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In this article, a variable flux reluctance machine (VFRM) with dc field excitation and modular structure is proposed and it exhibits controllable flux, simplified manufacture, better fault tolerant capability, and potentially reduced material consumption. Its operational theory is illustrated by using flux modulation principles, and the working harmonics considering the modular structure are analyzed. Besides, the winding factors of modular VFRM are derived considering the flux gap width. The parameters are optimized by two-dimensional finite element method to maximize the back electromotive force (back-EMF) and the ratio of phase self-inductance to mutual inductance. Moreover, the electromagnetic performance including open circuit air-gap flux distributions, open circuit air-gap flux densities, flux linkage, back-EMF, inductance of armature windings, output characteristics, loss, power factor, and efficiency-map are compared for 12s10r and 12s14r nonmodular and modular VFRM. Additionally, the fault including short circuit and open circuit fault are analyzed. Finally, a modular 12s14r VFRM prototype is manufactured and tested to validate the theoretical and finite-element analyses. [ABSTRACT FROM AUTHOR]

Finite control set model predictive torque and flux control of ac motor drives commonly selects optimum inverter switching states through a cost function with a required weighting factor. The weighting factor should be well-tuned in accordance with the motor specifications and operating points. Additionally, the control performance of the drive is degraded under the parametric uncertainties. In this article, a predictive torque and flux control method is proposed for interior permanent magnet synchronous motor drives without a cost function. As a result, the tuning of the weighting factor is avoided. Besides, an estimation scheme based on a data-driven model is adopted, which enhances the robustness of the drive against parametric uncertainties. Instead of directly using the motor parameters, the input and output data of the control system, i.e., voltage and current, are used for estimating three new coefficients employed in the predictions. The performance of an interior permanent magnet synchronous motor drive under the proposed control method is evaluated and compared with those under the conventional predictive torque control method and a recently developed predictive torque control method without a weighting factor. The results confirm the effectiveness of the proposed control method and its superiority over the other two methods. [ABSTRACT FROM AUTHOR]

Mutually coupled switched reluctance motors (MCSRMs) are alternatives in the family of reluctance machines that can overcome switched reluctance motor's (SRM's) system-level integration and control challenges by utilizing standard three-phase voltage source inverters. In this article, a novel segmented-rotor, fractional-slot, tooth-wound MCSRM with notched rotor design is presented, which has very low torque ripple compared to other machine types in the SRM family. The torque ripple is reduced to 3.6% without utilizing any current profiling techniques or torque sharing functions. The ripple minimization is achieved primarily through rotor segment shaping, which has a strong influence on stator flux densities, flux linkages, and torque harmonics. The design strategy, along with the optimization details, is presented for a 120 W, 12 slot-8 pole MCSRM. The designed MCSRM is prototyped for experimental verification and validation of the finite element analysis results and design methodology. [ABSTRACT FROM AUTHOR]

This article analyses the electromagnetic performance of dc-biased current vernier reluctance machines (DCB-VRMs) with distributed windings. Taking example of 12-stator slot machines, the coil connection and current configuration are illustrated. Moreover, the back electromotive force (EMF), torque capability, etc., are analyzed by finite-element analysis (FEA). In addition, the torque density of DCB-VRMs equipped with distributed and nonoverlapping windings are compared. The results show that some combinations of distributed winding machines present a higher torque capability thanks to the higher pole ratio. [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]

Torque smoothness is a strict requirement for synchronous reluctance motor (SynRM) industrial applications. The speed fluctuations induced by the high-frequency and low-frequency torque ripples deteriorate the drive performance. To suppress high-frequency torque ripples chronically omitted by conventional high-frequency signals injection methods at low-speed operation, this article proposes a bi-axes high-frequency signals injection (Bi-HFSI) scheme. A novel signal injection method is adopted, and the torque power spectrum can be broadened with discrete peaks effectively suppressed. In addition, aiming at decreasing low-frequency torque ripples, the Fourier iterative learning control algorithm that is effective in suppressing periodic disturbance is applied. It is combined with the Bi-HFSI scheme which mainly limits torque ripples at low frequencies including 1st, 2nd, and 6th harmonics. Theoretical analysis is presented, and the proposed method is verified by experiments on a 3-kW SynRM drive platform. [ABSTRACT FROM AUTHOR]

The use of permanent magnet-assisted synchronous reluctance motor (PMA-SynRM) is increasing due to its advantages and superiority over induction motors. The undesirable effects of the encoder measurement error on the drive systems especially during low-range speeds may cause disorder in drive performance and sometimes its instability. For the low-cost application that requires a low-resolution encoder, this problem is felt obviously. This article presents a mathematical solution in order to compensate for the instability problem of a PMA-SynRM control at low speeds based on an augmented state unscented Kalman filter (ASUKF). First, a mathematical analysis for the effect of encoder error on the speed control instability is performed, and then an augmented nonlinear dynamical model for the PMA-SynRM is derived. Using an ASUKF on the presented augmented model of the PMA-SynRM, the error of the encoder is detected and accurately estimated. Using the estimated errors and pure motor state variables, the accuracy and robustness of the control are increased and its stability is guaranteed. The experiments performed for a 0.35 kW PMA-SynRM confirm the performance validity of the proposed method. [ABSTRACT FROM AUTHOR]

