axis flux can help to improve the saliency ratio and reluctance torque. Additionally, the asymmetrical flux linkage achieves a closest current phase angle between the maximum field torque and the maximum reluctance torque. To highlight the advantages of the proposed HE-WRSM, a general WFSM was adopted as the basic machine and analyzed under the same operating conditions. All performances of the basic machine and proposed HE-WFSM were predicted using finite element analysis (FEA) in Jmag-Designer. Finally, it was confirmed that the proposed HE-WRSM can achieve high reluctance torque utilization. [ABSTRACT FROM AUTHOR]

This study proposes a novel asymmetric rotor structure with tuning‐fork flux barriers for a permanent magnet (PM)‐assisted synchronous reluctance machine (PMA‐SynRM) to improve the torque characteristics. The proposed asymmetrical rotor structure can effectively decrease the flux leakage inside the rotor, as well as ensure the maximum values of the magnetic torque and the reluctance torque are near the same current phase angle as each other to achieve better utility. To realise this, the frozen permeability method is implemented to separate the total torque into the reluctance torque and the magnetic torque via a two‐dimensional finite‐element method – JMAG‐Designer. To achieve the optimal torque characteristics in the proposed model, the Kriging method and a genetic algorithm are used for getting the optimised model. The contribution of this investigation into motor performance is validated by comparing the proposed model with a conventional PMA‐SynRM with a symmetric rotor structure. Beyond that, all machine models are the same size, have the same number of magnets and are operated under the same conditions. A prototype of the proposed model is experimentally verified, i.e. the simulation results agree with the experimental results. [ABSTRACT FROM AUTHOR]

This study proposes a two‐phase single‐air‐gap axial flux permanent magnet (AFPM) motor that offers a trapezoidal back‐electromotive force (EMF) waveform to improve the performance of the only‐pull drive technique compared with the radial flux PM (RFPM) motor. The only‐pull drive technique provides the benefit of allowing the use of thin magnets in the motor without suffering from irreversible demagnetisation. In the proposed motor, the design geometry is primarily considered to achieve the desired trapezoidal shape of back‐EMF. The effects of the geometry are explained with the help of air‐gap flux density, flux linkage, and the leakage flux. Both the radial flux and the proposed motor adopt the same design concept and hold equal electromagnetic loadings. The profile of back‐EMF and the electromagnetic torque driven by the only‐pull drive technique are compared with that of RFPM motor with non‐trapezoidal back‐EMF. Furthermore, the split configuration is proposed for the AFPM motor to reduce torque ripples. The demagnetisation analysis is performed to confirm the operating point of the magnets in a split‐AFPM motor. The results reveal that the AF motor is a good candidate for the only‐pull drive technique. [ABSTRACT FROM AUTHOR]

In this paper, a permanent magnet (PM)-less, brushless, wound-rotor vernier machine (BL-WRVM) is proposed for variable speed applications such as electric vehicles and washing machines. The wound rotor is excited through an already existing brushless topology, which requires a dual inverter configuration to generate an additional subharmonic component in the stator magnetomotive force (MMF). Different from permanent magnet vernier machines (PMVMs), the proposed BL-WRVM provides easy regulation of the rotor flux for variable speed operation. A 24-slot, 4-pole stator, and 44-pole outer rotor were designed, and 2D finite element analysis (FEA) was carried out to determine the performance of the proposed machine. To improve the performance of the proposed machine, optimization of the rotor and stator winding turns was done. The optimized model was further analyzed for wide-speed operation, and its performance was then compared with that of an equivalent permanent magnet vernier machine (PMVM). The proposed machine has the advantage of low cost due to its PM-less structure and is suitable for variable speed applications. [ABSTRACT FROM AUTHOR]

This paper proposes an optimal design for a salient pole wound field synchronous machine (WFSM) with a single flux barrier to improve torque performance and obtain a wide operating range, simultaneously. The proposed WFSM motor can effectively decrease q -axis inductance to improve the saliency ratio ( X_{d}/X_{q}) and increase the reluctance torque. To maximize the saliency ratio and improve the torque characteristics, the single flux barrier is optimized, considering the magnetic saturation that uses Kriging method based on Latin hypercube sampling and a genetic algorithm. The 2-D finite element analysis results by the aid of JMAG-Designer shows that the saliency ratio X_{d}/X_{q}$ , the reluctance torque, and the total torque of the optimal model are increased by 9.27%, 20.45%, and 6.17%, respectively, compared with those of the basic model. Finally, the performance of the optimal motor is verified through an experimental test, which indicates good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

