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An 8-pole 48-slot dual three-phase synchronous reluctance motor has been tested under half control mode, that is, when only a single three-phase system is supplied while the other is not operating. Changing the terminal connections of the motor prototype available, two different winding configurations have been tested. This allows their performances to be experimentally compared. At first, the cross coupling effect between the axis in $dq$ reference is analyzed, by measuring the flux linkages for different current combinations. The torque characteristics are compared in terms of torque map, maximum torque capability and torque ripple. Then the finite element analysis has been used to explain the experimental results and to investigate the radial forces on the rotor. Finally, the impact of a lack of symmetry between the two three-phase system is investigated. [ABSTRACT FROM AUTHOR]

In this article, an analytical model to predict the instantaneous torque profile in a synchronous reluctance (SyncRel) machine is developed, which can predict the machine's torque performance based on either inductance or flux-linkage harmonics. High-performance torque-ripple-sensitive applications have stringent torque ripple and noise and vibration requirements to satisfy the overall system requirements. The prediction of the torque ripple is critical in these applications to identify the root cause and then mitigate the torque ripple through design alternations under different loading (current) conditions of the machine. The developed analytical model provides a simpler, intuitive, and significantly less time consuming yet reasonably accurate alternative approach compared to multiple finite-element runs on the same baseline design. The developed analytical model provides design support through fast iterations with design variations or for motor electronic controller implementation. A 2-D finite-element model has been developed to validate the proposed analytical model. The analytical model is also validated with experimental data of a 30-slot four-pole SyncRel machine. [ABSTRACT FROM AUTHOR]

This article deals with the design of a synchronous reluctance (SynRel) motor for full-electric vehicle applications. In particular, the design is focused on “premium” vehicles and aims at the development of rare-earth free electric motor technologies featuring low cost manufacturing. Different solutions are proposed and compared with focus on the rotor design; the investigated topologies employ asymmetric rotor structures with “fluid shaped” barriers without radial ribs to maximize the average torque and minimize the torque ripple. As this choice is very critical for the mechanical strength of the rotor core at high speed, it has been decided to fill the flux barriers with epoxy adhesive resin. The use of the resin requires accurate mechanical analysis in order to assess the rotor robustness at high speed. The article presents the performance of optimized designs without radial ribs and it is focused on the identification of the best properties for an epoxy resin able to enhance the mechanical integrity of the rotor. Moreover, experimental tests on resin cylinder samples have been carried out in order to verify the contact pressure between the resin and a laminated core. The results of this study could be a useful guideline for the designers interested in using this technology for high speed SynRel motors. [ABSTRACT FROM AUTHOR]

This article proposes a novel dual three-phase flux-modulated switched reluctance motor (SRM) drive with maximum torque per ampere (MTPA) capability. Different from the existing open-winding structure, the stator winding is in dual three-phase connection, which effectively eliminates the side effects of the zero-sequence harmonic voltage component. Hence, the modulating region of the space vector pulsewidth modulation can be enhanced together with the increase of the dc-link voltage utilization ratio. The mathematical models of the dual three-phase flux-modulated SRM in the stationary reference frame and synchronous rotating reference frame are analyzed in detail. By considering the inductance nonlinearity, the MTPA control strategy is proposed based on the polynomial fitting method, which not only improves the torque capability but also simplifies the calculation of the current control system. The contributions of fundamental and harmonic currents to the electromagnetic torque are considered. By online adjusting the ratio of the dc-biased current component to the ac current component, the torque capacity can be improved. Besides, the effectiveness of the proposed MTPA control strategy can be enhanced by suppressing the harmonic current components caused by distorted back electromotive force. Experimental validations are provided to verify the effectiveness of the proposed SRM drive. [ABSTRACT FROM AUTHOR]

A new method to detect the initial rotor position of switched reluctance machine (SRM) is presented in this article. Unlike most conventional position estimation methods, the proposed method does not need any extra premeasurement and only the data with finite element method (FEM) are required. First, a linear regression model (LRM) is presented to describe the relationship between FEM and measured inductance characteristics. Then, to detect the position, the residual sum of squares of the proposed LRM is considered as an objective function, which is a convex function with rotor position. The rotor position can be estimated by minimizing the objective function with the golden-section search method. Finally, the accuracy of the proposed estimation algorithm is validated by the experimental results on a three-phase 12/8 pole SRM prototype. Compared with the existing position estimation methods, the proposed method has higher accuracy and less measurement effort. The proposed method can serve as a supplement to provide accurate initial position information for incremental position sensors. [ABSTRACT FROM AUTHOR]