To solve the coupling between torque and suspension force in the conventional bearingless switched reluctance motor (BSRM) and improve suspension performances, the novel hybrid stator type bearingless switched reluctance motor (HSTBSRM) with double-slice structures is proposed. The torque magnetic circuit is completely independent of the suspension magnetic circuit, and the natural decoupling between the torque and suspension force is achieved. First, the structure, magnetic circuits, suspension, and rotation mechanism are analyzed. The mathematical models of radial suspension forces are deduced in detail. According to the maximum radial bearing capacity, the main parameters of the suspension part are designed. Finally, the 3-D finite-element analysis is carried out to verify the magnetic circuit, suspension mechanism, and models. [ABSTRACT FROM AUTHOR]

High-speed machines exhibit the advantages of super-high-power density, high efficiency, etc. and have been gaining more research attention in recent years. This article proposes an elaborate high-speed vernier reluctance machine (HSVRM) topology. The main advantages are as follows: (1) the stator adopts the so-called half-quasi-squirrel cage winding so that one side of all conductors is short connected and the other side is powered by modular inverter, (2) dc-biased current is fed into each conductor independently so that the machine can operate with the principle of magnetic field modulation, and (3) ladder rotor is equipped to weaken the torque ripple of the machine. Obviously, the machine topology significantly resolves the shortage of overlong end length and improves the fault-tolerant ability. In this article, the basic principle and electromagnetic characteristics of the machine will be analyzed by finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

Due to the flux leakage and large detent force, the thrust force ripple of transverse-flux linear motor is relatively large, which restricts its further application. Also, the field of most existing transverse-flux machines is hard to be altered and regulated considering the permanent magnet (PM) excitation. Therefore, to suppress the force ripple and strengthen the flux regulation capability of transverse-flux machines, a novel hybrid excitation transverse-flux tubular motor with complementary structure is proposed in this article. The key is that a complementary and parallel structure is constructed in this motor, and hybrid excitation of both dc windings and small auxiliary PMs installed at opening of the slot is adopted in this motor as well. In addition, unequal teeth design of dc winding and ac winding is also employed to increase the thrust force density. Finite element calculation results verify the effectiveness of the proposed machine. [ABSTRACT FROM AUTHOR]

This article proposes a novel topology optimization method using the Gabor filter, which is widely used in the field of image processing. The proposed method is applied to the optimization of a synchronous reluctance motor; its average torque is maximized, and simultaneously, the torque ripple is minimized. It is shown that the proposed method results in a motor with thin layer-shaped flux barriers, which achieves a better torque performance in comparison with a conventional model and a motor optimized using normalized Gaussian network (NGnet). [ABSTRACT FROM AUTHOR]

This article proposes an alternative for robust control of synchronous reluctance motors using linear matrix inequalities to obtain fixed gains that ensure current and speed regulation, under parameter uncertainties and variations. The proposed design procedure is based on a polytopic model, which takes into account: i) uncertainties and variations of the mechanical and electrical parameters of the motor, ii) one step delay from digital implementation of the control law, and iii) internal model based controllers to guarantee reference tracking. Less conservative linear matrix inequalities, relying on slack variables, ensure robust pole location and certify the closed-loop stability for the entire domain of uncertain and time-varying motor parameters, based on parameter-dependent Lyapunov functions. The linear matrix inequalities ensure a fast and systematic computation of the control gains, that are also easy to be implemented, not adding computational complexity when compared, for instance, to usual strategies based on PI controllers. Experimental results for a 2.2 kW commercial motor are provided, validating the proposed procedure, and illustrating good tracking of currents and speed references, with suitable dynamic responses and reduced cross-coupling effects, when compared to sliding mode and PI controllers. [ABSTRACT FROM AUTHOR]

Electric motors used for irrigation applications contribute to a major part of worldwide energy demand. Efficiency improvement of motors used in these applications is the need of the hour. Usually, line-start (LS) induction motors are used in these applications. However, they are relatively inefficient compared to permanent magnet (PM) motors. On the other hand, PM motors have high initial cost compared to induction motors. In view of this, magnet-less machines like synchronous reluctance motors (SyRM) and PM assisted SyRM are being preferred. SyRM has poor power factor compared to induction motor and hence PM assisted SyRMs are becoming popular. In this article, a 2-pole multi-barrier LS ferrite assisted SyRM is proposed for a bore-well submersible water pump. Two-pole rotor geometry is not extensively studied for LS SyRMs. Further, the issues of ferrite magnet demagnetization for 2-pole LS applications are not explored. A separate cage is avoided by utilizing the rotor flux barriers as a cage, thereby reducing the number of ribs while housing the magnets. This improves the power factor and efficiency of proposed motor. Analytical and finite element analysis (FEA) are used for design of the proposed motor. Further, a prototype is fabricated and experimental results are presented. [ABSTRACT FROM AUTHOR]

