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This article presents a structural strength analysis and noise reduction method for high-speed long primary moving-magnet-type linear synchronous motors (MMT-LSMs) applied to electromagnetic launch systems under high acceleration. The stresses and deformations of the mover and frame at different mover offset distances are analyzed and calculated to reveal that the permanent magnets (PMs) placed ectally on both sides of the mover core are easily damaged and need to be protected by sleeves. Then, the mover stresses with different sleeve materials and varied PM-sleeve interference values are compared for subsequent optimization. Furthermore, tooth harmonic is the main cause of vibration and noise when electromagnetic force waves are exerted on this MMT-LSM. Three improved methods are discussed comprehensively to reduce vibration and noise, including pole/slot combination, slot width, and pole arc coefficient. Finally, the experiment platform is built with the implementation of the modal and vibration acceleration experiments to verify the proposed analysis method. [ABSTRACT FROM AUTHOR]

This article reviews the state-of-the-art back electromotive force (EMF) based sensorless schemes for synchronous machines. Field-oriented control (FOC) of a synchronous machine requires real-time rotor position for decoupled torque and flux control. Extraction of rotor position without a sensor or sensorless control has been an enabling technology for the past few decades. Sensorless control using back EMF voltage induced by rotor movement is the most widely used method. However, the connections and differences between different methods have not been thoroughly investigated and documented. This article first reviews basic sensorless methods. The two implementation forms of an observer are examined to facilitate analysis. A detailed analysis puts in evidence the connections behind different methods in both stationary and synchronous reference frames. A summary is drawn that is meant to offer a few key points regarding different sensorless methods. Finally, a conclusion is given to summarize the major contributions of this article. [ABSTRACT FROM AUTHOR]

This article presents a new type of double stator swing rotating permanent magnet spherical motor (DSSRPMSM), which can realize swing, rotation, and helical motion and is used in industrial robots, gyroscopes, satellite communications, and other fields. The proposed spherical motor consists of two stators and a hollow rotor with permanent magnet (PM) poles on its inner and outer surfaces. Compared with most spherical motor with hollow coil and traditional PM synchronous motor, the structure of the motor is different and novel, and it is difficult to find a more perfect design theory and method. Thus, this article introduces the new idea of motor design in detail. First, the structure and working principle of the motor are introduced, and the original design of the motor is carried out. The 2-D rough estimation and 3-D FEM accurate simulation calculation are carried out, and the electromagnetic characteristics of the motor are obtained, including magnetic flux density distribution, torque, and loss. The simulation results meet the design specifications of the motor. A prototype was built and tested. The experimental results are in good agreement with the 3-D FEM analysis. The design method provides a theoretical basis for the design of this kind of spherical motor. The research results lay a foundation for the subsequent optimization of the motor. [ABSTRACT FROM AUTHOR]

A modified configuration for Permanent Magnet Assisted Synchronous Reluctance Motors (PMaSyRM) is studied in this paper. Conventionally, the PM materials are inserted in the flux barriers region of the rotor. Consequently, the PMs sizing parameters will be restricted to the available space that may limit the efficient use of PMs benefits. In this study, a portion of the rotor structure is replaced with an Interior PM (IPM) rotor so that an axially segmented integration of IPM and SyRM is obtained. Thus, the PMs design is performed specifically in the IPM segment independent of the SyRM scheme, while the SyRM segment remains PM-less. The main motivation of this concept is to improve the contribution of the PM material in the total torque as well as utilizing the special property of the proposed rotor configuration for pulsating torque reduction. A computationally cost-effective algorithm is proposed for the optimal design of IPM-SyRM motor by which a low-power design is carried out for a lightweight electric vehicle. The results for torque profile characteristics, PM volume, power-factor, and efficiency are compared with a conventional PMaSyRM that has been optimally designed as the reference case. Finally, a prototype is constructed to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

Linear flux-switching permanent-magnet (LFSPM) motors have been proposed for electromagnetic launch system (EMLS). Benefiting from the permanent magnet (PM) settled on the long double-sided primary and the yokeless secondary, the proposed structure has the advantage of high thrust force density and simple structure compared with the traditional linear permanent-magnet synchronous motor (LPMSM) and linear induction motor (LIM), which makes it more suitable for the EMLS. However, it suffers from the deficiency of relatively high detent force due to the permanent magnets (PMs) settled on the primary, which will also exert an influence on the thrust ripple. Different from the traditional rotary motor, the linear motor also suffers from the end force caused by the end effect. So, a new structure of secondary, which is called symmetric unequally spaced (SUS) secondary in this paper, is proposed to improve the electromagnetic performance from the point of the detent force and thrust ripple for the motor. The thrust ripple and detent force are effectively declined by applying the proposed method without the sacrifice of the average thrust force. The validity of the method is verified by finite element analysis (FEA). A prototype with SUS secondary is manufactured to verify the simulation result. [ABSTRACT FROM AUTHOR]

