Search

Relatively high torque ripple limits the further development of the switched reluctance machine, and the application of the ripple suppression method will reduce the efficiency of the system. To simultaneously improve the efficiency and torque ripple of the switched reluctance machine, a new commutation and online optimization strategy is proposed. According to the torque per ampere characteristics of the machine, two rotor position angles are defined, which are the boundaries for the high and low torque per ampere operation modes of the two adjacent phases, respectively, and for different operating modes, specific torque hysteresis control schemes are performed. Furthermore, an objective function is constructed with the efficiency and torque ripple coefficient, and during the operation of the machine, the defined boundary angles are online optimized by the genetic algorithm to maximize the value of the objective function. The effectiveness of the method is verified by detailed simulation and experiment under different operating conditions. [ABSTRACT FROM AUTHOR]

This article presents a general projection vector framework for the analysis of flux and position observers applied to sensorless control of synchronous reluctance (SyR) machines, with emphasis to parametric errors sensitivity. The stator resistance immunity property of Adaptive Projection vector for Position error estimation (APP) technique is demonstrated in maximum torque per ampere (MTPA) conditions. Out of MTPA, additional resistance adaption is devised for accurate estimation of stator flux and torque. Alternatively, inductance adaptation might be preferred to resistance's, when dealing with inaccurate motor flux-maps. Inductance adaptation is shown to decrease the steady-state position error. All the proposed APP observers with adaptation techniques are subjected to stability analysis. The merit and the feasibility of the proposed scheme are experimentally demonstrated on a 1.1-kW SyR machine test bench. [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]

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

The direct torque control (DTC) and direct force control (DFC) method were introduced to reduce the torque and levitation force ripple in single-winding bearingless switched reluctance motors (SWBSRMs). However, it still has some disadvantages. Firstly, the flux-linkage control is not suitable for the DTC method in SWBSRMs. On the one hand, it can increase the torque ripple. On the other hand, the RMS current can be increased and then the torque-ampere ratio is decreased. Secondly, the vectors selection is also unreasonable, which can increase the torque ripple further. In order to solve these problems, an improved control method based on DTC and DFC method for SWBSRMs is proposed in this paper, which can obtain high torque-ampere ratio and low torque ripple simultaneously. In the proposed method, the flux-linkage loop control is not needed and the space voltage vector table is improved. The experimental results show that the torque ripple is reduced by 66.7%, the torque-ampere ratio is increased by 200% and the switching times in one electrical period are reduced by 47.3%. [ABSTRACT FROM AUTHOR]

This paper presents a new design of dual-pole (4-pole and 8-pole) Line Start Synchronous Motor (LSSM) with consequent magnetic pole structure. The proposed structure reduces the Permanent Magnet (PM) volume in the rotor core by 67 percent with respect to the reference dual-pole machine. Given the direct impact of the PM magnetic field on producing negative torque components such as braking torque and pulsating torque, lower PM volume can potentially limit the production of such negative torques. Therefore, in addition to cost saving benefits, the proposed structure contributes to a smooth start-up process. Meanwhile, different geometrical structures of PMs and flux barriers are discussed, their impacts on the overall motor performance are highlighted, and general design guidelines are provided. In particular, six different rotor structures with different PM arrangement and/or flux barrier arc angle are analyzed in Finite Element (FE) and their steady-state and transient performance metrics are compared. Finally, the best motor candidate is selected for further analyses, and prototyping. [ABSTRACT FROM AUTHOR]

In conventional 12/8 bearingless switched reluctance motors (BSRMs), the generation and control of torque and levitation forces are always coupled and interacted, which increases the complexity of the current control algorithm. In this paper, a novel BSRM with 12 stator poles and 4 rotor poles is proposed to simplify the control of torque and levitation, which has wide flat inductance region. Through allocating the generation of torque and levitation forces to different inductance regions of each phase, the levitation control can be similar as that of magnetic bearings, and the torque control can adopt the methods of conventional switched reluctance motors, e.g. current chopping control and angle position control. Accordingly, the current control algorithm of proposed BSRM becomes very easy and flexible. Extensive experiments were completed to verify the demonstrated performance of proposed motor. [ABSTRACT FROM AUTHOR]

