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Within the field of industry applications, the induction machine (IM) is the most used motor type, due to its robustness and line-start ability. However, the need to constrain global warming demands new sustainable technologies with high efficiency. Therefore, line-start synchronous reluctance machines could be an opportunity to achieve a high efficiency for several industry applications, especially for constant-speed drives. This paper introduces a unique rotor design for line-start synchronous reluctance machines (LSSynRMs). Additionally, the influence of the rotor bar material/resistance and the stator resistance in comparison to common IMs for industrial applications is investigated. Finite element method calculations were used for the design and the efficiency enhancement was verified using experiments. Within the context of this analysis, a 4-kW-rated IM with an efficiency rating of IE3 was chosen as a benchmark motor. The new rotor-cage design decreases the motor losses at steady state by about 28%. This promising approach could be used to upgrade IMs in industry environments instead of replacing them. Nevertheless, a challenge in the design is a good balance between the steady-state performance and synchronization capability, which in turn limits the range of industrial applications for highly efficient LSSynRMs. [ABSTRACT FROM AUTHOR]

To meet the higher operational efficiency regulations of electric motors due to energy-conservation concerns, specific design efforts have been dedicated to those motors for different industrial application requirements. Since the synchronous reluctance motor (SynRM) is generally designed based on the same stator structure as that of the induction motor and operated at synchronous speed, whereas no electrical contact to its rotor, it is capable of providing a robust structure and no rotor copper loss. Such features are very attractive for the related hoist, punch, roller, and pump applications that are commonly adopted in the metals industry. By equipping adequate power factor correction and line-start capabilities, the detailed designs and performance analyses of the SynRMs with a common rotor structure composed by laminated electrical steels will be proposed. Based on this common rotor structure, the operational characteristics of the SynRMs for fulfilling different specifications will all be thoroughly investigated. Confirmed by experimental validations, valuable guidance for related SynRM constructions and applications can thus be provided for metals industry and motor designers. [ABSTRACT FROM AUTHOR]

A novel 8/10 two-phase switched reluctance motor is proposed. Thanks to this unique design, the flux paths are shortened, resulting in lower magnetomotive force requirements. There is no negative torque, bringing a higher total torque. The space is more effectively utilized to provide a higher torque density. Flux reversals in the iron cores are reduced, causing a significantly lower loss. The associated conceptual diagrams, optimized design procedures, detailed flux study, and loss analysis are presented. The proposed motor is compared with two existing 9/12 and 6/10 switched reluctance motor in terms of topology advantages, peak and average torques, torque density, core losses, etc. Moreover, a new efficiency index is introduced to more reasonably perform comparisons. Furthermore, finite element method is employed in the investigations. Finally, the motor is prototyped whose experimental results including torque-angle measurements and open-loop control confirm the novelty and superiorities of the proposed motor over the existing ones. [ABSTRACT FROM AUTHOR]

In this paper, the intermittent control is proposed for switched reluctance machine (SRM) drive to both increase the efficiency and decrease the cost of the traction system for low-cost electric vehicles. With the purpose of maintaining the average machine torque required by the load, the intermittent control imposes a higher phase torque during a shorter time. The simulation and experimental results achieved with three different SRMs show that the intermittent control increases the system efficiency by reducing the converter losses and the core losses. Additionally, three different strategies of the control have been proposed to analyze their impact automotive application based on the criteria of efficiency, machine vibration, and torque pulsation. It can also be easily applied for any SRMs using average-torque-control-based methods. [ABSTRACT FROM AUTHOR]

The direct torque control (DTC) method was introduced into the switched reluctance motor to reduce its inherent output torque ripple. However, the conventional DTC method produces negative torque more or less, which reduces the torque–ampere ratio of motors. This paper proposes a new DTC method by three improvements. First, the hysteresis-loop control of flux is removed. New selection rule of voltage vectors is established to reduce the torque ripple. Second, the sectors divided in electrical space are reorganized by their actual positions according to the inductance profile. The boundaries between certain sectors are calculated and updated according to real-time working conditions. Finally, the alternative voltage vectors for increasing or decreasing torque are distinguished by whether any phase is excited. Therefore, the output torque tracks the reference accurately, which reduces the torque ripple. Moreover, the negative torque is avoided by the real-time regulation of the turn-off angle, and the torque–ampere ratio is increased accordingly. Simulation and experimental results verify the demonstrated performance of the proposed DTC method. [ABSTRACT FROM AUTHOR]

