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

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]

Robustness, simple construction, and low cost are some of the advantages of switched reluctance machines (SRMs). These are all desirable characteristics of an electric motor, especially in the automotive sector, where high-temperature and high-speed operation, and low cost are always in demand. However, the acoustic noise generation by conventionally controlled SRMs can prevent its use in applications where acoustic comfort is required. Acoustic noise is radiated by the stator frame when a vibration mode is excited by the respective spatial order at a forcing frequency that is close to the stator's modal natural frequency. The excitation surface wave is the radial force density waveform, which is a function of time and spatial position. In this paper, a phase radial force shaping method is proposed by using harmonic content analysis. A generic function for the radial force shape is identified, whose parameters are calculated by an optimization algorithm to minimize the torque ripple for a given average torque. From the phase radial force profile, a current reference is obtained. The proposed methodology is experimentally validated with a four-phase 8/6 SRM through acoustic noise measurements at different speed and load conditions. [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]

Magnetic saturation characteristics of synchronous reluctance motors (SyRMs), with or without permanent magnets, are highly nonlinear. These nonlinear effects can be included in the current controller by changing its state variable from the stator current to the stator flux linkage using the known saturation characteristics. A direct discrete-time variant of the flux-linkage-based current controller is developed in a state-space framework. If the magnetics are modeled to be linear, the proposed control structure reduces to the standard current controller in this special case. Experimental results on a 6.7-kW SyRM drive demonstrate that the proposed flux-linkage-based controller enables a higher closed-loop bandwidth and is more robust against parameter errors, as compared to the standard current controller. [ABSTRACT FROM AUTHOR]

Vibration and acoustic noise are considered as major factors preventing the widespread use of switched reluctance motor (SRM) drives in industrial and commercial applications. In this paper, a new active vibration cancellation strategy for radial vibration is proposed based on the optimal current switching instants. The mechanical impulse response method has been used to estimate the radial vibration of the stator and an optimization routine was developed to define the optimal instants for phase current switching in such a way that the resulting vibration would cancel the vibration caused by prior switching. Experimental verification was conducted on an 8/6 SRM and the results show significant reduction in the stator radial vibration which in turn contributes to reduction of acoustic noise. [ABSTRACT FROM AUTHOR]

Phase inductance is a key parameter in the design of switched reluctance machines (SRMs) because the torque, torque ripple, losses, and the dynamics of phase voltages and currents are related to the phase inductance. Therefore, accurate calculation of the inductance profile of an SRM is important in determining the SRM behavior. Instead of using the time-consuming finite element analyses (FEAs), or the analytical methods that require prior knowledge of flux linkage from either an FEA simulation or an experimental test such as the curve fitting and flux path based methods, this paper proposes a fast and accurate analytical approach to determine the phase inductance of an SRM with any common topologies, dimensions, and phase currents at any rotor position. In the proposed approach, the magnetic field distribution and the permeance parameters in the air region are first determined by solving the partial differential equations of magnetic potentials based on Maxwell's equations. The air-region permeance parameters are then substituted into a magnetic circuit network to include the impact of the saturation effects of steel on the phase inductance profile. The agreement between the results of the proposed analytical method and two/three-dimensional FEAs and experimental results validates the analysis. [ABSTRACT FROM AUTHOR]

A sensorless control strategy with one-phase lacking fault-tolerant capability is proposed in this paper for the switched reluctance motors (SRM). This strategy consists of a phase inductance slope zero-crossing detection scheme and a series of phase inductance partition logic algorithms, which is capable of capturing at least one-phase aligned position under both normal operation and one-phase lacking fault operation. With the recorded index position in each electric period, the rotor position can be estimated for sensorless driving accordingly. To ensure stable calculation of the phase inductance in this method, the SRM should be started and operated under single pulse control mode. Thus, for sensorless starting, an idle phase inductance double thresholds based sensorless synthetic starting scheme is also developed. The proposed strategy is easy for implementation and can ensure stable sensorless operation in full speed range. Moreover, it does not need any prior measuring process, complicated logic algorithm, or complex mathematical calculation. The theoretical analysis is conducted, and experimental results are provided to verify the feasibility of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper presents the comparative analysis of the characteristic features of two 4/2 switched reluctance motors (SRMs) designed for a very high-speed drive. The use of two-phase construction of SRM with irregular air-step gap makes it possible to achieve the required parameters of the drive. The analysis presents the comparison of two distinct structures designed for the same very high-speed drive. In this paper, a novel mathematical model that takes into account the nonlinearity of the magnetic circuit is presented. The results of numerical calculations and laboratory tests of the influence of the possible use of an anisotropic magnetic material in the rotor magnetic circuit are presented. The influence of control parameters on the motor properties is specified. Both the structures were compared with the respect to employed electric parameters. It is important for high-speed structures that a maximal speed of the motor should not affect permissible parameters of the rotor in a negative way. The high-speed structures should be properly designed to ensure a safety margin. The selected laboratory test results that show electric parameters are presented following the specification of the first critical speed based on the Campbell diagram, the maximum speed limited by allowable stresses. It was shown that both the structures analyzed fulfill the condition of a safety margin. A number of thermal problems of the structures analyzed are discussed. The design assumptions related to the possibility of using a higher current density in the motor windings were verified under laboratory conditions. [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]

