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This article proposes a multiobjective optimization design framework for a double stator brushless hybrid excitation motor (DSBHEM) to provide high torque, wide flux regulation ability and low torque ripple. The design variables are divided into sensitive level and insensitive level by sensitivity analysis. The response surface model (RSM) and nondominated sorting genetic algorithm 2 (NSGA2) are organically combined to generate a set of Pareto solutions for the sensitive level variables, from which the optimal values of the sensitive level variables are obtained. In addition, the optimal values of insensitive variables are obtained through single parameter scanning optimization, and a set of final optimal design variables are obtained. The electromagnetic performance of the initial design and the optimal design are compared with finite element analysis. Finally, a prototype is manufactured to verify the proposed concepts. [ABSTRACT FROM AUTHOR]

With high surrounding temperatures, winding resistance increases and thus lowers the operational efficiency of a motor. To meet the large application requirements and conform with the ever-increasing energy-efficiency regulations for pump equipment in the metals industry, consistent efforts have focused on producing single-phase motors that can deliver superior performance at a low cost. Because the steady-state rotational speed is synchronized and no driver circuit is required, a direct-on-line synchronous reluctance motor is a potentially viable alternative to the commonly adopted induction motors. Its inherently simple structure and comparably low operational speed necessitate a challenging structural design for accomplishing the high-efficiency objectives of pump applications. These challenges and their potential solutions are reported in detail. By employing a systematic design scheme and including thermal concerns of the performance, a competitive high-efficiency single-phase direct-on-line synchronous reluctance motor for pump applications in various metal industry equipment was offered. [ABSTRACT FROM AUTHOR]

This article proposes a novel asymmetric interior permanent magnet (AIPM) rotor topology that has a mixed V-shape and spoke-type PM configuration, designated as a 1.5-layer PM structure, and asymmetric arrangement of V-shape PMs and asymmetric flux barriers. The AIPM rotor topology is employed for IPM synchronous machines to utilize the magnetic-field-shifting (MFS) effect for increasing average torque by reducing the current angle difference between peak PM and reluctance torque components. Three machines, i.e., the proposed 1.5-layer AIPM, a symmetrical 1.5-layer IPM-I, and a conventional V-shape benchmark IPM-II are designed and optimized using the same stator, rotor diameter, and total PM usage by global parametric optimization considering the mechanical stress. The effect of asymmetric features of the 1.5-layer AIPM rotor design, i.e., asymmetry of V-shape cavity as well as position and dimensions of flux barrier, on maximum torque and open-circuit air-gap field are investigated. The electromagnetic performances of three machines are compared. It confirms that the proposed AIPM machine has the highest maximum torque and the smallest cogging torque simultaneously. It is also revealed that the torque enhancement is achieved by both the 1.5-layer structure and MFS effect. Finally, a prototype of an AIPM machine is manufactured and tested to validate the analyses. [ABSTRACT FROM AUTHOR]

This article compares the performance of an existing three-phase synchronous reluctance machine (SynRM) with an identical machine that is upgraded to a five-phase machine. Two different methods are possible to convert the existing three-phase machine to a five-phase one with minimum cost. In the first method, a five-phase SynRM (SynRM 1) is obtained by replacing the existing stator by another one that has an integer number of slots per pole, i.e., a multiple of five. In the second method, a five-phase SynRM (SynRM 2) is obtained by rewinding the existing stator with a special type of winding. This is because the slot number of the existing stators is not a multiple of five. The novelty of the article is that two five-phase SynRMs are compared with the original three phase reference machine in terms of torque and torque ripple, in healthy and fault conditions. At rated condition and optimal current angle, SynRM 1 performs better than SynRM 2 in terms of rated torque: SynRM 1 and 2 have 11.8% and 6.6% higher torque than the three-phase machine. But, SynRM 1 has 25% more torque ripple than the three-phase reference machine, while SynRM 2 has 17% lower torque ripple. At faulty case, SynRM 1 and 2 work at 74% and 79% of the healthy rated torque of the three-phase SynRM, while the three-phase SynRM works at only 43% with a very huge torque ripple. Finally, experimental measurements are obtained to validate the theoretical work. [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]

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]

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]

