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In order to relieve the computational burden and reduce the ripples in thrust force and current of linear vernier permanent-magnet motors, this article proposes three-vector-based model predictive current control (MPCC) with efficient voltage vectors selection. The proposed method avoids the traversal of all the possible voltage vectors. Only three nonadjacent active voltage vectors are predicted and evaluated by the cost function. Two active voltage vectors can be precisely determined according to the relationship of three cost function values. The prediction workload can be reduced with the efficient voltage vectors selection. Also, the two active voltage vectors along with the null voltage vector are used to synthesize the final applied voltage vector based on deadbeat principle. The proposed three-vector-based MPCC method extends the modulation area from discrete points to the whole regular hexagon. Thus, the ripples in thrust force and current can be minimized. Theoretical analyses and experimental results are given to verify the effectiveness of the proposed MPCC. [ABSTRACT FROM AUTHOR]

The consequent pole permanent magnet (CPM) machine is well known for its high magnet utilization ratio and poor vibration performance. This article focuses on electromagnetic vibration and its reduction design in CPM machines, and the conventional surface-mounted permanent magnet (SPM) machine is used as a benchmark. First, the asymmetrical magnetic field and unbalanced radial force of the CPM machine are investigated with emphasis. The slot-pole combination and force modulation effect are the two reasons for the unbalanced radial force generation. Afterward, two new designs to reduce the vibration caused by the unbalanced radial force are proposed, and the reduction principles are described in detail. Finally, the prototypes of the 12-slot/10-pole SPM and proposed CPM machines are manufactured. The tests are conducted to validate the theoretical analysis and proposed vibration reduction design. [ABSTRACT FROM AUTHOR]

In this article, a targeted step skewing of rotor segments scheme is proposed to reveal the modulated vibration reduction mechanism in integral-slot interior permanent magnet synchronous machines (IPMSMs). First, the vibration characteristics of a 72-slot/12-pole integral-slot IPMSM are investigated. The dominant vibration at specific frequency band is introduced. Then, in order to analyze the main source of vibration, the magnetic field modulation effect and radial force modulation effect are investigated in detail. The results show that the high-order radial force can excite large vibration by radial force modulation effect. This kind of vibration is defined as modulated vibration. Afterwards, the optimal shift angle and number of rotor segments are determined by comparison. Finally, the conventional and proposed 72-slot/12-pole integral-slot IPMSMs are manufactured to validate the theoretical analysis. The experimental results verify that the proposed method can effectively reduce the modulated vibration of the 72-slot/12-pole integral-slot IPMSM. [ABSTRACT FROM AUTHOR]

In this article, we propose an unconventional method, i.e., generalized finite difference method (GFDM), to analyze the electromagnetic performance of surface-mounted permanent magnet (SPM) machine with eccentric rotor shape. The remarkable characteristic of this method is that it is meshless. In this method, the solution region is discretized in the form of nodes, and the nodes can move with the moving structure. This is very helpful in modeling the SPM machine because there is no remeshing process during the rotation. However, mesh generation is required in the traditional finite-element analysis (FEA). First, the basic principle of the proposed GFDM is introduced. Second, the whole field domain is divided into five types of regions, viz., PMs, air gap, slot openings, slots, and stator core. Third, the differential equations satisfied by each region are discretized into algebraic equations by the GFDM. The interfaces need to be dealt with separately because of the discontinuity of the derivative of the vector potential. Then, the systems of equations are solved to analyze the electromagnetic performance of an SPM machine. Finally, this method is implemented on a 12-slot, 10-pole SPM machine. Meanwhile, the effectiveness of this method is verified by an FEA and experiment. [ABSTRACT FROM AUTHOR]

This article proposes a modified flux observer for sensorless direct torque control (DTC) of the dual three-phase permanent-magnet synchronous motor. The proposed method can improve torque performance without a position sensor. The flux observer is proposed to obtain the stator fluxes and rotor fluxes. The stator fluxes can be utilized to calculate the amplitude of torque and flux for DTC system. Meanwhile, the position information can be detected from the rotor fluxes by using a normalized phase-locked loop. This new flux observer can overcome the disadvantages due to the dc bias, initial value, and harmonic components. The stability of the proposed observer is also analyzed in this article. In addition, a fault-tolerant DTC scheme for open-circuit fault is introduced. The performances of torque control and position estimation are evaluated under healthy, open-circuit fault, and fault-tolerant conditions. Simulation and experimental evaluation are carried out to confirm the effectiveness of the proposed sensorless DTC scheme. [ABSTRACT FROM AUTHOR]

In this paper, an interior permanent magnet (IPM) machine is presented and optimized for heavy-duty vehicle direct-drive applications. Since efficiency decrease and serious heating come along with excessive core loss under flux weakening control, a rotor topology with the combination of the eccentricity structure and magnetic barriers is proposed. The key is to achieve the comprehensive optimization of the proposed rotor topology to satisfy the different requirements under diverse operating points. Then, a multi-objective automatic parallel optimization method is applied, which simultaneously analyzes multi-condition operation without weight coefficients defined artificially. The 3D Pareto solution set is generated by using nature inspired evolutionary algorithm based on the high-precision metal-modals of optimal prognosis, which reduce the needed computation cost significantly. Moreover, the back electromotive force total harmonic distortion, torque and core loss of the optimal machine are analyzed at corresponding operating points. Finally, the finite-element results are validated by experiments based on a prototype machine. [ABSTRACT FROM AUTHOR]