This study investigates the characteristics of a spoke‐type permanent magnet (PM) motor with one of three magnet shapes, rectangular magnet (RM), trapezoidal magnet (TM), or inverted TM (ITM) in order to compare motor performance for the same magnet volume. The three magnet shapes vary in terms of upper thickness, lower thickness, and width of the magnet. Two‐dimensional (2D) finite element method is performed to analyse torque, inductance, core loss, efficiency, and demagnetisation reliability. Advantages and disadvantages of each magnet shape are presented based on the analysis results. The ITM motor shows higher efficiency at its rated load due to the reduced core loss resulting from the decreased armature reaction field coupled with the increased magnetic reluctance circuit of the rotor near the airgap. However, the ITM motor shows lower maximum torque due to the reduced reluctance torque and demagnetisation reliability with a heavy over‐current. ITM is thus suitable for applications that require low core loss with small starting torque, e.g. fans, TM is helpful for increasing maximum torque, and RM is appropriate for low‐cost applications that require high demagnetisation reliability. Therefore, magnet shape should be carefully considered based on the required specifications of the motor application. [ABSTRACT FROM AUTHOR]

This paper presents an advanced design procedure for stator-based and rotor-based permanent magnet (PM) machines to improve the electromagnetic performance by incorporating the spoke-type magnet configurations, phase-group concentrated coil windings, and an unaligned arrangement of two rotors/stators. The dual-rotor switched flux PM machine (SFPMM), designated as the stator-PM machine, and the dual-stator spoke-type interior PM machine (S-IPMM), termed the rotor-PM machine, are designed by the proposed design procedure to obtain high torque density and low pulsating torques for direct-drive applications. A quantitative comparison is performed between the proposed SFPMM and S-IPMM, and a conventional SFPMM with concentrated windings is adopted as the referenced model to evaluate the contribution of the proposed design procedure. The machine performance including back electromotive force, cogging torque, and electromagnetic torque is first analyzed by a finite element method under the same operating conditions. Finally, a prototype of the dual-stator S-IPMM is manufactured, and some key simulation results are verified by the experimental tests. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a novel permanent-magnet (PM)-assisted synchronous reluctance machine (PMA-SynRM) with axially integrated magnets for improving machine performance by using a finite-element method (FEM). The proposed PMA-SynRM features a simple structure with high performance by incorporating the advantages of a SynRM and a surface-mounted PM machine (SPMM). In particular, the rotor parts of the SynRM and SPMM are assembled to make the “ $q$ -axis” located 45° (elec.) from the $d$ -axis. Thus, the magnetic torque and reluctance torque of the proposed PMA-SynRM reach the maximum values at the same current phase angle, for efficient production of the total torque. To highlight the advantages of the proposed PMA-SynRM, a conventional PMA-SynRM is adopted for comparison under the same operating conditions. The FEM analysis results finally demonstrate that the proposed PMA-SynRM has a higher total torque and power factor, as well as greatly reduced torque ripple, when compared to the conventional PMA-SynRM with the same magnet amounts. In addition, the Mises stress analysis indicates that the configuration of the proposed PMA-SynRM exhibits the advantage of avoiding stress deterioration in the rotor ribs. [ABSTRACT FROM AUTHOR]

A small axial-flux permanent magnet vernier motor (PMVM) is investigated to satisfy the requirements of high drive torque, low speed, low noise, and low-power consumption for application in the camera auto-focusing lens drive. The proposed axial-flux PMVM is constructed with ring-type magnets in the rotor and has strict dimensional constraints due to its location in the lens barrel. The design approach is an alternative motor design method coupled with the analytical method or the finite-element method. The proposed motor’s electromagnetic performance was verified by means of both methods. Finally, a prototype was built and tested, showing an adequate range of speed while also meeting the noise limits, and consuming less than 2 W of power. [ABSTRACT FROM PUBLISHER]

This paper focuses on the design and analysis of a high-speed axial flux permanent magnet (PM) machine for an aerospace flywheel energy storage system. The design target is to experimentally verify the sinusoidal back electromotive force (EMF) considering the mechanical stress limitation of the machine at a speed of 32 000 r/min. Two machine models based on ferrite and SmCo PMs have been proposed. First, the back EMF analysis using a 3-D finite-element method is performed to determine the performance of the two models. Second, the mechanical stress analysis is performed to check the durability of the rotor strength. Finally, the selected model utilizing the ferrite PMs has been manufactured and tested at 32 000 r/min to validate its effectiveness at high-speed operation. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel dual-rotor, axial field, fault-tolerant flux-switching permanent magnet machine (FSPMM) with high-torque performance for direct-drive applications, in which the phase-group concentrated-coil windings and the unaligned arrangement of the two rotors are used. The adoption of the phase-group concentrated-coil windings is made to obtain a unity displacement winding factor, and to enhance the flux-focusing effects together with the use of a spoke-type PM configuration. The unaligned arrangement of the two rotors will help to achieve increased flux magnification and also to suppress the cogging torque and the torque ripple. In particular, the proposed configuration for FSPMMs exhibits the advantage of fault tolerance, benefiting from the electromagnetic isolation of phases and a dual three-phase channel of supply. The operating principle and the design criteria of the proposed FSPMM are discussed in detail. To highlight the advantages of the proposed FSPMM, two conventional FSPMMs are adopted for comparison under the same operating conditions based on a 3-D finite-element method. As a result, it is demonstrated that the proposed FSPMM exhibits significantly improved performance with not only higher torque (power) density but also lower cogging torque and torque ripple, compared with the conventional FSPMMs. [ABSTRACT FROM AUTHOR]