This article investigates and compares two popular combined winding configurations for bearingless machines, the multiphase (MP) and dual-purpose no-voltage (DPNV) windings. Each of these winding configurations has the ability to independently create suspension force and drive torque using the same stator coils. The article develops analogous bearingless motor force and torque models, space vector equivalent circuits, and a current regulation architecture for each combined winding approach. A comprehensive comparison is made between the two combined winding topologies by using these analogous models and through an experimental study. It is shown that, from a motor design perspective, these combined winding topologies are equivalent for certain design conditions, but that each winding places very different demands upon the drive power electronics. The article concludes that the optimal choice of winding configuration depends on the machine parameters and the expected loading and drive cycle. When compared in terms of total current stress exerted on the bearingless drive, the MP winding is preferred when over half of the coil current is used to produce torque rather than force. In terms of the drive's volt-ampere rating, the DPNV winding is shown to be advantageous for high operating speeds and low torque values. [ABSTRACT FROM AUTHOR]

In this article, we present a bearingless motor with a novel segmented dipole interior permanent magnet (IPM) slice rotor. The segmented dipole IPM rotor contains a unique pattern of interior permanent magnets arranged to generate a dipole air gap flux pattern. The magnets are encapsulated within an electrical steel rotor structure. The stator contains a three-phase, four-pole winding for suspension and a three-phase, two-pole winding for rotation. We present analyses of several candidate rotor designs. The analyses indicate that the segmented dipole IPM rotor achieves a reduced tradeoff between force and torque capacity and relatively symmetric force dynamics as compared to prior art designs and alternate topologies. Symmetric and decoupled force dynamics allow a simple force decoupling algorithm to be used. We designed, constructed, and tested a prototype system. We experimentally demonstrate that the prototype system can achieve stable levitation and open-loop rotation. [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]

Measuring and quantifying the electromagnetic characteristics of switched reluctance motors (SRMs) are indispensable for advanced motor control and performance enhancement. This article reports on a novel method in obtaining the flux-linkage characteristics of an SRM without rotor clamping devices and position sensors. This approach combines measurement with data reconstruction. For the measuring step, flux-linkage samples at four torque-balanced positions were measured indirectly. Considering the magnetic coupling among phases, two different excitation forms were adopted to further increase accuracy. Then, for the reconstructing step, a fuzzy logic-based approach was applied to reconstruct the complete flux-linkage characteristics with measurement results. The construction results were compared to measurements results from the traditional rotor clamping method, and good agreements can be found, demonstrating the effectiveness of the proposed method. Furthermore, based on reconstructed electromagnetic characteristics, dynamic simulation of an SRM prototype under different control modes was carried out and analyzed in MATLAB. Comparison with dynamic experiments further verifies the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper mainly takes a 6/4 switched reluctance motor (SRM) as an example to analyze the temperature of the motor. In order to establish the equivalent thermal circuit model (ETCM) conveniently, the mechanical structure of the motor is simplified to a certain extent, and the characteristic nodes are divided. Then the heat transfer process in the rotor region, the stator region and the whole motor during the operation of the motor is analyzed, and the ETCM of those regions are established respectively. This method of establishing ETCM is also applicable to superconducting motors. Based on the basic principles of heat transfer, the calculation method of thermal resistance in each ETCM is given in this paper. Then, the three-dimensional (3-D) finite element (FE) temperature field model of the motor is built and compared with the ETCM. Finally, the accuracy of the ETCM is verified by experiments. [ABSTRACT FROM AUTHOR]

In this article, based on flux modulation theory, an airgap-harmonic-based multilevel optimization design approach is proposed for a double-stator flux-modulated permanent-magnet (DS-FMPM) motor. The proposed DS-FMPM motor is purposefully designed, so as to realize the design requirements of driving cycle. In the proposed optimization approach, based on three fundamental elements of general flux modulation theory, motor optimization design is carried out from three levels. Furthermore, a response surface method, sensitivity analysis, and a genetic algorithm are purposely employed in different levels to obtain optimal motor design. In addition, electromagnetic performances of a DS-FMPM motor are demonstrated in detail. Finally, a prototype motor is manufactured and tested. Both simulation and experimental results verify the feasibility of the DS-FMPM motor and the effectiveness of the proposed airgap-harmonic-based multilevel optimization design approach. [ABSTRACT FROM AUTHOR]

In this article, a new torque sharing function (TSF) method is proposed for torque ripple reduction in switched reluctance machines (SRMs). The proposed TSF achieves lower current tracking error by establishing a new current reference generation strategy. The phase current reference is first derived from the torque command using offline calculations and also from the phase current response that is obtained from the dynamic model of the SRM. Then, an optimization problem is formulated to shape the current reference for the objective of minimizing the torque ripple and copper losses, while maintaining the required average output torque at the given operating speed. The dynamic simulation of the SRM model is also utilized in the optimization problem. Compared to the existing conventional and optimization-based TSFs, the proposed TSF exhibits lower current tracking error due to the consideration of the current dynamics. Better torque–speed performance with improved average torque and reduced torque ripple is also obtained, especially during commutation. Simulations and experiments under different operating conditions are carried out to verify the proposed TSF method. [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]