This paper investigates the comparative design optimizations of a five-phase outer-rotor flux-switching permanent magnet (FSPM) machine for in-wheel traction applications. To improve the comprehensive performance of the motor, two kinds of large-scale design optimizations under different operating conditions are performed and compared, including the traditional optimization performed at the rated operating point and the optimization targeting the whole driving cycles. Three driving cycles are taken into account, namely, the urban dynamometer driving schedule (UDDS), the highway fuel economy driving schedule (HWFET), and the combined UDDS/HWFET, representing the city, highway, and combined city/highway driving, respectively. Meanwhile, the computationally efficient finite-element analysis (CE-FEA) method, the cyclic representative operating points extraction technique, as well as the response surface methodology (in order to minimize the number of experiments when establishing the inverse machine model), are presented to reduce the computational effort and cost. From the results and discussion, it will be found that the optimization results against different operating conditions exhibit distinct characteristics in terms of geometry, efficiency, and energy loss distributions. For the traditional optimization performed at the rated operating point, the optimal design tends to reduce copper losses but suffer from high core losses; for UDDS, the optimal design tends to minimize both copper losses and PM eddy-current losses in the low-speed region; for HWFET, the optimal design tends to minimize core losses in the high-speed region; for the combined UDDS/HWFET, the optimal design tends to balance/compromise the loss components in both the low-speed and high-speed regions. Furthermore, the advantages of the adopted optimization methodologies versus the traditional procedure are highlighted. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of the helical motion of the rotatory-linear 2-degree-of-freedom split-stator induction motor (2DoFSSIM) are investigated, which cannot be regarded as the simple superimposition of the 1DoF rotary and linear motions. A set of torque and force equations of the helical motion is deduced. It illustrates that the interacting electromagnetic torque and force are opposite to the directions of rotary and axial movements, respectively. For the rotating movement, the interacting torque is related to the axial velocity. Moreover, the axial velocity significantly influences the output torque performances and no-load speed. Similar conclusions can be obtained for axial movement of the helical motion. The 3-D finite-element method is applied to calculate the exact output performance considering the interacting influence. Furthermore, the prototype machine is manufactured and tested to verify the analytical results. [ABSTRACT FROM AUTHOR]

This paper discusses the design of a synchronous reluctance motor designed to replace a 5.5 kW industrial induction motor. End plates are axially placed at both ends of an industrial motor to fix the lamination of the rotor. It is manufactured from magnetic materials to ensure manufacturing convenience and price advantage. With its construction from magnetic materials, a lower output of the motor due to axial flux leakage is observed. This paper analyzed the drop in output caused by the axial flux leakage in the end plate constructed of magnetic material and methods to compensate for the said output drop. The first method to improve the output degradation problem was to fabricate the end plate as a non-magnetic material. This, however, was found to be inefficient due to the need for different mass production apparatus for the new material. A new method proposed in this paper involved using the end plate constructed of magnetic material but incorporating a new shape to the end plate with the saliency ratio to resolve the decreased output problem. This method converts the magnetic flux leaked in the axial direction into reluctance torque. The 3-D FEA was performed for the validity of the method, and reliability was verified through the production and testing of the actual models. [ABSTRACT FROM AUTHOR]

Variable flux reluctance machines (VFRMs) are developed as magnetless electrical machines. To extend the application of VFRMs, the enhancement of torque density is a key during machine design. In this paper, a novel second-harmonic current injection method is developed for torque density enhancement for 6-stator-slot/4-rotor-tooth (6/4) VFRM. By using the analytical method, the optimal current profile with injected second-harmonic current is obtained. The average torque of 6/4 VFRM is improved by 20% with the proposed method under all load conditions. Moreover, the proposed current profile has fixed harmonic proportions and is easily applicable to machines with different specifications. All the conclusions are confirmed by both finite-element analyses and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes an enhanced brain emotional learning-based intelligent controller for synchronous reluctance motor (SynRM) drives. The controller is based on an emotional learning and decision making mechanism in the brain via emotional cues and sensory inputs. Furthermore, the enhanced controller improves learning process in the amygdala to avoid internal instability. In spite of the development for interior-stability, the proposed controller could keep its ability to deal with challenges related to SynRM drives. The proposed controller is also contributed with a speed deviation control. The new deviation controller is based on model but parameter-free. The updated system is implemented in real-time by a PC-based three-phase 370 W laboratory SynRM. The proportional-integral (PI) controllers used in a standard rotor field-oriented control structure are replaced with those of the proposed method. The speed and d-axis stator current references are accurately tracked. The achieved performances by the proposed controllers are compared with those of optimized conventional PI controller in different situations. Considering the results, the enhanced system shows superiority over the traditional system in terms of fast dynamics, easy tuning, and robustness against disturbances and parameter variations. [ABSTRACT FROM AUTHOR]

Consequent-pole permanent magnet (CPM) machines have considerable potential for low-cost applications because they can improve the permanent magnet (PM) utilization ratio. However, the phase back electromotive force (EMF) of CPM machines with Ns/(mt) = odd (t is the greatest common divisor of the stator slot number Ns and the rotor pole-pair number p, and m is the phase number) is asymmetric, i.e., the phase back EMF has even-order harmonics, which will increase torque ripples. This paper utilized the staggered rotor to eliminate the even-order harmonics and reduce the cogging torque of CPM machines, thereby potentially decreasing torque ripples considerably. The axial flux barrier in the middle of the rotor was used and optimized using three-dimensional finite element (FE) analysis to reduce the axial leakage flux of the CPM machine with the proposed staggered rotor. Furthermore, the axial magnetized PM was embedded in the flux barrier, which improved the flux density of the airgap above the iron-pole and, consequently, further increased the output torque. The electromagnetic performance of the proposed machine, including the open-circuit airgap flux density, back EMF, average torque, torque ripples, and PM utilization, was compared with that of the conventional CPM machine. Results showed that the proposed machine obtained a similar torque and PM utilization ratio but a much lower torque ripple compared with the conventional one. [ABSTRACT FROM AUTHOR]

