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In this article, a leaf spring insertion to the stator back iron is proposed to reduce vibration and acoustic noise in a switched reluctance machine (SRM). The back iron of the tooth tip is curved out and the material made up of carbon spring steel is placed to dampen the vibration due to radial force. A 6/4 stator/rotor pole SRM is designed and its natural vibration mode frequencies are determined through finite-element analyses. The optimal current waveform is applied to the SRM model using the multidisciplinary coupled simulation method to determine the radial force with the harmonic orders. In the final step, the proposed leaf spring architecture is optimized to achieve the most dampening for the effective radial force harmonic orders. The simulation and experimental results confirmed the effectiveness of the leaf spring insertion in reducing the noise and vibration in SRMs. [ABSTRACT FROM AUTHOR]

In this article, we deal with design considerations of a new ac hybrid-excitation permanent-magnet machine with axial stator. Due to the presence of an axial stator, the machine features a typical three-dimensional geometric structure and field distribution. A simplified reluctance-based network is developed to capture the main design features of the machine. The analytical equations are deduced relating the main geometric dimensions to the machine design criteria: speed, power, and flux regulation capability. The influence of key machine geometric parameters, i.e., radial/axial air-gap length, stack length, and bore diameter, on output power, flux density, and flux regulation capability is investigated. It is found that there is a design tradeoff between the machine power density and flux regulation capability. The d/q-axis inductance and its ratio, which has an influence on flux weakening capability and operation performance, is examined. Finally, a 6-pole/36-slot prototype is built. Intensive experimental tests are carried out to verify the machine characteristics. [ABSTRACT FROM AUTHOR]

A typical flywheel energy storage system (FESS) includes an electrical machine, a flywheel, and magnetic bearings, which are independent of each other. Therefore, the structure of FESS is complicated, which leads to the problems of high cost and low integration. This article presents a novel stator PM excitation solid rotor machine (SPE-SRM) for FESS, which integrates an electrical machine, flywheels, and a magnetic bearing. The design method of the SPE-SRM is presented specifically. First, the structure and operation principle of the SPE-SRM are illustrated. Second, the design and optimization of the flywheel-rotor are presented with considering of power, energy storage, and mechanical strength. Third, the magnetic equivalent circuit of the SPE-SRM is established to simplify the design. Besides, the armature reaction and leakage flux factor are investigated. Fourth, the performance indexes, including torque, suspension force, no-load back electromotive force (back-EMF), losses, and temperature rise are fully analyzed by the finite element analysis. Finally, a 22 kW prototype is manufactured and tested. The rationality of the concept and design is validated by experiments. The SPE-SRM has the merits of high integration, robust structure, and low cost, so it has the potential for wide application in FESS. [ABSTRACT FROM AUTHOR]

Recently, model-based predictive current control (MB-PCC) has been presented as a good alternative to classical control algorithms in terms of simplicity and performance reliability. However, MB-PCC suffers from the high dependence on system parameters, which may deteriorate its performance under parameters variations. On the other hand, synchronous reluctance motors (SynRMs) are susceptible to suffer from inductances variations due to the magnetic saturation. Accordingly, in this article a new model-free predictive current control of SynRMs based on a recurrent neural network (RNN-PCC) is developed and proposed. The proposed RNN-PCC relies on the identification of the SynRM currents without considering any parameters. Simulation and experimental results show that both RNN-PCC and MB-PCC have similarly excellent dynamics, while better control performance and tracking errors can be achieved thanks to the proposed RNN-PCC. [ABSTRACT FROM AUTHOR]

Dc-field excited modular variable flux reluctance machines (VFRM) are passive salient-pole rotor and independent stator winding, which makes it suitable for aerospace applications. Fault-tolerant operation is commonly required to improve its reliability. Hence, the performance under winding open-circuit faults is analyzed and the fault-tolerant control strategy is presented to increase the output capacity in this article. First, the dc-rectified output voltages and power of the VFRM under both normal and open-circuit faults are derived. Then, phase angle control strategy of the fault-tolerant operation for a 12-slot-14-rotor-pole (12s14r) modular VFRM is proposed, where the control sequence is optimized to achieve the maximum output power of the generation system. Compared with the classical fault-tolerant method, a higher applicability of the proposed method in terms of the types of fault-tolerant operations can be achieved. The electromagnetic properties, including the armature current and the capacity of electrical power output, are analyzed with finite-element analysis. The effectiveness and feasibility of the proposed fault-topology and control strategy are verified by the 12s14r VFRM prototype in normal, fault, and fault-tolerant operation. [ABSTRACT FROM AUTHOR]

This article reveals the flux leakage design and modeling principle of a flux leakage controllable permanent magnet (FLC-PM) machine by considering driving cycles. The key is to obtain the relationship between flux leakage characteristics and multiple operating conditions. Based on the flux leakage controllable concept, an FLC-PM machine with an artfully designed flux leakage region is proposed. The design principle of the machine is investigated by analyzing the magnetic circuit of the machine in multiple operating conditions. The flux leakage factor is introduced to characterize the variable magnetic field in multiple operating conditions. On this basis, the mathematical model of the FLC-PM machine is deduced, and the driving characteristics of the machine are studied in detail. In order to evaluate the presented principle of the FLC-PM machine, a prototype is manufactured for experiments. Through the theoretical analysis and experimental testing, it is verified that the proposed principle is feasible and effective. [ABSTRACT FROM AUTHOR]

