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In order to meet the demand of a linear ultrasonic motor with large thrust in narrow space, a novel Π-type linear ultrasonic motor with double driving feet is proposed. In this paper, the structure of a stator is designed. The working mode and structure size are determined by finite element simulation. To amplify the amplitude of driving foot, an optimization design for the stator is performed. After that, a novel pre-load device that separates from the stator is put forward, which can not only improve the output but also help to improve the operation stability and prolong the life of motor. Additionally, a prototype of the proposed motor with the novel pre-load device was fabricated and the performance tests were implemented. The experimental results show that the suggested motor has structural stability and high dynamic performance, such as a no-load speed of 273 mm/s and 238 mm/s in two directions, corresponding to a maximal thrust of 80 N and 110 N. [ABSTRACT FROM AUTHOR]

Due to the unique flux distribution, biased flux machines (BFMs) could be driven by biased current to realize flexible flux weakening or strengthening control. In this paper, the electric machines with biased flux are investigated. The key techniques such as constructing biased flux in coils, exploring topologies, developing coil connection patterns, and designing drive circuits are presented. Based on that, the general design guideline for double stator BFMs is concluded. To verify this analysis, one 12/11 (stator teeth/rotor teeth) double stator BFM prototype is built and tested. The proposed double stator BFM has good torque and efficiency performance. Meanwhile, the biased current including dc zero sequence is used to adjust the exciting field. The simulation and experimental results verify the validity and effectiveness of this machine design method and control strategy. The flexible flux modulation characteristic makes this kind of machines suitable for applications with wide speed range. [ABSTRACT FROM AUTHOR]

This study presents dynamic demagnetisation investigations of less-rare-earth (LRE) flux switching permanent magnet (LRE-FSPM) motor under three-phase short-circuit (SC) fault. Owing to relatively low coercivity of ferrite PMs, it is necessary to investigate demagnetised risk of LRE PM motors. Actually, motors suffer from larger demagnetising risk under SC faults than normal conditions. Hence, it is essential for LRE PM motors to comprehensively investigate and enhance antidemagnetisation capability during design stage. Here, by integrating electrical-magnetic field calculation and driving control circuit, dynamic demagnetisation characteristics of the LRE-FSPM motor under SC faults are calculated as an example. To fairly evaluate demagnetisation withstand capability of LRE-FSPM motor, the non-rare-earth (NRE)-FSPM motor is also presented and compared as a referenced motor. Then, the dynamic demagnetisation characteristics of two motors are analysed and compared, including demagnetising d-axis current, operating points, and demagnetised area. It is found that, the proposed LREFSPM motor exhibits improved operating points and less demagnetised area, which is only about one-third of that of NREFSPM motor. Finally, the demagnetisation calculation results not only verify the validity of dynamic demagnetisation investigation approach, but also prove the reasonability of LRE-FSPM motor, which provide a promising research path for the design of LRE PM motors. [ABSTRACT FROM AUTHOR]

On the basis of predecessors, a theory named inverse transient complex inductance vector is proposed for air-gap eccentricity fault diagnosis of interior permanent magnet synchronous motors, and a specific voltage sequence injection method with simple implementation is proposed here. It is a real-time visualised diagnostic approach. A unique fault index is proposed to diagnose eccentricities. The absolute value of the fault index is positively correlated with the total eccentricity degree. Three types of artificial eccentricities and one type of artificial partial demagnetisation are tested. Both simulations and experiments match the proposed theory and diagnostic approach. The approach gives a clear distinction in detecting air-gap eccentricity and partial magnet demagnetisation. It performs best in the low-speed operating condition. [ABSTRACT FROM AUTHOR]

Magnetostriction can be used to induce linear incremental motion, which is effective in giant magnetostrictive inchworm motors. Such motors possess the advantage of combining small step incremental motion with large force. However, continuous rotation may be preferred in practical applications. This paper describes a novel magnetostrictive rotary motor using terfenol-D (Tb0.3Dy0.7Fe1.9) material as the driving element. The motor is constructed of two giant magnetostrictive actuators with shell structured flexure-hinge and leaf springs. These two actuators are placed in a perpendicular position to minimize the coupling displacement of the two actuators. The principal design parameters of the actuators and strain amplifiers are optimally determined, and its static analysis is undertaken through finite element analysis software. The small movements of the magnetostrictive actuators are magnified by about three times using oval shell structured amplifiers. When two sinusoidal wave currents with 90° phase shift are applied to the magnetostrictive actuators, purely rotational movement can be produced as in the orbit of a Lissajous diagram in an oscillograph, and this movement is used to drive the rotor of the motor. A prototype has been constructed and tested. [ABSTRACT FROM AUTHOR]