A total of three types of doubly salient synchronous reluctance machines have been comparatively studied to improve the torque performance using current harmonic injection methods. These machines are derived from the switched reluctance machines (SRMs) with different winding configurations, such as the double/single-layer mutually coupled SRMs (MCSRMs) and fully pitched SRMs (FPSRMs), by supplying them with sinewave current. Such current supply mode can lead to higher torque/power density and lower vibrations and acoustic noise compared with the conventional rectangular current supply. The proposed torque analytical model can predict the instantaneous torque of the doubly salient SRMs with sinewave current excitation and the current harmonics also can be selected in order to reduce the torque ripple and/or increase the average torque. It has been found that the third current harmonic injection shows the best performance for single-layer MCSRMs and FPSRMs because it improves the average torque and reduces the torque ripple at the same time. However, it has little influence on doubly-layer MCSRMs. To improve the torque performance of such machines, other harmonic currents, e.g., fifth and seventh, need to be used. Both static and dynamic tests have been carried out to validate the predictions. [ABSTRACT FROM AUTHOR]

This paper investigates the design principles and performance optimization for segmented-rotor switched reluctance motors (SRSRMs) with different rotor pole numbers for belt-driven starter generators of hybrid electric vehicles. For the design principles, several constraints are derived for the numbers of stator and rotor poles, the dimensions, and the number of winding turns. Two SRSRMs with 16/10 and 16/14 stator/rotor poles are presented according to these principles. For the performance optimization, the two motors are optimized individually for maximizing the torque. To evaluate the effect of different segmented-rotor numbers, the overall performances of the two SRSRMs are investigated and compared. It is found that the 16/14 SRSRM has higher flux linkage and static torque. The 16/14 SRSRM exhibits higher torque and lower torque ripple at low speed operation, whereas at high speed, the 16/10 SRSRM performs better in terms of torque and power densities. Compared with the 16/14 SRSRM, the 16/10 SRSRM has higher final steady speed under the same startup condition. The 16/10 SRSRM can achieve higher steady speed under starter mode and provide higher generated power under braking mode. Moreover, the 16/10 SRSRM exhibits higher efficiency in the most feasible speed range, especially in high speed range, and it has wider high-efficiency area. Finally, a 16/10 SRSRM is prototyped and tested to validate the simulation results. [ABSTRACT FROM AUTHOR]

Rotary-linear switched reluctance motors (RLSRMs) have been introduced to realize simultaneous rotary and linear motions in one structure. This paper proposes the modeling of RLSRM in two manners: analytical and finite-element methods. In the first approach, a model is proposed based on position-wise functions which describe the governing equations of the motor. The derived equations are utilized in a block diagram to comprise the model. In the second approach, static FEA is utilized to improve the former model by obtaining the inductance profile of the motor. The models separate the rotary motion from the linear motion in order to calculate the torque and force. The analytical model is faster than the FEA-based model because of the independency to FEA. However, it is less accurate. The FEA-based model needs prior static FEA and considers the fringing and saturation effects more accurately. The FEA-based model is computationally more efficient than the 3-D transient FEA. The motor’s performance parameters obtained via the models versus the 3-D transient FEA as well as the experimental test results indicate the accuracy and efficiency of the proposed models. [ABSTRACT FROM AUTHOR]

Magnetic gears are expected to be a maintenance-free system with low-noise and low-vibration characteristics by a noncontact power transmission. However, conventional magnetic gears are not suitable for use with high-speed motors because the mechanical strength is weak due to the use of permanent magnets in a high-speed rotor. Additionally, the magnet eddy current losses in the high-speed rotor seriously decrease the gear's efficiency during a high-speed operation. This paper presents a novel reluctance magnetic gear that can realize the high-speed drive and high efficiency. The high-speed rotor of the proposed magnetic gear is constructed by only an iron core. Therefore, the structure is very simple and robust, adding that it is possible to rotate in the high-speed region. Moreover, the proposed magnetic gear achieves high efficiency in the high-speed region because the magnet eddy current loss in the high-speed rotor is not generated because no magnets are used. The downsizing of the system and a high efficiency power transfer are realized by applying the proposed reluctance magnetic gear. [ABSTRACT FROM AUTHOR]

This paper presents a third harmonic injection (THI) based nonlinear controller for a wide speed range operation of interior permanent magnet synchronous motor (IPMSM) drive. Due to magnetic saturation, constant motor parameters lead to an unsatisfactory performance for the controller. Therefore, an adaptive backstepping based nonlinear controller is developed for an IPMSM drive to achieve high dynamic performance coping with parameter uncertainties. A sinusoidal THI technique is integrated to increase the dc bus utilization, which facilitates a higher operating speed range. The field control permits extended speed range utilizing the reluctance torque and field weakening. Stability of the control law state variables are demonstrated through Lyapunov stability criterion and global asymptotic stability of the drive is assured through the application of criterion supported by Barbalat's lemma. Feasibility of the proposed drive is tested in both simulation and experiment for laboratory 3.73 kW IPMSM drive. A performance comparison of the proposed THI-based nonlinear controller is shown with conventional benchmark tuned PI controller, and nonlinear controller without THI. Rapid convergence to command speed, reduction in speed oscillations over the rated speed, and a visible reduction in phase current with THI is achieved through the proposed drive. [ABSTRACT FROM AUTHOR]