In order to improve the performance (low torque ripple, low suspension ripple, and high power factor) of the permanent magnet assisted bearingless synchronous reluctance motor (PMa-BSynRM), the multiobjective optimal design based on fast nondominated sorting genetic algorithm (NSGA-Ⅱ) of PMa-BSynRM rotor topology is investigated in this article. First, the structure and operation principle of the PMa-BSynRM are introduced. Second, the initial rotor design that gives optimizer the ability to produce a variety of barrier shapes and the comprehensive sensitive analysis that evaluates the influence of each design variable on optimization objectives are presented. Third, the optimal design is selected from the Pareto front, which is generated by NSGA-Ⅱ, and validated by finite-element analysis. The simulation results confirm that the torque and suspension force capacity of optimal motor are improved significantly in comparison with initial design, whereas the value of power factor reaches 0.81. Finally, the optimal prototype motor is manufactured, and experimental results confirm the validity and superiority of the optimized design. [ABSTRACT FROM AUTHOR]

Commonly, healthy five-phase permanent magnet assisted synchronous reluctance machines (PMaSynRMs) are modeled in harmonic fixed rotating (dq1dq) reference frames. Such approaches feature several levels of detail, namely, constant parameters or saturation in four axes, i.e., 4-D saturation or cross-saturation effects in conjunction with space harmonics in 5-D models. In this article, a 6-D model is proposed that comprises all aforementioned nonlinearities not just in faultless but also in open-phase fault conditions. Moreover, magnetic axial asymmetry introduced by discrete skew is taken into account and included in the investigated modeling. The proposed 6-D model is based on flux maps obtained from static Finite-Element program posteriori modified to comprise the skewing effect. Very close to finite-element precision is guaranteed and experimental validations have been performed to confirm the authenticity and contrast the effectiveness of the open-phase model with skew. [ABSTRACT FROM AUTHOR]

In this article, a new fault-tolerant control strategy for a triple redundant 3 × 3 phase permanent magnet assisted synchronous reluctance motor under a single-phase open-circuit fault has been proposed. In order to reduce the cost of the system, a two-level three-phase inverter is constructed to drive the parallel-connected motor under normal and fault-tolerant conditions. In normal operations, the current and torque are equally distributed to the three modules of the motor, while in a fault-tolerant state, they should be redistributed according to a specific ratio. The optimal ratio is obtained by investigating the control strategy of minimum copper loss and minimum torque ripple. The torque ripple of the normal module is increased to offset the torque ripple of the fault module, thereby reducing the total electromagnetic torque ripple after the failure. It means that no auxiliary switching devices need to be added even if the failure happened, which can significantly reduce the complexity and improve the reliability of the control system. To verify the theoretical analysis, simulations and experiments have been conducted. The results are in good agreement with that of theoretical analysis. [ABSTRACT FROM AUTHOR]

In this article, a new controllable leakage flux multilayer barrier permanent magnet (PM) motor is proposed by adopting a new design concept of controllable leakage flux, where the PMs are uniquely placed in the d-axis magnetic circuit of the synchronous reluctance motor (SynRM). Compared to the conventional q-axis PM placement SynRM, the higher PM utilization and better flux-weakening capability can be obtained. For further comparison and verification, both of the controllable leakage flux multilayer barrier PM motor and the motor with traditional q-axis PM setting are designed. In addition, a multiobjective optimization method based on the correlation analysis method is proposed to obtain the optimized output torque and flux-weakening performances. Then, the performances of the two optimal motors are analyzed and compared in detail. Finally, two prototype motors are manufactured and tested. Both the theoretical and experimental analyses verify the effectiveness of the flux-weakening enhancement design and the proposed motor. [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 paper presents a novel design concept for Synchronous Reluctance (SynRel) machines aimed at reducing the torque ripple. Two general sizing approaches based on the homothetic scaling principle are defined and compared. An in depth analysis on the torque ripple, for a wide range of scaled geometries, evaluated by finite element, has been carried out at different operating conditions. A further analysis is performed on 4 scaled geometries that have been optimized starting from 4 random rotor geometries. It is shown that the main rotor geometrical variables converge to similar values for all scaled machines. The accuracy of the proposed model is then validated by comparing the FE simulated torque ripple waveforms with the experimental data carried out, for a range of operating conditions, on a machine prototype. The outcome of this work is a fast and accurate scaling technique for the preliminary design of SynRel machines with reduced torque ripple. [ABSTRACT FROM AUTHOR]

This article proposes a novel transient 3-D lumped-parameter (LP) thermal model and a 3-D finite-element (FE) thermal model of a triple redundant nine-phase permanent magnet-assisted synchronous reluctance machine to predict the asymmetric temperature distribution under various fault conditions. First, the predicted transient and steady-state temperatures are compared between the 3-D LP and the 3-D FE thermal models under fault conditions with uneven loss distribution. Also, the temperatures predicted by the LP and FE thermal models, which account a number of practical issues are comprehensively compared with the test results under healthy and short-circuit fault conditions. The relative merits of the two thermal models are discussed. It is shown that both models have reasonable accuracy in predicting the machine's thermal behavior under fault conditions and can be chosen according to the requirements. [ABSTRACT FROM AUTHOR]