This article proposes a new duty-ratio-based direct torque control (DR-DTC) with enhanced harmonic current suppression for a dual-three-phase permanent magnet (DTP-PM) motor. First, a new virtual voltage vector construction method based on the carrier-based modulation technique is proposed. Twelve virtual voltage vectors with null average voltage values in two harmonic subspaces are constructed. The sequences of the constructed virtual voltages can be calculated directly in the natural coordinate system. In addition, the whole sequences are standard symmetrical, which can be easily generated by a digital controller. After that, an online harmonic current compensation method is investigated. Additional controllers compensate for the harmonic currents induced by the back electromotive force and nonlinear factors. Since the virtual voltage vectors have null average voltage values in two harmonic subspaces and the online harmonic current compensation method is designed, the proposed DR-DTC can be introduced to the DTP-PM motor with a single neutral point and two neural points. With the proposed strategy, the capability of harmonic current suppression can be significantly improved, and the processes of virtual voltage construction can be simplified. In addition, the advantages of the conventional DR-DTC can be inherited. Finally, experiments are carried out to validate the feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

This article proposes a novel remedial direct torque control (RDTC) for the postfault operation of the dual three-phase permanent-magnet (DTP-PM) motor. The DTP-PM motor is configured as a two-neutral points model and fed by an eight-leg voltage source inverter. Also, the harmonic torque induced by the third harmonic back electromotive force and zero-sequence currents is considered at the postfault operation. First, the switching tables for different fault conditions are pre-established. The proposed strategy can be applied to different postfault operations with one phase open by replacing the switching table simply. At the normal operation, the redundant auxiliary legs are disabled. So, the proposed eight-leg voltage inverter is the same as the conventional six-leg one. At the postfault operation, the auxiliary leg in the faulty three-phase windings provides an additional control degree of freedom. Hence, the fault-tolerant capability of the DTP-PM motor with two neutral points can be enhanced. Also, the proposed strategy compensates for the harmonic torque by modifying the reference torque. Based on the proposed RDTC, the postfault operational performance can be significantly improved. Finally, the simulations and experiments are conducted to validate the feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

This article proposed a self-adapted model predictive current control (SA-MPCC) method to reduce the switching loss of the five-phase open-end winding permanent-magnet synchronous motor (OW-PMSM). The proposed SA-MPCC method regards the OW-PMSM drive system as two separate parts by utilizing the flexibility of the OW-PMSM system, thus generating and applying the phase voltage to armature winding independently. The virtual voltage vectors and multivector duty cycle modulation strategy is adopted to maintain a good steady-state and dynamic behavior. Then, the self-adapted decision is generated to choose one inverter work solely, or two inverters work cooperatively. When one inverter is used, another inverter is closed. The first inverter is clamped to optimal virtual voltage vectors when two inverters work together. The clamping to virtual voltage vectors or zero vectors can reduce the switching loss in both sides of the dual inverter. Finally, the experimental results verify the effectiveness of the proposed SA-MPCC method. [ABSTRACT FROM AUTHOR]

The conventional model predictive power control suffers from heavy computational burden and large power ripple. To address the problem, this paper proposes a simplified three-vector-based model predictive direct power control, which can greatly optimize the control set. Firstly, a switching table is designed to exclude the redundant virtual voltage vectors (VVs). Only half of the candidate VVs are retained. Then, the effect of each VV on power is analyzed in detail. The deviation of reactive power is used as the evidence to further simplify the control set. In this way, the prediction behavior is reduced from 12 to 2, which effectively reduces the computational burden. In addition, the concept of power deadbeat is employed to determine the duty cycles of the two virtual VVs and one zero VV. Thus, the power ripples and current harmonics can be considerably suppressed. With this proposed method, the calculation complexity is reduced, and the steady-state performance is improved. The simulation and experimental results are given to verify the proposed method. [ABSTRACT FROM AUTHOR]

Position estimation error caused by the cross-saturation effect seriously affects the performance of signal injection based sensorless control, especially for the surface permanent-magnet synchronous motor (SPMSM) with load. In this paper, a position estimation error compensation method is proposed to improve the accuracy and stability of sensorless control for a dual three-phaseSPMSM. Based on the space vector signal injection, the initial position is obtained by the demodulation of high-frequency current response. By analyzing the relationship between the stator flux and stator current, the optimal compensation angle can be achieved. The position estimation error can be dynamically compensated under load conditions with the combination of initial position and compensation angle. Due to the convergence of compensation angle, the compensation process has weak dependence on prior knowledge of the motor. Simulation and experimental results are presented to validate the proposed method. [ABSTRACT FROM AUTHOR]