The torque production mechanism of switched reluctance machines (SRMs) is investigated from the perspective of air-gap field modulation principle. The unipolar stator current excitations can be divided into DC and AC components and they induce the air-gap magneto-motive force (MMF) respectively. Meanwhile, thanks to the salient structure in SRMs, the air-gap MMFs induced by the two sources above can be modulated to obtain the synchronized air-gap fields for torque production. It is revealed that a multitude of field harmonics contribute to the torque together. The MMF-permeance model is built and the analytical deduction of the field modulation effect is provided, with which the orders of the field harmonics contributing to the torque output can be identified. Moreover, finite element method is employed to verify the predictions on various SRM topologies. Finally, aprototype machine is fabricated and measuredfor validation. [ABSTRACT FROM AUTHOR]

In this paper, a dual-consequent-pole transverse flux motor and its electromagnetic design method are proposed. Both the stator and rotor of the proposed motor are designed to own the consequent-pole configurations. The unique motor structure improves the space utilization and the torque density. Firstly, the detailed structure and principle are introduced, and the development of the torque density of the proposed motor is discussed. Secondly, the electromagnetic design method's theory, considerations and flow process are listed. Then, the selections of some main structure parameters are proposed (e.g., pole-pitch, thickness of PMs and pole-arc coefficients of PMs). The electromagnetic performances of the proposed motor are compared with the existed transverse flux machines. At last, a prototype is manufactured and some primary experiments are done to verify and evaluate the proposed motor topology. [ABSTRACT FROM AUTHOR]

A segmented bilateral switched reluctance linear motor (SRLM) applied to long rail propulsion system is first proposed. The electromagnetic thrust, flux density and inductance characteristics of two SRLMs are compared and analyzed by finite element method. The results show that the SRLM with segmented primary and secondary has a higher thrust and is fully decoupled, which simplifies the sensorless control system. In order to solve the problem of detection difficulty of the pulse currents, negative torque and eddy currents in traditional pulse injection method, a new position estimation method of the SRLM based on the coupled voltages of idle phase is proposed in this article. The merits of the position detection method are that it does not need to consider the accuracy of pulse currents detection, the frequency of injected pulse voltage can be further improved, and the influence of back EMF in the process of motor operation can be offset, thus greatly expanding the velocity range of pulse injection method. According to the position detection method, the specific control strategy and program flow chart of the SRLM sensorless operation are presented. Finally, a prototype test platform is built, and the experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Hybrid stepper motors, which convert the input pulse train into rotating angle increments by using an open-loop control strategy, are widely used in industrial applications. The bearing is a key and vulnerable component in stepper motors, and the bearing faults affect the positioning accuracy and output torque of motors. Order analysis is an effective method in bearing fault diagnosis under varying speed conditions. The rotating angle curve is necessary for order analysis, but angle or speed sensors are not installed on hybrid stepper motors. In this article, a method of estimating the rotating angle from motor current is proposed and applied to bearing fault diagnosis. First, a variational nonlinear chirp mode decomposition method is introduced to decompose the current signal and extract a dominant mode that has a strong correlation with motor rotation. Second, the rotating angle is calculated, and the synchronous vibration signal is resampled using the rotating angle curve. Finally, the bearing fault type is identified from the envelope order spectrum of the resampled signal. The proposed method can accurately diagnose bearing faults and has potential applications in condition monitoring of stepper motors. [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]

Switched reluctance machines (SRMs) have been studied by many researchers as an alternative to the other types of electrical machines for use in electric and hybrid vehicle applications. SRMs are fault tolerant and have wide speed operating range. However, they suffer from several disadvantages, including high vibration, acoustic noise, and torque ripple. In this article, the placement of rectangular windows in both the rotor and stator poles is proposed to reduce the vibration and acoustic noise of SRMs. An iterative optimization algorithm in a wide speed range of operation using finite-element analysis (FEA) tools provides the best position and dimension of window design parameters. Multiphysics FEA is also performed to predict the vibration and acoustic noise of the optimized design. The results of this study present that placing windows in both the stator and rotor of the SRMs can significantly reduce the acoustic noise compared with the baseline SRMs. Based on the simulation results, the optimum design has been constructed as a prototype and tested in a wide speed operating condition. The simulation and experimental test validation results prove the effectiveness of the proposed design in mitigating the acoustic noise and vibration. [ABSTRACT FROM AUTHOR]

