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This paper presents the efficiency improvement of a pole-changing vernier machine (PCVM) by considering the residual magnetic flux density ( B r ) of low coercivity force (LCF) permanent magnets (PMs). The PCVM operates in two modes: vernier machine (VM) mode and permanent magnet synchronous machine (PMSM) mode, achieved through pole-changing. Pole-changing involves reversing the magnetic flux direction of LCF PM to alter the number of rotor pole pairs. By changing the number of rotor pole pairs, the PCVM operates as a VM mode at low speeds, providing high torque, and as a PMSM mode at high speeds, offering high efficiency. To achieve this, a combination of high coercivity force (HCF) PM and LCF PM is utilized in a single structure. The magnetic flux direction in the LCF PM is determined by B r , and the highest efficiency is achieved when B r reaches its maximum value | B r m |. This paper focuses on improving efficiency by obtaining B r m in VM mode and − B r m in PMSM mode through the design process. Additionally, finite element analysis (FEA) is employed to compare the performance of the improved model, which considers B r , with that of the conventional model, designed without considering B r . The improved model achieves higher B r values in each mode compared to the conventional model, resulting in increased torque density. Consequently, this leads to improved efficiency. [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 paper proposes a variable-flux Vernier machine with dual consequent pole configuration to realize wide speed-range operation. The rotor has a consequent pole structure with high coercive force (HCF) material composed permanent magnets (PMs), whereas the stator has PMs positioned between the flux modulation poles. Stator-mounted PMs are made of low coercive force (LCF) materials that can be easily demagnetized or magnetized for variable-flux machines. By changing the magnetization state of the LCF PMs, suppression of magnetic flux was increased to reach higher-speed operation. Demagnetization of the stator LCF PMs reduced the total magnetic flux to reach a higher speed range. In addition, reverse magnetization allowed the machine to achieve further speed-range enhancement. The proposed machine was improved with a parametric selection process. Machine performance of each magnetization state was analyzed by way of speed torque curves and efficiency maps. [ABSTRACT FROM AUTHOR]

This paper proposes the novel topology of a high-efficiency dual output stator-permanent magnet (PM) machine (DOSPMM) for two different washing machine operating speeds. The proposed machine consists of two machines integrated into a single machine: Machine I is an outer rotor type Vernier machine with low speed and high torque for washing mode operations. Machine II is an inner rotor type flux-reversal PM (FRPM) machine with high speed and low torque for dehydrating mode operations. Each machine was designed to be highly efficient for the assigned operating mode. Both machines also possess robust rotors due to stator positioned PMs. To demonstrate the superiority of the proposed machine, performance comparisons with conventional machines for general washing machine applications were performed via finite-element method (FEM) analysis. A prototype of the proposed machine was built and experimental results of the prototype machine were presented for a validation of the work. [ABSTRACT FROM AUTHOR]

This paper presents an optimal design for a surface-mounted permanent magnet (SPM) motor to suppress torque pulsations and save the magnet cost, by using multi-grade permanent magnets. Based on a conventional SPM motor with single-grade bonded NdFeB magnets, the proposed SPM motor is designed with two-grade bonded NdFeB and one-grade ferrite magnets, and then optimized by combining the Kriging method with a genetic algorithm, for further minimizing torque pulsations and saving the magnet cost by maintaining the high average torque. As a result, the cogging torque, torque ripple, and magnet cost of the optimized SPM motor are highly reduced compared to those of the conventional SPM motor. Furthermore, the optimized SPM motor is verified to have superior endurance against the magnet’s irreversible demagnetization within three times of the rated current excitation. All motor characteristics, including airgap flux density, cogging torque, electromagnetic torque, and demagnetization ratio are first predicted with the aid of a finite-element method. Finally, the optimal design and analysis results are validated by the experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes the novel flux barrier by using the modified Taguchi method to reduce the cogging torque. In the optimizing process the modified Taguchi method is utilized to consider multiple objective quality characteristics simultaneously such as the torque ripple and the efficiency as well as the cogging torque. The optimal novel flux barrier can effectively reduce the cogging torque and torque ripple and it is verified through 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]