This paper investigates the torque production and the torque ripple reduction of a six-stator/seven-rotor-pole (6/7) variable flux reluctance machine (VFRM). As a main advantage, the 6/7 VFRM produces higher torque density, but less torque ripple compared with the 6/4 VFRM. The instantaneous torque equation of the 6/7 VFRM is derived by considering the spectra of the winding inductance and current. Based on the derived equation, the average torque is found to be mainly produced by the mutual inductance between the field and armature windings. The even-order harmonics of self-inductance and odd-order harmonics in mutual inductance between the field and armature windings are eliminated due to the opposite polarity connection of the armature coils in each phase. This results in the elimination of the third harmonic torque ripple, while a multiple of the sixth harmonic torque ripple exists. In order to mitigate the sixth harmonic torque ripple, the harmonic current injection method is implemented into the field winding. The field harmonic current is calculated from the analytical torque ripple equation. The performance of the proposed methods is verified by both finite element analysis (FEA) and experiment. [ABSTRACT FROM AUTHOR]

One of the major topics of switched reluctance machines (SRMs) is how to reduce the acoustic noise and vibration without decreasing the efficiency. In this paper, a few novel current profiling methods are proposed to reduce the acoustic noise by flatting the radial force sum and to reduce optimal torque ripple with best efforts to enhance the efficiency. The proposed method is adopted to the 18/12 pole SRM, which has identical outer dimensions and competitive torque, output power, efficiency, and operating region of the permanent-magnet motor used in the hybrid vehicles. It is found that the proposed method can improve not only the radial force ripple characteristic but also the iron loss minimization. The efficiency enhancement is also found to be possible in a few cases depending on the demanding criteria; thanks to the phase shift of the fundamental component of the current waveform. The proposed method is verified in the experiments. [ABSTRACT FROM AUTHOR]

A criteria to design the rotor of multi flux-barrier synchronous reluctance (REL) machines is proposed. In particular, the focus will be on the proper design of flux-barriers geometry. An analytical model is adopted to compute the impact of the rotor flux-barriers on the torque, focusing on the torque ripple. Thanks to proper assumptions, the analytical model is simplified so as to highlight the main causes of torque ripple. Such an analytical model allows to derive the angles of the flux-barrier ends corresponding to the minimum torque ripple in a closed form. This result has never been presented in the past literature and it represents a useful tool as far as the motor design is concerned. Rotors with one, two, and three flux-barriers per rotor pole are taken into account. However, the advantageous analytical model can be extended to any number of flux-barriers per pole. Some examples referring to four-pole synchronous REL machines with different numbers of stator slots are investigated and illustrated. The results are compared with a full-featured analytical model and validated through finite element simulations. [ABSTRACT FROM AUTHOR]

A synchronous reluctance motor drive exhibits an inherent unlimited speed range capability; in fact, the maximum speed of this kind of machine is bounded only by mechanical limits. In order to exploit this peculiar characteristic of the drive while assuring the lowest power losses, a proper control algorithm has to be used. In particular, while the working speed is increasing, the control must be able to command the reluctance motor under the maximum torque per ampere condition at first, into the flux-weakening region, and then on the maximum torque per voltage trajectory. To this purpose, a novel voltage control loop is presented in this paper. It is combined with a field-oriented current control and profitably exploits a polar coordinate representation of the current reference to operate the reluctance machine in compliance with current and voltage rating constraints in all the different operating conditions. Additional merits of the proposed scheme are the ease of implementation and the simple design. The stability of the proposed control algorithm is proved through a small signal analysis and simulations and experimental tests confirm its effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, a unified controller for switched reluctance motors is proposed for wide speed operations. The proposed controller achieves minimum output torque ripple at low and medium speeds and operates in a single-pulse mode at high speeds. Overlapping regions between the phases are controlled such that direct instantaneous torque control (DITC) and current control (CC) can be implemented simultaneously on different phases. This simplifies the torque sharing during commutation and minimizes torque ripple due to imperfect current tracking and mutual torque. A demagnetization curve concept to demagnetize the phase currents at an optimum angle is introduced to ensure high torque per ampere and single-pulse mode operation. This results in extending low ripple operation to medium speed ranges. The seamless combination of DITC, CC, and the demagnetization curves leads to torque ripple minimization, automatic excitation angle control, and smooth operation over a wide speed range. The effectiveness of the proposed unified controller is verified through simulation and experimental studies. [ABSTRACT FROM AUTHOR]