A hybrid field model (HFM) based on the combination of magnetic equivalent circuit (MEC) and exact conformal mapping (ECM) is developed to calculate the open-circuit field of interior permanent-magnet (IPM) motor. In the proposed HFM, the IPM and iron saturations are transformed into equivalent current on the rotor surface and stator bore. ECM can calculate the air-gap field analytically using the equivalent current. Once the air-gap field is obtained, the MEC in the iron region can be solved and gives the new value of equivalent current, which forms a calculation loop. Hence, iterative solving process is required to determine the equivalent current and iron permeability in the rotor and stator. In order to verify the proposed model, both finite-element (FE) analysis and experiment are performed on IPM motors with V-type rotor and conventional “-” type rotor. Their results demonstrate the high accuracy of HFM. [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]

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

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]

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

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

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

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

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 an optimized design in the permanent magnet-assisted synchronous reluctance motor (PMa-SynRM) rotor structure design with hybrid adopted materials for enhancing the motor characteristics and operation. Two types of permanent magnet (PM) materials are embraced in the PMa-SynRM rotor of rare-earth and ferrite PMs. The optimized design for the PMa-SynRM rotor structure considers the motor magnetic equivalent circuit for reducing the reluctance of the hybrid PMs to improve the motor performance. Moreover, the irreversible demagnetization of the ferrite PM which occurs due to the reversing of the magnetic field of the rare-earth PM is presented. The analytical rotating losses computation with the hybrid adopted materials at the design process is introduced. The rotating losses of the PMa-SynRM are investigated as core, magnet, proximity, ohmic, and friction losses. The core loss in the PMa-SynRM occurs due to the altering of the flux densities in numerous fragments of the iron structures. The loss measurements can be accomplished by measuring the electric parameters of the PMa-SynRM at a defined operating point. The magnetic modeling of the improved 6 KW PMa-SynRM manufactured prototype structure is derived and rotational losses are computed, validated, and compared with the finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

Magnetic equivalent circuit (MEC) modeling is a challenging work to machines with novel structures, although it is an effective tool in the design process. The parameterized dynamic MEC modeling method is developed in this paper for the analysis of a novel rotor-segmented axial-field switched reluctance machine (RS-AFSRM). The “parameterization” is the feature leading the general MEC models in each interval of the rotor position, and the “dynamic” characteristic depends on the change of the flux patterns in the air region with the rotor displacement. By the proposed MEC model, the RS-AFSRM is analyzed on the smooth transition with efficient computation. The results obtained through the developed MEC models are verified by both the static and motion-coupled analyses. [ABSTRACT FROM AUTHOR]

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

The stator vibrations of a bearingless synchronous reluctance motor are investigated with simulations. The influence of the Maxwell stress tensor and magnetostriction on the stator vibrations is studied at different operational conditions. An energy-based magnetomechanical model of iron core is implemented and the influence of the magnetostriction in the iron core on the stator vibrations is further investigated and compared with the case where the magnetostriction is not modeled. The objective of the research is to find out how the stator vibrations can be used to detect the off-center rotor position. The results show that a single frequency component is not able to assess this phenomenon but a combination of two components makes it possible. [ABSTRACT FROM AUTHOR]

This study presents the design of a robust five-phase ferrite (Fe) permanent-magnet-assisted synchronous reluctance motor (PMaSynRM) to mitigate two major design challenges: irreversible demagnetization and mechanical deformation. Recently, rare-earth magnet-based five-phase PMaSynRMs have been proposed for vehicular applications due to their better fault tolerance, higher torque density, and low torque ripple compared to their three-phase counterparts. However, rare-earth magnets are expensive and, their supplies were disrupted multiple times in past few years. Therefore, to avoid rare-earth magnets in traction motors, this study proposes a five-phase PMaSynRM with Fe magnet. Special attention is paid to avoid irreversible demagnetization and deformation as these are two major concerns in any Fe-based machine. The rotor structure is uniquely optimized with additional geometrical parameters to reduce the risk of irreversible demagnetization. To increase the structural stability of the rotor, optimal center post and weight reduction notches are adopted. The proposed Fe-based five-phase PMaSynRM has been comparatively studied over a rare-earth magnet-based PMaSynRM. The lumped parameter model and finite element model have been utilized for design optimization and performance analysis. Finally, A 3 kW prototype of the proposed five-phase Fe PMaSynRM has been fabricated, experimentally tested, and compared with the benchmark rare-earth PMaSynRM to validate the proposed design and simulations results. [ABSTRACT FROM AUTHOR]

