Search

This paper employs an overhang structure for axial flux permanent magnet motor to enhance the torque density. However, the overhang structure requires a computationally expensive 3-D finite-element method (FEM) for analysis, because a quasi-3-D FEM cannot be applied to such a geometry. Thus, in order to reduce the computational cost of above-mentioned topology, this paper adopts a field reconstruction method (FRM). The conventional FRM is applicable only in the case, where the slot pitch to teeth length ratio is the same along radial direction. To address this problem, we introduce a virtual air gap concept so that it can take into account parallel slot effect as well as overhang effect. In this paper, the effectiveness of the proposed method is verified by the 3-D FEM and experimental results. [ABSTRACT FROM AUTHOR]

In this study, an investigation of winding structures is performed for 3-phase unbalanced and asymmetric winding permanent magnet (PM) machines including different slot-pole combinations. There are two different cases for unbalanced winding (UBW) structure: 1) Stator slot number of the machine is divisible by three, 2) Stator slot number of the machine is not divisible by three. Only the first case is examined in this paper. The unbalanced winding layouts are created for minimum unbalance and maximum winding factor. Total magneto motive force (MMF) distributions for nine different slot-pole combinations and their harmonic contents are presented. Variation of the amount of unbalance for different slot-pole combinations is also provided in the paper. Key issues arising from the asymmetric and unbalanced windings such as degree of asymmetric and unbalanced magnetic pull are explored. A prototype motor with 39-slots and 12-poles has been manufactured for experimental verification. A comparison between the finite element analysis (FEA) results and experimental results is presented for the prototype motor for both no-load and on-load conditions. It is shown that the asymmetric and unbalanced winding PM motors have significant potential for applications requiring smooth torque operation. [ABSTRACT FROM AUTHOR]

Recently, dual-rotor motor (DRM) has emerged as an alternative for an induction motor (IM) or a permanent-magnet (PM) motor for electric vehicle application, due to its better drive performance and better torque density. This paper presents an analytical model for the hybrid IM-PM configuration of DRM. The analytical model can be used to predict induced bar currents, electromagnetic torque generated, and magnetic fields in various regions of the motor. The mentioned calculations are performed under steady-state conditions. The analytical method is developed using the subdomain model approach in 2-D polar coordinates. Appropriate governing equations along with boundary conditions across all the sub-domain regions of the DRM are employed to calculate the magnetic vector potential in all the regions. The developed analytical model has been validated with finite-element analysis for various operating conditions, and high accuracy has been achieved for all the results. [ABSTRACT FROM AUTHOR]

This paper aims to analyze the characteristics of a surface permanent-magnet Vernier motor (SPMVM) according to the pole ratio among the rotor magnet pole pairs, stator teeth, and winding pole number. The SPMVM has the same operational principle as a magnetic gear, and it is operated using the space harmonics of the air-gap flux density due to the magnetomotive force and air-gap permeance. In this paper, first, the design parameters of the SPMVM are specified based on an analytical calculation of the air-gap magnetic flux density. Moreover, various combinations of the rotor magnet pole pairs and stator teeth number are made and compared according to the operational principle of a Vernier motor using a 2-D finite-element method. [ABSTRACT FROM AUTHOR]

In this paper, a new permanent magnet (PM) linear motor is proposed. This motor has a special structure with complementary stator flux, which helps to reduce the flux leakage and improve the utilization of the PM. The PMs are installed in a leaning manner, which increases the effective area of the PMs and enhances the field excitation. Hence, the force density of the motor can be improved and it will be, especially suitable for applications within a limited space. The motor structure and working principle are first explained. The design of the motor is then comprehensively investigated. An electromagnetic optimization method based on tabu search algorithm and finite-element method is proposed for the motor to improve its force density. [ABSTRACT FROM AUTHOR]