Sensorless operation can significantly improve the reliability of the high‐speed permanent‐magnet (HSPM) machines. Thus, from the point of view of the whole system, it is necessary to consider sensorless control at the design stage for the HSPM brushless DC machines. In this paper, an integrated design is presented for sensorless control using the third‐harmonic back‐Electromagnetive force (EMF). Finite element (FE) method is used to integrally design the machine considering electromagnetism, temperature, and rotor structure strength, and the optimum rotor and stator structures are determined to obtain sufficient third‐harmonic back‐EMF for sensorless control. Simultaneously, the temperature distribution and rotor structure strength are predicted by the FE method. Finally, a prototype is fabricated and the experimental system is built to verify the machine structure, design method, and sensorless control strategy. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In this paper, a multimode design method is proposed for motor design under multiple operation conditions. Based on the driving cycles in electric vehicles, five typical operation conditions and the corresponding five driving modes are determined for the multimode design. To investigate the method conveniently, a flux controllable stator permanent magnet (SPM) memory motor is selected and taken as a design example. In the design process, by using the sensitivity analysis method, the significance of the parameters in various driving modes are evaluated effectively. Based on the motor driving demands, the whole optimization design is divided into three steps, where different optimization method is applied in each step. To verify the feasibility of the multimode design method, the operation performances of the motor in different driving modes are investigated in detail. Finally, a prototype motor is built and tested. Both the simulation and experimental results reveal that the proposed design method can offer an effective design optimization for the flux-controllable SPM memory motor, where multimode operations are indispensable. [ABSTRACT FROM PUBLISHER]

While interior permanent magnet (IPM) machines have been considered state of the art for traction motors, synchronous reluctance (SynRel) motors with advanced materials can provide a competitive alternative. IPM machines typically utilize neodymium iron boron permanent magnets, which pose an issue in terms of price, sustainability, demagnetization at higher operating temperatures, and uncontrolled generation. On the other hand, SynRel machines do not contain any magnets and are free from these issues. However, the absence of magnets as well as the presence of bridges and centerposts limit the flux-weakening capability of a SynRel machine, and limit the achievable constant power speed ratio without having to significantly oversize the machine and/or the power converter. In this paper, a new material referred to as the dual-phase magnetic material, where nonmagnetic regions can be selectively introduced within each lamination, will be evaluated for SynRel designs. The dual-phase feature of this material enables nonmagnetic bridges and posts, eliminating one of the key limitations of the SynRel designs in terms of torque density and flux weakening. This paper will present the design, analysis, and test results of an advanced proof-of-concept SynRel design utilizing dual-phase material with traction applications as the ultimate target application. [ABSTRACT FROM PUBLISHER]

In motor manufacturing, blanking process of non-oriented electrical steel inevitably induces plastic deformation and residual stress near the blanked edge and thus leads to the deterioration of magnetic properties. However, as for the newly developed non-oriented electrical steel, the scale of grain size is close to both blanking clearance and thickness. Grain size integrated with blanking clearance thus significantly affects the blanked edge quality. In order to reveal the effects of grain size and blanking clearance on magnetic properties deterioration, systematic blanking tests have been conducted using various non-oriented electrical steel sheets (same chemical composition, three thicknesses, and three grain sizes) in a considered clearance range. The blanked edges are characterized by means of optical microscopy, scanning electron microscopy, and micro-hardness tests. Magnetic domain structures are also observed by magnetic force microscopy. The iron losses are measured by single sheet tester method. The burnished ratio decided by clearance and grain size can be taken as the indicator to assess the deterioration of magnetic properties. The blanked edge with larger burnished ratio leads to lower increase of micro-hardness, less degradation of domain structure, and less deterioration of iron loss. In this paper, about 5.8% iron loss can be reduced by optimization of blanking clearance, which is quite pronounced for energy saving. In further study, an approximate linear function of the ratio of optimum clearance to gain size with D^-1/2 is empirically proposed to demonstrate the grain size dependence on optimum clearance determination. This paper thus provides an in-depth understanding and guidance for reducing the deterioration of magnetic properties caused by the blanking process. [ABSTRACT FROM PUBLISHER]