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]

In this paper, a high-temperature superconductor dual-stator spoke-type linear vernier machine (HTS-DSSLVM) is proposed for wave energy extraction, which offers high-thrust force density and better power factor due to leakage flux reduction. HTS bulks are introduced in between the split flux modulation teeth to shield the leakage flux and hence improve the force density and power factor. The electromagnetic characteristics of the machine are comprehensively investigated and compared with that of a recently presented dual-stator spoke-type linear vernier machine (DSSLVM). The results show that the proposed machine yields higher thrust force and better power factor than the DSSLVM due to reduced leakage flux in the proposed machine. [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]

This paper presents the design, optimization, and prototyping of a transverse flux-type-switched reluctance generator (TFSRG) with an integrated rotor consisting of the main and permanent magnet (PM) auxiliary poles. In the initial model, an integrated rotor has a simple structure, consisting of one magnet core and a yoke bar. The yoke bar was radially laminated and inserted in the rotor yoke to minimize loss of the magnetic flux, which flows along the axial direction. We analyzed the cogging torque and back-EMF characteristics of the proposed TFSRG using the finite-element analyses (FEA). The cogging torque in the analysis results for the initial model of the proposed TFSRG was relatively high cogging. To reduce a cogging torque, both corners of the stator and PM auxiliary poles were optimized using a circular fillet shape. To satisfy a design condition, the design variables of a circular fillet shape were effectively determined using the optimization algorithm, and the initial and optimal models were compared with the analyzed results by a FEA for steady state and a dynamic performance simulation for transient state, respectively. To verify the analyzed results, an optimized prototype TFSRG was manufactured and measured. The measurement results were in good agreement with analysis results, and the output performance of the prototype was verified by the experiment set. [ABSTRACT FROM PUBLISHER]

This paper proposes the optimal design of a new interior permanent magnet (IPM)-type brushless dc (BLdc) motor using low-price ferrite magnets. The new IPM motor has the structure of C-type ferrite magnets featuring a flared shape to obtain high motor performance. To maximize the flux density and minimize the torque ripple, the flared-shape rotor structure is optimized by algorithms, such as the Kriging method based on Latin hypercube sampling and a genetic algorithm. The analyses of basic and optimal designs utilize a 3-D finite-element method, and then, the validity of the optimal design is verified through fabrication of actual prototypes. [ABSTRACT FROM PUBLISHER]

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]

Conventional permanent magnet (PM) motors operate in both magnetizing (pull) process and reversible demagnetizing (push) process on the recoil line of magnets. Therefore, thin-surface PMs may easily undergo a risk of demagnetization at the push process under certain fault conditions, which lead to deterioration of motor performance. Thus, thick magnets, whereas contributing the significantly high cost, are usually used to minimize this risk in the PM motors. In this paper, a novel operation technique, that involves only the pull process, has been proposed for a unique design of two-phase brushless DC motor to avoid the irreversible demagnetization of the magnets. The motor, operated only in the pull process, is kept away from the push process of the operation. Therefore, the motor sustains its initial magnetic operating point above the knee point during the normal operation as well as under the short circuit fault conditions. Finite-element analysis is performed to validate the concept of the proposed technique. [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 focuses on the design and the analysis of an ultrahigh speed axial-flux permanent magnet (AFPM) machine for an aerospace flywheel energy storage system. The superiority of the proposed AFPM machine is the material-efficient PM shape, which contributes to obtain a sinusoidal back electromotive force (back EMF) and, hence, reduces the torque pulsations of the machine such as torque ripple. The harmonics present in back EMF have a large influence on iron loss and torque pulsations, which are always unacceptable in the applications involving the speed as high as 1 000 000 r/min. Analytical modeling is first performed to determine the PM shape for the proposed models. Then, the advantages of the proposed models are verified by comparing with the basic model with the conventional ring-shaped PMs using the 3-D finite-element method. The results show that the proposed models have a nearly ideal sinusoidal back-EMF waveform that significantly reduces the torque ripples compared with the basic model. [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]