Consequent-pole (CP) permanent magnet (PM) configuration suffers asymmetric electromagnetic characteristics although it saves PM usage. The CP-based stator-PM synchronous machines are investigated in this paper, with particular reference to symmetrical issues. The electromagnetic performances of the CP-based stator-PM synchronous machines are firstly evaluated. Afterwards, the rule of even order harmonics cancellation is presented for different slot/pole number combinations and winding layouts, based on which symmetrical phase flux-linkages can be obtained although the unbalanced magnetic flux naturally occurs. Moreover, based on the three-dimensional finite element analysis, the unipolar end leakage-flux caused by the asymmetric magnetic field is identified, and the risk of the shaft magnetization is revealed. Finally, a pair of prototype machines are fabricated and measured to validate the analyses. [ABSTRACT FROM AUTHOR]

This paper is about the mechanical design and analysis of a yokeless and segmented armature axial flux permanent-magnet (PM) synchronous machine, which consists of two external rotors and an inner stator. Although this new electrical machine has many advantages such as high torque density, shorter axial length, and high efficiency, its mechanical construction is yet challenging. This is mostly due to the high axial force between the stator and the two rotors, which can be further increased by the inevitable manufacturing and assembly tolerances. Based on the determined geometric dimensions of the electromagnetically relevant components, a reliable mechanical construction is developed in this paper. Subsequently, stress, deformation, thermal, and modal analyses are performed based on finite-element method (FEM). Finally, the first prototype is successfully manufactured and measured. It can be concluded that the proposed construction is reliable and the measured data match well with the results of the electromagnetic analysis. [ABSTRACT FROM AUTHOR]

Linear magnetic-field modulated (LMFM) motor exhibits high thrust force by effectively employing the magnetic-field modulation effect. In this paper, a new mover separated LMFM (MS-LMFM) motor is proposed, which successfully alleviates the space confliction between permanent magnets (PMs) and windings in the existing LMFM motor. The structure and the operation principle of the existing and proposed motor are described, and the major design parameters are optimized for maximum thrust force. Moreover, electromagnetic performances of both motors are compared by finite-element method. Theoretical and simulation analysis shows that the proposed motor can exhibit enhanced force performance than the existing one under fixed copper loss. Simultaneously, reduced iron and PM losses can also be obtained by proposed motor. Finally, a 3-D modeling MS-LMFM motor is built for a global observation of motor structure and further verification of the 2-D analysis. [ABSTRACT FROM AUTHOR]

This paper presents a novel double salient motor design in which the permanent magnets are implanted in the stator to provide additional magnetic flux sources for enhancing its performance and reducing the inherent cogging torque. The feasible cones method is adopted to calculate the dimensional sizes of the proposed short flux path motor. The assembled stators concept is employed to design the magnetic flux paths of the double salient permanent magnet (DSPM) motor and also transfer the heat generated by the windings outside the motor. Due to the nonlinear properties of the doubly salient structure, this paper utilizes both magnetic circuit analysis and finite element analysis to evaluate different operating characteristics of the designed DSPM motor. Experimental data are provided to verify the proposed design. [ABSTRACT FROM AUTHOR]

This paper formulates the difference in base frequency and maximum torque between distributed and concentrated windings taking into account the air-gap modulation of concentrated-winding permanent magnet (PM) motors. The design superiority is typically confirmed for each winding type during a development period by using time-consuming finite element analysis (FEA). We propose a quantification that enables motor designers to easily judge, at the initial design stage, a superior winding type and to shorten a design period. Throughout our formulation, we found that the distributed-winding PM motors, in principle, have larger q-axis inductance and smaller d-axis inductance than the concentrated-winding motors, which leads to a decrease in the base frequency. On the other hand, the distributed winding inherently has higher winding factor and needs shorter stack length of core than the concentrated winding for identical torque output, which results in an increase in the base frequency. And also, we theoretically quantified the difference in reluctance-torque contribution between the two winding types and found that it was too small to have much impact on practical design. We applied the proposed formulae to a 0.2-kW concentrated-winding Nd-Fe-B magnet motor and were able to quantify the base frequency, the maximum torque, and the minimum stack length of core for a distributed-winding motor with high accuracy without having to rely on FEA. The FEA and measurement results demonstrated the validity of the proposed approach for the fabricated distributed-winding PM motor. [ABSTRACT FROM AUTHOR]