In order to reduce thrust force and stator flux ripples, this article proposes a simplified three-vector-based model predictive thrust force control method for a double-side linear vernier permanent magnet motor. First, a simplified control set is designed to select two active voltage vectors (VVs) in the prediction stage, instead of evaluating redundant VVs. Null VVs are applied to adjust the amplitude of the modified VV, which can realize a full-range modulation by the predefined cost function. To simplify the tuning work of the weighting factor, the variables in the cost function only consider the stator flux term. Then, the duration time of the selected VVs is distributed reasonably through a novel cascaded optimization process. Also, the deadbeat principle is adopted to calculate the duty cycle. With the proposed method, the thrust force and stator flux ripples can be considerably minimized. The simulated and experimental results are conducted to verify the proposed control method. [ABSTRACT FROM AUTHOR]

Linear vernier permanent-magnet (LVPM) motors have a bright future in long stroke applications, because of their merits of high efficiency, high force capability, and low cost. However, the position sensor for the LVPM motor costs huge. In this article, a sensorless control based on an improved mover flux observer is proposed. The proposed mover flux observer combines a disturbance observer and a feedback controller. It can be easily implemented, which results in low computation burden. Due to simple tuning parameters of this observer, the mover flux observer can have strong robustness to the dc bias and the initialization errors of integrators that are main weakness of flux model. This proposed observer also does not introduce error in either the estimated mover flux amplitude or phase. Then, a phase-locked loop is used to detected position information from the mover fluxes. Finally, the LVPM motor operates by using the estimated position and speed signals. Simulation and experimental results of the LVPM motor demonstrate the accuracy and dynamic performance of the proposed sensorless operation. [ABSTRACT FROM AUTHOR]

Permanent‐magnet (PM) segmentation is a plain and valid way for eddy current (EC) loss reduction in fractional‐slot concentrated‐winding (FSCW) machines and it has no passive effect on the machine itself. In this study, compared with PM asymmetrical segmentation, the authors prove that symmetrical segmentation adopted by most scholars, in general, is the optimal choice by using both analytical method (AM) and time‐stepped transient finite‐element method (FEM), when the skin effect is neglected. Furthermore, two surface‐mounted PM machines with FSCW are proposed to investigate the effect of PM symmetrical segmentation on EC loss in rotor PMs. The actual effect of PM segmentation is to cut off the EC path and increase the resistance value in return circuit, thus decreasing EC density in PMs. In addition, some theoretical expressions evaluating the EC loss with consideration of magnet segmentation effect are derived step by step. Finally, Maxwell FEM software is used to verify the theoretical analysis, showing that the proposed AM is able to accurately predict the EC loss with different segmented numbers. [ABSTRACT FROM AUTHOR]

The Double Permanent Magnet Vernier (DPMV) machine is well known for its high torque density and magnet utilization ratio. This paper aims to investigate the torque generation mechanism and its improved design in DPMV machines for hub propulsion based on the field modulation principle. Firstly, the topology of the proposed DPMV machine is introduced, and a commercial PM machine is used as a benchmark. Secondly, the rotor PM, stator PM, and armature magnetic fields are derived and analyzed considering the modulation effect, respectively. Meanwhile, the contribution of each harmonic to average torque is pointed out. It can be concluded that the 7th-, 12th-, 19th- and 24th-order flux density harmonics are the main source of average torque. Thanks to the multi-working harmonic characteristics, the average torque of DPMV machines has significantly increased by 31.8% compared to the counterpart commercial PM machine, while also reducing the PM weight by 75%. Thirdly, the auxiliary barrier structure and dual three-phase winding configuration are proposed from the perspective of optimizing the phase and amplitude of working harmonics, respectively. The improvements in average torque are 9.9% and 5.4%, correspondingly. [ABSTRACT FROM AUTHOR]

This paper introduces a high-force-density linear actuator for an artificial heart, which is based on the concept of a magnetic screw–nut. The novelty of the proposed magnetic screw is adaptation of Halbach permanent-magnet (PM) array disposed helically. PMs are placed on both the screw and the nut. The configuration of the newly designed magnetic screws is presented, and its electromagnetic performances are analyzed. The proposed Halbach magnetized magnetic screw is evaluated as compared with a radially magnetized magnetic screw using the time-stepping finite-element method, verifying the advantages of the proposed structure. [ABSTRACT FROM AUTHOR]

In this paper, a linear permanent-magnet vernier machine is proposed, in which both magnets and armature windings are placed in the short mover, while the long stator consists of an iron core only. Hence, it is suitable for long-stroke applications such as urban rail transit. The proposed machine integrates two magnetization directions of magnets together, which can reduce leakage flux and enhance flux density. Meanwhile, since different topologies and different slot/pole number combinations have an effect on the winding factor, several general rules are established. It is revealed that the thrust force ripple of the proposed machine is lower than its cogging force ripple, which is explained by a built analytical model. Both the analytical model and the finite-element results are validated by experiments based on a prototype machine. [ABSTRACT FROM AUTHOR]

This paper proposes a high force density tubular permanent-magnet (PM) motor, termed as tubular stator-PM venier motor, for artificial hearts. The novelty of the proposed motor is to artfully integrate two different magnetization directions of PMs and ferromagnetic poles together. The proposed motor incorporates the merits of vernier PM motors and stator-PM motors, offering high back electromotive force, improved force density, minimized cogging force, and reduced PM volume. The influence of the magnet pole ratio on the performance is investigated. The proposed motor is designed and compared with an existing vernier PM motor by using the time-stepping finite-element method, verifying the validation and the advantageous performance of the proposed motor. [ABSTRACT FROM PUBLISHER]