To meet the severe operating conditions in the metal industry, more thorough design and operational assessments about those implemented electric motors for specific applications must be emphasized. With its inherent robust structure, the induction motor is generally adopted to fulfill such driven objective. However, due to global warming and energy conservation concerns, those strictly enforced regulations have potentially increased the complexity and cost of high efficiency induction motor. Since the synchronous reluctance motor (SynRM) has relatively simpler structure with no copper loss in its rotor, it is a very attractive alternative for accomplishing the high-efficiency objectives of those common hoist, punch, roller, and pump applications. In addition, to eliminate drive circuits that can further reduce the overall system construction costs, the rotor barriers of the SynRM can be equipped with direct-on-line capability (DOL_SynRM) with conductors filled in. The impacts to the operational performance of these DOL_SynRMs for different applications will all be thoroughly investigated. The competitive high-efficiency DOL_SynRMs for driving various metal industry equipment can thus be offered. [ABSTRACT FROM AUTHOR]

This article compares the doubly salient permanent magnet machine (DSPMM) having 18/13-pole number combination with 18/17-pole biased flux permanent magnet machine (BFPMM) to verify its improvement in torque characteristics. In such DSPMM, the stator/rotor-pole number combination is 18/13 rather than the conventional one (i.e., 18/12) to achieve balanced three phases, sinusoidal phase flux linkage and back electromotive force (back EMF), small cogging torque, and low torque ripple. On the other hand, an 18/17-pole BFPMM having the similar structure with the 18/13-pole DSPMM is analyzed, which has the best torque performance among such machines with the same stator pole number. To further improve average torque, the inner-type flux focusing (IFC) method is employed in both 18/13-pole DSPMM and 18/17-pole BFPMM. Then, both machines are optimized under the fixed copper loss and envelope size. The comparison shows that both machines have comparably small torque ripple while the 18/13-pole DSPMM with IFC (IFC-DSPMM) exhibits 35% higher torque density and 100% higher ratio of torque to PM volume. An 18/13-pole IFC-DSPMM is manufactured and tested to experimentally validate the predicted results. [ABSTRACT FROM AUTHOR]

Three-phase line-start synchronous reluctance motor (LS-SynRM) is started by asynchronous torque generated by the rotor conductor bars, and runs synchronously by reluctance torque generated by the inductance difference. In this article, the rotor structure of an LS-SynRM is designed and optimized, based on the theory and characteristics of LS-SynRMs during starting and steady-state operation. First, the influence of the number of rotor flux barriers and the flux barriers ratio on the dq-axis inductance is simulated, and a better structure of rotor flux barriers is obtained. Second, according to the transient theory, a method of separating each torque during the starting process of LS-SynRMs is proposed, and the main reason for the poor starting ability of the initial LS-SynRM is analyzed. Based on the optimized structure of rotor flux barriers, the influence of the area and distribution of the rotor conductor bars on the starting ability of the LS-SynRM is studied, and the structure of rotor conductor bars under the condition of starting with heavy load (constant load) is determined. Finally, through the prototype test, the rated efficiency of the LS-SynRM is 2.8% higher than that of the SCIM is replaced by three phase squirrel cage induction motor (SCIM), which verifies the accuracy of the simulated results. At the same time, the starting current and the pull-in torque under a specific inertia are tested, and the improved effect of the synchronization ability of the improved LS-SynRM was verified. [ABSTRACT FROM AUTHOR]

In the design of modern, high-performance switched reluctance machines, the highly restrictive sets of constraints and requirements severely limit the number of feasible solutions. In order to improve the chances of attaining a successful design, this work proposes a novel and fully analytical approach to the preliminary design analysis. Initially, the correct number of independent design variables is identified. Subsequently, constraints and requirements are introduced one by one, in order to progressively discard all of the unfeasible candidates. At the end of this process, the actual design space is attained, whose main characteristic is to be populated only by feasible candidates. A design case study shows how the proposed methodology allows: 1) to verify the design feasibility; 2) to reduce the number of candidates by orders of magnitude; and 3) to gain useful insight into the design problem and thus select the most convenient strategy to finalize it. As a result, a highly effective design process is attained, so that considerable computational resources can be saved. [ABSTRACT FROM AUTHOR]