This paper investigates a novel miniature-size resonant moving-magnet linear actuator designs to be used in miniature linear compressor applications. The miniature linear actuator has a slotless stator and a tubular topology. It utilizes moving magnets in which the magnets are lined up in the Halbach array structure. Finite-element and analytical analyses of the actuator are performed to determine the flux density and thrust force. Experimental thrust force behavior at the resonant frequency is determined. It is shown that the finite-element method simulation, analytical, and experimental results agree with each other. [ABSTRACT FROM AUTHOR]

In this paper, a permanent magnet alternator which presently relies on magnetic slot wedges is redesigned to give lower iron loss. The new segmented stator design is used as the basis for a validated loss study—comparing bonded lamination stacks with those held together with a punched notch. Segmentation is shown to improve the production process, reduce losses, and remove the need for wedges, while not significantly altering the acoustic performance. In the first series of prototypes, however, where notching is used to secure lamination packs, the process is shown to have adversely affected material properties of the nickel iron laminations and overall measured losses increased. In the second prototype, with thinner laminations and glued stacks, iron loss predictions and measurement agree and are less than the present slot wedge design. [ABSTRACT FROM AUTHOR]

This paper proposed an electromagnetic-thermal-fluidic coupling model for the accurate evaluation of electromagnetic and thermal performance of a permanent magnet synchronous machine. 2-D transient finite-element method is used to investigate electromagnetic loss including copper loss, iron loss, and magnet eddy loss. The calculated electromagnetic power loss is taken as the main source of the thermal-fluidic field and the materials property is in turn updated according to the temperature distribution. The simulation result of a rated 8 kW permanent magnetic machine is compared with the measured result, which validates the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

This paper presents a composite solid rotor designed to improve starting performance of the line-start permanent-magnet synchronous motor (LSPMSM). The rotor is mainly constituted by the solid steel which can inherently generate high starting torque. Moreover, the axial slots milled on the rotor surface deepen the flux penetration into core and a brass made cage attached to the rotor enlarges the eddy current density. With above promotions, the induction torque increases, and hence drives the motor to startup and synchronize under heavy load conditions. The enhanced starting capability by applying the proposed rotor for an LSPMSM is validated by the 2-D time-stepping finite-element method (FEM). To guarantee a well match with the 3-D construction where end effects occur, an equivalent circuit is built in the 2-D method to represent the uneven ring fractions. Simultaneously, considering the non-axial currents in core ends, conductivity of the solid-rotor segments in 2-D field is corrected by a multistep optimum-seeking technique. Calculation precision of the 2-D FEM covering end effects is certificated by the corresponding 3-D FEM with good results agreement. [ABSTRACT FROM AUTHOR]

This paper aims at describing the influence of shielding on the magnetizing magnetic field measured with an H-coil system, used in a double-yoked single-sheet tester. By the mean of a positioning system especially conceived for the purpose of this paper, the magnetic field is measured at different distances from the laminated sheet. The evolution of this field along the perpendicular line thus defined shows a distinctive behavior, whether the measure is realized in the presence of a magnetic shield or not. A description of the obtained experimental results is made, and a comparison with numerical models is realized. Finally, an explanation over the observed phenomena based on physical principles of electromagnetism is proposed. [ABSTRACT FROM AUTHOR]

Electromagnetic devices containing permanent magnet (PM) are common and typical electromagnetic devices that have advantages of low-power consumption, small size, high sensitivity, and its optimization problem has aroused widespread concern. Calculation accuracy of electromagnetic properties and efficiency of optimization processes are two important factors that affect the optimization effect of electromagnetic devices. A fast calculation method was proposed in this paper that aimed at electromagnetic devices with PM characteristics of strong non-linearity and low solving precision. The response surface method was used to derive the basis function, and the error between actual measured values and calculated values was modified by the Kriging method. On the basis of the calculation model, the distributed collaborative strategy was adopted to fulfill the parallel execution of the fast computation. Simultaneously, the updating strategy of particles was improved, and the robustness of the multi-objective particle swarm optimization algorithm in solving the optimization problem of electromagnetic devices with PM was enhanced. Effectiveness of the method proposed in this paper was verified by the case study of a specific type of electromagnetic relay with PM. [ABSTRACT FROM AUTHOR]