A new linear permanent-magnet (PM) motor, termed as modular linear flux-reversal PM (M-LFRPM) motor, is proposed. This is particularly attractive for high reliability urban rail transit. Its PM materials and armature windings are set in the mover (train), while the long stator (rail) is composed of irons, hence improving efficiency and reducing cost. The key of the proposed motor incorporates the concept of fault-tolerant teeth to provide the desired decoupling among phases. The structure and features of the proposed motor are presented, and an optimal design is performed. By using finite element method, the advantages and validity of the proposed motor are verified. The analysis results show that the proposed M-LFRPM motor not only retains the advantages of the conventional LFRPM motor, but also improves its fault-tolerant capability. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel linear permanent-magnet (PM) motor, termed as double-stator tubular PM (DSTPM) motor, for artificial hearts. The key of the proposed DSTPM motor is to design the appropriate size of the inner and the outer stators so that the inner and the outer cogging forces can be counteracted by each other, thus minimizing the motor cogging force. To achieve this purpose, two stators are designed to have a special angle difference of 90 electrical degrees. Since one stator is located inside the mover, the inner space is fully used. Hence, the thrust density is enhanced and the axial direction length is reduced. Also, the PMs and the redundant windings are set in the stators, and the moving parts have only solid-iron salient poles. The electromagnetic characteristics of the proposed motor are analyzed by using the time-stepping finite-element method, confirming the validity of the proposed motor. [ABSTRACT FROM AUTHOR]

A new partitioned stator hybrid excitation (HE) with an internal magnetic ring machine was proposed in this article. The key of the design is to adopt an inner magnetic ring to reduce the inside stator magnetic reluctance. As a result, the working magnetic field harmonics can be improved, which in turn improve the torque and flux regulation abilities. Besides, by following the design of partition stator, the space competition of permanent magnet, armature winding, and field winding can be effectively alleviated as compared with a single stator HE machine. The structure and operation principle of the conventional and proposed machines are described. Moreover, electromagnetic performances of both machines are compared by using finite element method. Theoretical and simulation analysis results show that the proposed machine can exhibit higher torque and enhanced flux regulation ability than the conventional one. [ABSTRACT FROM AUTHOR]

This article focuses on the electromagnetic vibration source and its reduction design in fractional-slot concentrated-windings (FSCWs) permanent magnet (PM) machines. First, the electromagnetic force and vibration characteristics of a 12-slot/10-pole FSCW PM machine are investigated. Then, four electromagnetic vibration sources are investigated and compared, in which the machine operating state is considered. The result shows that the electromagnetic force modulation and stator magnetomotive force (MMF) harmonics are the two sources that contribute most to the vibration underrated and heavy load condition, respectively. Afterward, two new designs to reduce the vibration caused by the electromagnetic force modulation and stator MMF harmonics are proposed, and the reduction principles are described in detail. Finally, the prototypes of the existing and proposed 12-slot/10-pole FSCW PM machines are manufactured. The tests are conducted to validate the theoretical analysis and proposed vibration reduction design. [ABSTRACT FROM AUTHOR]

In this article, the efficiency function of the permanent-magnet (PM) machines is reconstructed by the quantitative loss expressions. Then, the efficiency function is used to quantitatively analyze the maximum efficiency point and the specific high-efficiency region. General principles of improving the maximum efficiency and the regulation of the specific high-efficiency region for PM machines are investigated. First, the loss expressions of PM machines, which vary with the speed and the current, are presented. Moreover, an accurate efficiency function is established to calculate the efficiency map of PM machines quickly. Furthermore, the maximum efficiency point and the specific high-efficiency region of PM machines are derived, as well as their variation principles with loss distributions are studied. Furthermore, a 12-slots 10-poles PM machine and a 48-slots 22-poles PM machine are designed to verify the analytical results. Subsequently, their electromagnetic performances and the efficiency maps are calculated and compared by the finite-element method. Finally, both PM machines are prototyped and experimental results are given for validations. [ABSTRACT FROM AUTHOR]

This article investigates the effects of phase shift on the inductance and short-circuit current (SCC) in permanent-magnet (PM) machines with dual three-phase winding configurations. First, the relationship between the phase shifts and slot/pole combinations, for the dual three-phase winding configurations, is discussed. Second, analytical expressions of the inductance are derived for the 48-slot/22-pole PM machines with different phase shifts based on the winding function theory. Afterwards, the SCC amplitude of different phase shifts is comparatively analyzed. The investigation reveals that the 7.5° and 30° configurations have great significance to improve the self-inductance value. Thereby, the 30° configuration has comparable SCC amplitude compared to the 7.5° counterpart, while being lower than the 15° configuration one. Moreover, the 30° configuration exhibits lower eddy-current loss and preferable torque performance than its counterparts. Furthermore, the finite-element method is used to calculate electromagnetic performances for evaluation. Finally, some experiments on the prototype machine are carried out for validation. [ABSTRACT FROM AUTHOR]