This paper proposes two novel traction motors with ferrite magnets for hybrid electric vehicles (HEVs), which have competitive torque density and efficiency as well as operating range with respect to a referenced rare earth magnet motor employed in the third-generation Toyota Prius, a commercialized HEV. The two proposed traction motors, named as dual stator radial flux permanent magnet motor (DSRFPMM) and dual stator axial flux permanent magnet motor (DSAFPMM), adopt the same design concept, which incorporates the unaligned arrangement of two stators together with the use of spoke-type magnet array and phase-group concentrated-coil windings for the purpose of increasing torque density and reducing torque ripple. A finite element method is utilized for predicting the main characteristics, such as back electromotive force, cogging torque, electromagnetic torque, iron loss, and efficiency in both of the proposed motors. Moreover, a comparative study between the proposed DSRFPMM and DSAFPMM is performed under the same operating condition. As a result, it is demonstrated that both of the proposed ferrite permanent magnet motors could be good alternatives for traction application, replacing the rare earth magnet motors. [ABSTRACT FROM AUTHOR]

This paper focuses on the design and analysis of a novel material-efficient permanent-magnet (PM) shape for surface-mounted PM (SPM) motors used in automotive actuators. Most of such applications require smooth torque with minimum pulsation for an accurate position control. The proposed PM shape is designed to be sinusoidal and symmetrical in the axial direction for minimizing the amount of rare earth magnets as well as for providing balanced axial electromagnetic force, which turns out to obtain better sinusoidal electromotive force, less cogging torque, and, consequently, smooth electromagnetic torque. The contribution of the novel PM shape to motor characteristics is first estimated by 3-D finite-element method, and all of the simulation results are compared with those of SPM motors with two conventional arched PM shapes: one previously reported sinusoidal PM shape and one step skewed PM shape. Finally, some finite-element analysis results are confirmed by experimental results. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel transverse flux type permanent magnet reluctance generator (TFPMRG), which contains a permanent magnet (PM) in its U-shaped salient stator pole. A U-shaped stator core is designed with the short flux path to reduce the mutual effect between phases. Moreover, the proposed TFPMRG shape is designed for using PM instead of an excitation circuit to provide the field excitation, which increases the output power and efficiency. Both the transverse flux type switched reluctance generator (TFSRG) and the TFPMRG are designed using 3-D finite-element analysis (FEA) and a torque equation called the D-2L method. Finally, the design results of the TFSRG and TFPMRG are confirmed with 3-D FEA. According to the results, the output power and efficiency of TFPMRG are higher than those of TFSRG. [ABSTRACT FROM AUTHOR]

In this paper, an optimal design for a concentrated flux interior permanent magnet (CFIPM) motor is proposed to improve efficiency and obtain a wide operation range simultaneously. For enhancement in efficiency in the constant torque region, the saliency ratio is increased with respect to the initial model. Two points, 3000 rpm (based speed) in the constant torque region and 7000 rpm (maximum speed) in the constant power region, are chosen so as to compare the torque in our design with that of the initial model. A 2D-finite element method (FEM) was used to calculate the inductances of the d-axis and q-axis with a change in the CFIPM rotor shape. In the optimal design, the Kriging method based on Latin hypercube sampling (LHS) and a genetic algorithm (GA) were employed. The validity of the optimal design was verified by 2D-FEM and current vector control. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling of a novel permanent magnet (PM) pole shape for a surface-mounted permanent magnet (SPM) motor so as to generate sinusoidal back EMF and linear electromagnetic torque. Conventional SPM motors have a square-shaped PM pole structure; therefore, square back EMF is generated along with the torque pulsations. This novel SPM motor has sinusoidal PM pole shape in the axial direction; therefore, sinusoidal back EMF is generated due to the sinusoidal magnetic flux distribution. Sinusoidal back EMF eliminates most of the cogging torque; thus, a linear electromagnetic torque is generated. Square and sinusoidal current excitation is provided as to analyze the electromagnetic torque characteristics of SPM motor models. As compared to square current excitation, sinusoidal current excitation shows better linearity as well as average electromagnetic torque for the novel SPM motor model. 3-D finite element analysis (FEA) is utilized to analyze and compare the back EMF, cogging torque, and electromagnetic torque of conventional and proposed novel PM pole shaped SPM motor models for both square and sinusoidal current excitation. [ABSTRACT FROM PUBLISHER]