The Ironless Permanent Magnet Linear Synchronous Motor (ILPMLSM) with nonoverlapping windings is widely used in precise applications due to its simple structure, low thrust ripple, and fast response, while the disadvantage is low thrust density. The novel asymmetrical double-layer winding ILPMLSM with quasi-Halbach magnets can improve the thrust density while keeping simple structure. However, the double-layer windings are asymmetric and the primary has finite length. To solve the problem of this asymmetry and investigate its influences on electromagnetic characteristics, an improved 2-D analytical model is proposed, which introduces “virtual periodic primary” and solves the magnetic field of each winding layer. By the results of finite element and experiments, the proposed analytical model is verified. Moreover, the analytical model requires less computation time, which is helpful for optimizing design of this motor. [ABSTRACT FROM AUTHOR]

This article presents an analysis on the field weakening capability of a flux intensifying synchronous motor (FI-SM) with a small quantity of inset permanent magnets (PMs) on the rotor surface. Differing from other FI-SMs whose rotors are constructed by interweaving PMs and flux barriers (FBs), for the presented FI-SM, the PM dimensions can be easily adjusted without significantly altering the rotor configuration, thus offering more flexibility in rotor design and making it more feasible to analyze the influence of the added PM on flux density distribution, inductances, PM flux linkage, and field weakening capacities in conjunction with armature current. This article, through investigating this design potential, aims to provide an approach for design and analysis of this type of motor to enhance the performance and improve the field weakening capability. Experiments are conducted to validate the simulation. [ABSTRACT FROM AUTHOR]

Permanent magnet assisted synchronous reluctance (PM-SyR) motors often present relevant magnetic saturation, especially if overload capability is exploited. The knowledge of current-to-flux relationship is mandatory for proper motor control, and it becomes even more critical in the case of sensorless applications. Reliable standstill self-commissioning tests have been recently developed for synchronous reluctance (SyR) motors without producing rotor movement. This procedure can be extended to PM-SyR motors, but being at standstill, it does not retrieve the flux contribution related to the permanent magnets (PMs). This article integrates the identification of the flux characteristics including a novel test for estimating the PM flux linkage, obtaining the complete magnetic characteristic of the PM-SyR motor. The identification session is performed at standstill and without a position transducer, independently of the mechanical load being connected or not. Such conditions are considered the most demanding for self-commissioning tests. The machine is first excited with a proper sequence of bipolar high voltage pulses to determine its current-dependent flux components. Then, the estimate of PM flux linkage is retrieved at standstill by evaluating the local saliency along the negative q-axis. The proposed method is supported by detailed finite element analysis and experimentally verified on two PM-SyR motor prototypes, confirming the accuracy of the PM flux linkage estimate. [ABSTRACT FROM AUTHOR]

Optimal design of electric machines, having complex 3-D magnetic flux path, such as transverse flux or axial flux motors, is computationally demanding owing to the unavailability of a fast 2-D finite-element method (FEM), which leads to the indispensable use of costly 3-D FEM models. With multiobjectives and large design parameter vector, this task is further exacerbated. To accelerate the design procedure, unlike conventional methods, this article proposes the use of two information sources, an expensive but accurate high-fidelity 3-D-FEM model and a fast but inaccurate low-fidelity 2-D-equivalent FEM model to exploit corresponding opposite merits of each and construct a multifidelity surrogate model (response surface) with minimum number of expensive 3-D-FEM simulations. The low-fidelity 2-D model, which intrinsically does not exist for such machines, is generated by ensuring equal magnetic reluctance along main magnetic path despite deformation of model's geometry. The proposed methodology is applied to optimize a novel magnetically levitated transverse flux permanent magnet linear synchronous motor, considering suspension characteristics (lateral and normal stiffnesses) along with thrust as objectives and a seven parameter design vector. Results show significant design time-saving without compromising surrogate accuracy. The optimized design is fabricated and relevant experimental measurements are taken. [ABSTRACT FROM AUTHOR]

To meet different loading requirements in the metal industry, special attention must be paid to the operational performances and start-up characteristics of those electric motors implemented for desired driven applications. However, because of the global warming and energy conservation concerns, the enforced operational regulations have increased the complexity of those commonly applied induction motors for supplying the desired equipment driven forces. By adopting the same stator, the synchronous reluctance motor (SynRM) can be achieved with properly redesigned rotor structure of an induction motor. Due to its robust structure and lack of secondary copper loss, it is very competitive for the related hoist, punch, roller, and pump applications. Furthermore, by inserting adequate ferrite permanent magnets and conductors into the rotor barriers, composition designs of the direct-on-line SynRMs (DOL_SynRMs) will also be proposed. The operational characteristics of the DOL_SynRMs for fulfilling different specifications will all be thoroughly investigated and confirmed by experimental measurements. The DOL_SynRM structures that can provide potential alternatives for related high-efficiency metal industry-driven applications can thus be validated. [ABSTRACT FROM AUTHOR]