High-speed switched reluctance machines (SRMs) have been a timely topic recently. However, for ultrahigh-speed SRMs over 100,000 rpm, the acoustic noise is a significant issue in many applications such as high speed spindles, compressors/ turbochargers, flywheels, and etc. In this article, a multiphysics acoustic modeling of ultrahigh-speed SRMs is presented based on finite element analysis (FEA). First, a three-dimensional electromagnetic FEA is conducted to calculate the radial force on the stator teeth. Then, a modal analysis and a harmonic response analysis are shown in the frequency domain to estimate the natural frequencies and vibration of the whole motor. An acoustic response analysis is done to estimate the sound pressure level (SPL) using the superposition of the surface vibration. To verify the model, experiments are done to measure and compare the natural frequencies and the SPL of a 4/2 ultrahigh-speed SRM at 100,000 rpm. The results show that the SPL of the motor is as high as 115 dB at 10 mm away from the motor, which matches the simulation result (113 dB) well. The impact of the bearing is proven to be negligible compared with the noise generated by the radial force. Finally, a parametric study example of using the proposed model to guide the design of SRMs has been conducted. It is shown that “hot dog” shaped motors have less noise than “pancake” shaped motors under the same motor volume, speed, and power. [ABSTRACT FROM AUTHOR]

This article proposes an improved analytical method for accurate evaluation of flux-linkage characteristics for a given switched reluctance machine (SRM). Initially, air-gap inductance is calculated using an approximated analytical method, which incorporates the effect of fringing fluxes. Then, precepts of a conventional method are used to compute these characteristics under saturation, with a proposed new analytical model for nonuniform flux distribution in stator and rotor poles. Finally, for error quantification, these characteristics are benchmarked against those from a standard finite element analysis (FEA) based software. Both mean and standard deviation of the estimation errors are presented to quantify estimation accuracy. To establish its general validity, these characteristics are evaluated using the proposed method for six SRMs of different geometries and compared with those obtained from FEA. For further benchmarking, speed-torque characteristics obtained from the proposed method and FEA are presented and compared. Finally, both flux-linkage and torque-speed data are experimentally obtained from a 5 kW, 270 V, 12 000 r/min, 6/4 SRM and presented for validating the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

The second harmonic current injection method is recently developed to enhance the torque density of variable flux reluctance machines (VFRMs). This article investigates the feasibility and effectiveness of the second harmonic current injection method in VFRMs with different stator/rotor pole combinations. By using magnetic gearing effect, it is found that the second harmonic injection method can only be applied to the 6j/(6i ± 2)j (i, j = 0, 1, 2…) stator/rotor pole VFRMs for the torque density enhancement. For the other stator/rotor pole combinations, the second harmonic current has no contribution in average torque production but only leads to excessive torque ripple. Further, by using global optimization method and finite element analysis, 6/8 stator/rotor pole combination is proved to be the optimal stator/rotor pole combination for 6-stator-slots VFRMs with the second harmonic current injection method, being able to exceed the maximal torque density of conventional VFRMs by 12% at a fixed copper loss. [ABSTRACT FROM AUTHOR]

This article proposes an analytical formulation of a maximum torque per ampere (MTPA) technique, accounting for the magnetic saturation of the iron core, specifically developed for synchronous reluctance motors (SynRMs). The proposed MTPA is based on a magnetic saturation model of the SynRM, which has been obtained after simplifying a more complete magnetic model, including also cross-saturation effects. This simplified magnetic model, and consequently the proposed MTPA, can be easily parameterized directly starting from a unique set of tests for the off-line identification of the motor, without the need for any complex, time-consuming, and cumbersome finite-element analysis of the machine under test. The proposed MTPA has been tested experimentally on a suitably developed test set-up. Results obtained with the proposed MTPA have been compared experimentally with both the classic MTPA and the real MTPA. Results clearly show that the proposed technique permits a significant increase of the torque per ampere (TPA) with respect to the case of the classic MTPA, which does not consider magnetic saturation. TPA increase varies from 5% at 3 Nm load to 18% at 12 Nm load. Moreover, the loss of maximum torque, with respect to the real MTPA, obtained at the maximum speed and load torque with the proposed MTPA is about 15%, whereas the loss of maximum torque obtained with the classic MTPA is about 38.5%. [ABSTRACT FROM AUTHOR]

A systematic approach based on a novel space-shifted three-layer winding (SSTLW) to eliminate both the sub- and superharmonics of fractional slot concentrated winding ac machines is presented. In this proposed three-layer fractional slot winding, the number of turns in one layer and the relative positions of other two layers are optimized to cancel subharmonics. The cancellation of superharmonics is achieved through series connection of two SSTLWs through effective doubling of the number of slots. The cancellation of the dominant sub- and superharmonics using this approach leads to reducing the total harmonic distortion, torque ripple, PM eddy current loss, and rotor core loss, while simultaneously improving power factor and saliency ratio. The proposed design methodology and ensuring improvements have been validated through finite element analysis for the widely used 12-slot/10-pole and 18-slot/14-pole permanent magnet synchronous machine (PMSM) configurations. A prototype three-layer winding is built for a 10-pole PMSM to validate the simulation results experimentally. [ABSTRACT FROM AUTHOR]