This paper addresses a simple and computationally efficient dynamic model for brushless permanent magnet (PM) motors under PM demagnetization faults. The impact of stator slots and spatial disposition of the windings are taken into account to improve the accuracy of a lumped-parameter $abc$ model. This model is suitable for tracking the dynamic behavior of fault components, as it can be accompanied by any control scheme and/or be used for model-based fault detection schemes. In addition, parameters of this model can be automatically tuned by an optimization process in the offline phase of the healthy machine. Finite-element simulations are carried out for proving the effectiveness of the proposed model. Verification is done in both time and frequency domains for four PM motors with different rotor and stator configurations. The simulation results are experimentally verified. [ABSTRACT FROM AUTHOR]

Demagnetization faults in permanent magnet synchronous motors may generate specific fault harmonic frequencies in the stator currents and the zero-sequence voltage component (ZSVC) spectra. Hence, by analyzing the stator currents or/and the ZSVC spectra it is possible to develop fault diagnosis schemes to detect such faults. In order to have a broad view of such effects, a representative set of stator windings configurations must be considered. By analyzing different stator windings configurations this paper shows that the amplitude of the harmonic frequencies of both the stator currents and the ZSVC spectrato be analyzed are significantly influenced by the stator windings configuration. It is also proved that depending on the winding configuration, new harmonic components may emerge in both spectra. The results presented in this paper may help to develop fault diagnosis schemes based on the acquisition and further analysis of the stator currents and the ZSVC harmonic components. [ABSTRACT FROM PUBLISHER]

This paper presents a methodology for the design, analysis, and graphical optimization of ironless brushless permanent magnet machines primarily for generator applications. Magnetic flux in this class of electromagnetic machine tends to be 3-D due to the lack of conventional iron structures and the absence of a constrained magnetic flux path. The proposed methodology includes comprehensive geometric, magnetic and electrical dimensioning followed by detailed 3-D finite element (FE) modeling of a base machine for which parameters are determined. These parameters are then graphically optimized within sensible volumetric and electromagnetic constraints to arrive at improved design solutions. This paper considers an ironless machine design to validate the 3-D FE model to optimize power conversion for the case of a low-speed, ironless stator generator. The machine configuration investigated in this paper has concentric arrangement of the rotor and the stator, solenoid-shaped coils, and a simple mechanical design considered for ease of manufacture and maintenance. Using performance and material effectiveness as the overriding optimization criteria, this paper suggests optimal designs configurations featuring two different winding arrangements, i.e., radial and circumferentially mounted. Performance and material effectiveness of the studied ironless stator designs are compared to published ironless machine configurations. [ABSTRACT FROM AUTHOR]

Electromagnetic design of a 1.12-MW, 18 000-r/min high-speed permanent-magnet motor (HSPMM) is carried out based on the analysis of pole number, stator slot number, rotor outer diameter, air-gap length, permanent magnet material, thickness, and pole arc. The no-load and full-load performance of the HSPMM is investigated in this paper by using 2-D finite element method (FEM). In addition, the power losses in the HSPMM including core loss, winding loss, rotor eddy current loss, and air friction loss are predicted. Based on the analysis, a prototype motor is manufactured and experimentally tested to verify the machine design. [ABSTRACT FROM PUBLISHER]

A model of permanent-magnet synchronous machine (PMSM), including the electromagnetically originated torque ripple, is presented in this paper. This unique representation of such equivalent circuit is highly critical to understand the torque ripple content and to develop an appropriate mitigation scheme for low torque ripple applications requiring four quadrant operations. This research proposes a method to quantify the various sources of torque ripple and modifies the existing dq-model to enhance the modeling capabilities for both surface-mount and interior PMSMs. Finite-element (FE) analysis is used for modeling various PMSMs to verify the lumped circuit model proposed in this research. The theoretical results obtained from analytical and FE analysis are validated using experimental test. [ABSTRACT FROM AUTHOR]