In this paper, a new high reliability linear drive device, termed as stator-permanent-magnet tubular oscillating actuator (SPM-TOA), is proposed for artificial hearts (AHs). The key is to incorporate the concept of two independent phases into this linear AH device, hence achieving high reliability operation. The fault-tolerant teeth are employed to provide the desired decoupling phases in magnetic circuit. Also, as the magnets and the coils are located in the stator, the proposed SPM-TOA takes the definite advantages of robust mover and direct-drive capability. By using the time-stepping finite element method, the electromagnetic characteristics of the proposed SPM-TOA are analyzed, including magnetic field distributions, flux linkages, back- electromotive forces (back-EMFs) self- and mutual inductances, as well as cogging and thrust forces. The results confirm that the proposed SPM-TOA meets the dimension, weight, and force requirements of the AH drive device. [ABSTRACT FROM AUTHOR]

This article proposes a torque improvement method for dual m-phase synchronous reluctance machines by phase shift technique. The emphasis is put on the relationship of d–q axis inductance harmonics and phase shifts. First, all feasible phase shifts for various slot/pole combinations are discussed in general. Second, the influences of phase shift on reluctance torque performance are investigated based on inductance analysis. It is founded that the first main torque harmonic can be eliminated when phase shift equals to π/2m (m is odd) and π/m (m is even), respectively. This is the optimal phase shift covering all the m cases. Third, the optimal phase shift with torque improvement and ripple reduction is verified by the theoretical analysis and finite element method. Finally, the dual 3-phase 24-slot/10-pole synchronous reluctance machines with 30° and 60° phase shifts are fabricated. The experiments on the prototype machine are carried out for validation. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of eccentric magnet design on sideband electromagnetic force (SEMF) and hence high-frequency vibroacoustic performance of integral-slot surface-mounted permanent magnet (SPM) machines. Also, the tangential SEMF components are considered to investigate their contribution for high-frequency vibration and acoustic noise. Firstly, the mechanism of sideband current harmonics introduced by space vector pulse-width modulation technique of open-winding drive system is derived. Moreover, the critical components of sideband synthetic magnet field in air-gap are derived to obtain the radial and tangential SEMF density components, and the effects of concentric magnet design of that is discussed. Then, the vibration synthesis model and acoustic radiation model are used to predict the vibroacoustic performance of machines. The results shows the eccentric magnet design can reduce the high-frequency vibration and noise of integral-slot SPM machines. Finally, two integral-slot SPM machines with concentric and eccentric magnets are manufactured and tested to validate the theoretical investigations. [ABSTRACT FROM AUTHOR]

This article proposes a novel parametric equivalent magnetic network (EMN) modeling approach for multiobjective optimization of a surface-mounted permanent magnet (SPM) machine. The key is to apply variable meshes under adjustable topology to establish parametric EMN model. First, a novel adjustable cross-shape mesh method with variable sizes and regular permeance is proposed, which can flexibly vary with parameters. The meshes are combined in EMN model to simultaneously achieve high accuracy, high computing efficiency, and structural parameterization. Second, comprehensive sensitivity analyses are utilized to separate variable EMN parameters with the parametric feature. Significant variables are employed in multiobjective differential evolution algorithm with response surface models. Then, the optimal parameters are balanced and determined from Pareto front with improved torque performance. Finally, a prototype is manufactured, and the effectiveness of the proposed EMN-based optimization design method is verified by finite-element analysis and experimental results. [ABSTRACT FROM AUTHOR]

By incorporating the merits of partitioned stator and flux modulation techniques, the partitioned stator flux modulation motors featuring high torque, have attracted much attention. This paper investigates four partitioned stator flux modulation motors with different types of PM arrays, including surface-mounted type, consequent-pole type, Halbach-array type, and half-Halbach type. The influences of key parameters on the average electromagnetic torque is conducted and compared. Then, based on the optimal designs, four motors are compared in terms of magnetic field distribution, back-electromotive force, torque characteristics, loss and overload ability. The result reveals that the half-Halbach motor is capable of utilizing more PM to improve electromagnetic torque. Also, the consequent-pole motor achieves the highest torque per PM usage. In addition, performance comparison under the same PM usage is carried out. The result shows that the half-Halbach motor not only exhibits the highest average torque but also achieves the highest PM utilization. Last, the prototype of half-Halbach motor is built for experimental verification. [ABSTRACT FROM AUTHOR]

In this article, a new equivalent thermal network (ETN) model for surface-mounted permanent magnet machines is proposed by applying a mesh-based method with bidirectional coupled winding solution. The key is to couple the winding temperature distributions with thermal network meshes in stator dynamically. First, the meshing method is proposed and combined in the lumped parameter thermal model to obtain temperature distributions instead of the average temperature. The mesh elements have identical shapes and unified thermal conductivity, which can greatly enhance the modeling flexibility and efficiency. Second, the slot winding is established by a 2-D analytical solution method under segmented boundaries with a temperature gradient. Then, the winding solution is coupled with mesh nodes and integrated in the ETN model to accurately predict the temperature distributions in slot including the maximum temperature and position offset. Finally, the effectiveness of the proposed ETN model is verified by comparison with the finite-element analysis and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a design technique for electric ship traction machines to achieve high torque density and low torque ripple by adopting dual m-phase windings with an appropriate phase shift. Firstly, the general relationship between the slot number and the phase number for dual m-phase windings is investigated. Secondly, the uniform analytical expressions of torque with different phase shifts are derived. Also, the optimal phase shift angle is summarized from the perspective of improving torque performance. Then, the 48-slot and 22-pole permanent-magnet machines for electric ship with different windings configurations are designed. The finite-element method is used to calculate their electromagnetic performances, such as back electromotive force, torque capability, stator magnetic motive force and radial force. Finally, some experiments on the prototype machine for electric ship are carried out for validation. [ABSTRACT FROM AUTHOR]