In this article, split-tooth stator slot permanent magnet (PM) machines, which have high fault-tolerant capability, are proposed. Compared with the existing 12-slot 10-pole (12S10P) stator slot PM machine, the torque can be improved by 66% by properly choosing the split tooth number and other geometric parameters. It is found that two split teeth stator slot PM machine (ST2) shows the best torque characteristics among the stator slot PM machines with different split tooth number. To further illustrate the merits and demerits of ST2, a conventional 6S4P surface mounted PM machine (SPMM) and a 6S4P variable flux reluctance machine serve as the benchmarks to compare with the 6S11P ST2, at both open circuit condition and load condition. The 6S11P ST2 shows 68% higher torque over the 6S4P VFRM. Although the torque of the 6S11P ST2 is around half of the 6S4P SPMM, the former has 70% higher torque per PM volume than the latter. Furthermore, demagnetization analyses under three-phase short-circuit and pure d-axis currents show that the 6S11P ST2 has much better demagnetization withstand capability over the 6S4P SPMM. A Prototype is manufactured and tested to validate the theoretical analyses. [ABSTRACT FROM AUTHOR]

In this article, an improved direct instantaneous torque control (DITC) based on adaptive terminal sliding mode control (ATSMC) is proposed to suppress torque ripple and enhance the anti-interference ability for switched reluctance motors (SRMs). The proposed speed controller used in the outer loop of DITC is based on the rate of change in load torque. The state of the system converges quickly to the equilibrium point and realizes fast output of the given torque without known disturbance upper bound. Moreover, a novel reaching law is proposed to reduce torque ripple and startup time. The stability of the adaptive terminal sliding mode motion is verified by using the Lyapunov function. The improved DITC system is implemented on a 16/10 segmented-rotor SRM. Compared with sliding mode control and terminal sliding mode control, the proposed ATSMC in the DITC system behave with better performances in aspects of the speed and torque response, antiinterference ability, robustness, and torque ripple suppression. Simulation and experimental results are given to verify the effectiveness of the improved DITC. [ABSTRACT FROM AUTHOR]

The rotor flux linkage of permanent-magnet synchronous motor (PMSM) is of great importance for monitoring and high-performance control. However, most of the existing online estimation methods need prior knowledge of other PMSM parameters such as stator resistance and dq axis inductance, which are difficult to realize in the rank-deficient models of electrical machines. This article proposes a simple online estimation method of rotor flux linkage for the dual three-phase surface-mounted PMSM (SPMSM) drives with the assistance of injected position offset. The independent estimation model has been developed for the rotor flux linkage by appropriate setting of positon offset between two sets of three-phase windings of dual three-phase SPMSM drives. The proposed method not only has little influence on the output torque and high signal-to-noise ratio for observation, but also offers the superior performance in estimation accuracy irrespective of the influence of VSI nonlinearity. In addition, the proposed position-offset-based method is suitable for the full-speed region including the field-weakening operation. Finally, comprehensive experimental results are presented to verify validity of the proposed method under different working conditions. [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]

Due to the significant advantages of cost savings, low temperature rises and high efficiency, synchronous reluctance machines (SynRMs) have attracted growing interest from academia to industrial applications. Numerous articles have been published to obtain a SynRM with improved performance (i.e., a high torque density and efficiency and a lower torque ripple) using different focusing points at healthy and faulty conditions such as rotor design, magnetic steel grade, stator winding, and fault tolerance control (FTC) strategy. Hence, this article reviews the scientific researches about SynRMs aiming to improve their performance. These scientific researches can be categorized into four sections: 1) optimal rotor design; 2) magnetic steel grade; 3) winding configurations; and 4) FTC strategies. [ABSTRACT FROM AUTHOR]

In this article, we developed an improved hybrid field model (IHFM) to predict the on-load performance of the interior permanent-magnet (IPM) motors considering both iron saturation and slotting effect. It combines the airgap analytical model based on the modified conformal mapping with the reluctance mesh method for stator and rotor. The reluctance mesh method can accurately predict the rotor saturation and tooth-tip saturation even their field distribution is complicated due to the armature reaction. Besides, IHFM will significantly accelerate computation speed using the analytical model for airgap region while keeping high accuracy. The finite-element analysis and experimental results of the flat-type and V-type IPM motors are demonstrated to verify the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

Energy storage is an emerging technology that can enable the transition toward renewable-energy-based distributed generation, reducing peak power demand and the time difference between production and use. The energy storage could be implemented both at grid level (concentrated) or at user level (distributed). Chemical batteries represent the de facto standard of storage systems for performance and maturity; however, batteries feature a quite large environmental footprint and use precious raw materials. Mechanical storage technologies could represent a viable alternative to chemical batteries, because of their reduced impacts on the environment and on raw materials. This article presents the design of a motor/generator for a flywheel energy storage at household level. Three reference machines were compared by means of finite element analysis: a traditional iron-core surface permanent-magnet (SPM) synchronous machine, a synchronous reluctance machine (SynchRel), and an ironless SPM synchronous machine. Simulation shows that the ironless machine is good candidate for distributed energy storage, because of its high efficiency, high discharge duration, and low losses. A prototype ironless machine was designed and manufactured. Experiments confirm the simulation results. [ABSTRACT FROM AUTHOR]