In this paper, a simplified control scheme is introduced for permanent magnet synchronous motors (PMSMs). The control strategy consists of a direct voltage controller that capitalizes on the motor's model to achieve accurate speed tracking. As such, no explicit currents loop regulation is needed which simplifies the control structure and unlike other control strategies, no motor's parameter knowledge, voltage or current transducer is required. But, the absence of current regulation loops yields higher energy consumption, which limits the motor's range of operation. Therefore, a genetic algorithm is presented to determine control gains with optimal current consumption ensuring operation at the full range of the machine. Simulation and experimental results for different situations highlight the performance of the proposed controller in transient, steady-state, and standstill conditions. Furthermore, the simplicity of the control scheme makes it a good candidate for a low-cost implementation of real-time PMSM drives. [ABSTRACT FROM AUTHOR]

This paper investigates the contribution of each order inductance harmonic to the torque (both average torque and torque ripple) of multiphase doubly salient synchronous reluctance machines (DS-SRMs). Such machines are similar to switched reluctance machines but supplied with sine wave currents. The investigations in this paper are as follows. First, a general analytical torque model based on Fourier series analysis of inductances has been built for machines with different phase numbers, slot/pole number combinations, and also winding configurations. The instantaneous torque for DS-SRMs with any given phase number can then be accurately predicted. Using such model, contribution of each order inductance harmonic to torque can be investigated separately. It is found that the torque ripple frequency of the DS-SRM only depends on phase number. For example, for an m-phase machine, there will be m $\times $ kth-order torque ripple if mod(mk, 2) = 0, where m is the phase number and k is a natural number. This paper also explains why certain phase numbers inherently produce lower torque ripple than others. The findings in this paper provide a future direction for potential torque ripple reduction methods either from machine design or advanced control. The simulations have been validated by experiments using a six-phase DS-SRMs. [ABSTRACT FROM AUTHOR]

In this paper, two permanent magnet flux-intensifying motors are designed and optimized to realize the characteristic ofLd>Lqand the flux-intensifying effect. Compared with the conventional interior permanent magnet motor with the characteristic ofLd< Lq, the advantages of a low irreversible demagnetization risk and a wide speed range can be obtained in the motors. To meet multiple design requirements effectively, a comprehensive sensitivity analysis method is first implemented to evaluate the influence of each design variable on the selected optimized objectives of output torque, reverse saliency ratio, and torque ripple. Second, a sequential nonlinear programming algorithm is used for realizing the multiobjective optimizations of strong-sensitive design variables. Then, the performances of the two optimal motors are analyzed and compared with the initial permanent magnet motor in detail. Finally, two prototype motors are manufactured and tested. Both the simulation and experimental results verify the validity of the new flux-intensifying motors and the optimization method. [ABSTRACT FROM AUTHOR]

This paper reveals a torque-angle approaching principle in a hybrid rotor permanent-magnet (HRPM) motor. The key is to obtain the relationship between angles of shifted surface-inserted PMs (SPMs) as well as assisted airspace barriers and the current angles of maximum PM torque as well as maximum reluctance torque. In order to find out this relationship, the PM torque and reluctance torque are separated accurately and effectively by the proposed torque separation method. In this method, the parameters in anabcreference frame are transformed to ad--qreference frame via Park transformation, and then the model considering cross-coupling and magnetic saturation effect is used to calculate four torque components. Moreover, the shifting of SPMs has been confirmed to have both influence on the current angles of maximum PM torque and maximum reluctance torque, while the assisted airspace barriers only affect the current angle of maximum reluctance torque. Thus, the total torque can be enhanced by optimal angles of shifted SPMs and assisted airspace barriers because of higher utilization of both PM torque and reluctance torque. In order to evaluate the presented principle in the HRPM motor, a prototype is manufactured for experiments. Through theoretical analysis and experimental testing, it is verified that the proposed principle is feasible and effective. [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]

This paper proposes a modular multilevel converter (MMC) based switched reluctance motor (SRM) drive with decentralized battery energy storage system for hybrid electric vehicle applications. In the proposed drive, a battery cell and a half-bridge converter is connected as a submodule (SM), and multiple SMs are connected together for the MMC. The modular full-bridge converter is employed to drive the motor. Flexible charging and discharging functions for each SM are obtained by controlling switches in SMs. Multiple working modes and functions are achieved. Compared to conventional and existing SRM drives, there are several advantages for the proposed topology. A lower dc-bus voltage can be flexibly achieved by selecting SM operation states, which can dramatically reduce the voltage stress on the switches. Multilevel phase voltage is obtained to improve the torque capability. Battery state-of-charge balance can be achieved by independently controlling each SM. Flexible fault-tolerance ability for battery cells is equipped. The battery can be flexibly charged under both running and standstill conditions. Furthermore, a completely modular structure is achieved by using standard half-bridge modules, which is beneficial for market mass production. Experiments carried out on a three-phase 12/8 SRM confirm the effectiveness of the proposed SRM drive. [ABSTRACT FROM AUTHOR]

This paper investigates different operating points of a ducted rotor brushless doubly fed reluctance machine (BDFRM) in subsynchronous, synchronous, and supersynchronous speed regions. The BDFRM has a ducted rotor and its stator houses two three-phase distributed windings. An example design of the machine is proposed for investigation. A control approach to maximize the torque capability of the given design is introduced. The static structural analysis result of the machine is also presented, which led to the final manufacturing of the machine laminations. Machine assembly and drive implementation steps are discussed. The built machine is experimentally tested in different speed regions. [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]