This article deals with the design of a normal saliency interior permanent magnet (PM) motor, also referred as flux-intensifying PM motor. A multibarrier rotor geometry is adopted and studied through an analytical model to obtain an almost sinusoidal airgap flux density waveform, so as to improve the performance and reduce the torque ripple. The developed analytical model is generic and applicable for any number of rotor flux barriers and for any number of poles. The motor performance improvement has been evaluated by finite-element analysis. Experimental validation has been carried out on a motor prototype. [ABSTRACT FROM AUTHOR]

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

A new analytical torque model based on dq0-axis frame has been developed for 3-phase, 12-slot/8-pole single layer doubly salient synchronous reluctance machines. This newly developed torque model, compared to the one often based on abc-axis frame, is necessary to simplify the investigation of dynamic performance such as torque–speed curve and efficiency maps. It has been found that the third-order current harmonic injection not only improves the torque performance (increased average torque and reduced torque ripple) in constant torque region but also maintains a similar torque level as the fundamental current supply in the flux weakening region. Moreover, although the fifth- and seventh-order current harmonic injection can reduce the torque ripple of machine, their dynamic performances are compromised due to low average torque and significant voltage distortion. Finite element simulations and dynamic tests have been carried out to prove the accuracy of the developed torque model and also the efficiency of the proposed current harmonic injection method. [ABSTRACT FROM AUTHOR]

This article proposes a new fault-tolerant permanent magnet (FTPM) machine with the improved salient ratio and reluctance torque ratio. The key of the proposed machine is the new slot–pole combination (20-slot/14-pole), which breaks the traditional rule which stipulates that the difference between slot number and pole number in FTPM machines is equal to 2. After the selection of slot–pole combination, the influence of the ratio of armature diameter to length and the injected current on salient ratio and reluctance torque ratio is evaluated, indicating that the relationship between the salient ratio and the reluctance torque ratio is contradictory in the FTPM machine. Therefore, the multiobjective method is employed to obtain optimal rotor parameters. In order to confirm the superiority and the uniqueness of the proposed FTPM machine, the comparison between the proposed FTPM machine and the two traditional FTPM machines (20-slot/18-pole) is analyzed. From the finite-element method and experimental results, it clearly depicts that the designed 20-slot/14-pole FTPM machine exhibits good fault-tolerant capacity, the improved salient ratio and reluctance torque ratio. [ABSTRACT FROM AUTHOR]

In this article, a dual-pulse mode control of a high-speed doubly salient electromagnetic machine (DSEM) for efficiency improvement over a wide speed range is investigated and implemented. The dual-pulse mode control method and operation principle are introduced. The influence of excitation angles and field current on the operation performance is analyzed by finite-element method based on the back electromotive force (EMF) and inductance characteristics. The loss distribution for various speed and load torque requirement is attained, and the control parameters are optimized. The excitation angle can reduce the back EMF at high speed through transformer EMF and flux-weakening armature reaction. A prototype of 12/8-pole DSEM drive system is developed and dual-pulse mode control in high-speed operation under low dc-link voltage is implemented. Both the simulated and measured results show that the torque capacity of the DSEM is improved and the loss is reduced over a wide speed range. [ABSTRACT FROM AUTHOR]

In order to increase structure compactness, critical rotor speed, and output torque of existing 12/12 bearingless switched reluctance motor (BSRM) with axial-biased permanent magnet, an improved modular permanent magnet BSRM is comprehensively investigated. First, basic structure and operation principle for torque and suspending force are briefly introduced. Second, magnetic design, including torque and suspending force, is taken into account. In addition, basic size estimation, self-starting capability, maximum suspending force, and selection of secondary air-gap are comprehensively considered in design. Third, several characteristics, such as torque, suspending force, etc., are deeply analyzed. Finally, a prototype motor is manufactured based on the above-mentioned analysis and design method. And the implemented experiment results show that the improved structure has good performance. [ABSTRACT FROM AUTHOR]

This paper investigates the two latest proposed drive system topologies for dc-biased vernier reluctance machines (VRMs), aims to find out the preferable drive system configuration, and explains the performance discrepancy between the two configurations. Different from the regular ac machines, the armature winding current waveforms of dc-biased VRMs are sinusoidal with dc bias. To provide the dc flow path, the two drive system topologies are associated with the machine, namely, an open winding converter with single-layer concentrated winding and a dual three-phase converter with double-layer concentrated winding. The two configurations are investigated and compared in terms of machine operation principle, power converter configuration, voltage utilization, system cost, and system efficiency. The theoretical analyses and experimental results validate that the two drive systems have their respective advantages. [ABSTRACT FROM AUTHOR]