In this article, the permanent-magnet (PM) eddy current loss in a four-phase fault-tolerant flux-switching PM (FT-FSPM) machine is investigated from the perspective of air-gap magnetic field modulation. It can be found that the PM eddy current loss in FT-FSPM machines results from the relative motion between air-gap field space harmonics and PMs. Some effective working harmonics produce the major PM eddy current loss. The proportion of PM eddy current loss generated by each working harmonic is studied in detail, revealing that the low-order (third) harmonic is the main factor. Then, two new structures are proposed to reduce PM eddy current loss, in which magnetic flux barriers are designed by reducing low-order harmonics from the aspect of magnetic field modulation theory. Electromagnetic performance is investigated by finite element analysis. The results show that the proposed structure is effective to suppress PM eddy current loss. Finally, an experimental test platform is established to verify the theoretical analysis results. [ABSTRACT FROM AUTHOR]

The linear permanent magnet vernier (LPMV) machines have been paid more attention in railway vehicles because of its simple structure and low cost. In this paper, the ring type winding (RTW) is adopted in both non-modular and modular LPMV machines to improve force density. The configuration and operating principle of two LPMV-RTW machines are presented. The coil connection and mechanism of RTW are explained and compared with conventional distributed winding (DW) and concentrated winding (CW). The back electromotive force and thrust force are investigated by the time-stepping finite-element method. It is found that non-modular LPMV-RTW machine possesses larger force density than non-modular LPMV-DW machine while modular LPMV-RTW machine has higher force density and utilization ratio of winding than modular LPMV-CW machines under the constant copper loss. Finally, the experiment result is obtained on the prototype, verifying the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper designs a double-side linear vernier permanent-magnet motor, which incorporates the merits of high thrust force capability, high power factor, and high efficiency. Since the parameters of the motor are very sensitive and the high thrust force capability comes along with the high force ripple, a framework of multiobjective optimization is proposed to improve the overall motor performances. The sensitivity analysis is used to select significant variables and the multiobjective differential evolution with ranking-based mutation operator is conducted with the response surface models to generate the Pareto solution set. The electromagnetic performances of the optimal motor are compared with the initial motor by simulating step by step based on finite-element analysis. Finally, a prototype motor is manufactured and the experimental results validate the improved motor performances. [ABSTRACT FROM AUTHOR]

This paper proposes a new equivalent magnetic network (EMN) model for vehicular dual-permanent-magnet vernier (DPMV) machines by applying a generalized modeling method. First, the magnetic circuit method and the meshing method are combined together to improve the modeling efficiency of the DPMV machine. The magnetic circuit method is used to generate conventional lumped parameter permeances to shorten time consumption, whereas the mesh method is utilized in disordered magnetic fields to obtain high precision. Second, a meshing solution for oblique region is proposed to enhance modeling flexibility. Moreover, the flux distributions in meshes are represented without magnetic field pre-delineation, which enables its utilization as a self-adaptive reluctance network model in design optimization. Finally, the proposed EMN model is used to predict the performance of the DPMV machine, considering leakage magnetic flux, local iron saturation, and magnetic field modulation effect simultaneously. Meanwhile, the effectiveness of the proposed EMN model is verified by comparison with finite-element analysis and experimental tests. [ABSTRACT FROM AUTHOR]

The linear vernier permanent magnet (LVPM) motor incorporates the merits of high efficiency, simple mechanism, and low cost, which have a bright future in urban rail transportation. This paper proposes a new sensorless direct thrust force control (DTFC) for the LVPM motor. The novelty is the introduction of a modified flux linkage observer, which has strong robustness against the interferences, no phase lag, and no attenuation. Compared with conventional flux linkage calculation methods, the proposed observer can provide desirable flux linkages, which increases the robustness of the sensorless DTFC system. Simulation and experimental results based on an LVPM motor drive demonstrate the accuracy and robustness. The validations in the aspect of the robustness to parameter errors, measurement errors, and noise show the superiorities of the modified flux linkage observer. [ABSTRACT FROM AUTHOR]

Cost-effective and high-performance linear motors attract more and more attention for many applications. This paper proposes a novel double-side linear flux-modulation permanent-magnet (DS-LFMPM) motor with low cost, high thrust force density, and high power factor. The novelty of the proposed DS-LFMPM motor is to improve power factor by using double-side topology. Its topology is presented, and its operation principle is investigated. From the harmonic spectrums of the flux density in the air gap before and after the modulation of the mover teeth and the stator teeth, it can be concluded that the proposed motor has good flux-modulation effect. Also, the expression of the orders of the harmonic spectrums is given. The design process of sizes and structure is particularly explained. The electromagnetic performances are predicted by using the finite-element method and the proposed motor is prototyped for verification. The results show that the proposed DS-LFMPM motor can produce high thrust force density and high power factor. [ABSTRACT FROM AUTHOR]