In this article, an integrated drive converter of segmented double-stator switched reluctance machine (SDS-SRM) with isolation and nonisolation charging capabilities for electric vehicle (EV) is presented. The proposed converter can not only reduce the number of the power switches, but also implement multiple operation modes. In nonisolation charging mode, the motor windings and existing power switches constitute a buck/boost converter to charge the battery. The appropriate rotor positions are obtained to achieve torque-free control, and the interleaved phase currents control method is introduced to reduce the charging current ripples. In isolation charging mode, the inner-stator is powered by the utility grid to drive the middle-rotor, and converts electrical energy into mechanical energy, while the outer-stator is operated in generation mode to convert mechanical energy into electrical energy. The SDS-SRM is served as a rotating transformer to transfer the electric power to charge the battery with the galvanic isolation function. A low power proof-of-concept prototype platform is built and experiments are carried out to verify the effectiveness of the proposed integrated drive converter and the corresponding control schemes. [ABSTRACT FROM AUTHOR]

In this article, a circulating-current-excited switched reluctance generator system using a standard diode rectifier is proposed and examined. It features a dc power source connected in series with the ring-connected windings, which provides the dc-bias current as the excitation current in the windings. Using a series-connected dc power source, a dc-bias current is easily realized in the ac winding. Compared with the existing machine having dc-bias in the ac winding, the proposed generator can provide dc power with a standard diode rectifier. Less active legs and no rotor position sensor are needed for the control of the circulating current of the proposed generator, which increases the reliability of the generation system. The system configuration and the operation principle are introduced in detail. Then, the electromagnetic performance of the proposed generation system is analyzed at both open-circuit and load conditions. The asymmetric current distributions are deduced and verified by the simulations. At last, the prototype is tested under varied operation conditions and the experiments agree well with the analysis. [ABSTRACT FROM AUTHOR]

Multiphase machines with a prime number of phases (five and seven) have shown better torque density than machines with other phase numbers. Unfortunately, these machines require a special stator design. Hence, this article proposes general rewinding techniques to obtain a five-phase winding from the existing standard three-phase stator frames. The proposed rewinding techniques are applied to construct a five-phase star-connected synchronous reluctance machine (SynRM 1) and a novel combined star-pentagon winding (SynRM 2). Simple mathematical formulations are introduced to compute the equivalent winding factor. The performance of five-phase SynRMs is analyzed using two-dimensional Ansys Maxwell transient simulations under the same copper volume for both healthy and faulty cases. SynRM 1 and 2 provide 6.56% and 13.35% higher torque compared to the three-phase SynRM at rated current and at optimal current angle. The torque ripple is decreased by 17% and 30%, respectively. Moreover, SynRM 1 and 2 offer a better performance at the faulty case; e.g., at one phase opened, the average torque of SynRM 1 and 2 is 82% and 108% higher compared to the three-phase SynRM. In addition, the torque ripple is reduced by about 63% and 81%. Finally, experimental results are done to validate the proposed winding techniques. [ABSTRACT FROM AUTHOR]

Vernier reluctance machine (VRM) with dc field coils in stator is a competitive rare-earth-free design for variable-speed industrial applications due to its robust structure and controllable excitation, while its torque density is relatively disadvantageous. To address this issue, this article proposes a new armature winding design method for VRM with dc field coils across two stator teeth. The key is to break the traditional winding design principle based on the flux modulation effect of fundamental dc field harmonic, and instead, reconstruct a novel harmonic winding to enhance the utilization factor of the modulated high-order dc field harmonics arising from the unique magnetomotive force distribution of dc field coils across two stator teeth. By this means, the torque density can be improved by 75.6% against the existing poor counterpart. In this article, the machine structure and operation principle are introduced, with emphasis on the high-order dc field harmonics distribution rule and its influence on the armature winding design. By finite element design and optimization, a comparative study is performed to evaluate the electromagnetic performance of VRMs using two different winding configurations with variable slot pole combinations. A prototype is fabricated and tested, and the results agree well with finite element analysis, which verifies the feasibility and advantages of the proposed winding design method. [ABSTRACT FROM AUTHOR]

This article deals with the lookup table (LUT) less sensorless control of synchronous reluctance (SyR) machines at zero and low speeds, where LUT-less stands for avoiding the use of flux-map LUTs or other predetermined machine parameters. The new signal-injection-based control scheme called the locus of incremental saliency ratio tracking is presented, where a pulsating high-frequency voltage component is used for position tracking and a second rotating signal-injection is dedicated to online estimating the incremental saliency ratio. A trajectory of constant incremental saliency ratio is used for torque regulation, resulting in stable control at all operating conditions, including overload. This despite the effect of cross-saturation, which is known to introduce position error and harm the control stability progressively with the load. The proposed scheme is validated experimentally on a 1.1-kW SyR machine test bench. Alternative LUT-less torque control laws are investigated, and their stability limits put in evidence using convergence analysis and experiments. [ABSTRACT FROM AUTHOR]