This article proposes an enhanced-torque switched reluctance motor with two sets of permanent magnets (PM-SRM) embedded inside the stator yoke and the end teeth of the neighboring modules. The PMs contribute to intensify the air-gap flux density and reduce the magnetic saturation in the stator poles. As a result, the output torque can be enhanced to a significant extent. The working principle of the proposed PM-SRM is clarified using its magnetic circuit model (MCM). The characteristics of the PM-SRM are obtained and compared with classical 12/8 and 6/5 SRMs and hybrid reluctance motors (HRMs) in terms of static and average torque and average torque per PMs volume. The steady-state performance of the PM-SRM in terms of current and torque waveforms is carried out, and the PM-SRM is compared with considered SRMs and HRMs in terms of output torque, power, and efficiency. All the comparisons demonstrate the out-performance of the proposed PM-SRM over other SRMs and HRMs. To validate the simulation results, a prototype of the PM-SRM is manufactured and the experimental results are obtained. Both the simulation and experimental results are indicative of the fact that the proposed PM-SRM can gain high torque and high PM utilization factor, simultaneously. [ABSTRACT FROM AUTHOR]

The rotor structure of synchronous reluctance machines (SynRel) is conventionally retained mechanically by iron ribs. In this paper, a novel structure for high-speed synchronous reluctance rotor is presented. The novelty of this paper is the proof of a concept of SynRel machine without iron ribs. Structurally, the rotor iron lamination segments are embedded in an adhesive resin material with high temperature resistance and mechanical strength. Three four-pole SynRel machines have been designed with the target of improving motor torque, and compared for different ribs configuration. It has been shown that the proposed motor performs enhanced torque, power factor, and efficiency with respect to conventional SynRel with iron ribs. An extensive sensitivity analysis of the ribless rotor geometry is carried out, followed by both mechanical analysis and experimental over speed test to guarantee its robustness above the operating speed range. The manufacturing procedure of this novel rotor is introduced. Finally, the experimental results on both SynRel prototypes are presented, showing the increase in torque, power factor, and efficiency of the proposed solution. This paper is a first step toward the definition of a viable and novel solution of SynRel machines with improved performance. [ABSTRACT FROM AUTHOR]

Torque estimation in permanent-magnet synchronous machines is highly desirable in many applications. Torque produced by a permanent-magnet synchronous machine depends on the permanent-magnets’ flux and dq-axes inductances. Consequently, precise knowledge of these parameters is required for proper torque estimation. This article proposes the use of a high-frequency signal for both PM flux and dq-axes inductances estimation. The high-frequency signals will be injected in the stator via an inverter superposed on top of the fundamental excitation. The proposed method can be used without interfering with the normal operation of the machine, the results being highly insensitive from machine's working condition. [ABSTRACT FROM AUTHOR]

Split-phase motor drives have advantages such as lower torque ripple, enhanced fault tolerance, higher power-to-weight ratio, and lower dc-link voltage requirement, making it an attractive alternative to the conventional three-phase drives. In the proposed series-connected topology, both the motors are connected in different phase sequences, allowing the fundamental component of the winding current to produce torque in the first machine, and sixth-order harmonic currents to produce torque in the other machine. Both the motors used are synchronous machines, which have advantages such as higher power density and easier control. The proposed method can be easily extended to other synchronous machines such as permanent magnet machines and reluctance machines. In this article, a mathematical model for series-connected split-phase synchronous motors is developed and validated experimentally for decoupled field-oriented control of dual split-phase synchronous machines. Furthermore, the developed model (series-connected system) is extended for open-circuit fault operation, and experimental results are presented for the first time. Simulation results as well experimental results for steady state, transient conditions for normal, and fault operation are presented to validate the proposed scheme. [ABSTRACT FROM AUTHOR]

A parametric analysis is carried out to investigate the dependence of the rotor iron losses on the stator and rotor geometry of several synchronous reluctance machines. Six four-pole rotors have been designed with different flux barriers per pole through a multiobjective differential evolution algorithm coupled to a finite-element analysis (FEA). Two different stators with 24 and 36 slots are considered. During the optimizations, a rapid finite-element evaluation has been used to predict the performance of the motors. After that, an accurate time stepping FEA is used for computation of the rotor iron losses. Finally, the interaction between the rotor iron losses and several rotor and stator geometrical parameters is highlighted. The effect of the current time harmonics have also been taken into account, weighting its impact on the rotor losses. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation of a novel low-cost speed sensorless control technique for a permanent magnet assisted synchronous reluctance motor (PMa-SynRM). A robust adaptive speed (RAS) observer is designed for estimating the rotor speed and position, respectively. The RAS observer estimates the PMa-SynRM speed and position from the back electromotive force space-vector determination without voltage sensors by using the reference voltages issued from the current controllers instead of the actual ones. The novelty of the proposed RAS estimation technique is the adaptation of the feedback error of the actual values. Thus, the proposed observer structure promises a higher degree of robustness against PMa-SynRM parameter changes in the sensitivity analysis presented in this paper. The dynamic model and experimental realizations of the proposed control technique are introduced. A 6-kW PMa-SynRM drive test setup is constructed including a dSPACE 1104 board as the control heart of the proposed system. The hardware-in-the-loop Typhoon HIL 402 device is used to experimentally emulate the PMa-SynRM and the inverter connected to a dSPACE MicroLabBox. The proposed RAS observer robustness is evaluated using a HIL model and experimental results under different conditions. A comparative experimental analysis between the proposed RAS and Luenberger observers has been performed. [ABSTRACT FROM AUTHOR]