The synchronous reluctance (SyR) machine is an attractive substitute of induction motors and synchronous permanent magnet motors, owing to its high efficiency and low cost of manufacturing. Yet, its design cannot be considered a mature topic, especially for what concerns the rotor geometry. Design equations are proposed for SyR machines by different authors, representing a good starting point and a useful guideline for designers, but they are far from giving accurate results. Conversely, the design procedures based on finite-element analysis (FEA) tend to rely on the brute force of optimization algorithms rather than on the designer's insight. In this article, a comprehensive design procedure is proposed, where design equations are complemented by the use of the iron saturation curve and the new fast FEA approach named FEAfix. This corrects the equations results via few static FEA simulations per design plane, i.e., per family of machines, rather than by FEA simulating the single machine under design. The general conclusion is drawn that the considered analytical model alone tends to overestimate torque by as much as 40% (average on the design plane). Upon augmenting equations with the saturation curve, the average overestimate drops in the vicinity of 10% error. Finally, the proposed FEAfix refinement guarantees 2% to 1% torque evaluation error, depending on the admitted computational time. High precision is, therefore, obtained while retaining the generality of the analytical approach. [ABSTRACT FROM AUTHOR]

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

This article investigates a novel two-converter-based operation of a brushless doubly fed reluctance machine (BDFRM). The BDFRM has a ducted rotor, and the stator is wound with two distributed windings, which are fed from two separate power converters. Operation theory with frequency sharing between the two windings is introduced. The prototype BDFRM design, machine assembly, and the corresponding motor drive implementation processes are discussed. The control strategy for frequency sharing mode of operation with two variable winding frequencies is discussed. Subsequently, the BDFRM drive is tested in frequency sharing mode at varying speed levels and loads. [ABSTRACT FROM AUTHOR]

Different from the regular ac machines, the armature winding current waveforms of dc-biased vernier reluctance machines (DC-biased-VRMs) are sinusoidal with dc bias. The power factor (PF) calculation process also shows great difference. This paper intends to analyze the PF theoretically based on the mathematical model. Then, investigate the approach to optimize the PF and the price to pay if measures are taken to further improve the PF. The PF of the DC-biased-VRM is expressed under synchronous rotating frame. A maximum PF control strategy is proposed by adjusting the distribution of three-dimensional dq0-axis currents. The scale of active power to reactive power is changed, and the PF can be regulated. Experimental results are provided to verify the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

A novel approach of exploiting the stator-temperature-monitoring system to perform sensorless rotor-position estimation is described in this paper. The rotor position is, in fact, estimated by processing the voltages induced in thermistor cablings, which are modified in order to work as search coils (SCs). Using SCs, some typical drawbacks of sensorless position-estimation techniques based on the manipulation of fundamental components of stator voltages and currents, such as those related to inverter non-linearities, stator-resistance voltage drops, magnetic saturation and cross-coupling, can be overcome or mitigated. According to the proposed approach, a rotor-position-tracking technique for synchronous reluctance motor drives is developed independently from motor parameters. Such a sensorless rotor-position-estimation technique can be directly used to build up a sensorless controller or to improve the performance of conventional model based sensorless control systems. Simulations and experimental tests confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Momentary power disruptions commonly occur in many industrial settings, and can trip large electric machines, which must then be brought to zero speed before the machine can be restarted. The resulting frequent interruptions in industrial processes can have negative effects on productivity. A restart algorithm brings the machine back to the original speed as soon as power is restored, without waiting for the machine to reach zero speed. This paper proposes an approach for implementing a restart algorithm for synchronous reluctance machines (SynRMs) that use a simple identification algorithm to determine the speed and position of the machine so that the appropriate voltage vector can be applied, thus minimizing the inrush current during the restart. The proposed method only requires nameplate machine parameters and needs no machine-specific tuning, making the approach suitable for implementation with both high-inertia vector and scalar-controlled SynRM. [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]

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]

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]