This article proposes a comprehensive investigation method for loss calculation and temperature rise prediction in high-speed and high-power switched reluctance machines (SRMs). The losses are analyzed in details and the sequential iterative fluid-solid coupling (SIFSC) scheme is proposed for thermal analysis. In the iterative design stage of the SRM, it is important and urgent to figure out the power losses and temperature distribution in the motor, which affects the endurance of the motor operation, such as the maximum speed and highest operating temperature. A simplified finite element (FE) model of a turn and a proximity loss separation method are developed for the skin and proximity (SP) loss reduction. Then, an additional eddy current loss calculation method is developed with a simplified FE model of the winding. Additionally, the SIFSC scheme is further proposed and implemented by sequentially calculating the fluid and solid fields for airflow velocity and temperature distribution. Compared to conventional thermal calculation schemes, the proposed SIFSC scheme is faster than direct coupling methods and more accurate than thermal network methods. The accuracy and effectiveness of this scheme is verified by the simulation and experimental test for a 160 kW and 18000 r/min 6/2 SRM prototype. [ABSTRACT FROM AUTHOR]

Compared with traditional linear motors, such as Linear Permanent Magnet Motors (LPMs) and Linear Induction Motors (LIMs), Linear Flux-Switching Permanent Magnet (LFSPM) motors have the merits of high efficiency, power density, with simple and robotic secondary structure. Despite these advantages, the flux-weakening ability of LFSPM motor is limited and thus the speed range of it is not ideal. As a promising choice, it is feasible to replace the PMs of LFSPM motors with coils made with High Temperature Superconducting (HTS) tapes. By using HTS material, High Temperature Superconducting Linear Flux-Switching Motors (HTS-LFSMs) have good flux-weakening ability while inheriting the edges of LFSM motors. Since the existence of HTS coils, the cooling system has a minimum size and has to take up certain room of the motor. When it comes to applications where the volume of motor is strictly restrained, there may not be enough room for a basic pattern of typical pole pitch combinations for HTS-LFSM, such as 12-7 or 12-9, leading to large thrust ripple. To solve this problem, a method of reducing thrust force using asymmetry mover structure is proposed based on a 9-5 pole pitch ratio. The mechanism and working principle are analyzed and the validation is verified with the help of Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

Both Linear Switched Reluctance Motor (LSRM) and Linear Flux-Switching Motor (LFSM) have the merits of none-adhesive thrust force and simple and robust secondary structures. Therefore, LSRM and LFSM are quite suitable for applications such as vertical lifting, wave power generation and urban railway transit. To further improve the power density of them, the field windings of LFSM and DC windings of LSRM can be replaced with High Temperature Superconducting (HTS) coils, and thus forming High Temperature Superconducting Linear Flux-Switching Motor (HTS-LFSM) and High Temperature Superconducting Linear Switched Reluctance Motor (HTS-LSRM). Despite their similar structure, they have different working principles and electromagnetic performances. To reveal their merits and drawbacks for urban railway transit system, a comparative investigation is conducted in this paper using Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

This article proposes a novel transient 3-D lumped-parameter (LP) thermal model and a 3-D finite-element (FE) thermal model of a triple redundant nine-phase permanent magnet-assisted synchronous reluctance machine to predict the asymmetric temperature distribution under various fault conditions. First, the predicted transient and steady-state temperatures are compared between the 3-D LP and the 3-D FE thermal models under fault conditions with uneven loss distribution. Also, the temperatures predicted by the LP and FE thermal models, which account a number of practical issues are comprehensively compared with the test results under healthy and short-circuit fault conditions. The relative merits of the two thermal models are discussed. It is shown that both models have reasonable accuracy in predicting the machine's thermal behavior under fault conditions and can be chosen according to the requirements. [ABSTRACT FROM AUTHOR]

The article proposes a nonlinear state observer (NSO) for robust position-sensorless control of switched reluctance motor (SRM) drives over medium- and high-speed range. A classical reference flux-linkage method is adopted to capture a feature position of the SRM, which avoids the use of 3-D magnetic characteristics and has better universality. However, the estimation accuracy of this method would be deteriorated due to flux-linkage errors. To ease the problem, the NSO is developed to enhance the robustness against flux-linkage distortions for more accurate position and speed estimation. This observer can first reconstruct complete position information from a low-resolution feature position. The adverse impact of flux-linkage errors on position estimation is then investigated through a novel small-signal approximation and suppressed by an augmented state estimator. Afterward, a parameter design scheme is given to ensure the observer's stability and improve the capability in distortion suppression. To baseline the performance, comparative experimental validation between the proposed NSO and a widely used linear prediction method is conducted on a 12/8 SRM setup. The results show that the proposed strategy can improve the overall position-sensorless control performance in both the steady and transient states. [ABSTRACT FROM AUTHOR]