Magnetic saturation characteristics of synchronous reluctance motors (SyRMs), with or without permanent magnets, are highly nonlinear. These nonlinear effects can be included in the current controller by changing its state variable from the stator current to the stator flux linkage using the known saturation characteristics. A direct discrete-time variant of the flux-linkage-based current controller is developed in a state-space framework. If the magnetics are modeled to be linear, the proposed control structure reduces to the standard current controller in this special case. Experimental results on a 6.7-kW SyRM drive demonstrate that the proposed flux-linkage-based controller enables a higher closed-loop bandwidth and is more robust against parameter errors, as compared to the standard current controller. [ABSTRACT FROM AUTHOR]

This paper investigates the demagnetization problem of permanent magnets for permanent magnet-assisted synchronous reluctance motors (PMa-SynRM) and applies “demagnetization ratio” as an index to evaluate demagnetization of permanent magnet (PM). The PMa-SynRM is often designed with multilayer flux barriers to improve saliency and reluctance torque in the rotor. Weaker or less PM (than that for interior PM motors) is embedded into the rotor which could be demagnetized in high-performance operation. PM demagnetization involves temperature, current magnitude, current phase angle, designed PM operating point, or combined effect of the above factors. This work investigates the demagnetization risk for PMs in all the layers of PMa-SynRM rotor considering these factors. In particular, the current phase angle for flux weakening operation is often omitted in demagnetization analysis. First, the motor performance to satisfy the operation condition over a wide speed range is analyzed and the proportion of motor torque components, i.e., reluctance torque and electromagnetic torque, considering temperature is investigated. Then, the flux density distributions on PMs at each position/layer are studied and the PM operating points are obtained based on the variation of excitation current, current phase angle, and temperature in order to evaluate the demagnetization risk. The analysis suggests that the high current phase angle combining the effect of high temperature is the major cause of irreversible demagnetization. Finally, a method incorporating the index “demagnetization ratio” is proposed to redesign the PMa-SynRM to avoid demagnetization. Experiments are conducted to validate the simulation. [ABSTRACT FROM AUTHOR]

This paper proposes a flux-intensifying permanent magnet-assisted synchronous reluctance motor (FI-PMa-SynRM) using surface-inset permanent magnet (PM) instead of embedded PM in the rotor. The proposed FI-PMa-SynRM employs a small amount of PM that is inset on the rotor surface facing $d$ -axis instead of facing $q$ -axis as in common PMa-SynRMs. It also differs from conventional flux-intensifying interior PM motor, where the PM is embedded inside the rotor. The proposed motor enables making use of the arrangements of two types of flux barriers (FBs): the cutoff FB and the magnet FB, collectively referred to the outer FBs, to enhance the torque output and reduce the torque ripple. The first objective in this paper is to explain the principles of the proposed FI-PMa-SynRM, and the second is to analyze the proposed technique for enhancement of the torque output with small PM volume while keeping the lowest possible torque ripple. The finite-element analysis is employed to validate the proposed motor and analyses, and the results demonstrate their advantages and effectiveness. [ABSTRACT FROM AUTHOR]

This paper presents an optimized design in the permanent magnet-assisted synchronous reluctance motor (PMa-SynRM) rotor structure design with hybrid adopted materials for enhancing the motor characteristics and operation. Two types of permanent magnet (PM) materials are embraced in the PMa-SynRM rotor of rare-earth and ferrite PMs. The optimized design for the PMa-SynRM rotor structure considers the motor magnetic equivalent circuit for reducing the reluctance of the hybrid PMs to improve the motor performance. Moreover, the irreversible demagnetization of the ferrite PM which occurs due to the reversing of the magnetic field of the rare-earth PM is presented. The analytical rotating losses computation with the hybrid adopted materials at the design process is introduced. The rotating losses of the PMa-SynRM are investigated as core, magnet, proximity, ohmic, and friction losses. The core loss in the PMa-SynRM occurs due to the altering of the flux densities in numerous fragments of the iron structures. The loss measurements can be accomplished by measuring the electric parameters of the PMa-SynRM at a defined operating point. The magnetic modeling of the improved 6 KW PMa-SynRM manufactured prototype structure is derived and rotational losses are computed, validated, and compared with the finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

This paper aims to reduce detent force (DF) of a moving-magnet-type linear synchronous motor by considering different permanent magnet (PM) widths and chamfer dimensions. DF is the main cause of thrust ripple, which can lead to worse operation performance. Through Fourier decomposition, it is found that the PM size is the key factor affecting DF significantly. The thrust and its ripple of different PM widths are obtained by using the finite-element analysis. After selecting the optimal PM width, considering the mechanical strength factor, the PM can be unavoidably chamfered, which further influences DF. Based on this, an optimized motor model is designed. The prototype is manufactured to verify its results. [ABSTRACT FROM AUTHOR]