This paper presents a research work on the electromagnetic loss modeling and demagnetization analysis for a high-speed permanent magnet machine (HSPMM). The iron loss is estimated by improved modeling considering harmonics and rotational magnetic field effects to achieve high precision; rotor eddy current loss is researched and comprehensively investigated using finite-element method (FEM). The auxiliary slot and PM beveling are also proposed to reduce the rotor eddy current loss for machine at high-speed operation. Temperature-dependent PM demagnetization modeling is utilized in HSPMM FEM analysis to investigate machine performance due to temperature variation, while optimized rotor structures are proposed and comparatively researched by FEM to improve the machine anti-demagnetization capability in harsh conditions. The HSPMM temperature is estimated based on the calculated loss results and machine computational fluid dynamic modeling. Experimental measurements on the prototype machine verify the effectiveness of the machine electromagnetic and thermal modeling in the paper. [ABSTRACT FROM AUTHOR]

A drive-system-based modeling approach for electromagnetically excited noise-vibration-harshness (NVH) simulation of a disc rotor permanent-magnetic axial-flux synchronous motor is introduced. The electric motor type requires a 3-D finite-element (FE)-based modeling for electrodynamics and magnetomechanical coupling. The methodic focus relies on orthogonal 3-D Fourier-representations for structural modal displacements and for magnetic force densities. The application of Galerkin-projection based on a supermesh construction between source FE meshes to equidistant 3-D grids is hereby required. A significant data reduction for model parametrization is achieved and a low-rank domain coupling matrix, including a high technical interpretability, is derived. Thus efficient NVH simulations of operation cycles including inverter and control influences can be performed within an order-reduced formulation. This paper is the first to derive a fully 3-D FE-based NVH analysis workflow for electric machines under realistic operating conditions for a routine industrial applicability. The high validity of the methodology is proven by a good agreement to real world measurements. [ABSTRACT FROM AUTHOR]

An automatic shape optimization procedure that estimates the inverter carrier harmonic losses generated at cores and magnets has been developed in order to improve the performance of interior permanent magnet motors used for variable speed/load applications. In the proposed procedure, an electromagnetic field analysis coupled with armature voltage equation is iteratively carried out at each rotor shape. The input of this analysis is the theoretical inverter voltage, which is determined by both the rotor shape and the driving conditions of the motor. The proposed procedure is applied to a 100 kW-class interior permanent magnet motor, in which the carrier harmonic losses become dominant under frequent driving conditions. It is clarified that the carrier harmonic losses can be reduced by more than 10%, whereas the other important characteristics are not deteriorated. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the core loss observed in the stator of a permanent magnet linear synchronous generator. Core loss is usually calculated using the classical Steinmetz equation, but it leads to erroneous results. Consequently, several researchers have proposed modified versions of this equation, taking into account the hysteresis loss, eddy current loss, and excess loss. In this paper, we calculated all loss coefficients from the Epstein test data using a curve fitting method. Moreover, we separated the rotating and alternating fields based on the time harmonics observed with changes in the magnetic flux density. In addition, we considered the 2-D and 3-D plane flux paths that cause magnetic flux leakage. Finally, the core loss of the linear machine was calculated using a modified Steinmetz equation that considers the flux path. [ABSTRACT FROM AUTHOR]

This paper focuses on the application of the variance-based global sensitivity analysis for a topological derivative method in order to solve a stochastic nonlinear time-dependent magnetoquasi-static interface problem. To illustrate the approach a permanent magnet (PM) synchronous machine has been considered. Our key objective is to provide a robust design of the rotor poles and of the tooth base in a stator for the reduction of the torque ripple and electromagnetic losses, while taking material uncertainties into account. Input variations of material parameters are modeled using the polynomial chaos expansion technique, which is incorporated into the stochastic collocation method in order to provide a response surface model. Additionally, we can benefit from the variance-based sensitivity analysis. This allows us to reduce the dimensionality of the stochastic optimization problems, described by the random-dependent cost functional. Finally, to validate our approach, we provide the 2-D simulations and analysis, which confirm the usefulness of the proposed method and yield a novel topology of a PM synchronous machine. [ABSTRACT FROM AUTHOR]

A novel surface-mounted outer rotor transverse flux permanent-magnet motor (SMOR-TFPM) with simple structure and good performance is proposed in this paper. The basic structure and operating principle of the motor are introduced. According to the deficiency of the SMOR-TFPM electrical performance, this paper presents an improved design of the stator so that the motor performance is improved by transforming parts of the leakage flux into the main flux. The finite element model of the motor is established, the influence of the relevant parameters on the no-load magnetic leakage coefficient is optimally analyzed based on the three-dimensional finite element method. The main parameters design of a three-phase and fifteen-pair-pole SMOR-TFPM is completed based on the improved design and optimization analysis. The coupling relationship of the interphase magnetic field is verified. Besides, the motor torque characteristics are researched and analyzed. The results prove that the structure and dimensions design of the motor is reasonable and the characteristics are stable, which has a certain feasibility. [ABSTRACT FROM AUTHOR]