This article proposes a simplified dual-electric-port drive for a flux-modulated switched reluctance machine (SRM) with flexible charging capability for electric vehicle applications. In the driving mode, the developed flux modulation control can be achieved by directly employing the modular three-leg converter compared to the conventional open-winding topology. The zero-sequence current excitation can be flexibly controlled between the dual port and the number of power switches is also significantly reduced. The corresponding carrier-based pulsewidth modulation method and harmonic current suppression strategy are both developed to improve the machine performance. In the standstill condition, flexible battery charging can be easily achieved by the drive circuit, including both the dc and ac charging, without using any additional passive components and power devices. Then, the current distribution control scheme and power factor correction strategy are further developed for the dc and ac charging, respectively. Compared with existing drive topologies, advanced flux-modulated control and flexible energy control both can be achieved with machine performance improvement and drive cost reduction. Experiments are carried out on a three-phase 12/8 SRM prototype to verify the effectiveness of the proposed SRM drive and control strategies. [ABSTRACT FROM AUTHOR]

Acoustic noise reduction is one of the main topics of switched reluctance motor (SRM) developments. One of the effective methods is flattening three-phase radial force sum. This method is verified in experiments by optimizing the current profile. Novel current waveforms have been proposed recently for acoustic noise reduction without sacrificing the efficiency in the 18/12 SRM, which has competitive power density, torque density, peak efficiency, and outer dimensions compared with the permanent magnet motor employed in hybrid electric vehicles. In this article, electro-mechanical analysis and acoustic analysis are carried out to verify acoustic noise reduction in the 18/12 SRM. The relationship between radial force sum Frsum, torque ripple Trip, and acoustic noise is investigated. Experimental confirmation is also included. [ABSTRACT FROM AUTHOR]

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

This article compares the characteristics of a dual three-phase synchronous motor under different operating conditions such as healthy, half-control, and postfault conditions. The inductances are analyzed to confirm the interaction between two three-phase systems, and induced voltages of each phase are measured to verify the interaction behaviors. The postfault characteristics are analyzed under open-circuit faults (single-open-switch and single-open-phase faults) and short-circuit faults (single-short-switch and one-three-phase-short faults). The predicted results are validated by experimental tests. Moreover, the half-control mode is investigated as a strategy to operate with high efficiency and tolerant mode. [ABSTRACT FROM AUTHOR]

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

In this article, a novel dual-consequent-pole transverse flux motor and its analytical model are proposed. Differ from existed transverse flux machines, the proposed motor owns core-tooth-to-magnet types of the consequent-pole configuration on both stator and rotor. This unique motor configuration improves the no-load permanent magnet flux linkage interlinking with armature winding, thus leading to an enhanced torque density. The structure and working principle of the proposed motor are introduced as the first half part. Then, based on the combination of equivalent magnetic circuit method and subdomain method, an analytical modeling method is proposed to estimate the electromagnetic performance of the proposed motor. The parameters of the equivalent magnetic circuit model, e.g., the magnetomotive force and reluctances are calculated based on the subdomain model technique, considering the influence of the cores’ saturation and the axial end effect during calculation. Based on the magnetic field distribution result, the electromagnetic performance is estimated. The analytical results are verified by both the finite-element method and the prototype experiment. [ABSTRACT FROM AUTHOR]

This article presents a power converter topology with integrated driving and charging capability of switched reluctance motor (SRM) drive for electric vehicle (EV) application. In the driving mode, the bus voltage can be adjusted flexibly by the front-end buck converter, which meets the requirements of the speed open-loop and closed-loop control. Besides, higher voltage demagnetization can be achieved by connecting the upper freewheeling diodes of the asymmetric half-bridge converter to the battery bank, thus can accelerate the demagnetization process, extend the dwell angle, and enhance the output of the motor. In battery charging mode, a bridgeless rectifier converter is constructed by utilizing two-phase windings of the SRM and the existing power devices of integrated power converter, without additional inductors and charging units. The battery charging and power factor correction control can be realized by closed-loop control of charging current. Detailed analysis and experiments on a 1 kW 12/8 structure prototype SRM validate the effectiveness of the proposed technologies. [ABSTRACT FROM AUTHOR]

Series-end winding motor drive (SWMD) is a novel motor drive with both high dc voltage utilization and zero-axis current control capability, which can replace the role of open-end winding motor drive in different types of ac machines. Three-phase SWMD has advantages of wide speed range, low-cost, high-density, and is easy for multiphase expansion. However, due to the complex vector selection process, the corresponding SVPWM method is computationally complex, especially for the multiphase application. Therefore, the main aim of this article is to propose a generalized carrier-based pulse width modulation method, which serves as the foundation for multiphase expansion of SWMD. By finding a general expression between the leg voltage and the phase voltage in the synchronous rotating framework, the proposed method can generate any desired phase voltage in a multiphase SWMD, whether it is sinusoidal or nonsinusoidal. The feasibility of the proposed drive and method has been verified by three kinds of electrical machines in experiments. [ABSTRACT FROM AUTHOR]