Tubular-switched reluctance linear launcher (TSRLL) with novel structure is proposed in this paper. The structure of switched reluctance motor is simplified, and the unbalanced force of common types of switched reluctance linear launcher is alleviated in TSRLL. The structure of the single-phase TSRLL with transverse flux is introduced thoroughly. The 3-D finite-element (FE) model of the proposed TSRLL is constructed, and electromagnetic analysis is performed by the FE method (FEM). To improve the electromagnetic force of the proposed launcher, the sensitivity analysis is conducted by means of 3-D FEM. The stator yoke thickness, mover cylinder’s thickness, stator pole arc, and pole width ratio of TSRLL are optimized, and the results of the sensitivity analyses are presented. TSRLL with two different polarity distribution patterns is compared via static FE analysis. The dynamic simulation of TSRLL with optimal specification and polarity distribution is carried out and demonstrated, of which the results agree well with the static analysis by FEM. [ABSTRACT FROM AUTHOR]

The conventional field weakening algorithm is more dependent on parameters and computational complexity. Therefore, the concept of advanced angle β is introduced, and the conversion of constant torque operation mode to field weakening operation mode is realized by increasing β. In this paper, the conventional field weakening control and advanced angle field weakening are modeled and simulated showing results that the advanced angle field weakening control can make the motor switch smoothly between the constant torque operation mode and the field weakening mode. The dependence of the parameters of the motor is small and the algorithm is simpler. At the same time, the theory of field weakening control of permanent magnet synchronous motor is fused in the vehicle control and the controller is developed. The external characteristic curve of the motor is calibrated by setting up the back-to-back motor test bench. The function of the controller is verified by hardware-in-the-loop experiment. After vehicle verification, it is confirmed that the data can normally enter the field weakening zone to meet the torque response and high-efficiency range. Under the new European driving cycle (NEDC) operating conditions, the efficiency of the whole controller can reach 81.97%. [ABSTRACT FROM AUTHOR]

In this paper, an outer rotor interior permanent magnet synchronous machine (IPMSM) with hybrid permanent magnet (PM) material is proposed. The key is to adopt the outer rotor structure with two-layer crescent barriers and hybrid PM material to maximize the output torque and reduce the usage of high-cost rare-earth PM. The ferrite PMs are filled in the middle of the crescent barriers with thicker thickness, while the rare-earth PMs are filled into the bilateral of the crescent barriers with thinner thickness. To verify the effectiveness of the proposed rotor structure, optimizations are first carried out among the conventional rotor structures with single kind of PM material and the proposed rotor structure with hybrid PMs. Then, detailed comparisons have been investigated. Results indicate that the proposed machine has higher torque density than the machine with only ferrite PM and can reduce almost half the usage of rare-earth PM in comparison to the machine with only rare-earth PM. Moreover, the proposed rotor structure is further optimized considering productivity. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) motors adopt interior V-type PMs and fractional-slot concentrated winding for improving the torque density and efficiency. However, the no-load magnetic coefficient will be increased, which would reduce the utilization rate of the PM. The structure parameters of the rotor should be designed reasonably, especially the bridge. This paper calculates the no-load leakage coefficient by establishing the analytical model of the no-load magnetic coefficient. It shows that, the bridge size has an important effect on the no-load magnetic coefficient. The analysis results are verified by the two-dimensional finite element analysis and tests. [ABSTRACT FROM AUTHOR]

This paper is a study on the application position of skew in order to reduce the cogging torque of a magnetic geared synchronous motor (MGM). The cogging torque affects the noise and vibration of the motor, so it should be reduced as much as possible. To solve this problem, a conventional permanent magnet (PM) synchronous motor is skewed to a PM. However, unlike other synchronous motors, the MGM has pole pieces (PPs), and a larger cogging torque is generated due to a larger reluctance difference. There have been few studies on the reduction of cogging torque of MGM, so it is essential to study the skew structure of MGM. Therefore, this paper has derived the optimum skew method by comparing and analyzing three models of MGM skewed to PM, PP, and PM and PP simultaneously. [ABSTRACT FROM AUTHOR]

In order to have direct and better control of reducing the torque/flux ripples of interior permanent magnet synchronous motor (IPMSM), this paper presents an online torque and flux estimation-based nonlinear torque and flux control (NTFC) scheme of IPMSM drive considering motor electromagnetic developed torque and stator air-gap flux linkage as virtual state variables. For conventional nonlinear controller, thed—q-axis currents ($i_{d}$ , $i_{q}$) are considered as state variables that indirectly controls the torque/flux which may not be suitable for high-performance drives. On the other hand, conventional direct torque and flux control (DTFC) scheme suffers from significant torque ripples. The proposed work overcomes the major drawback of both the conventional nonlinear and DTFC schemes through the significant reduction in torque ripples. Stability of the proposed drive is also demonstrated through Lyapunov's stability criterion and global asymptotic stability is assured through the application of criterion supported by Barbalat's lemma. Reduced torque ripples and robustness of the proposed NTFC scheme is validated through comparative simulation and experimental results with classical nonlinear controller and DTFC-based IPMSM drive. The proposed NTFC scheme achieves the lowest possible torque ripples in steady state at different operating conditions. [ABSTRACT FROM AUTHOR]