Currently, surface-mounted permanent-magnet (PM) rotors are more frequently employed than interior PM rotors in high-speed PM motors. It is mainly because the mechanical strengths of sleeve materials can be much higher than those of silicon steels. However, at high speeds, the current harmonics caused by pulsewidth modulation (PWM) converter induce high eddy current losses in PMs and sleeves when they are conductive. Moreover, because of the existence of nonmagnetic sleeves, the surface-mounted PM motors have very poor flux weakening abilities. Interior PM motors can not only avoid sleeves, but also reduce the influence of the PWM converters. Moreover, they can provide additional reluctance torque and have better flux-weakening abilities. A major drawback of interior PM rotors is their low mechanical strengths, which limit their surface velocities. In this article, high mechanical strength amorphous metal 2605SA1 is used to increase the surface velocity of an interior PM rotor. A surface-mounted PM rotor protected by carbon-fiber sleeve is designed to perform a comparison study. Both motors are built and tested. The advantages and disadvantages of the two motors in terms of mechanical, electromagnetic, and thermal behaviors are evaluated. [ABSTRACT FROM AUTHOR]

Based on the characteristic of doubly salient electromagnetic machines (DSEMs) that the incremental inductance varies with the rotor position, a sensorless startup strategy is proposed in this article. First, the pulse injection based method is adopted to estimate the initial rotor sector. The influence of the field current on the position estimation error is analyzed. Second, the startup method with no test pulse is introduced to start DSEM. Two key strategies are proposed: the commutation strategy based on the series incremental inductance detection and the anti-out-of-step control strategy based on the circulating current detection. The series incremental inductance is estimated in a chopping period and is compared with a preset threshold to obtain the commutation signal. The circulating current of the nonconducting phase is detected to monitor whether the DSEM is out of step. Furthermore, the current chopping mode is optimized, which has influence on the circulating current of the nonconducting phase. The proposed strategy can avoid the discontinuity of phase current caused by the test pulse in the existing technique. Finally, the effectiveness and the feasibility of the proposed method are verified by a series of experiments on the 9-kW 12/8 pole DSEM prototype. [ABSTRACT FROM AUTHOR]

A drive topology composed of a T-type single-phase three-level voltage source rectifier (VSR) and a four-level switched reluctance motor (SRM) converter is proposed in this article. The commonly used diode bridge rectifier presenting degraded power quality is replaced by the VSR to drive the SRM converter. Compared with the conventional split-dc converter, the four-level SRM converter of the proposed drive topology adopts one more switch and one more diode for each phase, but two more operation modes are formed. With the double-voltage demagnetization mode of the four-level SRM converter, the tailing time of demagnetization current is significantly reduced, which increases the utilization of inductance increasing region. All the operation modes of this converter can be implemented successfully, even in the multiphase excitation region. Moreover, a centralized control strategy is proposed to regulate the VSR and SRM together, within which the speed and grid-side power factor are regulated by the d-axis and q-axis component of grid-side current in VSR, respectively. Most importantly, the bidirectional energy flow is realized. An idea-proofed testbench is constructed. The results obtained from the comparative experiments confirm the validity of the proposed drive topology and its control strategy. [ABSTRACT FROM AUTHOR]

In order to combine the advantages of modularity and hybrid-excitation for motor torque and power density enhancement, this article proposes a 12/4 modular-topology, permanent magnet (PM) assist, hybrid-excitation switched reluctance machine (HESRM) with both segmented-stator and -rotor. The machine topology and basic operating principle are presented. Three key parameters of the machine are optimized for assessment on the torque production. The three-dimensional finite-element analysis is employed to consider the effects of end winding and core saturation. The static magnetic characteristics and dynamic performances are simulated and compared with a 12/4 segmented SRM (SSRM) without PM and a 12/10 segmented-stator HESRM. Two prototypes of the proposed 12/4 HESRM and a 12/10 segmented-stator HESRM with the same size are manufactured and developed for experimental verification. Both results show that the proposed motor can achieve higher dynamic average torque and higher power/torque density at high-speed operation. It also has a stronger starting capability, more rapid response for command changes, as well as better stability and tracking features. [ABSTRACT FROM AUTHOR]