There have been many discussions on the importance of balanced power supply for both best performance and for lower vibration during operation of industrial motors in petrochemical duty and related installations. Results of tests that were conducted on several low-voltage IEEE 841 motors to observe the effect on vibration due to unbalanced power supply will be presented. Various increments of voltage imbalance from 1% up to 10% were tested and monitored on several pole speeds. This paper will present actual test data collected, along with a discussion on how these results relate and impact the various vibration testing and operational conditions provided within industry standards. [ABSTRACT FROM PUBLISHER]

Refrigerator compressors are currently driven mostly by rotary line start or variable-speed (inverter-fed) motors with mechanical transmission. Direct driving of pistons by linear oscillatory resonant PM 1 phase motors has just been introduced to low power (less than 100 W) such applications. The present paper introduces a 3 pole PM mover 1 phase PM linear oscillatory motors, in terms of optimal nonlinear analytical design methodology, with FEM and dynamics validation. Both 50 and 250 Hz (inverter fed) operation for 2000 and 100 W is exemplified for minimum active materials costs and, respectively, minimum global costs (losses capitalized cost is added). For the line start case study (at 2000 W, 50 Hz) a circuit model for transients is introduced and the motor self-starting transients with full power delivery at above 91% efficiency is available. The 50 Hz motors are heavier around (5.7 kg/kW at 2000 W and 7.5 kg/kW at 100 W, respectively) than the 250 Hz motors around (1.2 kg/kW, 3 kg/kW) but the latter require inverter control. [ABSTRACT FROM AUTHOR]

An analytical method is proposed to predict and optimize cogging torque accurately. It is derived by the exact subdomain model, equivalent current sheet of magnet, and modified particle swarm optimization (PSO), in surface-mounted permanent magnet machines (SPMs) accounting for the effect of stator slotting and tooth-tips. The analysis works for internal/external rotor motor topologies, radial/parallel magnetization, as well as for any combinations of pole and slot numbers. Then, four important design parameters, viz. magnet thickness, air-gap length, slot-opening to slot pitch ratio, and pole-arc to pole-pitch ratio, are adopted as optimal variables, and the peak of fundamental order of the radial component of the air-gap flux density is constrained to optimize cogging torque by modified PSO based on forgoing model. Finally, the cogging torque of two prototype machines with both radial and parallel magnetizations is optimized notably. The paper validates the results of analytical prediction by finite-element analysis. [ABSTRACT FROM AUTHOR]

This paper deals with the optimization for performance and cost of the low-power permanent magnet synchronous machines used in automotive applications with focus on particularities of high-volume mass production and the constraints that arise. The described optimization loop is used to compare different 12/8 and 12/10 designs of interior permanent magnet (IPM) type. After showing that the 12/10 IPM exhibits the best performance–cost ratio, results obtained at different stages in the process (i.e., sensitivity analysis and constrained single-/multiobjective optimizations), for both no-load and load case, are provided. Finally, different aspects for reducing the complexity of the multidomain optimization problem (e.g., 3-D effects, iron losses, and effects of tolerances on the motor characteristics) are addressed. [ABSTRACT FROM AUTHOR]

This paper systematically studies a new kind of PM machines with both stator and rotor PM excitations, namely, dual-PM excited machines. The key is to rely on the PM-iron structure in the machine to provide both PM excitation and flux modulation. Besides the fundamental field component in the air-gap, some other predominant harmonics introduced by the flux modulating effect can also contribute to the electromagnetic torque production. Therefore, this kind of machines can be designed with high torque density. Four dual-PM excited machine concepts with the same rotor configuration but different stator structures are comparatively studied, which include double-stator PM machine, stator multitooth-PM machine, stator slot-PM machine, and stator tooth-PM machine (STPM). Based on the flux modulating effect, the general design principle of the dual-PM machines is proposed in this paper. Through analytically investigating the air-gap field harmonics, the physical insight of the dual-PM machines is brought forward. All the four machines are optimized using an improved Tabu search coupled with finite element method, and their electromagnetic performances are comprehensively studied and compared. A prototype of STPM is manufactured. Experimental tests are conducted and the results well verify the electromagnetic design. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a basic design method for the surface-mounted permanent magnet synchronous motor (SPMSM) for both distributed and concentrated windings. The design is based on the air-gap magnetic flux density distribution focusing on the image magnetic pole. The calculus equation of the air-gap magnetic flux density distribution is analytically derived by supposing the magnetic pole is located on the magnet surface and image planes. In this study, a three-phase and double-layer stator winding SPMSM that has a linear demagnetizing characteristic magnet, such as a ferrite or rare-earth magnet is considered. From the required specifications and design conditions, the design target values of the parameters that appear in the voltages equations of the d-q axis coordinate system are calculated. Then, the relational equations for the torque constant, d-axis inductance, copper loss, and the maximum current density are presented as a function of three design parameters under id = 0 control. They are the stator stack length, the number of coil turns in series in a phase, and the slot bottom length. Hence, this approach reduces the SPMSM basic design to the problem with these design parameters has to be solved. The proposed method makes it possible to address the concentrated winding as a special case of the distributed winding. The FEA results confirm the validity of the proposed basic design method for both distributed and concentrated windings. [ABSTRACT FROM AUTHOR]