This paper studies static eccentricity (SE) fault detection in axial-flux permanent-magnet (AFPM) machines using 3-D finite-element analysis. The use of numerical modeling makes it possible to precisely study the eccentricity fault detection in these types of machines. The simulations are validated using experimental measurements. To the best knowledge of the authors, SE fault detection in AFPMs has not been studied before. Hence, a new definition for the SE factor is presented in these types of machines. A motor with different degrees of rotor eccentricity is simulated, and the back electromotive force (EMF) of all coils of the stator is obtained. In addition, an appropriate criterion has been presented for the fault detection using the back EMF of the coils. This study indicates that the back EMF of the coils of the stator is a good criterion for eccentricity fault detection. It is observed that the unbalanced back EMF suggests a method for the indirect measurement of eccentricity that could be carried out during manufacturing and assembling processes or maintenance operation. [ABSTRACT FROM AUTHOR]

Permanent magnet linear synchronous motor (PMLSM) has been successfully applied in various industry fields due mainly to excellent dynamic characteristics and accurate positioning capability. However, PMLSM suffers force ripple, which deteriorates controllability, and it is often considered to be an expensive linear drive mechanism since it requires a large amount of rare-earth permanent magnet (PM) material in the stationary part. This paper introduces and analyzes a new design of winding and mover arrangement for doubly salient permanent magnet linear synchronous motor (DSPMLSM). The proposed design reduces force ripples, magnetic unbalance, and the amount of PM material used in the stationary part. Extensive finite element analysis (FEA) reveals the effectiveness of the proposed design. [ABSTRACT FROM AUTHOR]

In this paper, a novel high-temperature superconductor (HTS) permanent magnet (PM) vernier motor is proposed for direct-drive propulsion, which can directly offer the low-speed high-torque capability and the high-speed rotating field design to eliminate the gearing mechanism and maximize the power density, respectively. The key is to newly introduce HTS bulks to flux-modulation poles that can effectively modulate between the high-speed rotating field of armature windings and the low-speed rotating field of the PM outer rotor. Also, the use of HTS bulks can greatly reduce the flux leakage and hence improve the torque density. Based on using the finite element method, the motor performances are analysed. Hence, the validity of the proposed motor is verified. [ABSTRACT FROM AUTHOR]

The fault-tolerant capabilities are compared in this paper for the conventional double-layer switched-flux permanent-magnet machine and its single-layer counterparts, i.e., C-core, E-core, and modular. The comparison includes the interturn short-circuit and irreversible demagnetization faults. A combination of Simulink and finite element models is used in the study. Based on the predictions, it is found that the modular topology produces the lowest short-circuit current and also has the best demagnetization withstand capability while the conventional one produces the highest short-circuit current and has the worst demagnetization withstand capability. The frozen permeability method is employed to separate the flux produced by armature current and magnets, and the results showed that, besides the influence of short-circuit current, the available magnet volume and magnetic circuit configuration play an important role in the demagnetization process. It is also found that removing half of the magnets, such as using C-core, E-core, and modular topologies, generally improves the demagnetization withstand capability and also increases the torque per magnet volume. Measured results are also presented to validate the short-circuit current predictions and magnet demagnetization. [ABSTRACT FROM PUBLISHER]

The analysis and design of electrical machines often require analytical-models for performance assessment and system simulation. Inductances are important parameters of these models. The principles and drawbacks of the existing inductance calculation methods for electrical machines based on generalized electrical machine theory and the finite-element (FE) method are reviewed in this paper. To help alleviate some of the problems associated with these existing methods, the author has developed an improved FE inductance calculation method, and used it to evaluate inductances of equivalent circuit models. The new technique utilizes the same finite-element field solutions of electrical machines under actual multiphase excitations as are used for torque calculations. This eliminates the need for specially designed FE solutions, or for multiple solutions under current perturbations such as are required by existing FE methods. The new method has been verified by test results using a 30 hp permanent magnet synchronous machine under different load conditions. [ABSTRACT FROM PUBLISHER]