The focus of this article is the design of high efficiency electric motors adopted in power drive systems (PDS). The last efficiency standards are considered as constraint for the motor and drive design: they are introduced and described and their impact on the choice made during the design process are highlighted. As a particular case, the perspective of a motor manufacturer is adopted in order to understand which is the proper efficiency level of the motor required to fulfil the efficiency requirements of the PDS. This is not always clear and easy to understand because different standards apply in the two contexts. A design example of an industrial motor with 3 kW power is included, showing also experimental results on a prototypes. Also the standards related to the experimental tests, in particular those prescribing instrument accuracy, are considered and commented in the article. [ABSTRACT FROM AUTHOR]

The industrial application of the switched reluctance motor (SRM) is limited by its high torque ripples caused by the doubly salient structure. In this article, an improved direct torque control (DTC) with sliding mode controller and observer is developed to reduce the torque ripples of a four-phase SRM. First, a sliding mode controller based on a new reaching law is developed for designing a sliding mode speed controller (SMSC) for the DTC system. An antidisturbance sliding mode observer (ADSMO) is then proposed and combined with the SMSC to build a composite antidisturbance speed control strategy. Moreover, detailed simulation validations are carried out to reveal the effectiveness of the new reaching law, SMSC and ADSMO. Finally, experiments are conducted to verify the performance of the proposed SMSC–ADSMO in a DTC system with a four-phase SRM prototype. [ABSTRACT FROM AUTHOR]

The article presents a torque ripple minimization process using symmetrical rotor flux barrier shaping for synchronous reluctance (SyncRel) machines. High-performance applications demand stringent torque-speed, torque ripple, noise, and vibration requirements to satisfy the overall system performance. An iterative design approach incorporating electromagnetic, structural, and thermal analyses is presented that led to the design of a SyncRel motor with low torque ripple and minimized second-order vibration mode. The contributions demonstrated that the 30-slot, 4-pole SrncRel machine is a viable option for high-performance and packaging-constrained applications. Global response surface method that has the capability for parallel analysis has been used for the multiobjective optimization problem. A 2D finite element (FE) tool with the HyperStudy optimization routine has been used to implement the proposed design process. A quick and easy-to-use motor parameter-based model along with 2D FE analysis is used to evaluate the performance of the optimized design. Experimental results are provided to validate the iterative and comprehensive design, and design procedure. [ABSTRACT FROM AUTHOR]

Many electric traction drive systems (ETDSs) are driven by electric motors primarily composed of high-energy rare-earth (RE) permanent magnets (PMs), such as neodymium–iron–boron (NdFeB) and samarium–cobalt (SmCo). Given the high cost of RE materials, there is a great interest among various industry sectors in searching for breakthrough technologies that reduce the consumption of high-energy RE magnets in their electromechanical energy conversion systems. The reduction of the magnetic volume is typically realized either by replacing a portion of the high-energy RE magnet with the low-energy ferrite magnet (knows as hybrid structure) or by modifying the magnetic arrangement of the machine itself, where a portion of the physical RE magnets is removed and replaced by induced magnets (known as consequent-magnetic pole structure). For this purpose, this article presents a review of the current state-of-the-art motor typologies with less-RE PMs and their key design challenges, followed up by a series of recommended guidelines to overcome related design challenges. [ABSTRACT FROM AUTHOR]

In this paper, a new multi-tooth switched reluctance motor (MT-SRM) is proposed and then based on the original topology, three novel multi-tooth hybrid reluctance motors (MT-HRMs) are introduced to improve the torque characteristics of the SRM. The proposed structures are an MT-HRM with permanent magnets (PMs) between the side teeth of the adjacent modules, an MT-HRM with PMs in the yoke, and finally an MT-HRM with dual-PM configuration. The operating principles of the MT-HRMs are illustrated and the flux adjusting effect and outstanding torque production ability of the PMs are demonstrated through the theoretical and simulation results. The flux distributions and static torque and flux linkage profiles of the motors are obtained and compared. The four proposed motors are compared in terms of the steady-state current and torque waveforms. All the simulation results indicate that the PM-assisted structures can achieve higher torque and power than their PMless counterpart with deploying only three/six small PMs. The four motors are prototyped and the experimental results are carried out. Both the experimental and simulation results prove the effectiveness of the proposed MT-HRMs. [ABSTRACT FROM AUTHOR]

Conventionally, the converter of switched reluctance motor (SRM) is fed by the uncontrollable diode bridge rectifier (DBR), which leads to a low grid-side power factor (PF) and high current total harmonic distortion (THD). In this paper, an alternative solution for the grid-connected high-speed SRM drive system with improved PF is proposed. In the proposed drive system, the three-level active front end (AFE) is connected in cascade with the midpoint converter for SRM operation. A centralized strategy, which controls the AFE and SRM together, is proposed to govern the motor speed and grid-side PF by regulating the real power and reactive power of the system, respectively. Specifically, the real power, reactive power, and the voltage balancing of split capacitors are controlled by the model predictive directed power control (MP-DPC) algorithm, which significantly reduces the control complexity and guarantees the fast dynamic response. Consequently, satisfying speed regulation, high PF, low current THD, and bi-directional power-transfer capability are achieved. An idea-proofed testbench is constructed in laboratory, and the applicability of the proposed drive system is verified by a series of experimental results. [ABSTRACT FROM AUTHOR]