This paper proposes a design procedure in addition to some optimal design guidelines for line start permanent magnet (LSPM) motors, independent from their ratings. Major transient and steady-state characteristics of LSPM motors, including magnet braking torque, synchronizing torque, efficiency, and power factor, are analyzed with respect to the main motor design parameters, i.e., motor back electromotive force, reactances, and saliency ratio. The contradicting behaviors of the motor characteristics with respect to the motor parameters are fully investigated. Design guidelines are developed to wisely compromise the performance characteristics by selecting optimal parameters. A design procedure considering the guidelines is proposed. By following the procedure and guidelines, an LSPM motor is designed and optimal values of the motor parameters are determined. Accordingly, a prototype LSPM motor is built and tested. The finite element method (FEM)-based simulation results in close agreement with the experimental results confirm superior steady-state and transient performance characteristics of the motor, thus validating the developed guidelines and the proposed design procedure. [ABSTRACT FROM PUBLISHER]

This paper designs and compares two outer-rotor flux switching permanent-magnet (FSPM) motors, in which the two different PM topologies of the V-shape magnet and I-shape magnet are adopted respectively in their stator structures, namely, V-FSPM motor and I-FSPM motor. First, the design principles and motor topologies are introduced. Second, by using the comprehensive sensitivity method and sequential nonlinear programming algorithm, the two motors are optimized efficiently before comparison, where the torque and torque ripple are selected as the design objectives. And then based on the finite element analysis (FEA) method, the motor performances are evaluated in detail, such as back EMF, torque characteristics, and efficiency. To extensively explore the advantages of the two motors, the comparison work involving output torque, torque ripple, and PM usage efficiencies are further implemented under three different conditions. Finally, the two prototyped motors are manufactured and tested, respectively. The theoretical analysis is verified by the FEA results and experimental results, which reveals that both of the two motors can be interesting and potential candidates for the in-wheel traction applications. [ABSTRACT FROM AUTHOR]

This paper proposes a new interior permanent-magnet machine (IPMM) design in which the rotor consists of several rotor segments arranged in the axial direction, aiming to improve the utilization of rare earth permanent-magnet (PM) materials and reduce the torque ripple. The proposed design is optimized to feature a \text21\% reduction of rare earth PM materials and a \text50\% reduction of ripple torque ratio compared with the Camry 2007 design, which uses the conventional pole-shaping technique to suppress its torque ripple. Although the torque is reduced by \text9\% , the torque per magnet weight is improved by \text15\% , indicating the PMs are more efficiently used in the proposed design. The designs are verified by 3-D finite element. Despite the small torque reduction, the efficiency of the proposed design is still about the same as the Camry design. [ABSTRACT FROM AUTHOR]

The authors investigated whether working memory training improves motor-motor dual-task performance consisted of upper and lower limb tasks. The upper limb task was a simple reaction task and the lower limb task was an isometric knee extension task. 45 participants (age = 21.8 ± 1.6 years) were classified into a working memory training group (WM-TRG), dual-task training group, or control group. The training duration was 2 weeks (15 min, 4 times/week). Our results indicated that working memory capacity increased significantly only in the WM-TRG. Dual-task performance improved in the WM-TRG and dual-task training group. Our study provides the novel insight that working memory training improves dual-task performance without specific training on the target motor task. [ABSTRACT FROM AUTHOR]