To effectively find an optimal solution in the development process of electrical machines, it is essential to predict machine iron loss and thermal behavior in the predesign stage. Most existing publications only consider thermal behavior by roughly limiting the maximum current density. However, especially for high-speed application, iron loss can also be an essential part in thermal-behavior estimation. This paper proposes a simplified model to efficiently calculate iron loss and thermal behavior in the design procedure of switched reluctance machines. For this purpose, a maximum coenergy loop control method is implemented to facilitate the estimation of flux waveform and machine torque. Three different iron loss calculation methods are compared in terms of accuracy and time. Besides, a simplified lumped parameter thermal network is applied for machine sizing. Furthermore, the impact of number of turns and peak magnetomotive force on the losses and machine sizing is discussed. The efficiency and power density of various machine geometries are comparatively analyzed. Finally, the accuracy of the simplified model is verified by comparison with finite element simulations and experiment results. [ABSTRACT FROM AUTHOR]

Position sensorless control of synchronous reluctance machines is not easy due to nonlinear correlations caused by extensive magnetic saturation. This article investigates stability of a conventional saliency-based method and, for the first time, shows that the method becomes unstable at high torque with high magnetic saturation not due to cross-coupling effect itself but due to expansion of the cross-coupling effect through feedback of the estimated position. This instability occurs even when neither disappearance of the saliency nor reversal of the estimated d- and q- axes arises. A novel method to overcome this instability is proposed, which utilizes magnetic saturation depending on current phase angles. The proposed method was verified by simulations and experiment using a prototype machine. The results demonstrated that the proposed method achieved stable sensorless operation at the maximum torque, and thus, surpassed the conventional saliency-based method, the feasible torque of which was limited to 60% of the maximum for the prototype machine. [ABSTRACT FROM AUTHOR]

Modeling and accurate estimation of mutual flux in switched reluctance motors are complex due to interphase flux interactions, magnetic saturation, and harmonics. The mutual flux contributes significantly toward torque production of mutually coupled switched reluctance motors (MCSRMs); therefore, their accurate modeling directly influences the control design. In this article, a net-flux-based machine model is proposed to model MCSRMs. The model utilizes dual-phase excitation and multiphase excitation methods to generate the flux lookup tables from the finite-element model of the MCSRM. The modeling process is simple, as it does not require the segregation of the self- and mutual flux components, and machine performance can be predicted accurately using the net flux. The proposed modeling method is validated by implementing it for a fully pitched and concentrated-wound MCSRM and evaluating accuracy against the finite-element method. Details of the developed model are presented along with its comparison with existing methods. A prototype of a fully pitched MCSRM has been built, and the model is validated experimentally. Results show that the proposed model has excellent accuracy even under saturated operating conditions. [ABSTRACT FROM AUTHOR]

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

This article is a contribution to answer the following question: Is it possible to design a permanent magnet machine with the performance expected from rare-earth magnets but at a lower cost? Performance being understood as torque, size, efficiency, demagnetization, and temperature rise together. The question is addressed with a systematic exploration of different interior permanent magnet machine topologies mixing rare-earth and ferrite permanent magnets. The study starts from a production baseline, the Prius 2010 traction motor, with interior magnets placed in a single V pattern. It investigates various rotor designs, most specifically, single V and double V patterns as well as spoke configurations. The stator cross-section design and winding selection are fixed, providing a solid comparison basis from the point of view of machine cooling. For each rotor design, torque potential and machine material cost are assessed, the latter expressed as torque per dollar. A promising configuration was found based on a spoke pattern for which further modeling was performed to assess efficiency as well as mechanical strength and resistance to short circuits and to demagnetization. It reduces the rare-earth magnet volume by over 60%. [ABSTRACT FROM AUTHOR]