Fractional-slot concentrated-winding (FSCW) permanent magnet (PM) machines have been widely studied in recent years. This is mainly due to the several advantages, including high power density, high efficiency, short end turns, high fill factor, low cogging torque, good flux-weakening and fault-tolerant performance. However, the key challenges of utilizing FSCW-PM machines are the abundant stator magnetomotive force (MMF) harmonics. In this paper, the multiphase star–delta hybrid connection (SDHC) windings configuration that can eliminate some stator MMF harmonics is systematically studied. First, the general relationship between the number of slots and phases which are appropriate for the SDHC windings configuration is derived. In addition, the particular principle of the MMF harmonics elimination by the SDHC windings configuration is researched. In order to verify the analysis results, four three-phase SDHC FSCW-PM machines with different slot–pole combinations are built and calculated by the finite-element method. Finally, experiments on a prototype three-phase 12-slot ten-pole FSCW-PM machine are carried out for validation. [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 investigates magnet eddy-current (EC) loss of a five-phase flux-switching permanent-magnet (FSPM) machine. Using magnetic flux barriers in the two proposed rotor topologies, it is possible to reduce some space harmonics in the air-gap flux density, thus reducing magnet EC loss. A 1-D magnetic permeability model is adopted to account for the reduction of the main sub-harmonics as well. Then, the magnet EC loss of both the existing machine and two proposed machines is compared by using time-stepped finite-element analysis. It is shown that the 55.2% and 49.6% EC loss reduction can be achieved by adopting proposed I and proposed II topologies, respectively. The temperature of proposed machine is lower than that of the existing one, and the temperature of both winding and magnet in the new topologies was reduced by 24°. Therefore, the proposed machine model can provide a direct guidance for dependable design and performance optimization of FSPM machines. [ABSTRACT FROM AUTHOR]

The high-temperature superconductor (HTS) machines are more attractive due to the advantages of high power density and efficiency. This paper introduces a new HTS electromagnetic screw (HTS-EMS) that is developed for artificial heart. Two helical-shaped slots are introduced to the translator; the key to the HTS-EMS is that the HTS coils carrying dc currents are placed in the helical-shaped slots. The permanent-magnet array is placed in the rotor. Due to the high current density of the HTS coil, the power density of the HTS-EMS can be improved effectively. The electromagnetic performance of the HTS-EMS is analyzed, including the flux, thrust force, as well as torque. The proposed HTS-EMS is evaluated compared with the existing magnetic screw using time-stepping finite-element method, verifying the advantages of the proposed structure. [ABSTRACT FROM AUTHOR]

This paper presents a triple three-phase permanent magnet synchronous motor (PMSM) with shaped magnets for low vibration applications. Firstly, the features of the designed PMSM are investigated from three aspects, including triple three-phase windings, shaped magnets, and multi-layered housing. Then, the armature reaction, magnetomotive force, torque performance, and fault tolerance ability of the designed PMSM are investigated. Subsequently, the radial force of the designed PMSM with shaped magnets is studied, in which the radial force modulation effect is considered. In addition, the radial force and vibration reduction principle is elaborated in detail. The modal simulation and experiment are carried out, and the vibration reduction effect of the designed PMSM is verified by the multiphysics vibration predicted model. The result shows that the vibration can be effectively reduced by the shaped magnets and multi-layered housing design, and the output torque of the designed PMSM has been reduced insignificantly thanks to the triple three-phase windings. [ABSTRACT FROM AUTHOR]