This paper proposes a novel 12/8 switched reluctance motor (SRM) with segmental rotor for vehicle cooling fan application. Unlike conventional SRMs, the proposed motor adopts one body stator with hybrid stator poles and segmental rotor structures, thereby making the motor operate in short flux paths and parts of the flux paths magnetically isolated between the phases. Therefore, compared with conventional SRMs, the proposed structure not only improves the output torque density and reduces the magneto-motive force requirement and core losses of the motor, but also inherits the advantages of conventional SRMs like flexible control as well as the adaptability in harsh environment. To verify the proposed structure, a finite element method is employed to get characteristics of the proposed SRM. Meanwhile, a conventional 12/8 SRM, which has been used for vehicle cooling fan application, is also analyzed for comparison. Furthermore, the prototypes for the conventional and proposed 12/8 SRMs are manufactured and tested. Finally, the simulation and experimental results are presented and analyzed to verify the effectiveness of the proposed SRM. [ABSTRACT FROM AUTHOR]

The recent novel dc-biased sinusoidal current reluctance machines (dc-biased VRMs) adopt a doubly salient structure and concentrated windings, which is similar to that of switched reluctance machines (SRMs). The special point is that the phase current is in the form of an ac component superimposed with a dc component. Some literary works show that these machines would have better performance than the existing SRMs and variable flux reluctance machines. In this paper, the slot/pole combinations and winding configurations of the dc-biased VRMs are deeply investigated. First, relationships among slots/poles are given based on the operation principles. Then, several feasible slot combinations are obtained, and the electromagnetic performances including magnetizing inductance, virtual back electromotive force, torque quality, and losses are compared by the finite element analysis. Finally, the correctness of the proposed analysis is validated by the experiment on two 12/10 prototypes. [ABSTRACT FROM AUTHOR]

This paper presents the design and experimental validation of a synchronous reluctance motor (SynRM) using a multilayer (ML) ac winding that meets the ultra-premium/IE5 class efficiency requirement. Compared to conventional double-layer ac windings, the ML winding yields a more sinusoidal stator magnetomotive force (MMF) with a shorter end-turn length. The ML winding is characterized using an analytical stator MMF model with verification against finite element analysis (FEA). The proposed winding configuration is optimized under a given design benchmark. The multi-barrier rotor design is also optimized based on FEA using a genetic algorithm. The performance of the designed ML-SynRM is compared against a commercial premium efficiency induction motor and a conventionally wound SynRM for the same standard frame and cooling type. Results show significant efficiency gain with SynRM designs, and also, the designed ML-SynRM yields lower torque ripple with an improved power factor compared to the conventional SynRM. The prototype ML-SynRM is built, and its simulation results are experimentally validated against the benchmark including their performances at a thermal steady state. [ABSTRACT FROM AUTHOR]

This paper proposed a varying magnetic network modeling method of dual-rotor permanent magnet reluctance (DRPMR) machines based on magnetic circuits considering possible saturation and nonlinearity according to the physical structure, which is put forward to obtain the accurate inductance characteristics of the proposed machine. The feasibility of this analytical model is confirmed by the finite element method. Moreover, experiments are designed to validate the analytical results. It indicates that the analytical inductance characteristics of the DRPMR machine have good agreements with the experimental results. [ABSTRACT FROM AUTHOR]

This paper deals with a comparative study between reluctance (REL), permanent magnet assisted reluctance (PMAREL), and surface mounted permanent magnet (PM) synchronous machines with rotor eccentricity. Static, dynamic, and combined eccentricity cases are considered. For the sake of generality, this comparison is carried out at different levels of air-gap flux density, as different current angles, different PM materials, and different number of magnetic poles. Additionally, different stator windings arrangements, i.e, distributed and fractional slot concentrated windings are taken into account. Besides, different rotor geometries of REL and PMAREL machines are included. As a case of study, 36-slot machine is analyzed, considering three flux barriers per pole; however, the study can be applied to any machine geometry. Due to the structural criticality of the rotor iron ribs of the REL machines, the impact of the eccentricity on the mechanical stress acting on those ribs and the deformation of the rotor is studied. [ABSTRACT FROM AUTHOR]