This article presents a quasi-3-D analytical model for double-sided axial-flux permanent magnet machines (AFPMMs) with coreless structures. A simple, fast, and accurate technique is developed to calculate flux densities in different parts of the AFPMM combining the solution of Maxwell’s equations and the magnetic equivalent circuit (MEC). In this technique, Maxwell’s equations are used to generate flux sources that are used in the reluctance network of the MEC. After calculating all the reluctances and flux sources, the magnetic flux densities are obtained. This method takes into account the effects of permanent magnet (PM) reluctance, leakage flux between PM-to-PM, PM-to-rotor leakage flux at different PM edges, and the fringing flux effect. By considering these leakage fluxes as a factor called variation function in the design procedure of the machine, the analysis time is dramatically reduced compared to numerical methods while maintained high reliability. It should be noted that since considering saturation phenomenon effects in coreless AFPMM analysis does not give rise to significantly different performances, they are not included in the proposed model. Furthermore, the machine’s main features, such as the axial and tangential components of the no-load flux density in the air-gap and stator areas, as well as the back electromotive force (EMF), are derived by using magnetic field solutions and simple equivalent circuits. Finally, to validate the accuracy of the proposed method, the analytical results are compared to the case that no leakage fluxes are included in the analytical model and to the 3-D finite-element analysis (FEA) in terms of computation time and accuracy. [ABSTRACT FROM AUTHOR]

In this article, an exhaustive comparison is presented between two types of model order reduction methods, namely the proper orthogonal decomposition (POD) and the orthogonal interpolation method (OIM), for the characterization of a switched reluctance machine. The purpose of the comparison is to find out the best practices for the design of the machine control parameters and strategy. The control design itself is not presented here, but the needed information is at the focus. The comparison is based on the computation time and the complexity of the reduced-order model as well as the accuracy of the needed data as compared with the one obtained from the full-order model. The results show that OIM is more efficient in terms of calculation time, especially when considering a nonlinear problem. [ABSTRACT FROM AUTHOR]

In this paper, a novel topology for the flywheel battery is proposed, based on the axial split phase (ASP) bearingless switched reluctance machine (BSRM) concept. The topology and operating principle of the ASP-BSRM are explained, the electromagnetic characteristics, torque, suspension force and coupling performance are analyzed by 3-D finite element analysis (FEA). In order to improve the torque and suspension force of the ASP-BSRM, the single variable method by FEA is adopt to screen out the sensitive structure parameters, and a new multi-objective optimization design mothed based on random forest regression (RFR) and differential evolution (DE) is proposed to optimize the key parameters. The 3-D FEA of the complete system is performed, and simulation results verify the proposed topology overcomes the dead zone of suspension force and realize the decoupling between torque and suspension forces. Besides, the optimized torque and suspension force are improved by 4.15% and 12.91%, respectively. An experimental prototype is built to provide an experimental basis for investigation of the actual operating characteristics. The experimental results of the system are evaluated under different operating conditions and compared with FEA results. [ABSTRACT FROM AUTHOR]

To develop a high-performance synchronous reluctance motor (SynRM) drive system, a novel maximum power factor control (MPFC) using a current angle controller with stator resistance and stator flux estimators is proposed. First, a traditional maximum power factor control system using a saliency ratio of the SynRM to generate a fixed current angle command is described. Since the saliency ratio requires offline prepreparation and cannot be adjusted automatically, it is difficult to improve the performance of the MPFC in different operating regions because of the increasing of manufacturing cost and time-consumption. Therefore, an intelligent-maximum power factor searching control (MPFSC) using a recurrent Chebyshev fuzzy neural network (RCFNN) current angle controller is developed for the speed control of a SynRM. In order to search the online optimal power factor (PF) points of the SynRM under different operating conditions, the RCFNN current angle controller is designed to produce the compensated current angle command. Moreover, a proportional-integral speed controller is adopted to generate the stator current magnitude command, and the proposed intelligent-MPFSC is employed to generate the current angle command. Furthermore, the proposed intelligent-MPFSC system is implemented in a 32-bit floating-point TMS320F28075 digital signal processor. Finally, from the experimental results, the current angle commands of the optimal PF can be effectively obtained online at different speed operating commands with varied load torque. [ABSTRACT FROM AUTHOR]

The remarkable inductance nonlinearities of synchronous reluctance motors (SynRMs) could result in operating-point-dependent high-frequency (HF) current responses, and more HF losses with audible noises with conventional constant amplitude high-frequency signal injection (HFSI) methods applied. This article proposes an adaptive pseudorandom high-frequency square-wave voltage injection (AP-HFSVI) based sensorless control method for SynRM drives at low-speed operation. An adaptive HF current control strategy is applied using pseudorandom injection patterns to adapt to the nonlinear characteristic of SynRM inductances. The magnitude of the injected HF voltage signals can be adjusted adaptively with the load variation online via HF current adaptive control scheme, which processes and regulates the HF current components to be constant. Hence, the HF losses and audible noises can be effectively suppressed due to the decreasing magnitude of injected signals. The current power spectra density of the AP-HFSVI method is analyzed and compared with the conventional HFSI method. The effectiveness and superiority of the proposed sensorless control method are verified with experiments on a 3-kW SynRM drive platform. [ABSTRACT FROM AUTHOR]