Torque motor is one key component that directly influences the dynamic performance of jet pipe servo valve in aircraft. In this paper, a novel torque motor with hybrid-magnetization pole arrays is proposed. By changing the magnetization patterns of permanent magnets, the torque motor can significantly improve the output torque by range of 47–52% compared with traditional designs, while maintaining the system size and mass. The design concept and operating principle of the torque motor is presented. The magnetic field distribution is formulated analytically with equivalent magnetic circuit. Different from conventional study, the flux leakage of the permanent magnets and coils is included to improve the model precision. Subsequently, the output torque is derived mathematically from the airgap flux. Following that, the numerical calculation is conducted to validate the mathematical models of magnetic field and output torque. The design optimization is then carried out. One research prototype that can be mounted with either conventional magnet or the proposed hybrid array has been developed. The test rigs are constructed and experiments are conducted on the prototype. Both numerical computation and experimental results verify the significant improvement of torque generation of the proposed hybrid magnetization torque motor. [ABSTRACT FROM AUTHOR]

This paper proposes a new robust field-weakening approach for reluctance synchronous motors regulated by direct torque and flux control. Compared to the existing direct torque and flux control based field-weakening methods that cannot achieve maximized DC-link voltage utilization and are parameter dependent, the proposed approach contributes to improve the field-weakening performance of reluctance synchronous motor in two aspects. First, it extends the constant power speed range through autonomous stator flux reference adjustment, which maximizes the dc-link voltage utilization. Smooth transition between the maximum torque per ampere trajectory and field-weakening trajectory is also realized. Second, it enhances the parameter robustness of drives in very high-speed region by employing a torque reference adjustment scheme. This effectively avoids the instability of drives caused by machine parameter variations. The proposed approach is verified experimentally on a laboratory setup. [ABSTRACT FROM AUTHOR]

It is an effective approach to estimate rotor position of doubly salient electromagnetic machine (DSEM) from self-inductances, which changes with rotor position. To overcome the restrictions of low estimation accuracy as well as the inevitable commutation lag in the conventional sensorless startup method, this paper proposes a novel rotor angular position estimating technique for the DSEM sensorless startup. It starts with injecting three test pulses A + C- (phase A is connected to the positive rail of dc bus, and phase C is connected to the ground rail), B + A- and C + B- on armature windings, so two-phase series self-inductances can be identified according to the resultant currents. Then, the estimating expression of the DSEM rotor angular position is further obtained based on the geometrical relation in the rectangle composed of self-inductances, and the inevitable commutation lag in startup process is likely to be eliminated with the estimated rotor angular position. Moreover, the error of rotor angular position introduced by the nonideal linearity of self-inductances are analyzed in detail, and the boundaries of neighboring sectors are distinguished from normal sectors to compensate the estimation error of rotor angular position. Finally, to enhance the output torque performance during the DSEM startup process, a novel selection method for test pulses concerning rotor sector is developed. Compared to the conventional method, a quicker and superior startup performance is achieved since no negative torque is generated by the test pulses. The experiments on a 12/8-pole DSEM validate the correctness and feasibility of the proposed sensorless control methods. [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]

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

A novel hybrid control strategy combining vector control and current continuous conduction is proposed in this paper to improve the performance of a hybrid-excitation switched reluctance motor (HESRM). Vector control, widely used in ac machines, is redefined in HESRM based on static torque characteristic to simplify an HESRM controller and reduce torque ripple. However, at a high-speed and heavy-load operation, current tracking accuracy deteriorates and torque ripple reduction effect gets worse. Current continuous conduction is combined with vector control to improve current tracking accuracy and maintain smooth torque ripple. In the HESRM, the power generally falls nearly in proportion to the square of speed over based speed, and a traditional control technique can maintain only a narrow constant power range. This novel vector control is easy to achieve phase advance and current continuous conduction simultaneously. By combining these two together, the HESRM can extend the constant power in a wider speed range and efficiency is also improved. Simulations and experiments in different conditions are carried out to verify the effectiveness of a hybrid control strategy. [ABSTRACT FROM AUTHOR]

This paper presents a switched reluctance motor (SRM) torque ripple reduction strategy with deadbeat current control and active thermal management. In this method, the SRM torque is indirectly controlled by the phase current. A deadbeat current control method is used to improve the SRM phase current control accuracy, so that SRM torque control error can be reduced significantly. According to the online measurement of the power switching device temperature, the switching frequency will be reduced to prevent the SRM power converter from being damaged by over-temperature. The feasibility and effectiveness of the proposed strategy have been verified in both simulation and experimental studies. [ABSTRACT FROM AUTHOR]