Multiphysics analysis and experimental validation of acoustic noise reduction in a high pole count, high power, switched reluctance machine (SRM), through skewing are explored in detail in this work. An iterative optimization strategy covering electromagnetic, structural, and thermal domains is proposed to investigate the effect of different skewing methods and angles on a 24-stator slot/16-rotor pole (24/16) SRM rated at 100 kW. The contributions of this work are twofold. First, electromagnetic impact, considering average torque, torque ripple, radial and tangential air gap forces, of symmetric and asymmetric skewing on stator and rotor is studied in this work. Second, the impact of skewing methods on acoustic noise and vibration performance is studied and presented in detail. The study reveals that skewing both the stator and rotor by the same amount has superior electromagnetic performance over other types of skewing. Multiphysics simulations conducted, predict a 10.5 dBA reduction in the acoustic noise, compared to a baseline design with no skew, for an optimized rotor-stator skewing angle of 13.75°. Finally, 100 kW prototypes of the baseline and the optimized skewed SRM were constructed and subjected to wide speed range testing. Simulation and test results closely follow each other and validate the effectiveness of the proposed skew design in mitigating acoustic noise and vibration in high pole count SRMs. [ABSTRACT FROM AUTHOR]

Performance achievable in sensorless control of electrical drives strictly depends on the adopted synchronous machine. The combination of cross-saturation and saliency, both dependent by the current load and the rotor position, makes always the position estimation afflicted by an estimation error. When the machine is highly saturated, the sensorless control can even diverge resulting in a useless drive. Thus, it is of primary importance to know in advance the convergence region of the sensorless drive, i.e., the operating points, where the motor can be successfully controlled without a position sensor. The aim of this article is to show how to compute the estimation error, the saliency, and the convergence region (hereafter called self-sensing capabilities) starting from the flux linkages maps or, more generally, from the incremental inductances. The dependence on the rotor position is also considered. Finite element simulations and experimental measurements validate the proposed model. The code used to compute the self-sensing capabilities is available as an open source package. [ABSTRACT FROM AUTHOR]

This article investigates the design methods and performance optimization of segmented-double-stator switched reluctance machine (SDS-SRM). First, two segmented U-shaped single-stator SRMs are introduced, including inner-rotor and outer-rotor constructions. In order to enhance the torque and power density, these two kinds of single-stator SRMs are combined together to constitute an SDS-SRM. Then, the relationships of torque ripple coefficient with the mechanical offset angles of the inner and outer rotor teeth are investigated to obtain the optimal rotor structure, and the corresponding conduction phase sequences for double-stator excitation mode are also analyzed. Furthermore, the flux distributions of the inner and outer stators with different coil magnetic polarities configurations are researched, and it reveals that the phase windings both on inner and outer stators with NSSNNSSN polarities have better magnetic field decoupling characteristics. To evaluate the final topology of the proposed SDS-SRM, the static magnetic characteristics and dynamic performances are presented. Finally, the SDS-SRM prototype is manufactured and tested to validate the theory and simulation analyses. [ABSTRACT FROM AUTHOR]

This article proposes an online torque ripple minimization (TRM) technique using a fuzzy system (FS)-based d-axis current design for interior permanent magnet synchronous motor (IPMSM) drives. Existing control-based TRM techniques generally employ optimization algorithms to design the dq-axis currents that attenuate the torque ripples. However, complex iterations applied for the optimization algorithms increase computational complexity, which limits the applicability of such TRM techniques under transient state of the IPMSM drives. Unlike with existing methods, the proposed TRM technique designs reference d-axis current using a computationally efficient algorithm and remarkably minimizes the torque ripples. Moreover, the reference d-axis current is designed online based on an FS to keep the stator current of the IPMSM inside the rated value, especially at the transient state. The proposed TRM strategy is validated through simulation and experimental investigations by using a MATLAB/Simulink software and a prototype IPMSM drive with TI TMS320F28335 digital signal processor. Comparative theoretical and experimental investigations prove that the proposed TRM technique is computationally efficient and ensures more reduced ripples in the electromagnetic torque and dq-axis currents with d-axis current significantly close to zero than conventional maximum torque per ampere based technique without TRM and conventional current control-based TRM technique under critical load conditions. [ABSTRACT FROM AUTHOR]