Acoustic noise modeling, analysis, and reduction are critical in the design of switched reluctance machines for noise-sensitive applications. Although the analytical method can provide a fast simulation of the acoustic noise, it is generally less accurate compared to the numerical method. In order to improve the simulation accuracy, a novel analytical method is presented in this paper. The proposed method considers the excitation of the high-axial-order vibration modes to simulate the vibration behavior and the acoustic noise in the three-dimensional (3D) domain. Methods of obtaining the input data for the 3D analytical simulations are presented. The acoustic noise results obtained from the numerical simulations and experiments from an 8/6 switched reluctance motor drive are used to validate the analytical method presented in this paper. [ABSTRACT FROM AUTHOR]

A variable reluctance electric machine with a two-degree of freedom rotor motion characterized by rotation around the center of the rotor and orbiting around the center of the stator is studied. One motivation for adopting such rotor motion would be to allow torque generation through both the radial and tangential components of the electromagnetic forces created in the airgap, as opposed to common rotary machines in which torque is a byproduct of only the tangential component of the airgap electromagnetic forces. Furthermore, the rotor motion provides a built-in gearing action similar to that of a cycloidal drive, which allows natural torque multiplication and the tight integration of the electromagnetic and mechanical systems. The two-degree of freedom rotor motion also results in a counter-intuitive inertia characteristic of this machine concept which is elaborated in this paper for the first time. Due to the reluctance nature of the torque, and because of the distinctive rotor motion profile which resembles the motion of a cycloid, the studied machine is called a cycloidal reluctance (CR) electric machine (CRM). In this paper, the principle of operation of the CRM is explained, and its performance is compared to a counterpart switched reluctance machine (SRM). A prototype is built, and the theoretical torque calculations are validated by experimental measurements. [ABSTRACT FROM AUTHOR]

The belt-driven starter/generator (BSG), as a cost-effective solution, has been widely employed in hybrid electric vehicles (HEVs) to improve the stability and reduce the fuel consumption of the vehicles. It can provide more than 10% reduction in CO2. Electrical machine is the heart of the BSG system, which is functioned both as motor and generator. In order to optimize both aspects of motor and generator simultaneously, this paper presents a new multimode optimization method for the switched reluctance machines. First, the general multimode concept and optimization method are presented. The switched reluctance motor and the switched reluctance generator are the two operation modes. The optimization models are established based on motor and generator functions. Sensitivity analysis, surrogate models and genetic algorithms are employed to improve the efficiency of the multimode optimization. Then, a design example of a segmented-rotor switched reluctance machine (SSRM) is investigated. Seven design variables and four driving modes are considered in the multiobjective optimization model. The Kriging model is employed to approximate the finite element model (FEM) in the optimization. Finally, the optimization results are depicted, and an optimal solution is selected. The comparison between the initial and optimal designs shows that the proposed method can improve the foremost performance of the SSRM under all driving modes. [ABSTRACT FROM AUTHOR]

This paper presents a new structure of Permanent Magnet Flux-Switching Linear Motor (PM-FSLM) with a simple low weight modular primary and acceptable thrust ripple production. A flexible Magnetic Equivalent Circuit (MEC) is applied for modeling the proposed machine, which is capable to analyze the performance of different structures of PM-FSLMs. The saturation and end-effect phenomena are considered by a nonlinear permeability function and virtual zones at both ends of the machine, respectively. The machine operation under dynamic load is also investigated and its specifications are obtained. The proposed PM-FSLM has more power capability, lower current un-symmetry, and simpler mover structure compared to other ones, which can be mentioned as its benefits. Finally, the results of the proposed method are validated by the Finite Element Method (FEM) to show the effectiveness of the proposed MEC technique in terms of accuracy and processing time. The introduced linear machine and the proposed analysis method with adjustable accuracy are the paper novelties, which are presented in this work for the first time. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic thermal model which predicts the winding temperature of electrical machines at steady-state and transient conditions where windings are used in integrated battery chargers (IBCs) for DC charging in a stationary position. Using winding in high current charging process causes rising winding temperature which affects insulation life. Switched reluctance machines are a proper choice for using in electric vehicles (EVs) because of their advantages such as simple and sturdy structures. IBCs can reduce volume and weight of EVs and total cost is diminished because of integration. The analytical thermal model proposed in this paper can calculates the winding temperature in balanced and unbalanced currents injection because of the phase inductance in each rotor angle is distinct, so current excitation in each phase should be different for obtaining zero total torque and keeping rotor in a stationary position, also a reduced-order model is proposed with minor impact on the accuracy of the model. Special attention has been paid to monitor the winding temperature with considering the motor lifetime in DC charging mode, this view has not been addressed in IBCs before. The proposed model is then validated against experimental results and 3D finite element method. [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 paper combines the use of multi-phase configurations and current harmonic injection methods to achieve significantly improved performance for doubly salient synchronous reluctance machines (DS-SRMs). In order to understand the torque production mechanism of multi-phase DS-SRMs with current harmonic injection, some general analytical torque models have been developed. The models are based on Fourier Series analysis of self- and mutual-inductances. It has been established that with current harmonic injection, the torque ripple of both 5-phase and 6-phase DS-SRMs can be significantly reduced and the average torque can be enhanced. It contrast, harmonic injection always has a detrimental impact on 4-phase machines. The investigations of losses and dynamic performance with current harmonic injection for multi-phase machine have also been carried out and demonstrated that the proposed method can improve the efficiency in constant torque region and maintain comparable performance to fundamental current supply in the flux weakening region. Experimental validation based on single layer, 6-phase, DS-SRM has been performed. [ABSTRACT FROM AUTHOR]