This paper presents a design of a line start permanent magnet (PM) synchronous motor capable of operating in two different synchronous speeds without requiring a drive unit. The proposed design is based on variable pole numbers for the stator and the rotor. In general, the two-speed operation is realized by the combination of electromagnetic torque and reluctance torque, which enables the motor to operate as a synchronous PM motor at high speed and a synchronous reluctance motor at low speed. However, the proposed design enables the motor to operate as a PM motor at both low- and high-speed regions. The stator winding consists of two independent windings to switch the operating pole count for low- and high-speed applications. For the motor to operate in two different operating speeds, the rotor must be capable of creating two different magnetic polarities (pole numbers) to adapt itself to the operating stator pole number. For this purpose, PMs are specially arranged such that the magnetic flux density has a distribution similar to the resultant flux of two rotors with different magnetic pole numbers. This forms a rotor with dual magnetic polarity and enables the motor to operate as a synchronous PM motor at two operating speeds. The finite element analysis simulation results confirm the effectiveness of the proposed design in both steady-state and transient regime. To further validate the proposed solution, the performance of the motor has been verified by experimental measurements on the motor prototype. [ABSTRACT FROM AUTHOR]

Synchronous reluctance machines are very appealing for high-speed traction applications due to their robustness, simple structure, absence of magnets, and simple control. The absence of magnets means that synchronous reluctance machines are not susceptible to price variability and sustainability of rare-earth materials. Also, there are no concerns about demagnetization or uncontrolled generation mode. However, the challenge of achieving a good constant power to speed ratio is dependent on the mechanical aspects of the design. Conventional synchronous reluctance designs perform poorly compared to permanent magnet machines due to the presence of bridges and/or center posts that provide a path for performance-robbing leakage flux and the absence of permanent magnets that help saturate the bridges and/or center posts. Elimination or reduction of these features presents a challenge for rotor mechanical retention due to the reduction in radial stiffness that these members provide mainly for high-speed applications. A carbon-fiber sleeve on the rotor will provide the needed mechanical strength to enable a reduction of bridges and/or center posts. This paper will present the design details, analysis, manufacturing, and test results of a proof-of-concept carbon-fiber-wrapped synchronous reluctance machine targeting traction applications. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive manufacturing and assembly process of synchronous reluctance machines (SynRMs) is presented. One stator and two transversally laminated anisotropic (TLA) SynRM rotors are manufactured using cold-roll nongrain-oriented steel. To enhance the performance of the designed SynRM, a TLA segmented SynRM rotor is fabricated using cold-roll grain-oriented steel. The application of nonconventional photochemical machining to produce machine laminations is presented. Different stages of manufacturing, stator and rotor assembly techniques, rotor balancing procedure as well as specialized components used at various stages of the process are described. Performance characteristics such as static torque–angle curves are obtained experimentally to verify the accuracy of design, manufacturing, and assembly. [ABSTRACT FROM AUTHOR]

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

This paper presents the experimental validation of a novel cooling concept applied to a high-speed switched reluctance machine topology for traction applications. By circulating the coolant between the coils and the stator poles, the winding and the stator iron are virtually thermally decoupled. A number of test motorettes are used to demonstrate the potential of the cooling concept at current density values up to 27 A/mm2 continuously. The measurements are also used to validate a thermal model of the machine, and further improvements of both the model and the experimental setup are proposed. [ABSTRACT FROM AUTHOR]

DC-biased sinusoidal current vernier reluctance machines (dc-biased VRMs) have a doubly salient structure, and their phase currents contain an alternating current (ac) component and a direct current (dc) component. Hence, their main features are one set of concentrated windings compared with variable flux reluctance machines, low vibration and noise due to smooth current, compared with switched reluctance machines, and robust rotor structure. Besides, its achievable high slot fill factor can improve the torque density further. In this paper, based on the flux modulation principles, the torque production mechanism of dc-biased VRMs is analyzed, and two slot combinations of 12/8 and 12/10 are proposed. First, the machine topology and inverter main circuit are illustrated. Second, the torque production mechanism is explained. Furthermore, the inductance characteristic, optimal current configuration for maximum torque and lowest torque ripple are analyzed theoretically and by the finite-element analysis. Finally, one prototype was designed and built, and the proposed analysis is validated by the experimental results. [ABSTRACT FROM AUTHOR]