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

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

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

This article deals with an improved control for synchronous reluctance motor (SyRM)-based photovoltaic (PV) water pumping system, eliminating the speed controller of position sensorless field-oriented control (FOC) of SyRM. The solar water pump drive involves two stages of power conversion. The reference quadrature axis current of FOC is estimated from available PV array power that is being continuously tracked for maximum power point. This eliminates the requirement of an additional speed controller. This improves the transient behavior of overall control under dynamic conditions such as varying solar radiation. A pole is eliminated from overall characteristic equation of open-loop dc link voltage control transfer function. As a result, a single proportional integrator controller satisfactorily controls the whole pumping system. The system is much easier to tune, and by default, immune to aging and variation in pump's constant. This improves fidelity and reduces the overall cost of the system. Performance of this system is validated through a developed laboratory prototype of solar PV array-fed SyRM drive for water pumping. The overall system performance is examined under different environmental conditions. [ABSTRACT FROM AUTHOR]

In this article, we present a dual-stator structure-parallel fault-tolerant machine (DSSPFTM). In this machine, the radial-flux dual-stator structure with a higher density is adopted to the fault-tolerant system. For better performance in fault condition, the combination of permanent-magnet component (PMC) and reluctance component (RC) in the rotor and large-opening slot is proposed. Because of the same poles and torque-variation principle, the PMC and RC are combined. The PMC is devised to supply most of the torque in normal conditions, while the RC provides enough self-inductance for limiting current under short-circuit (SC) occasion. Most of the flux leakage is separated from the active flux and the overload ability is improved. The design process of DSSPFTM is described in steps and details. Based on the fundamental of maximum torque under normal conditions, PMC and RC are integrated together. The end flux leakage originating from the adjacency of RC to PMC and the effect of RC length on torque are analyzed. The back-EMF, torque, inductance, loss, efficiency, and SC analysis are demonstrated. The stress and deformation distribution of the rotor and the comparison with the traditional structure are conducted. A prototype DSSPFTM is designed and manufactured. The experiments accord with simulations, indicating that the DSSPFTM with fault tolerance can improve the torque density effectively. [ABSTRACT FROM AUTHOR]

Interturn short-circuit fault, also known as turn fault, is a common fault in electric machines, which can cause severe damages if no prompt detection and mitigation are conducted. This article proposes a turn fault detection method for permanent magnet machines based on current residual. After the impact of the turn fault is first analyzed on a simplified mathematical machine model to assess the fault signature, a finite-element model is developed to obtain healthy machine behavior. The residual between the measured and estimated currents by the model with the same applied voltages contains mainly the fault features. The quality of the fault detection can be improved because the fault signatures are enhanced, and the impact of the current controller bandwidth on fault signature is minimized. The dc components in the negative-sequence current residuals are extracted through angular integration, and their magnitude is defined as the fault indicator. The robustness of the fault detection against transient states is achieved. The effectiveness of the proposed method is validated on a triple redundant fault-tolerant permanent-magnet-assisted synchronous reluctance machine. [ABSTRACT FROM AUTHOR]

Solid-rotor switched reluctance machines (SRM), having the rotor machined from a single piece of metal, are one of the few viable options for motoring and/or generation under harsh operating conditions, including high speeds, high shaft temperature, and corrosive environment. Apart from double saliency and high degree of magnetic saturation as in any SRM, significant core losses due to high eddy currents, even under static conditions, make the characterization and modeling of solid-rotor SRM challenging. The objective of this article is to understand the magnetic characteristics of a solid-rotor SRM through extensive experimental studies and to develop a stator-side model for the machine which adequately captures its magnetic behavior. First, the flux-linkage characteristics of the solid-rotor SRM under test are measured over a wide range of excitation conditions and rotor positions. Applying a computationally efficient decomposition technique on each set of experimental data, the measured winding current is resolved into magnetizing and core-loss components to obtain a stator-side model of the machine. The proposed model is useful to predict the winding current and core-loss under different excitation conditions, which is necessary for simulation and performance prediction. The proposed method is more accurate than the existing methods, while being simple and fast to implement. [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 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]

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

This paper presents a PM pole with varied width in the axial direction for vibration mitigation in permanent magnet brush dc motors, which is proposed to decrease the deformation caused by radial pulsating force and bending moment together. First, the air gap flux density distribution and radial force density distribution are derived in detail. After two types of vibration modes and their reasons as pulsating force and bending moment are analyzed, the difficulty in vibration mitigation is pointed out. By investigating the change rule of the pulsating force and bending moment with PM pole width, a type of PM pole with varied width in the axial direction is proposed. Its principle of deformation reduction is presented, and the optimized pole shape is derived. A three-dimensional finite-element method is used to calculate the magnetic field, Maxwell force, modal analysis, and deformation of motors. In order to verify the effectiveness of the proposed method, the vibration of the proposed motor is compared with the other three types of traditional motors, including skewing slot or skewing pole. Finally, experimental results of two types of motors are compared to validate the proposed technique. [ABSTRACT FROM AUTHOR]