Although Switched Reluctnace Motors have many advantages, vibration is known as their most severe drawback acting as an impediment limiting their widespread use in industrial and domestic applications. Through electromechanical relationships, it is shown that the first-order time derivative of applied phase voltage and second-order time derivative of radial force directly affect the amplitude of generated vibration, especially at the beginning of demagnetization instance. Therefore, a set of criteria is stated in this paper meeting which ensures having low vibration intensity. In this paper, three types of demagnetization voltages are proposed which comprehensively meet the stated criteria. These voltages share the same characteristics contributing to the vibration reduction in Switched Reluctance Motor. Two vital parameters of Synchronous Counter and Coefficient are included in the proposed demagnetization voltages which must be meticulously chosen in order to be effective. Noticeable contribution of the proposed methods to the vibration alleviation is validated through simulation and experimental tests conducted under different working conditions. [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]

In this article, a high-precision equivalent magnetic circuit (EMC) model is first proposed for slotted permanent-magnet (PM) limited-angle torque motor (LATM) with nonuniform teeth, which leads to potential application in swing system substituting a lower torque density of the slotless structure. By the proposed relatively fine division method of magnetic reluctance in the stator tooth-tip segments, air-gap regions, and PM poles, the proposed EMC model can fully consider armature reaction and magnetic saturation problem. Subsequently, a multiobjective optimization method based on the EMC model is proposed to improve torque performance. Finite-element analysis is employed to validate the EMC model and optimization results. Following that, a curved nonwounded tooth shape is carried out and further optimized to decrease magnetic saturation of stator teeth and significantly improve symmetry of torque profile about stable equilibrium point, compared with the traditional straight tooth shape. Finally, the slotted LATM with curved teeth is prototyped, and its experimental results are presented and discussed. The simulation and experimental data show better accuracy of torque profile improvement. [ABSTRACT FROM AUTHOR]

Switched Reluctance Machines (SRM) are emerging as a possible alternative in terms of cost and supply stability to rare earth based electric vehicle traction systems. However, because of the huge amounts of energy stored and transferred back and forth between the DC source and the SRM, large DC-link capacitors must be used as buffers, which increases overall costs and size. This paper proposes a novel modulation technique which forces the exchange of energy between phases while decreasing the energy transfer between the DC bus and the SRM. This means lower DC bus currents (capacitor size and cost reduction) and lower Joule-effect conduction losses (better efficiency). The proposed modulation has been validated experimentally in a test bench and compared with the conventional torque-sharing function.

Switched Reluctance Machines (SRM) are considered promising rare-earth free candidates for the next generation electrified vehicles. One of the main drawback of this technology is the need of a large DC-link capacitor to balance the energy transferred back and forth between the DC source and the SRM. There are interesting novel modulations to reduce the current of the DC bus, focused on the capacitor size and cost reduction but leaving aside the thermal analysis and lifetime improvements. Carrying out the required dynamic multi-physics simulations for that purpose becomes highly time consuming and complex, especially when standardized or real driving conditions are needed to be taken into account. This article proposes a simulation methodology, simple to implement and with a relatively low computational cost, to estimate the lifetime of an automotive DC-link capacitor, with the current load it delivers as the starting point. The presented methodology has also been used to validate a novel SRM modulation technique and to compare it, in terms of reliability, with the conventional torque sharing function.