This paper presents a new asymmetrical rotor hybrid permanent-magnet (AR-HPM) motor with good torque performances. Different from the traditional symmetrical rotor structure, the asymmetrical rotor structure is employed to improve the torque production. This makes the reluctance torque and the magnetic torque reach the maximum at the same current phase angle. Based on the concepts, the motor is investigated by the finite-element method (FEM). The frozen permeability method (FPM) is applied to divide the torque into the reluctance torque and the magnetic torque. The electromagnetic characteristics and torque performances of the motor are compared with a conventional motor. The results show that the proposed design is efficacious in boosting output torque at the same operating conditions. Moreover, the results also demonstrate that the topology of the proposed AR-HPM motor features the advantage of avoiding the risk of demagnetization. [ABSTRACT FROM AUTHOR]

An offline torque sharing function (TSF) is introduced in this paper for torque ripple reduction in switched reluctance machines (SRM). This TSF uses static flux linkage characteristics of the machine obtained from finite element analysis or experiments that describe the machine dynamics to determine optimal current profiles such that the torque ripple reduction is achieved with minimal copper losses. Due to this feature, the proposed TSF performs well across a wide speed range. Additionally, the objective function of the proposed TSF uses only one weight parameter, which facilitates the use of this TSF. In this paper, an intuitive justification for the selection of this weight parameter is given, and the performance of this TSF is validated in simulation and experimentally on a 5.2 kW, four phase SRM. To baseline its performance, the proposed TSF has been compared to the offline TSF in the literature, which shows that it has better current tracking performance at higher speeds due to the inclusion of flux linkage characteristics. Finally, it has been compared to conduction angle control at speeds above the base speed to show that it can be a viable alternative for the control of SRM even in an operation region normally not considered for TSF. [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]

This paper presents an improved asymmetric half-bridge converter (AHBC) to enhance the output performance of a segmented-stator hybrid-excitation switched reluctance motor (SSHE-SRM) drive. Differences from conventional AHBC include an additional boost capacitor, a power switch, and two diodes added between the dc-bus and the AHBC. The static torque characteristic of a 12/8 SSHE-SRM is briefly analyzed and compared with a conventional SRM (CSRM). Based on the magnetic characteristic, the SSHE-SRM appears to have higher torque production capability. The improved AHBC is employed in order to increase the dc-bus voltage under dynamic operation. Higher voltage can be applied to phase windings and faster excitation and demagnetization currents can be obtained owing to the addition of capacitor voltage. Detailed simulations of the SSHE-SRM drive with the improved AHBC are carried out as well as compared with conventional AHBC. Finally, a 12/8 SSHE-SRM is prototyped. The SSHE-SRM drive based on the improved AHBC and conventional AHBC are experimentally tested. The measured results of static magnetic characteristic and dynamic performances are presented to validate the analysis and effectiveness of the novel converter. [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]

In this paper, a new 6/10 hybrid switched reluctance motor (HSRM) is proposed. This original topology deploys permanent magnets (PMs) between adjacent stator poles of a divided teeth SRM. The function of the PMs is to weaken the magnetic saturation in stator poles, which is a major obstacle of torque improvement for divided teeth SRMs. Besides, the magnetic flux in the airgap increases as well. Hence, the output torque can be increased significantly. The flux distribution of the topology is analyzed by using an equivalent magnetic circuit. The topology is optimized by using the genetic algorithm for the best torque performance. Additionally, the characteristics of the proposed topology are compared with a 12/10 SRM, a 6/10 two-teeth SRM, a 12-slot, 10-pole three-phase six-state PM brushless DC motor, and a flux switching permanent magnet motor of the same dimension. A prototype of the proposed topology is built for experimental verification. The simulation and experimental results indicate that the proposed topology can achieve high torque density and high PM utilization factor simultaneously. [ABSTRACT FROM AUTHOR]

In this paper, a design method for a wound field synchronous motor (WFSM) employing the dual stator winding and the winding connection change circuit is proposed. Through the design method, the WFSM can be operated as two different modes, and each mode is determined by the connection between the stator windings U, V, W and X, Y, Z. By applying the proposed method to the conventional WFSM, the operation mode of the motor is changed at a certain speed. The speed for the mode change is determined to maximize the efficiency of the machine. As a result, through the mode change, the line to line induced voltage, current phase angle, and phase resistance are decreased. In addition, the demand field current is also reduced to achieve the required torque due to the salient pole characteristics of WFSM. Consequently, the efficiency of the WFSM is increased due to the mode change. Finally, the effect of the proposed method and the validity of the simulation results are verified by the load test. [ABSTRACT FROM AUTHOR]

This paper proposes the design and development of an external rotor permanent magnet in-wheel motor for an electric bicycle application. The proposed machine utilizes V-shape magnets embedded in the external rotor to achieve enhanced magnetic flux concentration and, hence, high torque and power output. Detailed design principles and performance characteristics of the proposed machine are comprehensively evaluated with finite element analysis. Various design concerns are further investigated to ensure machine rigidity and operational safety. Finally, this paper validates the design concept with a prototype machine. High torque and high power output are achieved and the experimental results confirm the design simulations with good agreement. [ABSTRACT FROM AUTHOR]