This paper investigates a novel three-phase doubly salient permanent magnet (DSPM) motor. Because of the adoption of Π-shaped stator iron core segments, the asymmetrical magnetic circuit among different phases occurring in conventional DSPM motors with E-shaped stator iron core segments can be avoided, so that balanced and sinusoidal three-phase PM flux linkage and no-load electromotive force (EMF) can be achieved. First, based on a 12/7 stator/rotor pole combination, the operation principle of Π-core DSPM motor is discussed using the least magnetic reluctance principle. Then, the general airgap field modulation theory is extended to the Π-core DSPM motor for explaining its operation principle further and armature winding connection. The finite element analysis is used to validate theoretical analysis, as well as to calculate its electromagnetic performances. The results show that the 12/7-pole Π-core DSPM motor possesses higher average torque output capability and lower torque ripple compared with the 12/8-pole E-core counterpart. Finally, a 12/7-pole Π-core DSPM motor is built and tested so as to experimentally verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

With the advantages of good driving performance, high fuel economy, and low emission, the series-parallel hybrid electric vehicles (HEVs) are widely developed. Power-split device, which is a kernel part of HEV, can be based on planetary gear or compound-structure machine (CSM). A transverse-flux brushless double-rotor machine (TF-BDRM), which can form a CSM by being connected with a traditional permanent-magnet synchronous machine (PMSM), is investigated in this paper. The equivalent magnetic circuits are established, and the equivalent reluctances, and d- and q-axis armature-reaction reactance are deducted. It is found that the armature-reaction reactances are in direct proportion to pole-pair number. The reluctances of stator core, inner, and outer air gaps, transverse-flux (TF) tooth and leakage reluctance are analyzed, and it is found that the improvement of reluctances may affect other performances of the machine. Flux-concentration structure is investigated to increase the main flux of the machine. Flux-concentration factor ξFC is used to illustrate the effect of flux-concentration structure, which can be increased by the increase of the radial and circumferential thickness of permanent-magnet. The flux-density distributions of two typical situations are simulated, and the flux-density distribution laws in inner and outer air gaps are given. With manufacturing technology investigated, the TF-BDRM prototype is made, and experiments are carried out. The tested waveforms of the back electromotive force are approximately sinusoidal, and the tested torque ripple is obvious [ABSTRACT FROM AUTHOR]

The design of a novel low-noise high-force linear motor for precision positioning applications, such as in semiconductor lithography, is presented in this paper. New magnetic designs achieve low noise and vibration by reducing high spatial-frequency magnetic field components, which cause harmonic vibrations of a moving stage. To reduce such force harmonic content, our new motor has fine teeth, narrow slots with high slot aspect ratio, five phases, and a moving skewed Halbach magnet array. As compared with a commercially available iron-core motor, in our new design, the acoustic noise level in Pascals is reduced by more than 90%, corresponding to a 20 dB reduction in sound pressure level, even with a nonskewed magnet array. Using a skewed magnet array, the cogging-driven and velocity-dependent noise is further reduced by 90% in Pascals. This new linear motor simultaneously is capable of very high shear force densities in order to support high-acceleration motions, and thus provides new options for high-performance and quiet linear motion devices. [ABSTRACT FROM AUTHOR]

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

This paper proposes a new method for fast radial vibration computation in switched reluctance motors. Only a piecewise first-order linear function is used to calculate the total peak acceleration, which is rather fast. The overall radial vibration is the superposition of natural oscillation of each mode. Before that, several critical parameters need to be calculated or measured in advance, including weight factor, natural frequency and damping ratio of each mode, in order to obtain the respective analytical expression of natural oscillation of each mode. First, the total peak acceleration concerning the multiple of current and its slope is derived analytically from the perspective of abrupt change of radial force. Then, a simple method for calculating weight factors is presented for the distribution of peak acceleration of each mode from the total peak acceleration. Natural frequencies are measured and compared by three methods, including finite-element analysis, hammer impulse test, and dc pulse excitation. The calculation of damping ratio is improved since the traditional damping ratio calculation method cannot be used in a multiple degree-of-freedom system. Finally, both simulation and experiments are conducted to verify the effectiveness and accuracy of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper explores the leakage inductance of a single-tooth wound synchronous reluctance motor and its influence on motor performance. It is shown that the stator leakage inductance heavily influences the true saliency ratio in synchronous reluctance motors and a large stator leakage inductance has a serious detrimental impact on the operating power factor. It is also shown through analytical and finite element analysis analysis that synchronous reluctance motors with single-tooth windings suffer an inherent high stator leakage inductance that is dominated the air-gap harmonic leakage component, derived from the significant stator MMF harmonics experienced with this winding type. This explains for the first time the experimental results showing a low operating power factor compared to a distributed wound machine. Measurement of the stator leakage inductance is attempted on a prototyped machine and the standardized method is found to be lacking when single-tooth windings are employed. [ABSTRACT FROM PUBLISHER]

A novel maximum torque per ampere (MTPA) method based on power perturbation for a field-oriented control interior permanent magnet synchronous motor (IPMSM) drive system is proposed in this study. The proposed MTPA method, which is parameter independent and can improve the motor operation at both start-up and low speed, is designed based on the power perturbation by using the signal injection in the current angle. Moreover, the influence of current and voltage harmonics to the MTPA control can be eliminated effectively. Furthermore, to enhance the robustness of the control system, an online tuning scheme for an integral-proportional controller using a new wavelet fuzzy neural network with disturbance torque feedforward control is developed where the disturbance torque is obtained from an improved disturbance torque observer. Finally, some experimental results using an IPMSM drive system based on a low-price digital signal processor are presented. From the experimental results, the proposed control approach can guarantee the control performance of the speed loop, even under a cyclic fluctuating load. [ABSTRACT FROM PUBLISHER]