In this article, a time-efficient torque shaping technique for the switched reluctance machines is proposed to reduce the torque ripples while optimizing the copper loss. To reduce the computational time for solving the time-consuming bi-objective optimization problem, an efficient and desirable linear space for the SRM is utilized through the torque mapping between the linear space and nonlinear space. The feasible regions and properties of this torque mapping for SRM are studied in detail first. Then, based on this torque mapping, the current reference is generated by solving a convex optimization problem in the linear space and later converted to the current reference in nonlinear space. Compared to the traditional method that only adopts nonlinear space, the proposed current reference generation method requires less than 10% of the time. Furthermore, the proposed method saves more than 70% time consumed by the traditional method for the bi-objective optimization problem but possesses the similar torque ripple reduction performance. The effectiveness of the proposed method has been verified by extensive simulation and experimental tests on a four-phase 5.1 kW 8/6 SRM setup. [ABSTRACT FROM AUTHOR]

In this article, the integrated drive for three-phase switched reluctance motor (three-phase SRM) is proposed, and it combines a battery-powered bidirectional dc/dc converter to provide bidirectional power transfer in practice. In the proposed integrated drive, there is no relay to reconfigure and no need to add separate charging/discharging units and circuit components. Only one physical current sensor is used to sense the switch-bus current to provide all current signals not only for SRM driving, but also grid-to-vehicle/vehicle-to-grid functions at a standstill. The proposed integrated drive and its control are implemented and demonstrated by the provided results. [ABSTRACT FROM AUTHOR]

Noise, vibration, and harshness (NVH) issue in switched reluctance machines (SRMs), originating from their doubly salient structure and unique principle of operation, is addressed in this work by proposing a structural design modification in the stator, which increases stiffness to mass ratio of the structure. A 24-slot 16-pole (24s/16p) SRM designed with the aim of automotive application is studied here for the NVH optimization, at different target operating points, using stator pole bridges. Stator pole bridges link consecutive stator teeth to provide additional stiffness to the stator structure. Average torque reduction due to flux shorting in stator pole bridges is tackled by proposing a low-permeability material, with considerable stiffness, which has not yet seen its’ application in SRM NVH domain. Multiphysics aspects of stator pole bridge design encompassing electromagnetic radial force, mechanical stress, steady-state temperature distribution, and acoustic noise analyses are presented in this article. Possible manufacturing issues are considered during the design phase and appropriate measures are implemented to facilitate easier construction of two 100-kW prototypes. The final design with stator pole bridges and a baseline design without any stator pole bridges are prototyped, after rigorous multiphysics optimization, for extensive testing. Experimental results verify simulation outputs and report a maximum noise reduction of 12.52 dBA in the stator pole bridge model compared to the baseline SRM. [ABSTRACT FROM AUTHOR]

In this article, a partial parallel dual active bridge (PPDAB) converter is proposed to lower the current stress over the switching devices on the low-voltage side. Gallium Nitride (GaN) transistors are used to improve efficiency and power density at 1 MHz switching frequency. Moreover, in order to reduce the number of magnetic components and achieve more compact design, with a unique three-leg core geometry, a new method of integrating three transformers and their associated interfacing inductors is proposed. The integration is able to shorten winding length and therefore reduces winding dc resistance. Moreover, wounding the secondary windings on each outer leg in the core enlarges leakage inductance, which can serve as the interfacing inductor Lac in the PPDAB converter. Given that, a reluctance model to analyze coupling effect of the secondary windings as well as their current balance is derived and validated by finite element simulations. Based on both calculations and simulations, the proposed integrated transformer is found to be functionally equivalent to three discrete transformers, in which their primary windings are connected in series, and the additional Lac inductor. Additionally, given the same number of the turns of the windings in each parallel module, the ac currents in these three secondary windings can inherently balance. Finally, a fully GaN-based 1.2-kW 1-MHz 400V/50V prototype with a peak efficiency of 97.51% is built and tested to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this article, a wireless shaded-pole induction motor (SPIM) is proposed and implemented, which artfully integrates wireless power transfer into a single-phase SPIM to achieve the first wireless ac motor. Prominently, there is no controller at the SPIM side, as the controlling process is fully conducted at the transmitter side. Meanwhile, there is no need to specially design the motor, as all existing SPIMs can readily be used. The key is to propose a self-driving circuit in the receiver, which can provide variable-voltage variable-frequency control of the SPIM. As a result, the proposed wireless SPIM takes the definite advantages of electrocution-free and totally sealable. A 110 W prototype has been built for experimental verification. It can offer wireless speed control from 486 to 1330 r/min with the transfer distance of 30 mm and the transmission efficiency of 86.2%. [ABSTRACT FROM AUTHOR]

In this article, a variable-saliency-ratio permanent magnet motor is designed and optimized considering driving cycles. To satisfy the demands of multi-operation conditions of EVs, a variable resistance is adopted and a new variable-saliency-ratio design concept is proposed to enhance output torque, widen speed range and lower irreversible demagnetization risk effectively. A multiobjective optimization considering driving cycles is proposed, where the design objective of saliency ratio is firstly selected and optimized with multiobjective genetic algorithm method. Then, the operation performances of the motor in different operation conditions are investigated in detail. Finally, a prototype motor is built and tested. Both the simulation and experimental results verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]