In order to construct a high-performance synchronous reluctance motor (SynRM) drive system, an intelligent maximum torque per ampere (MTPA) tracking control using a recurrent Legendre fuzzy neural network (RLFNN) is proposed in this study. First, a traditional MTPA (TMTPA) control system based on FOC is introduced. Since the reluctance torque of the SynRM is highly nonlinear and time-varying, the MTPA tracking control is very difficult to achieve by using the TMTPA control in practical applications. Then, an adaptive computed current (ACC) speed control using the proposed RLFNN for the MTPA tracking control of a SynRM drive system, which does not use a lookup table and can effectively obtain the optimal current angle command of MTPA online, is described in detail. The ACC speed control is applied to generate the stator current magnitude command, and an adaptation law is proposed to online adapt the value of a lumped uncertainty in the ACC control. Moreover, the adaptation law is derived using the Lyapunov stability theorem to guarantee the asymptotic stability of the ACC speed control. Furthermore, the proposed RLFNN is employed to produce the incremental command of the current angle. In addition, the ACC speed control and RLFNN are implemented in a TMS320F28075 32-bit floating-point digital signal processor for a 4 kW SynRM drive system. Finally, the robustness and effectiveness of the proposed intelligent MTPA tracking control are verified by some experimental results. [ABSTRACT FROM AUTHOR]

Consequent-pole permanent-magnet machines are of particular interest owing to their special features. They have alternate hard and soft magnet poles. In this paper, a two-dimensional (2-D) analytical model is proposed for outer-rotor slotted-stator consequent-pole brushless PM (CPBLPM) machines. The model is developed from the quasi-magneto-static Maxwell's equations, which are analytically solved. The magnetic flux density expressions are initially derived and then other quantities such as the no-load induced voltage, electromagnetic torque, reluctance torque, cogging torque, self and mutual inductances as well as unbalanced magnetic forces (UMF) are computed. The suggested model is generic and applicable to CPBLPM machines with any number of poles and phases, type of magnetization patterns and current waveforms. A case study is presented to evaluate the performance of the proposed model. The accuracy of the 2-D analytical solutions is verified against those obtained from the finite element method (FEM). The proposed method can replace the FEM in designing and optimization of outer-rotor consequent-pole permanent-magnet motors. [ABSTRACT FROM AUTHOR]

The term Virtual Synchronous Machine (VSM) commonly refers to the emulation of synchronous machines operation by using power electronics converters. However, a wider application of this control technique is still pending on further refinement of its design aspects and digital implementation. In this paper, a systematic approach to design the VSM parameters is introduced. First, a simplified third-order small-signal model of a VSM based on the conventional model of synchronous generators is developed. Unlike the existing works published in literature, the proposed model takes into account the effects of inductive and resistive weak grids. The model is then used to design the controller parameters by appropriately placing the poles of the closed-loop system. VSM robustness is studied for weak grids dominated by either inductance or resistance, and the aspects of digital control implementation are addressed. All the control system features and improvements were tested on a 15 kW prototype of a battery-supported VSM connected to a weak grid. [ABSTRACT FROM AUTHOR]

A novel criterion for the utility of reluctance torque in permanent magnet (PM) motors is developed. The criterion, reluctance torque ratio α, can be quantified by using the PM flux linkage Ψp of the stator phase windings, the current I, and the direct- and quadrature-axis inductances Ld and Lq, respectively. It has been shown that the conventional salient-pole ratio is not helpful in clearly judging the utility, while the ratio α can be used to make such judgements across various types of motors with different applications and outputs. Through both theoretical consideration and experiments, it has been proved that a motor with large PM flux linkage utilizes little reluctance torque even if the salient-pole ratio Lq/Ld is over 2.0 and that a large Lq/Ld increases iron loss, thus decreasing motor efficiency. We have also shown that the above-mentioned loss increase is caused by the significant superposition of q-axis flux due to the large Lq and have concluded that, in the above-mentioned case, selecting a rotor geometry with less saliency can improve the efficiency. Results are given for two types of four-pole prototype motors with an output power of 0.6 kW, a rated rotation number of 3600 min−1, and Y-connection. [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 work presents the analysis, design and optimization of a permanent magnet synchronous motor (PMSM) for an electric vehicle (EV) used for campus patrol with a specific drive cycle. Firstly, based on the collected data like the parameters and speed from a test EV on the campus road, the dynamic calculation of the EV is conducted to decide the rated power and speed range of the drive PMSM. Secondly, according to these requirements, an initial design and some basic design parameters are obtained. Thirdly, optimization process is implemented to improve the performance of the designed PMSM. The permanent magnet (PM) structure, airgap length and stator core geometry are optimized respectively in this step. Different optimization processes are proposed to meet multiple optimization objectives simultaneously. Based on the finite element analysis (FEA) method, it is found that the harmonic of the optimized PMSM is lower than that of the initial design, and the torque ripple is reduced by 24%. The effectiveness of optimization on the core loss and PM eddy loss is validated and the temperature rise is suppressed effectively. Finally, a prototype is fabricated for the optimized PMSM and an experimental platform is developed. The test results verify that the optimized PMSM meets the requirements of the specific campus patrol EV well. [ABSTRACT FROM AUTHOR]