This paper first studies the electromagnetic force and vibration characteristics of the permanent-magnet-assisted synchronous reluctance machines (PM-SynRMs). First, an analytical method to calculate the radial force is proposed based on the Maxwell stress tensor method. The temporal and spatial orders of radial force are obtained by two-dimensional fast Fourier transform, then the combination of stator slots and rotor virtual slots of PM-SynRMs is proposed to give a guideline for the initial design of PM-SynRM to achieve low noise and vibration. A PM-SynRM is designed and a multiphysics model for electromagnetic vibration is established. The radial and tangential force under no-load and load conditions are calculated by finite element method, and then compared with the analysis results. Modal analysis is implemented to capture the structural parameters of the stator. Based on the proposed multiphysics model, the vibration responses under both no-load and load conditions are calculated through modal superposition method. Finally, a PM-SynRM is built and vibration test is performed to investigate its vibration characteristics. [ABSTRACT FROM AUTHOR]

This paper proposes a new hybrid permanentmagnet (PM)-assisted synchronous reluctance motor, where two types of PM materials of rare-earth PMs and ferrite PMs are employed in its rotor. To reduce the usage of rare-earth materials, a hierarchical design method is adopted in its rotor design, in which the design is divided into two levels: saliency ratio design level and PM usage design level. In saliency ratio design level, proper flux barrier dimensions are confirmed based on the principle of reluctance torque maximization. In PM usage design level, the optimal magnet ratio is first determined according to the relationship of main flux and leakage flux. Then, a tradeoff design is conducted to seek the superior combination of low torque ripple, high efficiency, and high power factor. Finally, for the purpose of validation, the electromagnetic performances of the new designed motor are investigated, including torque characteristics and antidemagnetization capabilities of ferrite. [ABSTRACT FROM AUTHOR]

Variable flux reluctance machines (VFRMs) are interesting candidates to substitute permanent-magnet synchronous machines in many applications. However, they suffer from large torque ripple. In this paper two methods, stepped rotor skewing and rotor teeth non-uniformity, are researched to reduce the torque ripple of 12/10 (stator/rotor-pole ratio) VFRMs. Based on semi-analytic results and finite-element simulations, the effectiveness of these two methods is validated in both non-saturated and saturated machines. [ABSTRACT FROM AUTHOR]

In this paper, a new hybrid permanent magnet (PM) synchronous motor with two-part rotor is proposed. The new motor is composed of surface mounted and interior magnet rotor segments on a stepped skewed shaft. The hybrid topology has wider constant power speed ratio than conventional surface mounted PM motors with relatively the same torque density. No-load and on-load finite-element analyses (FEA) are performed independently for both surface PM and interior PM synchronous motor. Superposition of the results is gathered to obtain the actual performance of the hybrid motor. The 2-D FEA results with skewed models are also performed at the final stage of the design. A prototype motor is manufactured and experimental results are obtained. Good agreement is observed between the simulations and test data for the proposed motor. [ABSTRACT FROM AUTHOR]

Line start synchronous motors (LSSM) have been recently introduced in the motor market to meet new efficiency class requirements. They exhibit high efficiency and power factor compared with induction motors. On the other hand, the difficult design, manufacture, and high cost due to the presence of permanent magnets limit their widespread use in the market. Another key factor that limits the LSSM diffusion is the need of having a wide variety of different laminations of different sizes, increasing the number of pieces to be stored, the number of mold geometries, etc. This paper investigates the opportunity to use a proper geometry of LSSM that allows the same stator and rotor laminations to be used for a different number of poles. From the manufacturing point of view, the adoption of a unique rotor lamination is extremely advantageous. It is shown that satisfactory performance can be achieved rearranging the stator winding according to the number of poles. Experimental measurements are carried out on an LSSM prototype in which the same lamination is used for 2-pole and 4-pole machines. [ABSTRACT FROM AUTHOR]

This paper deals with a detailed geometry analysis of the rotor structure for both synchronous reluctance and permanent magnet (PM)-assisted reluctance motor in order to suggest an automatic procedure to design the rotor structure. The shape of flux barriers is selected to achieve both high $d$ -axis inductance and low $q$ -axis inductance to obtain high output torque and high power factor. Methods to properly design the geometry of the ends of each barrier and PMs are adopted. In order to draw a rotor with proper shape, different modifications are discussed. All details are described to allow any reader to adopt the same procedures. After that, such a procedure is used to rapidly analyze the impact of some geometry changes on the machine performance to give a design guideline. The analyzing process starts from a reluctance motor considering the number of barriers, insulation ratio, split ratio, and slots per pole per phase. Then, the PMs are inset into flux barriers and the effect of PM width on torque, power factor, and flux weakening capability is investigated. At last, the demagnetization limit under overload operations is analyzed. [ABSTRACT FROM AUTHOR]

In-wheel type permanent-magnet synchronous motors for electric commuter cars are required to be compact and light to use limited wheel space effectively and reduce unspringing weight. Therefore, our previous papers presented a low-cost in-wheel axial-gap motor that uses ferrite permanent magnets. This motor adopted an open slot structure to reduce production costs. However, to achieve further size and weight reduction, we examine here in detail the adoption of a semiclosed slot structure instead of an open slot structure. Experimental results show that the semiclosed slot structure is effective in realizing size and weight reduction. [ABSTRACT FROM AUTHOR]