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

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

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

Vibration and acoustic noise in switched reluctance motor (SRM) drives have been investigated and addressed frequently. However, the focus of most the paper is on vibration of the stator frame due to radial electromagnetic forces acting on the stator teeth. In this paper, a comprehensive vibration analysis for a SRM assembly using finite element (FE) method is conducted, which considers the stator and rotor vibrations due to radial electromagnetic force as well as the effect of mechanical coupling on the vibration between the stator and rotor. First, an experimental modal test was performed to extract modal parameters and to observe the coupling effect. The parameters were then used to adjust and validate the FE model that was used to obtain transfer functions for vibration characterization. Using the frequency domain representation of the radial magnetic force vector and the calculated transfer functions, radial and tangential vibration components have been predicted. [ABSTRACT FROM AUTHOR]

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

Flux-linkage based sensorless control method is well-known and has been widely used in the control of electrical machines. The closed-loop flux observer (CLFO), which is the adaptive combination of the machine voltage and current models, is commonly adopted. It can cover a wide speed operation range and was considered to be able to solve the dc drift and initial value problem associated to the pure integrator used in the observer. However, it is reported in this paper that this popular CLFO cannot always work as expected. In some situations, dc-offsets cannot be removed by this flux observer, causing large system oscillation at fundamental frequency and is very harmful to the drive system. This important issue has not been reported and discussed in the existing literatures of the CLFO. In this paper, this phenomenon is experimentally illustrated and solution to damp this harmful oscillation is proposed and verified experimentally on a synchronous reluctance machine drive system. [ABSTRACT FROM AUTHOR]

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

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

Switched reluctance machines (SRMs) are witnessing increased interests and applications in the industry and scientific communities thanks to the advantages of rigid structures, high reliability and robustness, the absence of permanent magnets, fast dynamic response, and low manufacturing cost. SRMs have become a feasible and popular alternative to conventional electric machines, such as induction machines and permanent magnet machines, with variable speed drives in many applications. Since improving the electromagnetic and thermal performances of an SRM at the design stage is of significant value, this paper presents an in-depth literature review on the status and potential trends of the technology pertinent to the design and optimization of SRMs in the following aspects: the mathematical modeling of the electromagnetic and thermal fields in SRMs, the enhancement of the performances in terms of the torque ripple, acoustic noise, efficiency, and torque density, and the multiobjective design optimization incorporating all the above factors. Finally, the presence of SRMs and their design considerations for specific applications in electric vehicles, aircraft and aerospace systems, wind generators, high speed, and energy storage systems are extensively discussed in this paper. The existing approaches advancing the SRM technologies are systematically and comprehensively summarized and compared for each category. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

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

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

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

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

In this paper, an outer rotor interior permanent magnet synchronous machine (IPMSM) with hybrid permanent magnet (PM) material is proposed. The key is to adopt the outer rotor structure with two-layer crescent barriers and hybrid PM material to maximize the output torque and reduce the usage of high-cost rare-earth PM. The ferrite PMs are filled in the middle of the crescent barriers with thicker thickness, while the rare-earth PMs are filled into the bilateral of the crescent barriers with thinner thickness. To verify the effectiveness of the proposed rotor structure, optimizations are first carried out among the conventional rotor structures with single kind of PM material and the proposed rotor structure with hybrid PMs. Then, detailed comparisons have been investigated. Results indicate that the proposed machine has higher torque density than the machine with only ferrite PM and can reduce almost half the usage of rare-earth PM in comparison to the machine with only rare-earth PM. Moreover, the proposed rotor structure is further optimized considering productivity. [ABSTRACT FROM AUTHOR]

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

Permanent magnet (PM) motors adopt interior V-type PMs and fractional-slot concentrated winding for improving the torque density and efficiency. However, the no-load magnetic coefficient will be increased, which would reduce the utilization rate of the PM. The structure parameters of the rotor should be designed reasonably, especially the bridge. This paper calculates the no-load leakage coefficient by establishing the analytical model of the no-load magnetic coefficient. It shows that, the bridge size has an important effect on the no-load magnetic coefficient. The analysis results are verified by the two-dimensional finite element analysis and tests. [ABSTRACT FROM AUTHOR]

This paper is a study on the application position of skew in order to reduce the cogging torque of a magnetic geared synchronous motor (MGM). The cogging torque affects the noise and vibration of the motor, so it should be reduced as much as possible. To solve this problem, a conventional permanent magnet (PM) synchronous motor is skewed to a PM. However, unlike other synchronous motors, the MGM has pole pieces (PPs), and a larger cogging torque is generated due to a larger reluctance difference. There have been few studies on the reduction of cogging torque of MGM, so it is essential to study the skew structure of MGM. Therefore, this paper has derived the optimum skew method by comparing and analyzing three models of MGM skewed to PM, PP, and PM and PP simultaneously. [ABSTRACT FROM AUTHOR]