This paper attempts to design a direct driven axial flux permanent magnet synchronous generator (AFPMSG) with better accuracy considering magnetic flux leakages and fringing effect, using D^{2}L method. Design results of conventional and improved design processes are analyzed and compared using 3D finite element method (FEM). Single and multi-stack AFPMSG topologies are designed by using an improved design process. FEM structural analysis is utilized to improve power to weight ratio of three-stack AFPMSG. Finally characteristics of both single and three-stack AFPMSG topologies are analyzed and compared using 3D FEM analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a novel concentrated flux interior permanent magnet (IPM) type brushless DC (BLDC) motor that replaces low-price ferrite magnets, which has similar characteristics as the conventional IPM type BLDC motor that uses expensive NdFeB magnets. To minimize the cogging torque which is a disadvantage of the proposed model, optimal designs of rotor and permanent magnet were performed. In optimal design process, the Kriging method based on the Latin hypercube sampling (LHS) and a genetic algorithm (GA) are applied due to suitability to non-linear data. Furthermore, to improve the average torque of the proposed model, the current excitation range was changed according to inductance. Through the optimal design process and the proper current excitation range, we show that the optimal model using low-price ferrite magnets has similar performance as the conventional IPM type BLDC motor using NdFeB magnets. [ABSTRACT FROM AUTHOR]

This paper introduces a rotor core in an interior permanent magnet type brushless DC motor. The rotor core consists of a rotor surface having a non-uniform air gap and a novel magnetic flux barrier. We show that, in the rotor core, the rotor surface having the non-uniform air gap effectively reduces the cogging torque while the optimized magnetic flux barrier reduces the cogging torque, and increases the average torque and the efficiency. [ABSTRACT FROM AUTHOR]

This paper presents the shape design of the permanent magnet for a rotary type magnetic position sensor for an automobile acceleration pedal using a new two-dimensional (2-D) analysis method. Basically, its flux path is not uniform in the axial direction because the magnetic flux flows three-dimensionally (3-D) between the stator yoke and permanent magnet. So, the analysis and design of the magnetic position sensor has to consider the 3-D shape. We propose a 2-D analytical modeling method of magnetic position sensor account for fringing effects and optimize the shape of the permanent magnet for a high linearity characteristic. Then, the validity of the developed method is confirmed by comparing the calculated values with the measured values. [ABSTRACT FROM AUTHOR]

This paper presents a robust optimal design method using a hybrid response surface method (H-RSM) which directly finds an optimal point satisfying a target Z-value or a probability of failure. Through three steps, this paper achieves the goal that is to increase the open-circuit airgap flux (OCAF) in a surface-mounted permanent magnet motor and decrease its variation caused by variations of the airgap lengths including an additional one between permanent magnets and rotor back yoke. First, the OCAF equation is derived from the magnetic equivalent circuit (MEC) considering the additional airgap. Then, the equation is validated by comparing its results with those of the finite element method (FEM) modeled by the slotless stator. Next, the tolerance sensitivity analysis, using the partial derivative of the OCAF equation with respect to the airgap length, is performed to investigate the effects of design variables on the OCAF. It is shown that increasing the magnet thickness is effective for both increasing mean of the OCAF and reducing its variation. Finally, robust optimal design is performed using the H-RSM, in which all data are obtained from the FEM modeled by the slotted stator. The results of the robust optimal design are verified using the FEM. [ABSTRACT FROM AUTHOR]