In order to improve the performances of switched reluctance machines (SRMs), such as torque production and power density, combining segmented structure and hybrid-excitation is a proper and useful method. This paper develops a kind of segmented-stator hybrid-excitation SRMs (SS-HESRMs) assisted with permanent magnets (PMs) and investigates on them with different rotor pole numbers. To evaluate the effects of different rotor topologies, the static magnetic characteristics and dynamic performances of two SS-HESRMs with 12/10 and 12/8 poles are briefly presented. Moreover, both SS-HESRMs are compared with two segmented-stator SRMs (SS-SRMs) which have the same basic structure and stator/rotor pole combinations but without PMs. The results reveal that SS-HESRMs produce higher electromagnetic torque than SS-SRMs with the same stator/rotor pole configuration. The 12/10 SS-HESRM exhibits better characteristics, such as higher dynamic average torque, lower torque ripple, and higher power/torque density, than the 12/8 SS-HESRM at low-speed operation. While at high speed, the 12/8 SS-HESRM exhibits better characteristics than 12/10 SS-HESRM. The 12/10 SS-HESRM has stronger starting capability but lower steady-state speed under the same starting condition. Finally, a 12/10 SS-HESRM and a 12/8 SS-HESRM with the same structure and size are prototyped and tested to confirm the predictions. [ABSTRACT FROM PUBLISHER]

The high-frequency signals normally used for sensorless operations in anisotropic permanent-magnet synchronous motors cause unwanted torque ripple, noise, and vibrations. The target of the present research is to extend downwards the speed range in which the sensorless drive can work without any signal injection. Specifically, this paper proposes a new back-electromotive force observer that eliminates the instability that may arise in conventional observers when the motor drive operates in generating mode. Two different versions of the observer are proposed and discussed, to include motors with high harmonic content in the back-electromotive force. The detailed mathematical analysis of the proposed observer is supported by simulations and the practical feasibility is proven through experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of the axial electromagnetic force and vibroacoustic behavior of the external-rotor axial-flux motors. First, the spatial and temporal characteristics of axial force acting on the surface of magnets are derived analytically and validated through the 2-D Fourier decomposition. Subsequently, a multiphysics model is established to calculate the vibration and noise of an external-rotor axial-flux in-wheel motor, which integrates the control model, the electromagnetic model, the structural model, and the acoustic radiation model and takes the uneven distribution of axial force into account. The accuracy of the multiphysics model is verified by the noise test. The vibroacoustic mechanism of axial-flux motors is revealed based on the multiphysics model, the influence of current harmonics and dead time effect on the vibration and noise are also analyzed. Finally, the main orders of tested noise are explained by the theoretical analysis. It is found that the zeroth spatial order axial force is dominant for the generation of the vibration and noise in axial-flux motors. The harmonic current may deteriorate the vibroacoustic behavior, but depending on its amplitude and phase. This study provides guidance for the design of low-noise axial-flux motors. [ABSTRACT FROM PUBLISHER]

This paper presents an analytical model of the electromagnetic vibration and noise for an external-rotor axial-flux in-wheel motor (AFWM). First, the air-gap flux density is calculated and the influence of edging effect is taken into account through a radial correction function. On this basis, the electromagnetic force acting on the surface of the magnets is obtained. Then, the modal parameters and shapes are calculated and the surface displacement of the AFWM is obtained via a modal superposition method. Finally, sound radiation efficiency is explored to predict the electromagnetic noise. The analytical model is validated through simulation and experiment, respectively. It turns out that the analytical model can predict the electromagnetic vibration and noise of the AFWM quickly and effectively over a wide speed range, which is of great significance for the design of low-noise axial-flux motors. [ABSTRACT FROM PUBLISHER]

A concept of general flux-modulated electric machines is introduced in this paper, which is based on a proposed unified theory for such types of machines. It can explain the operating principles of a basic flux-modulated motor, a flux-switching motor, a vernier motor, and a dual-permanent-magnet (PM)-excited motor with PMs on both rotor and stator. Based on the proposed theory, a novel doubly-fed dual-stator (DFDS) motor is presented. Finite-element method of magnetic field with mechanical motion coupled computation is employed to evaluate the performances of the machines. Its design method using an optimization algorithm is also presented. Experiment results of a prototype are presented to showcase the performance of the proposed novel DFDS motor. [ABSTRACT FROM AUTHOR]