Switched reluctance machine (SRM) drive requires a large dc-link capacitor due to the low-frequency harmonics in dc-link current, which is generated during the current commutation between phases. Installing a bulky capacitor bank in the drive has a significant impact on the cost and the overall volumetric power density of the drive. This article analyzes the dc-link current ripple in SRM drive and proposes a control algorithm to reduce the dc-link current ripple while maintaining the machine performance. The proposed algorithm extracts the ripple components from the dc-link current using a high-pass filter. The controller ensures ripple energy circulation between the phases and reduces the pulsating energy requirement from the dc supply. The dc-link ripple is suppressed at a wide speed range of operation to enable efficient and reliable drive operation without adding any external hardware system. Simulation and experimental results are provided to prove the effectiveness of the proposed control technique for both steady-state and transient conditions. [ABSTRACT FROM AUTHOR]

The rotor topologies have a great influence on the vibration characteristics of permanent magnet assisted synchronous reluctance machines (PM-SynRMs). In this article, the vibrations of PM-SynRMs with different rotor topologies are studied and compared. First, the electromagnetic force harmonics of PM-SynRMs have been studied and the design rule about the combination of stator slots and “rotor virtual slots” is given to achieve low vibration. Then, a multiphysics model is established to calculate the vibration of the PM-SynRMs with different rotor topologies. The modal analysis is conducted through finite element method considering the orthotropic of materials and validated by the modal test. Besides, the prototype has been built and the vibration test is performed to confirm the accuracy of the vibration simulation. Based on the multiphysics model, the influence of the shapes of flux barriers and the number of “rotor virtual slots” is investigated. It proves that the design rule about the combination of stator slots and “rotor virtual slots” can achieve low vibration for PM-SynRMs. [ABSTRACT FROM AUTHOR]

In this article, a method to evaluate the dc-link capacitor rms current of a switched reluctance motor (SRM) drive under different operating conditions is presented. Square current reference in both hard and soft chopping modes of pulsewidth-modulated current control is considered. By approximating the current controller response and using a recently proposed flux linkage model, the switching-cycle-average phase voltage and current are evaluated over an electrical cycle. The phase voltage and current are further used to obtain the rms values of dc-link current and capacitor current. The proposed method is also used to determine the capacitor current for low-torque-ripple current reference and single-pulse operation. The analytical predictions pertaining to different control methods under different operating conditions are verified by simulation and experimental results obtained from a 4 kW, 1500 r/min, four-phase SRM drive. While the capacitor current is found to be maximum at the lowest operating speed with hard chopping, the maximum capacitor current is observed at an intermediate speed with soft chopping, both for a given magnitude of square wave current reference. The proposed method is useful to size the dc-link capacitor and evaluate its loss in an SRM drive. Furthermore, closed-form expressions for capacitor rms current are also derived, assuming perfect tracking of square wave current reference at low speeds. These expressions bring out the dependence of capacitor rms current on the machine characteristics. [ABSTRACT FROM AUTHOR]

The Ironless Permanent Magnet Linear Synchronous Motor (ILPMLSM) with nonoverlapping windings is widely used in precise applications due to its simple structure, low thrust ripple, and fast response, while the disadvantage is low thrust density. The novel asymmetrical double-layer winding ILPMLSM with quasi-Halbach magnets can improve the thrust density while keeping simple structure. However, the double-layer windings are asymmetric and the primary has finite length. To solve the problem of this asymmetry and investigate its influences on electromagnetic characteristics, an improved 2-D analytical model is proposed, which introduces “virtual periodic primary” and solves the magnetic field of each winding layer. By the results of finite element and experiments, the proposed analytical model is verified. Moreover, the analytical model requires less computation time, which is helpful for optimizing design of this motor. [ABSTRACT FROM AUTHOR]

With growing interest in electrification in automotive industries, the selection of suitable electric machine types based on application requirements is most important. In this article, three electric machine types, axial flux machine, interior permanent magnet (IPM) machine, and switched reluctance machine, are compared systematically to find the best candidate to drive engine accessories in a hybrid truck. These machine types are designed and optimized to meet the application-oriented design requirements and constraints. An extensive Pugh matrix is created where each machine type is scored based on efficiency range, cost, volumetric power density, gravimetric power density, acoustic noise and stress on the rotor, fault tolerance, heat rejection, and manufacturability. Each Pugh matrix component is assigned to a priority-based weighting, based on the application demand, to determine an accumulated score for each machine topology. A full-scale prototype of the best performing machine type is built and tested. Experimental results validate the multiphysics conclusions drawn in the work. [ABSTRACT FROM AUTHOR]