This paper presents two types of novel dual-stator two-phase permanent magnet synchronous machines (PMSMs) equipped with an advanced phase-group concentrated-coil winding and a spoke-type PM array for direct-drive applications. The key advantage of the proposed two-phase PMSMs is its superior flux-focusing effects, which greatly enhance the torque, benefiting from the whole machine configuration. To highlight the advantages of the proposed two-phase PMSMs, one three-phase PMSM and one two-phase PMSM with the conventional stator and winding configurations are adopted for comparison. All relevant machine characteristics, including the air-gap flux density, back electromotive force, and electromagnetic torque, are predicted by a 2-D finite-element method. Finally, one of the proposed dual-stator two-phase PMSMs is optimized to minimize cogging torque and torque ripples using the Kriging method and a genetic algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes two approaches to minimize torque pulsations, including cogging torque and electromagnetic torque ripple, for spoke-type interior permanent magnet (IPM) motors. The first approach is an improved skewing method, in which the rotor PMs are skewed by being symmetrical in the axial direction within one magnet pole pitch for not only reducing torque pulsations but also maintaining maximum available torque and eliminating unbalanced axial electromagnetic forces. The second one is a sinusoidal PM-shaping method with the aim of achieving the same advantageous effects as the proposed skewing method. Both the proposed methods adopt stepped rotor-PM schemes, and the effects of the rotor-PM step numbers on motor performance are investigated. To highlight the advantages of the proposed approaches, a spoke-type IPM motor with the conventional PM configuration is adopted as the basic model. All the motor characteristics, such as back electromotive force, cogging torque, and electromagnetic torque, are predicted by a 3-D finite-element method with the aid of JMAG-Designer. [ABSTRACT FROM AUTHOR]

This paper proposes novel ferrite-assisted synchronous reluctance machines (FA-SynRMs) having the merit of highly improved machine performance including torque, efficiency, and power factor. The particular superiority of the proposed FA-SynRMs is the utilization of an asymmetrical rotor configuration that contributes to the full use of torque components by allowing the magnetic and reluctance torques to reach their maximum values near or at the same current phase angles. To provide visible insights into the contribution, a frozen permeability method is utilized to separate the torque into the reluctance torque and the magnetic torque based on a 2-D finite-element method by the aid of JMAG-Designer. For highlighting the advantages of the proposed models, a conventional FA-SynRM with symmetrical rotor configurations is adopted for comparison under the same operating conditions. As a result, it is demonstrated that the proposed design is effective in improving the performance of FA-SynRMs. [ABSTRACT FROM AUTHOR]

In high‐speed axial flux hysteresis motors (AFHMs), the hysteresis ring and the hysteresis ring holder have the main roles of producing hysteresis torque in steady state and eddy current torque at sub‐synchronous speed, respectively. In conventional AFHM, and especially in the high‐speed AFHM types, the hysteresis ring holder is placed between the hysteresis ring and stator to produce more eddy current torque at the time of starting. Since the minimum magnetic air gap can cause better motor performance, the previous research exchanges the hysteresis ring place and its holder. However, it has worst motor dynamic response as a result. To cope with these issues, a new model is proposed in this study. A thin copper piece is attached at the bottom of the hysteresis ring to improve the eddy current torque and consequently motor dynamic response. Then finite element analysis is done in order to acquire the accurate copper thickness and investigate the new proposed AFHM. Furthermore, experimental setups are provided and AFHM results in all cases are measured. The obtained test and simulation results show that the new proposed model make a better dynamic performance for the AFHM. [ABSTRACT FROM AUTHOR]

This paper proposes a novel grid-connected to rotor type doubly fed induction machine (DFIM) in which the rotor winding is connected to the grid instead of the stator winding. The size and weight of the stator can be reduced on the proposed grid-connected to rotor type DFIM, because the proposed type can use the rotor core more efficiently compared to a conventional grid-connected to stator type DFIM. In order to verify the size and weight reduction of the proposed type, the loading distribution method (LDM) is utilized. As a design result, the outer diameter and weight of the stator on the proposed type have been decreased. Equivalent circuit analysis and finite element analysis (FEA) were performed to verify the design results and to analyze the characteristics of the novel DFIM. Finally, these analysis results are confirmed by experimental results. [ABSTRACT FROM PUBLISHER]