This paper proposes a novel tubular double-stator vernier permanent-magnet (TDS-VPM) motor for artificial hearts. The key of the proposed motor is double-stator and vernier structures. Due to its vernier structure, more PMs can be adopted in the proposed TDS-VPM motor and the useful harmonics of the air-gap flux density are increased, thus improving thrust density. Furthermore, double stator, namely inner stator and outer stator, has an appropriate 90° (electrical degree) angle difference. Since the inner stator is located inside the mover, the motor space is fully used. Hence, the thrust density is enhanced and the axial direction length is reduced. Meanwhile, the angle difference between the inner and the outer stator can reduce the cogging force of this TDS-VPM motor. The electromagnetic characteristics of the proposed motor are analyzed using the time-stepping finite-element method, confirming the validity of the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper proposes a new linear hybrid excited flux reversal motor with inset permanent magnets (PMs). The proposed motor adopts the excitation windings in the primary, hence offering the desired flux control capability. The novelty of the proposed motor is to design a modular primary structure. Then, it has very symmetrical and sinusoidal back electromotive force (back-EMF) and smooth thrust even at various excitation currents. In addition, because of the inset PMs, the proposed motor is free from PM irreversible demagnetization. The electromagnetic performances of the proposed motor are analyzed using the time-stepping finite-element method, such as magnetic field distribution, back-EMF, and thrust, verifying the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) excited vernier machines capable of high torque density have good potential for electric vehicles while requiring high rare earth PM consumption. To achieve a high torque density at a reasonable material cost, hybrid PM excited vernier machines incorporating both expensive rare earth and low-cost ferrite magnets are investigated in this paper. Various combinations of PM arrangements for the hybrid permanent magnet excited vernier machine are investigated to acquire low cost and superior torque density. The best solution obtained is that the PM on the stator adopts rare earth material while the rotor uses ferrite. Furthermore, the PMs on the stator are arranged in an iron-cored Halbach array, which can reduce leakage flux and enhance flux density effectively and the ferrite PMs are used in the rotor, therefore, high-temperature demagnetization is avoided. Then, the reluctance torque and the cogging torque can offset each other effectively, which is beneficial to reducing the torque ripple and smoothing the electromagnetic torque. Finally, a prototype is manufactured and tested to verify the correctness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this article, a novel parallel hybrid excitation field modulated machine with efficient utilization of multiworking harmonics is proposed. The key of the proposed machine is to efficiently integrate the parallel hybrid excitation and multiworking harmonics to enhance average output torque and flux regulation capability. First, operation principle and air-gap magnetic field harmonics of the machine are investigated by using field modulated principle, which reveals the contribution of each working harmonic to flux linkage and torque. Then, performances of the machine are analyzed, such as open-circuit back-EMF, flux regulation capability, torque-speed characteristics, etc. Also, the proposed machine is compared to conventional ones for evaluation. Finally, a prototype is manufactured and tested to validate the theoretical and simulated results. [ABSTRACT FROM AUTHOR]

This paper proposes a new fault-tolerant linear permanent-magnet (PM) motor, termed as fault-tolerant primary PM (FT-PPM) motor. The proposed motor offers high power density, high efficiency, high fault tolerance and low cost, suitable for maglev transportation applications. Both PMs and windings are set at the steering device of the train, while the only iron stator is fixed between two rails along the whole line. Meanwhile, the new motor topology incorporates the concept of fault-tolerant teeth (FTT) to provide the desired decoupling among phases. The electromagnetic performances are analyzed such as field distributions, inductances, back-EMFs and thrust force. Moreover, by adopting assistant mover teeth, two methods are proposed to reduce the end-effect. Furthermore, the short-circuit current is analytically derived and predicted. The finite-element analysis (FEA) and transient co-simulated results are given for verification. [ABSTRACT FROM PUBLISHER]

In this article, we analyze the vibration of the spoke-type permanent-magnet (PM) machine with an asymmetric rotor considering the modulation effect of the stator teeth. First, the semianalytical expression of the radial pressure is derived to quickly estimate the radial pressure characteristic. The equivalent spatial order of the radial pressure is determined by considering the modulation effect. Second, a structural finite-element (FE) model is set up. The modal test validates the accurateness of the structural FE model and modal analysis. Third, the vibration is predicted by an FE method and verified by the experimental results. The results show that the radial pressure harmonics become richer, and the fundamental frequency and lowest nonzero order of the radial pressure are both reduced due to the asymmetric magnetic barrier. Furthermore, the zero-order radial pressure is no longer the dominant vibration source in this integer-slot PM machine with an asymmetric rotor. Some high-order radial pressures that can be modulated as equivalent low-order harmonics excite the low-order and large vibration. In terms of vibration and noise, the equivalent lowest nonzero-order harmonic should be fully considered in the performance optimization for the asymmetric rotor design. [ABSTRACT FROM AUTHOR]

This article proposes a new asymmetric modular permanent magnet assisted synchronous reluctance motor (PMaSynRM) to offer low torque ripple and high reliability. First, the stator is segmented into three modules without magnetic coupling. The influence of flux gaps between modules is investigated on torque performance. For the torque improvements, the multilevel optimization strategy is conducted, which simultaneously enhances the fault-tolerant capability. Besides, the torque ripple reduction methods are proposed with the asymmetric rotor and shifted end-slots. The analytical formulae of asymmetric flux barrier angle are derived. Then, the asymmetric flux barrier is designed to reduce the 12th harmonic, and the end-slots are shifted to minimize the additional 2nd harmonic component caused by flux gaps. Finally, the enhanced fault-tolerant capability of the proposed modular PMaSynRM is also evaluated. The effectiveness of the proposed approach is verified by both simulation and experiment. [ABSTRACT FROM AUTHOR]

This article proposes a practical design guide for a linear electromagnetic actuator based on the concept of magnetic screw transmission, in which manufacturing and assembly technologies are investigated. The surface-inserted design is first used to form a required helical-shape magnetic pole, which exhibits simple processing, high precision, and robust structure. Moreover, different topologies are developed using the 3-D finite-element analysis aided design, with the goal of optimizing thrust force. In addition, different number of permanent-magnet (PM) segments are first proposed to reduce the cogging effect. Afterward, the linear actuator integrates the rotary machine and the magnetic screw together to construct a compact design and decouples the magnetic circuits. The decoupling design focuses on the self-shielding effect of the Halbach PM array, and the special bearing supports are selected to avoid the eccentricity. Finally, a prototype is built using the developed techniques. Experiments are carried out on a linear test bench, verifying the theoretical analysis. [ABSTRACT FROM AUTHOR]