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The multi-step direct model predictive control (M-DMPC) could reduce the switching frequency and improve the efficiency of the motor drive system while ensuring good steady and dynamic performance. However, the conventional M-DMPC, which uses the exhaustive optimisation method is with exponential time complexity, so it is difficult to realise in a short sample period. This study proposes a multi-step direct predictive torque control (M-DPTC) algorithm for two-level voltage source inverter fed surface-mounted permanent magnet synchronous motor (SPMSM) drive system. In the proposed algorithm, first, in order to reduce computation time in multi-step predictive process, a simplified multi-step predictive model is established. Compared with the complex operations, like square root and trigonometric function used in the conventional predictive model, only look-up table and addition operation are utilised in the proposed model for multistep prediction. Second, compared with the exhaustive searching method, the proposed optimisation method avoids the exploration of all possible switching sequences and has logarithmic time complexity. Combining the above two measures, the proposed M-DPTC can be achieved in a relatively shorter sample period. Simulation and experimental results for a 6-kW SPMSM are presented to validate the proposed algorithm. [ABSTRACT FROM AUTHOR]

This work focuses on two prime objectives. The first is to detect chaos in the fractional-order model of a permanent magnet synchronous generator (PMSG) and the second is to suppress chaos using a novel predictive control scheme in the fractional order sense. The main contributions of the work, therefore, lie in discovering the minimum commensurate order for which chaos exists in the fractional-order PMSG (FOPMSG), studying its dynamical behaviour ranging from Hopf bifurcation to stability analysis and the proposal of a single-state predictive controller to stabilise the chaotic FOPMSG in both commensurate as well as incommensurate orders. The proposal of predictive controller for controlling chaos in a fractional-order variable-speed drive is a novel attempt. Lower control effort, effectiveness, simplicity in design and application, convenience in inclusion of non-linearity, etc. highlight the promising potential of the proposed predictive control scheme. Circuit implementation results which are in good qualitative agreement with that of simulated results, confirm that the work attains the objectives successfully. [ABSTRACT FROM AUTHOR]

The design and the experimental validation of a continuous-time model predictive control (CTMPC) for a permanent magnet synchronous motor (PMSM) drive with disturbance decoupling is discussed. The CTMPC approach uses Taylor series expansion to derive a closed-form solution to the problem of model predictive control even though the system behaviour is described by a non-linear model. This type of controller requires an exact knowledge of the system model to guarantee an accurate prediction of the system behaviour, while the PMSM is usually subjected to model uncertainties and external disturbances such as the load torque. Moreover, in the proposed approach, the predicted speed tracking error is directly used to determine the required voltage command without the need for a cascaded control scheme. As a result, the load torque is seen as unmatched disturbance which makes exact disturbance decoupling more challenging. To overcome such a problem, a non-linear disturbance observer is designed and combined with the CTMPC method to enhance the prediction accuracy under parameter variation and unknown load torque. The feasibility of the proposed approach is experimentally investigated, and good transient and steadystate performances are obtained. [ABSTRACT FROM AUTHOR]

This paper proposes a robust optimization algorithm, enabling global optimum tracking and manufacturing uncertainty factors handling, for high-speed permanent magnet motor design. A new robustness criterion is introduced, considering effectively the impact of the construction tooling uncertainties on the design variables in all objectives. An adaptive-network-based fuzzy inference system is adopted acting as a surrogate for the time-consuming finite-element (FE) analyses and results in computationally fast robust electric machine design procedure. The procedure has been validated through FE high-speed motor design. [ABSTRACT FROM AUTHOR]

At present, the drivers with different control methods are used in most of permanent magnet synchronous motors (PMSM). A current outputted by a driver contains a large number of harmonics that will cause the PMSM torque ripple, winding heating and rotor temperature rise too large and so on. In this paper, in order to determine the influence of the current harmonics on the motor performance, different harmonic currents were injected into the motor armature. Firstly, in order to study the influence of the current harmonic on the motor magnetic field, a novel decoupling method of the motor magnetic field was proposed. On this basis, the difference of harmonic content in an air gap magnetic field was studied, and the influence of a harmonic current on the air gap flux density was obtained. Secondly, by comparing the fluctuation of the motor torque in the fundamental and different harmonic currents, the influence of harmonic on a motor torque ripple was determined. Then, the influence of different current harmonics on the eddy current loss of the motor was compared and analyzed, and the influence of the drive harmonic on the eddy current loss was obtained. Finally, by using a finite element method (FEM), the motor temperature distribution with different harmonics was obtained. [ABSTRACT FROM AUTHOR]