Axial-flux permanent magnet (AFPM) machines are gaining popularity in low-speed and high torque applications due to their high torque density, high efficiency, and compact structure. In this article, a dual-rotor slotless AFPM (DRSAFPM) machine equipped with equidirectional toroidal winding (EDTW) is proposed and compared with that equipped with conventional single-layer and double-layer concentrated windings (CWs). First, the differences between the DRSAFPM machine with EDTW and that with conventional CWs in coil layout, electromotive force (EMF), and winding magnetomotive force are revealed. Considering the special coil layout of the EDTW, the coil factor and size equations of the DRSAFPM machines with EDTW and conventional CWs are presented. Second, the electromagnetic performance including air-gap field, back-EMF, torque, and efficiency of the DRSAFPM machines with EDTW and conventional CWs are analyzed based on the three-dimensional finite-element method. The simulation results validate the correctness of the coil factor and size equations and indicate the EDTW–DRSAFPM machine has superiority in back-EMF amplitude and torque density. Finally, a prototype of the EDTW–DRSAFPM machine is manufactured and tested, which validates the feasibility of the EDTW–DRSAFPM machine and the correctness of the analysis. [ABSTRACT FROM AUTHOR]

This article proposes a consequent-pole unequal Halbach vernier wheel motor (CPUHVWM), which effectively reduces the self-flux leakage between permanent magnets, and an optimization method is proposed to improve the motor optimization efficiency and shorten the optimization time. The key variables are selected by the sensitivity analysis, and a polynomial function suitable for the optimization algorithm is constructed based on the response surface method. Based on the particle swarm optimization algorithm, the weights of different particle search areas are assigned to improve the overall optimization efficiency of the algorithm. Furthermore, to verify the superiority of the performance of the proposed structure and the applicability of the algorithm, the other two similar motor structures are compared, and the algorithm is adopted for the optimization. The optimized electromagnetic characteristics are compared by the finite element method. Finally, the prototype with the optimal parameters is built, and the effectiveness and advantages of the optimization algorithm are verified by experiments. [ABSTRACT FROM AUTHOR]

This article presents a new type of surface-mounted three-phase permanent magnet synchronous motor with the same number of poles and slots which has obvious advantages in cogging torque. Since the same-pole and same-slot three-phase permanent magnet motor has three or more slot types and the slots are not evenly distributed on the circumference, this article adopts an accurate subdomain model that considers the position and slot width of each slot separately to perform an analytical calculation of the magnetic field. The motor is divided into three subdomains and modeled by Maxwell’s equations, and the magnetic scalar vector equation satisfied by each subdomain is solved by the method of separation of variables. A 24-pole 24-slot three-phase permanent magnet motor consisting of 13-pole 12-slot and 11-pole 12-slot is used to verify the correctness of the proposed analytical computational model. Compared with the finite element analysis, the proposed analytical model shows high accuracy in the calculations of the magnetic flux density of the three subdomains. [ABSTRACT FROM AUTHOR]

In this article, two double flux modulation permanent-magnet machines (DFMPMs) with PMs on both stator and rotor are introduced. The two DFMPMs share a similar operation principle. However, due to the different stator-PM arrangements, the two DFMPMs show different performances. In order to analyze their performance characteristics, their analytical models are built and verified by finite element analysis (FEA). Moreover, to quantitatively compare their electromagnetic performances more accurately, the two DFMPM topologies are optimized, respectively, and compared in terms of back-EMF, cogging torque,rated torque, torque ripple, power factor, and efficiency. Finally, the DFMPM topology with relatively better performances is built and tested. The experimental results match well with the FEA simulations. [ABSTRACT FROM AUTHOR]