This article deals with an intelligent grid integrated solar photovoltaic (PV) powered water pumping system driven by three-phase reluctance synchronous motor (RSM) drive. Here, a dc–dc converter is utilized for executing maximum power point tracking algorithm. A voltage source inverter is used for feeding the dc power to a three-phase RSM, from a solar PV array. A three-phase voltage source converter is used at the grid side for a bidirectional power transfer among the utility grid, water pump, and the PV array. This system provides rated water discharge throughout the day despite change in atmospheric conditions and feeds the surplus power to the three-phase utility grid. Moreover, during fault in any of the sources, the performance of the water pump remains unaffected. A high efficiency RSM drive without position/speed sensor is utilized here to drive the water pump. An intelligent power sharing concept, between the PV array and the grid, is used here, in which, automatic switching among all operating modes happens according to the availability of the PV array power and the grid supply. Moreover, the preference is given to the PV array power over the grid supply because of its availability at no cost. This control provides inherent power quality improvement and unity power factor operation at the grid side in all operating modes. The suitability of the system is tested through test results recorded on an experimental setup developed in the laboratory. [ABSTRACT FROM AUTHOR]

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

Embedded applications like electric and hybrid vehicles are increasingly using electrical machines with a very high power/mass ratio. In this context, the design of such machines, very often operating at high speeds, becomes essential. However, in order to remain economically attractive, these machines cannot use rare earth magnets but at best include (low cost) ferrites. In this context, a significant number of publications have shown that synchronous reluctance machine (SynRM) may be a good choice. However, this type of machine gives poor performances due to the difficulty to get high saliency ratio. This saliency ratio may be improved by the use of low-cost ferrites that saturate the rotor magnetic bridges. The determination of the height of the magnetic bridges becomes then a problem of the prime importance to ensure both high-speed integrity and high saliency ratio. This article proposes a fast model based on the “Beam Theory Method (BTM),” which is intended to be integrated in an electromechanical optimization process. This method will be compared to another one that has been previously introduced for this type of problem: the equivalent ring method. The maximum mechanical stress at critical regions of the rotor of the assisted SynRM can then be calculated for different rotating speeds and rotor iron bridge thicknesses. By adopting the concept of stress concentration, both methods are compared with the results of finite element analyses. Finally, a prototype of the assisted SynRM is used to validate these results from finite element simulations. [ABSTRACT FROM AUTHOR]

This article proposes a concept for homothetic scaling of Synchronous Reluctance (SynRel) machines with the aim to generate a design for a wide range of power ratings. A generalized modeling approach, based on the saliency ratio, is presented in detail to analytically evaluate the magnetic behavior of the scaled SynRel machines. The analytical model has been applied to a wide range of machines and validated through finite element analysis. General scaling functions are derived to size and evaluate the performance of the scaled machines using the data resulting from the analytical model. The accuracy of the proposed functions is validated, for a range of operating conditions, comparing the results with the experimental measurement carried out on two 4-poles SynRel prototypes. These have been designed using the homothetic method proposed, which has been proven to be a quick and accurate preliminary sizing tool for SynRel motors. [ABSTRACT FROM AUTHOR]

In this article, a novel system-level robust design optimization method is presented to improve the performance of switched reluctance motor (SRM) drive systems under multiple operating conditions. Based on typical driving cycles of electric vehicles (EVs), five typical driving modes of the SRM are determined. The optimization objectives in each driving mode are established. The significant parameters of the motor and controller of each driving mode are selected as the optimization variables by using the sensitivity analysis. In order to simplify the optimization process, correlation analysis is performed to determine the coherence of the objective functions of all driving modes. Then, a sequential Taguchi method is applied to find an optimal design which is less sensitive to the noise factors. To verify the effectiveness of the proposed method, an SRM drive system applied in EVs with a 12/10 SRM and angle position control method is investigated. It is found that the proposed method can significantly reduce the torque ripple and improve the comprehensive performance. Finally, a 12/10 SRM is prototyped and tested to validate the simulation results. [ABSTRACT FROM AUTHOR]

In the control of variable flux reluctance machine (VFRM) excited by zero-sequence current, neglecting the zero-sequence resistive voltage drop would cause a large calculation deviation of the stator voltage, which can saturate the inverter and influence the switching from constant torque region to flux-weakening region. To solve with this problem, a flux-weakening control method considering the zero-sequence resistive voltage drop for VFRM is proposed. Firstly, the relationship between dq-axis voltages, zero-sequence voltage and the maximum voltage is presented. Secondly, based on the deduced voltage constraint, the calculation of optimal reference currents in flux-weakening region is presented by using Lagrange multiplier method. Since the zero-sequence voltage is considered, the calculation accuracy of the stator voltage and the utilization rate of DC link voltage are improved, which improves the output power capability. Finally, the proposed method is verified by the experimental results. [ABSTRACT FROM AUTHOR]

In this article, a rotor magnetic potential (RMP) model is proposed, which can accurately describe the rotor surface magnetic potential distribution under the interaction of multi-excitation sources. Furthermore, a new magnetic equivalent circuit (MEC) model is used to model the complex saturation in the bridge region, which employs an improved nonlinear reluctance modeling method. Then, the unknown parameters in the RMP model are obtained by solving the MEC model. In this article, the RMP model and MEC model are combined to consider the stator and rotor saturation effects, and the magnetic field is calculated accurately. Compared with the existing RMP model, the proposed one can take into account the effects of the stator saturation and PM magnetic field. Compared with the existing MEC and equivalent magnetic network (EMN), the area of the nonlinear reluctance in this paper varies with excitation conditions, which can accurately consider the saturation effects in the bridge region. This improvement can improve calculation accuracy on the basis of reducing the number of nonlinear reluctances. Moreover, the proposed method does not need to consider the change of the air-gap reluctances caused by rotor rotation. Finally, the proposed method is verified by both finite element analysis and experiments. [ABSTRACT FROM AUTHOR]