This paper deals with stator-flux-oriented control of permanent-magnet (PM) synchronous motors and synchronous reluctance motors (SyRMs). The variables to be controlled are the stator-flux magnitude and the torque-producing current component, whose references are easy to calculate. However, the dynamics of these variables are nonlinear and coupled, potentially compromising the control performance. We propose an exact input–output feedback linearization structure and a systematic design procedure for the stator-flux-oriented control method in order to improve the control performance. The proposed controller is evaluated by means of experiments using a 6.7-kW SyRM drive and a 2.2-kW interior PM synchronous motor drive. [ABSTRACT FROM AUTHOR]

The demand for increased power and improved fuel economy are driving changes in alternator technology for automotive applications. To meet these demands requires a drive system with capabilities of torque assist, regenerative braking and power generation to supply vehicle loads while keeping the battery charged. Furthermore, to minimize add-on cost, the system must be air-cooled with minimal changes to the vehicle hardware and operate at 12 V with the same or smaller packaging footprint of the current alternator. In this paper, a low cost 12 V, 4 kW air-cooled permanent magnet-assisted synchronous reluctance machine drive system for a micro-hybrid vehicle is presented. The design and analysis in terms of machine, inverter, controller, and control algorithm are discussed in detail. Thermal performance of the system under different operating conditions, which is another key aspect for the harsh environment application, is also studied. Fuel economy analysis of the proposed low-cost micro-hybrid system for a Segment B vehicle shows significant reduction in fuel consumption resulting in a direct benefit to the customer. Finally, a prototype drive system was built and tested and found to meet the cost, performance, and packaging requirements. [ABSTRACT FROM AUTHOR]

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

In this paper, a new vibration reduction control of the switched reluctance machine (SRM) is proposed, which takes into consideration the undesirable effects of the torque ripple. The control approach aims to reduce the variation of the sum of radial forces while optimizing the control parameters of the machine to achieve the torque ripple minimization. Thus, a reference current adapter is used in order to handle the tradeoff between the vibration reduction and the torque ripple reduction. It produces an auto-tuning reference current that limits the variation of the torque and of the total radial force. The effectiveness of the proposed control strategy is proved by simulation and experimental results. Comparisons with conventional control methods investigating vibrations, noise, and torque ripple are provided, which show the advantages of the control approach based on an auto-tuning reference current. [ABSTRACT FROM AUTHOR]

The price fluctuation and the unstable supply chain of rare-earth permanent magnet (PM) have posed potential risks for further application of rare-earth PM motors. To alleviate the consumption of rare-earth PM material, a less-rare-earth PM brushless motor with two types of PM materials is proposed in this paper. The key of this motor is that the rare-earth PM is purposely combined with a non-rare-earth ferrite PM, forming the hybrid PM excitation. To design the proposed motor efficiently, a multi-objective stratified optimization strategy is proposed, where the selected five optimization objectives of output torque, PM cost, cogging torque, torque ripple, and efficiency are divided into two levels. Then, different optimization methods are skillfully combined to meet the specific design requirements. The corresponding electromagnetic performances are analyzed and compared with the baseline rare-earth PM brushless motor. Finally, several experiments of the two motors are carried out for evaluation. Both theoretical analysis and experimental results verify the feasibility and validity of the proposed motor and the optimization method. [ABSTRACT FROM AUTHOR]