Recently, stator dc current excited vernier reluctance machines (dc-VRMs) which have concentrated field and armature windings in stator, are gaining more and more research interest due to their features of robustness rotor structure, low cost, and easy heat dissipation. This paper proposes a novel field winding connection for dc-VRMs. Taking the stator/rotor slots of 12/10 machine as an example, the electromagnetic performance including back electromotive force (EMF), pulsating torque, and capability are analyzed using the theoretical and finite element analysis. The results show that compared with the previous machine having the same stator/rotor slots, machine with the proposed field winding connections exhibits a doubling back EMF, and 60% higher torque density. [ABSTRACT FROM AUTHOR]

This paper presents a novel methodology for the variable leakage flux interior permanent-magnet (VLF-IPM) motor taking advantage of the variable leakage flux property in the rotor core controlled by the $q$-axis current, without any additional components. The fundamental phenomenon is explained with finite-element analysis results; then, the theoretical equations expressing the variable flux linkage controlled by the $q$-axis current have been conducted. The proof-of-principle model was designed, and the fundamental properties, such as torque–speed envelope and efficiency map, were evaluated. It was shown that the proposed motor can reduce energy consumption on duty-cycle driving. [ABSTRACT FROM PUBLISHER]

Synchronous reluctance (SynRel) machines are gaining more and more importance in various fields of application thanks to their known merits like rugged construction, high efficiency, absence of field windings, and no or reduced need for permanent magnets. Out of the possible design variants, in this paper, SynRel motors with uniform mechanical air gap and circularly shaped flux barriers are considered and a conformal-mapping approach to their analytical modeling and simulation is proposed. A suitable conformal transformation is introduced to compute the reluctance of each rotor circularly shaped flux barrier and the result is then used to analytically determine the air-gap flux density distribution and the electromagnetic torque of the machine in arbitrary operating conditions. The accuracy of the methodology proposed is assessed against finite element analysis. [ABSTRACT FROM AUTHOR]

This paper systematically presents the development of novel stator electrically field excited synchronous machines having salient pole rotors without any coils or magnets. This kind of new machine does not use slip-rings/brushes required in the conventional rotor wound field machines and combines the synergies of wound field machines, permanent magnet (PM) machines, switched reluctance, and synchronous reluctance machines. This paper describes the machine topologies, winding configurations, electromagnetic performance, and torque/power density, as well as acoustic noise and vibration, together with a comparison with the Toyota Prius interior PM machine in terms of torque/power speed characteristics. [ABSTRACT FROM AUTHOR]

In this paper, a bidirectional cross-linking transverse flux permanent magnet synchronous motor is presented, which has a larger space utilization ratio than the traditional transverse flux machine. The stator core unit can make full use of rotor permanent magnets, and effectively increases no-load back-electromotive force (back-EMF), with the features of easy manufacturing. The structure and the driving principle of this motor are introduced. The 3-D magnetic circuit model is established, and the analytical expression of the no-load back-EMF and the torque are derived. In addition, the magnetic field and torque are analyzed by the 3-D finite element method (FEM). A prototype was designed and manufactured. The back-EMF and static torque experiments were carried out. The theoretical analyses agreed with the experimental results well. That verified the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

The torque behavior of a synchronous reluctance motor [including the permanent magnet (PM) assisted configuration] is deeply analyzed. An analytical model is developed, showing the dependence of the torque ripple on the rotor geometry. The results of this model allow to individuate the position of the flux-barrier ends so as to minimize the torque ripple. In addition, the proposed strategy to minimize the ripple is not only based on a suitable choice of the flux-barrier ends, but this choice is combined with the adoption of a rotor formed by two different laminations. This strategy allows an optimal compensation of the torque harmonics so that a smooth torque is achieved. Some motor prototypes have been manufactured and tested in a suitable testing bench. The torque versus position characteristics have been measured at very low speed, to avoid a reduction of the high-order torque harmonics. The experimental results confirm the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper presents a detailed comparative study of two starting and running methods for a single-phase permanent magnet synchronous motor, equipped with a squirrel-cage rotor. The analysis of the motor performance is realized for a pulse width modulated (PWM) inverter fed motor and for a capacitor-start, capacitor-run motor. The developed approach may be extended to any 1-phase ac motor—induction, synchronous reluctance or synchronous permanent magnet. [ABSTRACT FROM AUTHOR]

There are two step motor principles for building up linear microactuators: variable reluctance (VR) and hybrid. While the VR motors use only soft magnetic material for guiding the magnetic flux, hybrid motors use permanent magnets as a source of static magnetic flux, as well. The benefit is a greater driving force, while the drawback is a more difficult fabrication process. The working principle of the hybrid motors requires the flux created by the permanent magnets to be of the same magnitude as the flux created by the excited coils. Therefore, it was investigated how to ensure that the two fluxes match. This paper describes the approach taken and the resulting advances in the fabrication of the micromotor. [ABSTRACT FROM AUTHOR]