This paper proposes a new position sensorless method for a direct torque control system using the inductance inflection point of a switched reluctance motor (SRM). The SRM essentially requires knowledge of the rotor position in the torque control system; this is because it generates torque by exciting the stator windings according to the rotor position. This rotor position information is an important factor used to obtain phase commutation point and to calculate instantaneous torque. Various rotor position detection methods have been used, but most of the methods increase the construction cost by requiring additional hardware and use many parameters for high-order analysis modeling, causing problems such as increasing the number of calculations. Therefore, in this paper, we propose a method using the inductance inflection point to solve these problems. It is possible to estimate the position of the rotor by detecting where the inductance inflection point occurs due to the rotor and stator overlapping with each other, and the phase commutation point and instantaneous torque can be calculated. The calculated instantaneous torque is used for direct torque control and torque ripple reduction through the torque-sharing function. The proposed method is verified through simulation and experiments. [ABSTRACT FROM AUTHOR]

In this paper, improvement of torque quality and magnetic losses of a concentrated winding high-speed permanent magnet (PM)-assisted synchronous reluctance motor (PMaSRM) that can operate in the wide speed range are investigated. Optimization studies have been carried out to enhance the torque quality. In addition, ac copper losses in the stator coils and iron losses in laminations at high frequencies have been investigated. Since the PMaSRM can operate in a wide constant power-speed range, the field weakening performance has also been investigated. The motor performance results of the PMaSRM at both no-load and on-load conditions are examined by using Flux 2-D FEA software. A prototype motor based on the simulations has been built and validated in order to show the feasibility of such technology for white good applications. [ABSTRACT FROM AUTHOR]

In this paper, the optimal design for a permanent magnet-assisted synchronous reluctance motor (PMA-SynRM) is proposed in terms of efficiency, maximum torque, and minimum torque pulsations. Design variables, objective functions, and constraints are selected for this optimal design, which is divided into two steps. Step I utilizes the pole/slot combination of the PMA-SynRM and winding methods. The chosen 4-pole/36-slot model with distributed winding maximizes the rated efficiency. In Step II, the optimal design of the stator parameters is obtained using the response surface method and the precise torque and torque ripple are calculated using the finite-element analysis (FEA). The proposed stator slot openings are minimized to minimize the air-gap flux leakage, and consequently, realize a smooth electromagnetic torque. Finally, a few FEA results are validated by experimental results. [ABSTRACT FROM AUTHOR]

This paper deals with the optimization design process of an interior-type permanent magnet synchronous motor (IPMSM) for electric compressors of air conditioners applied to electric cars and hybrid vehicles. Based on a prototype IPMSM, we identified the current level for efficiency and cogging torque using finite-element analysis (FEA). The IPMSM’s main design variables are optimized to primarily satisfy the target of efficiency and cogging torque. A second optimization design is carried out using the response surface method (RSM) for the main design variables obtained from the Taguchi method analysis. As a result, the optimization design is carried out through a two-step optimization design process using the Taguchi method and RSM. The IPMSMs are analyzed using FEA, and their validity is confirmed by comparing the test results against each step-by-step model. We validate an effective optimization design process using a two-stage design process. We conclude that the proposed approach provides an effective design method for engineers. [ABSTRACT FROM AUTHOR]

Switched reluctance (SR) machines are attractive because they present relatively high efficiency and torque density in spite of lacking permanent magnets. This paper focuses on a two-objective optimization of an external rotor SR motor with a stator that has concentrated coils and a rotor with magnetically isolated modules. The objectives are minimum loss and mass, and 11 independent dimensionless geometric variables are considered as inputs that affect them. A combined design of experiments (DOE) and differential evolution (DE) approach is proposed. The DOE methodology is used to reduce the search space by eliminating from consideration input variable values, leading to poor-performing designs. Following this initial DOE study, an optimization study based on DE is run over the reduced search space, which leads to significant savings in computation time. Furthermore, a directed graph-based method for comparing different designs on the Pareto front to rank the best compromise designs is proposed. [ABSTRACT FROM AUTHOR]

This paper presents a design of a new line-start synchronous reluctance motor (LSSynRM) that has a markedly robust structure, vibrates little, and is lighter in weight. These advantages stem from the combination of flux barriers with a 3-D net structure achieved by the 3-D printing technology. In addition, the lamination and the 3-D printing performance of the induction motors, SynRMs, and LSSynRMs, respectively, are compared. The characteristics are investigated experimentally and analytically by using a prototype and a finite element analysis tool. [ABSTRACT FROM AUTHOR]