This paper presents a 12/8-pole, three-phase, modular-stator hybrid excitation switched reluctance machine (MSHSRM) assisted with permanent magnets (PMs) as well as its design consideration and performance evaluation. The basic operating principle is illustrated through a specific form of this machine, and the magnetic equivalent circuit model is built and analyzed. Then, the main parameters of the machine are optimized by the finite-element method. The static magnetic characteristics and dynamic performance of this novel machine are simulated and compared with other two SRMs, one is segmented 12/8 SRM without PM, and the other is the conventional 12/8 SRM with unsegmented structure. Finally, two motor prototypes, including one MSHSRM and one conventional SRM of the same size are manufactured. The static magnetic characteristic and dynamic operation of two motor drives are measured to confirm the predictions. The simulation and experimental results indicate that this MSHSRM has higher power and stronger load capacities than the conventional SRM in whole speed range with higher torque/power density and higher torque per ampere. [ABSTRACT FROM AUTHOR]

A switched reluctance motor (SRM) with 12/10 poles is investigated in this paper. Compared with the conventional SRMs with single mode, the machine is not only able to be worked as a six-phase motor but also could be used as a three-phase motor, which is thus named multimode SRM (MMSRM). The primary dimensions of the stator and rotor cores are calculated by considering it as a six-phase SRM with long magnetic paths, and the performances of three-phase mode with short magnetic paths are used to test the parameters. The arcs of stator and rotor pole are treated as the optimization objects to minimize torque ripple and copper loss per torque and maximize torque per ampere of the MMSRM. A function is selected to solve the multiobjective problem and the final values of arcs of stator and rotor pole are determined based on the results of finite-element method. The effects of arcs of stator and rotor pole on electromagnetic performances of MMSRM are discussed independently, and a prototype is manufactured to test the simulations. A good agreement between the simulated and measured results verifies the validity of the analytical method and results. [ABSTRACT FROM AUTHOR]

This paper presents a new simplified finite-control-set model predictive control strategy for synchronous reluctance motors operating in the entire speed range. It is a predictive control scheme that regulates the stator flux and the load angle of the synchronous reluctance motor, incorporating the ability to operate the drive in the field-weakening region and respecting the motor voltage and current limits as well as the load angle limitation needed to operate this type of motor in the maximum torque per voltage region. The proposed control strategy possesses some attractive features, such as no need for controller calibration, no weighting factors in the cost function, good robustness against parameter mismatch, and smaller computational cost compared to more traditional finite-control-set model predictive control algorithms.

Simulation and experimental results obtained using a high-efficiency synchronous reluctance motor demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

This paper proposes a brushless double mechanical port flux-switching permanent-magnet motor for potential application in hybrid electric vehicles. To realize the design objectives of high-torque capability, low-torque ripple, and low-magnetic coupling between the inner and outer motors, a new multilevel design optimization method is proposed to conduct a multiobjectives optimization. First, by adopting the comprehensive sensitivity approach, the whole optimization design process is divided into three levels: nonsensitive level, mild-sensitive level, and strong-sensitive level. Then, to improve the whole design efficiency, the response surface method and multiobjective genetic algorithm are applied in the mild-sensitive level and strong-sensitive level, respectively. Based on the proposed design method, a compromise design among the three design objectives is considered and realized. Finally, a prototype motor is built to verify the validity of the proposed design method and motor operation. [ABSTRACT FROM PUBLISHER]

In order to take advantage of conventional switched reluctance motors (SRMs), the SRM is integrated with the bearingless motor technology and then a reluctance type of bearingless motor is created, named as bearingless SRM (BSRMs). Not only electromagnetic torque but also the levitation forces should be controlled in BSRMs, which is different from SRMs. The levitation forces should always exist even when winding fault occurs. Therefore, the absent levitation forces that ought to be produced by the fault winding should then be compensated by other winding. This paper proposes the compensation strategy of levitation forces for BSRMs when one stator winding is short circuited. The short-circuit fault is investigated and the short-circuit current is expressed for the derivation of radial forces. Then, the winding compensation rule and the mathematical model of levitation forces are developed to facilitate the compensation control for the motor levitation. After that, the proposed compensation strategy is verified by simulation results in MATLAB/Simulink. Experimental results are also presented to demonstrate the performance. [ABSTRACT FROM PUBLISHER]

An improved model-free predictive current control (IMFPCC) method for synchronous reluctance motor (SynRM) drives is presented in this paper. The main advantages of previous MFPCC are that it does not require specific SynRM models and it requires neither motor parameters nor back-EMF estimations. However, this approach has two disadvantages: 1) two current measurements are required in each sampling period, which may lead to the detection of undesirable current spikes caused by instantaneous switching inside the inverter, and 2) an unresolved problem of stagnant current-variation updates, which undermines the prediction performance. This paper intends to eliminate these two drawbacks while retaining all the merits of MFPCC. The proposed IMFPCC is simple and easy to realize. Furthermore, no pulsewidth modulation (PWM) technique is required. A 32-bit microprocessor, TMS320F2809, is utilized to implement both the proposed IMFPCC and the model-based predictive current control (MBPCC) for a performance comparison. Experiment results are provided to validate the proposed method and verify its feasibility. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel maximum-force-per-ampere strategy for the current distribution of planar switched reluctance motors (PSRMs) for efficiency improvement. This strategy is the first of its kind for planar motors, and it is used to generate the desired thrust force with the minimum sum of squares of the three-phase current. To formulate this strategy, a constrained optimization problem with time-varying parameters is first developed. Then, the problem is transformed into an unconstrained problem with a barrier function. Additionally, a self-designed adaptive genetic algorithm is introduced to solve the unconstrained optimization problem for locating the optimal currents. Comparative studies of the proposed and conventional strategies for a PSRM system are carried out via simulation and experiment, and planar trajectory tracking for the system with the proposed strategy is experimentally performed. The validity of the proposed strategy is also verified. [ABSTRACT FROM PUBLISHER]