To meet the increasingly stringent regulations on operational efficiencies of electric motors, efforts have been devoted to design and construct motors with less power losses. Without the need of rotor conductors, and hence, no secondary copper loss, the feasibilities of applying synchronous reluctance motor (SynRM) have attracted many attentions on the related industries. Since the operation of SynRM is mainly based on the reluctance torque, appropriate electromagnetic steel selections for the motors will be the key factors. To adequately evaluate the performance of SynRM, with the available magnetization and hysteresis characteristics of the commercial steel sheets, the SynRMs that are composed of different electromagnetic steels at various operational specifications will be thoroughly investigated. From theoretical analyses of the selected SynRMs by different stator and rotor material compositions along with experimental validations, valuable guidance for related SynRM constructions and operations can thus be provided for steel manufacturers and motor designers. [ABSTRACT FROM PUBLISHER]

This paper deals with an analytical model of reluctance synchronous motor, able to consider both stator slotting effect and magnetic saturation in the stator and rotor iron paths. It joints the field distribution at the air gap to a lumped-parameter magnetic network. Local saturation factors are defined so as to adjust the flux-density distribution. The analytical approach exhibits great potentiality, since it is a formulation based on an harmonic study, and it is easily adaptable to any motor geometries. As an example, 36-slot 4-pole machine is analyzed, considering three flux barriers per pole. Finite element analysis confirms the results achieved by means of the analytical model. [ABSTRACT FROM PUBLISHER]

This paper employs grain-oriented electrical steel (GOES) in an axial-flux switched reluctance motor (AFSRM) to improve its torque characteristic, taking advantages of the material's excellent magnetic properties in the rolling direction. Based on the study on the parameter and switching characteristics of an AFSRM, GOES can be divided into pieces and arranged in the rotor and stator teeth so that the magnetic flux mainly travels along the rolling direction of the material. AFSRMs with different lamination shapes and deviation angles between the magnetic flux and rolling direction of the GOES have been studied to further improve the output performance; the maximum electromagnetic torque of the proposed design shows a 20.5% increase in comparison with that of the conventional nonoriented electrical steel motors under identical conditions. The rotor retaining ring is composed of epoxy resin lamination to constrain the rotor teeth modules. Thermal and stress analyses under fault conditions are analyzed to verify the reliability of the retaining ring. Furthermore, an AFSRM prototype is built and experiments are conducted to validate the calculated data. [ABSTRACT FROM PUBLISHER]

An analytical calculation of the winding flux linkages and torque is proposed for fully pitched mutual coupled switched reluctance motors to develop a machine model without using numerical methods. The proposed technique is not empirical and does not require any finite-element analysis (FEA). The design parameters and the material properties of the machine are the only inputs to the model, which can predict the winding flux linkages and torque at any phase currents and rotor positions. The model is applicable for the rotor positions where the stator and rotor poles overlap. Initial assumptions and then the step-by-step procedure for flux linkage, co-energy, and torque calculations are provided. The flux linkages and torque predicted through the proposed modeling technique are compared with the FEA results. Finally, experimental results of flux linkage and torque are provided to verify the accuracy of the proposed modeling technique. [ABSTRACT FROM AUTHOR]

In this paper, a harmonic field current injection method is proposed for torque ripple reduction in 6-stator/4-rotor-pole (6s/4r) variable flux reluctance machines (VFRMs). Initially, the torque production of VFRM is analyzed based on an analytical torque model and harmonic analysis. The torque ripple of 6s/4r VFRM is found to have multiples of third harmonics. Then, one finite-element analysis (FEA)-based and one analytical equation-based method are developed to calculate the magnitude of the injected harmonic current. Both methods are proved to be effective in torque ripple reduction. Finally, the influence of the inductance mismatch on the proposed method is investigated. It shows that the torque ripple reduction performance is not affected much unless the fundamental component of nominal inductance is underestimated. The feasibility and effectiveness of the proposed methods are validated by both 2-D FEA and experimental test. [ABSTRACT FROM AUTHOR]

Non-permanent-magnet machines are generally known to be less power dense than permanent magnet counterparts, but the absence of permanent magnets in these machines makes them well suited for high temperature applications. This offers a degree of freedom in improving their power density, because they can operate at higher electrical loading while maintaining acceptable efficiency. This paper presents a high temperature dc-biased reluctance machine that is structurally similar to a conventional switched reluctance machine. This non-permanent-magnet machine has a dc field winding and an ac three-phase armature winding. The machine is equipped with a high temperature 280 °C rated insulation system. Test results showing machine performance under continuous operation against the FreedomCar 2020 specifications as well as at high temperature up to 280 °C are presented. Compared with an initial design using conventional insulation designed for operation at 200 °C, the high temperature insulation system enabled the machine to operate at twice the temperature rise and achieve 43% increase in power. [ABSTRACT FROM AUTHOR]