This paper addresses the design and investigation of an improved torque density dc-biased Vernier reluctance machine (dc-biased-VRM), which is characterized by salient rotor structure, and merely one set of concentrated windings in stator. First, a 12-stator slot, 10-rotor slot dc-biased-VRM is designed. Then by analyzing the magnetic flux distribution with finite-element analysis, it is found that the flux always doesn’t flow across half of the stator teeth. Therefore, these teeth are removed and a novel 6/10 dc-biased-VRM with 20% higher torque density is obtained. Besides, by optimizing the stator/rotor tooth width combination and tooth shape, the torque ripple is lowered. Finally, a prototype is manufactured and experimental results show good agreement that is observed between the simulation and test data for the proposed motor. [ABSTRACT FROM AUTHOR]

In this paper, an improved flux-barrier geometry configuration of transversally laminated rotor synchronous reluctance machine (TLR-SynRM) is proposed to suppress the torque ripple. The flux-barrier geometry configuration has two remarkable features. First, its flux barriers are step shaped and their shapes could be described by the parameter X. Second, the widths of multi-flux barriers in the middle regions are changing in a gradient style. The conformal mapping method is introduced to calculate the reluctances of the improved flux-barrier geometry configuration, and the corresponding magnetic equivalent circuit is established to analyze how the parameter X influences air-gap flux density distribution in order to obtain the minimum torque ripple. Based on the above analysis, the results are used to improve the flux-barrier geometry configuration. Last, the effectiveness of the improved flux-barrier geometry configuration is verified by finite-element analysis. [ABSTRACT FROM AUTHOR]

The commercialized electric turbocharger (ETC) made by Valeo includes a high-speed switched reluctance motor (SRM), ball bearings, impeller, and controller. SRMs are generally very noisy and have low efficiency (70%) at high speed. No ETC has yet been commercialized that includes a permanent magnet (PM) motor. The Korea Electrotechnology Research Institute, Changwon, South Korea, is developing a high-speed surface PM type of synchronous motor and a pulse width modulation-driven inverter. This system operates at a power density of 3 kW/kg at 100000 r/min and is intended to fit 1600 cc diesel vehicles to reduce turbolag to within 0.5 s. The design and analysis of the PM synchronous motor (PMSM) for the ETC have been successful by considering the electric and mechanical performance using multiphysics analysis. Validation by experiment was performed and matched within 1% error in terms of the efficiency. Design, analysis, and experiments with the PMSM for ETC applications were conducted successfully by utilizing an action–reaction torque sensor and the resistance load test method. [ABSTRACT FROM AUTHOR]

Due to the advantages such as high energy density, high power density, high cyclic life, and environmentally friendly, the flywheel battery has the potential to solve the problem of energy storage. In order to improve the torque density and suspension performance of bearingless synchronous permanent magnet (PM) synchronous motors (BPMSMs), a novel rotor structure with V-shaped PMs is designed in this paper. Furthermore, the interior BPMSM (IBPMSM) with V-shaped PM which used for flywheel batteries of electric vehicles is researched in detail. Especially, the influence of geometrical parameters of V-shaped PM on suspension force and electromagnetic torque is investigated. Moreover, the corresponding static electrical magnetic characteristics including inductances and electromagnetic torque are also studied. The finite-element method is employed to evaluate the theoretical analysis of the proposed IBPMSM. In addition, the optimized motor is validated to have good suspension performance by some experiments. [ABSTRACT FROM AUTHOR]

In this paper, a new rotary-linear switched-reluctance motor with a magnetic decoupled structure is introduced. The rotational motion of the motor, managed by a sliding-mode controller, is coordinated with the proportional-derivation linear motion by using a fuzzy logic block. Consequently, both rotational and linear motions can be realized simultaneously. In addition, the decoupled magnetic paths of the motor in two directions are analyzed by finite-element method, with the force and torque measurements suggesting the feasibility of the motor. Both the simulation and experimental results show that the motor is totally decoupled in the linear and rotary directions. The linear movement and the rotation at the same time validate the effectiveness of the motor design and the proposed control method, with highly accurate responses for the two degrees of freedom movement. [ABSTRACT FROM AUTHOR]

This paper deals with the optimal state reference calculation for synchronous motors having a magnetically salient rotor. A lookup table computation method for the maximum torque-per-ampere locus, maximum torque-per-volt limit, and field-weakening operation is presented. The proposed method can be used during the start up of a drive, after the magnetic model identification. It is computationally efficient enough to be implemented directly in the embedded processor of the drive. When combined with an identification method for the magnetic model, the proposed method enables the plug-and-play startup of an unknown motor. Furthermore, a conventional reference calculation scheme is improved by removing the need for one two-dimensional lookup table. A 6.7-kW synchronous reluctance motor drive is used for experimental validation. [ABSTRACT FROM AUTHOR]

The self-inductance of doubly salient electromagnetic motor (DSEM) varies with the rotor position; it is an effective approach to rotor position in the DSEM driving system. With knowing the initial rotor position by the conventional method, this paper proposes a novel sensorless startup method, which is based on the feature that there must be a change in the magnitude relation of two proper phase self-inductances when the rotor goes from one sector to the other. Accurate and quick estimation of rotor sector is achieved with only one test injection pulse required, and the injected test pulse will not produce negative torque unless the rotor passes the commutation instants. Compared to the conventional sensorless startup strategies, the proposed method owns advantages in commutation accuracy and output torque. The experiments on a 12/8-pole DSEM validate the correctness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]