This paper proposes a promising cost-effective phase current detection scheme for different multiphase switched reluctance motors (SRMs) by employing the multiplexed current sensors. According to the phase current characteristics for the odd-numbered multiphase SRM with m phases and even-numbered multiphase SRM with n phases, the phase windings are specially divided into (m + 1)/2 and n/2 groups, respectively, and each group shares one Hall-effect current sensor. By building the matrix functions to express the relationship between phase currents and sensor currents, the phase currents can be calculated in real time with a simple algorithm and fewer current sensors. Compared to existing phase current detection schemes, the developed method has high universality and can achieve the intact phase current detection without losing any excitation, freewheeling, and demagnetization currents. Moreover, the presented method is easy to implement without any converter change and pulse injection, which shows great potential for massive industrial application to avoid the voltage penalty, current distortion, higher switching loss, and further electromagnetic interference issues. The simulation and experiments are carried out to validate the feasibility and effectiveness of the developed phase current detection scheme. [ABSTRACT FROM AUTHOR]

Control issue in electrical drives mainly deals with the dynamic behavior, which is based on the deviation of variables. The deviations play a straightforward role in presenting the various capabilities and merits of the electric drive systems. This paper describes, for the first time, a deviation-based torque control of synchronous reluctance motor (SynRM) drives with no need to know the motor parameters. The proposed control system is designed by using a normalized deviation model to derive linear and simple relationships amongst different machine signals. Therefore, the commonly used proportional–integral current regulators are replaced by novel deviation equations. As a result, the proposed approach provides facilities to electric drives, including control system simplicity, parameter independency, and no need for controller tuning. The theoretical findings are verified by those experiments. The obtained results are reported for a typical SynRM drive. In addition, performance comparison of the control system with a general PI controller-based field-oriented control scheme is carried out. It is expected that the proposed approach contributes to other electrical drives to simplify the machine equations, reduce control complexities, such as the number of conventional controllers, and overcome the problem of machine parameter dependency. [ABSTRACT FROM AUTHOR]

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

This paper discusses systematic efficiency considering the efficiency of both a motor and airflow in an inverter-driven single-phase brushless direct-current (BLDC) motor with two different lamination designs for a cordless vacuum cleaner. In other words, multi-physical lamination design has to be conducted, and hence, the shape and placement of a whole electromagnetic structure are investigated in terms of a tradeoff between the electrical and mechanical efficiencies. In this paper, a single-phase BLDC motor for cordless vacuum cleaners is designed to satisfy starting and continuous torques by means of asymmetric air gap, and fluid analysis is performed to determine which shape of a single-phase BLDC motor has better system efficiency. The prototype of a single-phase BLDC motor has been tested, and the speed of the operation is ranged from 84468 r/min up to the rated speed of 100020 r/min. The motor efficiency of 94.7% has been measured to verify a good match with the estimated efficiency of 94.5%. [ABSTRACT FROM AUTHOR]

In this paper, a novel switched reluctance motor with two magnetically dependent stator and rotor sets (TMDSRM) is proposed and tested. The novelty of the TMDSRM is that there is an assistant exciting winding (short for exciting winding), which is placed between the two-stator sets and can be energized by controllable dc current to boost the air-gap flux density and to improve the output torque and torque density. What deserves to be mentioned the most is that the air-gap flux density is compensated when armature winding is in commutation because of the exciting winding carrying dc current and being permanently energized, and thus, the torque ripple is reduced. This paper describes the magnetic structure and the principle of the proposed motor in detail. Moreover, finite-element analysis has been carried out to investigate the influence of exciting field on electromagnetic torque of the motor. A prototype TMDSRM is manufactured, and the experimental results are presented. [ABSTRACT FROM AUTHOR]

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

Using a data-driven approach, this paper provides electromagnetic, structural, acoustic, and thermal guidelines for designing synchronous reluctance machines. Design spaces of different rotor geometries are created and simulated using finite element packages to evaluate the self- and mutual-correlation of different physical performances, such as average torque, torque ripple, efficiency, power factor, saliency ratio, sound pressure level, mechanical stress, and average winding temperature. Then, a statistical analysis is conducted to extract knowledge and guidelines for relating the design and objective spaces. It is demonstrated that not all the objectives must be incorporated into the design process since some of them are non-conflicting. Hence, a motor designer can numerically evaluate which design variables should be changed and by how much in order to fulfill the design specifications. Multiple designs are selected based on different multi-physical requirements. Useful guidelines for selecting the appropriate motor speed and voltage ratings are proposed while considering structurally reliable designs. [ABSTRACT FROM AUTHOR]