This article mainly investigates the torque characteristic of a novel tiered type permanent magnet spherical motor (T-PMSpM), which has the advantage of relatively larger torque ability compared with most existing spherical motors. The investigated T-PMSpM is capable of continuously rotating while the rotating shaft can tilt in all directions. Therefore, both the rotating torque and tilting torque need to be studied. Considering that the rotating principle is similar to the conventional permanent magnet synchronous motors, more attention is being paid to the tilting performance since it also decides the tilting range of the T-PMSpM. First, the key factors that significantly influence the tilting torque are found out based on the analytical expression of the tilting torque. Then, these key factors are analyzed aiming at expanding the tilting range as well as the magnitude of the tilting torque. Finally, the rotating torque is obtained and analyzed based on the above-optimized structure. The three-dimensional finite-element method is adopted for accurate calculation. A prototype motor of the T-PMSpM has been manufactured, and an experimental procedure is designed to measure the output torque for verification. [ABSTRACT FROM AUTHOR]

Fractional slot concentrated winding (FSCW) permanent magnet (PM) motors are becoming an attractive solution in low-speed applications due to their superior advantages. A new topology of FSCW motor is introduced in this article, which consist of single stator and two PM rotors with different and opposite direction rated speed. The stator torque reaction is reduced significantly due to the opposite rotational direction of rotors. Some performance characteristics of proposed topology are investigated by designing and manufacturing a 0.5 kW prototype motor. The back-emf voltages, torque reaction, torque ripple and core losses are obtained via finite elements method (FEM) and are compared with two conventional FSCW motors. The prototypes of case-studied motors are tested experimentally in order to validate the advantages of proposed motor. [ABSTRACT FROM AUTHOR]

Flux reversal linear rotary permanent magnet actuator (FR-LRPMA) is a two-degree-of-freedom actuator with two ferromagnetic (Fe) poles and two permanent magnet (PM) poles mounted on the surface of each stator pole. The flux linkage waveform of the actuator is more sinusoidal than that of the traditional topology, which are analyzed by the ideal linear model of one stator section of the proposed actuator. In order to reduce the amplitudes of the cogging torque and detent force, a key space gap parameter of the FR-LRPMA between the Fe pole and PM pole is studied in the circumferential and axial directions. The expressions of cogging torque and detent force are derived by the magnetomotive force analytical method, which are used to obtain the optimal space gap parameter value. The electromagnetic characteristics of the actuator are analyzed by the finite-element method. The amplitudes of cogging torque and detent force are reduced and the back electromotive force waveform is more sinusoidal than that of the original topology, which are verified by the experiment. [ABSTRACT FROM AUTHOR]

In external rotor permanent magnet synchronous motors with non-overlapping windings, the higher frequency harmonics of the radial forces generate considerable resonant vibrations and acoustic noise. Therefore, diversity of spatial and specifically frequency harmonic ordinal numbers of representative slot and pole number combinations are derived analytically with open circuit and under load. Amplitudes of radial force waves are calculated by means of the finite element method and 2-D Fourier analysis. The obtained results confirm the analytical investigation. Determining factors on amplitudes are studied on machines having different slot and pole numbers and double-layer windings. Higher frequency harmonics significantly depend on the pole and tooth shape as well as the current profile. With open circuit, the calculations are validated by experiments. The findings are applied to reduce the noise of a centrifugal fan. [ABSTRACT FROM PUBLISHER]

Analytical expressions for the no-load magnetic field distribution of slotless brushless permanent-magnet (PM) machines with static, dynamic, and mixed rotor eccentricities are presented. The proposed analytical expressions can be used for slotless brushless PM machines with any radius-independent magnetization pattern. The analytical expressions and the results for six different magnetization patterns are presented. Based on the analytical magnetic field distribution, the line and phase back-electromotive force waveforms, local traction components and unbalanced magnetic forces are obtained. The analytical results are compared with those from finite-element analyses to validate the derived expressions. [ABSTRACT FROM AUTHOR]