In order to understand the impact that certain design changes may have on the performance over a wide speed range, a series of 12-slot 8-pole concentrated winding interior permanent magnet synchronous motors (IPMSMs) are analyzed. Fundamental theory of operation is used to describe the desirable characteristics in terms of the lumped parameters, and finite element analysis is carried out to show how these characteristics may be realized through the motor geometry changes. The motor geometry changes aim to create an IPMSM design with high d-axis inductance for the wide speed range operation, low harmonic content in the back electromotive force waveform, and low cogging torque. A prototype is constructed and test results are presented for verification. [ABSTRACT FROM PUBLISHER]

In this paper, an analytical quasi three-dimensional method is used to model an axial flux permanent magnet (AFPM) machine with various eccentricities. AFPMmachines (AFPMMs) have various advantages but they are sensitive to geometrical imperfections for manufacturing aspect. The main aim of this paper is to propose a general analytical model to analyze the AFPMMs with various types of eccentricities. The radial and tangential magnetic flux densities in the air gap under healthy condition are obtained via combination of Maxwell's equations and Schwarz-Christoffel (SC) mapping firstly. Next, in order to investigate the eccentricities, equations for air gap length and radii are deduced. The back electromotive force (EMF) is calculated and compared with those from healthy condition and finite element (FE) analysis, respectively. The results show that the analytical predictions agree well with the FE results. Moreover, using this method has a significantly less time consuming than the 3D FM simulation process, which is a great advantage of this method. Finally, the analytical model is verified via experimental results. [ABSTRACT FROM AUTHOR]

This paper focuses on the analysis of the starting capacity and temperature field of the line-start permanent magnet synchronous motor with the anti-salient pole. In order to further improve the performance of the traditional LSPMSM, the magnet structure is optimized to get better starting properties. Further, the models have been applied to investigate the impact of anti-salient pole on the efficiency and power factor. The temperature field of proposed motor with anti-salient pole has been compared to the traditional LSPMSM with classical rotor. Prototype machines with the two rotors have been built and tested. Experimental results are compared in terms of starting, efficiency, power factor and temperature. It has been found that anti-salient pole improves the overall properties of the LSPMSM. [ABSTRACT FROM AUTHOR]

Products that use micro permanent magnet brushless DC (PM BLDC) motors have the advantages of being small in size, lightweight, highly efficient, and more reliable. The product trend within the electronic technology moves toward the direction of miniaturization and high quality and thus the PM BLDC motor industry has a great potential for developments. Based on a case study on the micro PM BLDC motors for driving cooling fans, this study is to investigate the way of applying a systematic design for analyzing design parameters of brushless DC motors. The objective of this study is to reduce development costs and enhance the quality of motor operations. For a conventional motor design, designers use analytical methods to analyze and calculate the design parameters and performance parameters so that they can build a mathematical model for permanent magnets. However, in reality based on the consideration of product development parameterization and design optimization, conventional methods of analyzing magnetic circuits might fail to effectively meet the project deadlines and performance requirements within this industry. Moreover, for the application of micro PM DC motors to product designs, a motor is required to meet different requirements for its design specifications depending on the characteristics of different functions or implementations. Its design parameters need to change accordingly. Therefore, by integrating an approach of magnetic circuit analysis, a process of designing motor products was firstly determined by using the FORTRAN programming language in this study so that the specifications can be stipulated for a preliminary design. After that, the operation performance was determined by calculations and a model for finite element analyses was created based on the results. The JMAG software was also used for the analysis of motor designs. This approach can enhance the efficiency of micro motor designs and analyses so as to reduce the time spent on remodeling and numerical analysis. A fast parametric design method is proposed in this study and its effects and results were further verified. [ABSTRACT FROM AUTHOR]

Eccentricity is a common fault during the operation of electrical machines due to manufacturing error and effect of rotor deflection. Therefore, eccentricity fault has been a research hotspot in recent decades for the reliable running of machines. The monitoring signals for detecting eccentricity have been proposed in many published papers. However, the effects of rotor slot number on the magnitudes of characteristic signals are seldom investigated. Thus, this paper presents the relationship between the number of rotor slots and the monitoring signals under static, dynamic and mixed eccentricity on the basis of the previous papers. The theoretical analysis shows that not all electrical machines generate the principal slot harmonics in the stator current. But these harmonics in the air-gap magnetic field are easily detected for all machines when the machines are under static or dynamic eccentricity. Moreover, the effect of rotor slot number on the low-frequency components under mixed eccentricity is also predicted. Detailed simulations are presented for a high voltage submersible motor with 40, 41, 42, 43 and 44 rotor slots under various conditions. And these results well verify the theoretical predictions. [ABSTRACT FROM AUTHOR]