Motor current signature analysis (MCSA) based on the 50/60-Hz sidebands has become a common test in industry for monitoring the condition of the induction motor rotor cage. However, many cases of unnecessary motor inspection or outage due to false alarms produced by rotor axial duct interference have been reported. If the number of axial ducts and poles is identical, this can produce 50/60-Hz sideband frequency components in MCSA that overlap with that of rotor faults, resulting in false alarms. However, there currently is no practical test method available for distinguishing rotor faults and false indications other than testing the rotor offline or under the startup transient. In this paper, the feasibility of using the rotor fault frequency component produced by the space harmonic waves is evaluated as a solution for the first time. Since the fifth or seventh space harmonics have a spatial distribution of flux that does not penetrate in the rotor yoke to reach the axial ducts, they do not produce false alarms. The proposed method is verified on 6.6-kV motors misdiagnosed with broken bars via the 50/60-Hz sidebands of MCSA. It is shown that it provides reliable online indication of rotor faults independent of axial duct influence and can be used for screening out false alarms. [ABSTRACT FROM PUBLISHER]

The design of multipolar ferrite-assisted synchronous reluctance (FASR) machines is formalized via a two-step procedure. At first, one rectified machine pole is analyzed, and key figures of merit are expressed in equations to derive general guidelines for high-performance designs. Then, rotating machines are modeled as the combination of multiple rectified poles within a stack cylinder having constrained outer dimensions. It is demonstrated that, at a given output torque, the number of poles can be optimized to minimize either the Joule loss or the magnet remanence. The design approach is both finite-element analysis and experimental testing on an FASR machine, rated 795 \N\cdot \m at 168 r/min. It has been prototyped to compete with a previous solution based on rare-earth magnets, which shows similar performance. [ABSTRACT FROM PUBLISHER]

In order to solve the coupling problem between torque and suspending force control in the conventional bearingless switched reluctance motor (SRM), this paper presents a novel bearingless SRM with a biased permanent magnet (PM). Different from the conventional bearingless SRM, the proposed bearingless SRM consists of two motors, in which each motor has two radial control degrees of freedom. In order to realize decoupling control, torque flux is completely independent from radial force flux. When the rotor center is eccentric, suspending force is generated by the control flux from the suspending force pole and the biased flux from the PM. Therefore, in order to explain the advantages of the proposed structure, conventional structures are also compared. Furthermore, the basic design method for the proposed structure and the mathematical model for the suspending force are described. The decoupling and self-starting characteristics are deeply analyzed. The validity of the proposed structure has been verified using finite-element analysis and some experimental results. [ABSTRACT FROM PUBLISHER]

The reluctance synchronous motor (RSM) is identified to be well suited for the variable-gear (VG) electric vehicle (EV) drive. It is shown in this paper, however, that the RSM drive's position-sensorless capability is limited at zero or very small current magnitudes due to a limited saliency magnitude. In this paper, a novel epoxy–resin-casted rotor with no iron ribs is proposed to increase the saliency of the RSM at zero reference current. This rotor RSM is simulated in finite-element (FE) analysis, built, evaluated, and compared with conventional flux barrier rotor RSMs. The effect of rotor skewing on the position-sensorless control (PSC) capability of the RSM is also evaluated by means of FE analysis and measurements. Other performance aspects are also considered in this paper. It is concluded that, overall, the skewed epoxy–resin-casted rotor RSM drive has no PSC problems in the entire load and speed regions and is well suited for VG EV drives. [ABSTRACT FROM PUBLISHER]

This paper presents the numerical modeling of a classical switched reluctance motor (SRM) and a mutually coupled SRM (MCSRM); both have three phases with 12 slots and 8 poles. The multiphysics models have been developed, which can take into account the electromagnetic characteristics, mechanical vibration, and acoustic noise of the foregoing machines. A 2-D electromagnetic model has been used to calculate the magnetic force which is the main source of vibration of the entire motor system. The vibration of the motor is calculated by a mode superposition method, while the acoustic noise is predicted by a 3-D finite-element acoustic model. In order to validate the numerical models, experiments have been carried out. A good agreement between measured and numerical results has been observed, and it is found that the vibration and the noise levels of MCSRM are considerably lower than those of classical SRM. [ABSTRACT FROM PUBLISHER]