This paper describes the design procedure followed to realize a high-speed synchronous reluctance machine for aeronautical application. The attention is mainly focused on the rotor design that is the most critical part of any synchronous reluctance machine; in particular for high-speed applications. After a preliminary optimization of the rotor geometry, a multiphysical design that considered mechanical, thermal, and electromagnetic properties was developed. The main steps of the design procedure together with an extensive analysis of the final design are presented here. Two prototypes have been realized using different rotor lamination materials in order to validate the design procedure. [ABSTRACT FROM PUBLISHER]

In order to simplify the manufacturing process of variable reluctance (VR) resolvers for hybrid electric vehicle/electric vehicle (HEV/EV) applications, a novel VR resolver with nonoverlapping tooth–coil windings is proposed in this paper. A comparison of the winding configurations is first carried out between the existing and the proposed designs, followed by the description of the operating principle. Furthermore, the influence of actual application conditions is investigated by finite-element (FE) analyses, including operating speed and assembling eccentricity. In addition, identical stator and windings of the novel design can be employed in three resolvers of different rotor saliencies. The voltage difference among the three rotor combinations, as well as the detecting accuracy, is further investigated. Finally, prototypes are fabricated and tested to verify the analyses. [ABSTRACT FROM PUBLISHER]

The relationship between the well-known competitive torque density and less-competitive power factor of reluctance synchronous machines (RSMs) is investigated in this study. The investigation was carried out by implementing a complete machine model in the optimization, with varying machine-pole number and flux-barrier number combinations. Furthermore, the study consists of a multiobjective design optimization implementing a weighted-factor optimization technique. Determination of the weighting of this specific parameter relationship enables the designer to select an optimum multiobjective relationship during optimization. A specific machine was selected for analysis, then analyzed and manufactured for validation of simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a novel 6/5 segmental rotor-type switched reluctance motor (SRM) for cooling fan application. Unlike conventional structures, the rotor of the proposed structure is constructed from a series of discrete segments, and the stator is constructed from two types of stator poles: exciting and auxiliary poles. Meanwhile, the windings are only placed around the exciting poles, resulting in short flux paths and no flux reversal in the stator of the proposed SRM. Hence, the proposed structure may increase the electrical utilization and reduce magnetomotive force (MMF) requirement compared to conventional SRMs. To verify the proposed structure, the operation principle and the design rules of the proposed structure are illustrated and expounded. The finite-element method (FEM) is employed to get the static and dynamic characteristics of the conventional 12/8 and proposed SRMs. Furthermore, the prototype is manufactured and tested. Finally, the simulation and experimental results are presented and analyzed to verify the effectiveness of the proposed SRM. [ABSTRACT FROM AUTHOR]

The symmetric structure conventionally used in two-phase switched reluctance machines (SRMs) leads to dead torque zone and issues with startup. When a phase is at the fully aligned position with respect to the rotor, the complimentary phase is completely unaligned. Within this region, excitation of either phase fails to generate sufficient startup torque. Significant research has been focused on the design of machines with large, unidirectional startup torque specific to the direction of rotation required by the given application. In this work, a conventional two-phase SRM is analyzed to reveal the underlying geometric constraints leading to startup difficulties. To overcome this, a phase shift design strategy is proposed to ensure both large starting torque and bidirectional startup capability. The design is investigated and validated through both simulation and experiments, and the results show the validity of this new configuration. [ABSTRACT FROM PUBLISHER]

This paper presents advancements in the control techniques of switched reluctance machines (SRMs) for traction and automotive applications. The high performance of the SRM drive system is embodied in the smooth torque output and high-efficiency control methods in the motoring and generating modes of operation. Wide speed operating ranges for both motoring and generating operations are considered. An SRM designed and built for an off-road traction application is used as an application example. Simulation results for the proposed techniques using an SRM system designed for off-road traction application are presented. [ABSTRACT FROM PUBLISHER]

This paper investigates the rotor cavity positioning and the combination of stator slot and rotor effective slot number on the eddy-current loss for interior permanent-magnet/reluctance machines operating under deep field-weakening conditions. A new closed-form expression for the stator and rotor eddy-current loss is developed. The optimal barrier-positioning for the minimum total loss and the effect on the eddy-current loss of varying the stator slot and rotor effective slot number are investigated for one-, two-, three-, and full-layered rotors. [ABSTRACT FROM PUBLISHER]