This article proposes an optimized direct instantaneous torque control (DITC) scheme for switched reluctance motor (SRM) drives with a novel adaptive dynamic commutation strategy, which can effectively reduce torque ripple and improve system efficiency. To minimize torque ripple, two operational modes are developed for torque tracking during commutation regions. In Mode I, the torque error is compensated by the outgoing phase during the current buildup region of the incoming phase; in Mode II, the torque error is compensated by the incoming phase during the demagnetization region of the outgoing phase. To implement the proposed DITC scheme in a more effective conduction range, the commutation instants are dynamically adjusted according to the varied operation conditions. For each phase, the turn-on and turn-off angles are modified in each electrical cycle by a torque error regulator and a phase current endpoint detector, respectively. By employing the proposed strategy, the torque generation capability is fully utilized for minimized torque ripple, and the phase currents work within a more effective conduction range for improved system efficiency. The simulation and experiments on a three-phase 12/8 SRM are carried out to verify the feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

This article investigates the most elementary phase voltage modulation (PVM) for a more generic five-phase permanent magnet synchronous motor drive under a single-phase open fault. Most works on this topic are intended for some specific motor types, and in most cases, it assumes the inverter can still be treated as a linear switching-mode power amplifier. This article figures out that due to an oscillating neutral, the phase voltage is unable to be linearly modulated, which is to say the simplest sinusoidal pulsewidth modulation is problematic to fit a newly developed well-decoupled model under single-phase open fault. To this end, a nonlinear transform incorporating the faulty phase voltage is theoretically proposed, which alleviates the influence of oscillating neutral on PVM, and several approaches to cancel the need for phase voltage sensors are comparatively investigated. Accordingly, the PVM with repetitive control and back electromotive force compensation is put forward to fix the “faulty inverter” in practice. Plausible PVM approaches are tested experimentally, and the superiority of the proposed PVM is confirmed by experimental results. [ABSTRACT FROM AUTHOR]

This article presents a simple analytical model for the sizing of synchronous reluctance (SynRel) machines. The accuracy of the method is achieved by modeling a simple rotor geometry that presents all the characteristics of a real machine. The analytical equations proposed are able to guarantee accurate and fast results during the preliminary design of the machine. A generalized sizing approach, based on the saliency ratio, is presented in detail. The method is flexible and can be adapted for any SynRel machine. The accuracy of the proposed model is validated for a range of operating conditions, comparing the results with both finite element simulations and experimental measurement carried out from an existing four poles SynRel 15-kW prototype. [ABSTRACT FROM AUTHOR]

The synchronous reluctance motor is becoming a very attractive alternative to the ac induction machine. This is due to the lack of rare-earth metals in their construction and a higher efficiency, which was brought about by recent progress in rotor design. However, in order to achieve an efficient and low-cost operation of the synchronous reluctance motor drive, an adaptive sensorless algorithm should be utilized to cope with machine nonlinearities. This article describes an adaptive observer, which can provide an estimation of rotor position and speed, as well as core loss and inductance parameters. A modified pulsewidth modulation (PWM) switching scheme and a current derivative measurement method are proposed, together with an extended Kalman Filter design. Experimental results are shown to demonstrate the method performance and feasibility. [ABSTRACT FROM AUTHOR]

Finite-set model predictive current control (FS-MPCC) has been employed for machine drives owing to the good dynamic performance. Sensitivity to parameter variation is one of the main barriers to its widespread application. To overcome this barrier, this article proposes an improved FS-MPCC for surfaced permanent magnet synchronous machines (SPMSMs). The contribution of this article is developing a novel current update mechanism, where the variation of resistance, rotor flux linkage, and inductance is considered, in which a modified coordinate system that contains a stationary and rotary axis frame is introduced. In this case, the predicted parameter can be obtained more accurately based on this mechanism, which can suppress the disturbances caused by model parameter mismatch. In addition, SPMSM parameter mismatch effect on FS-MPCC performance is analyzed in this article, which testifies that resistance mismatch influence on current prediction error can be neglected in practical system. The proposed FS-MPCC is validated and compared with different state-of-the-art methods. Improvement of the proposed control strategy is validated by means of experimental results on a 2-kW test rig. [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]

A bearingless machine should be designed to maximize the average and to minimize the ripple in the electromagnetic torque and levitating force. In a bearingless synchronous reluctance machine (BSynRM), the complex rotor design and the levitation winding create a rich spatial and temporal spectrum of the magnetic flux density in the airgap, which affects both the torque and force ripple. In this article, a novel method is introduced to compute the electromagnetic forces from the spatial harmonics of the airgap flux density. A new indexing method is introduced to classify the spatial harmonic wavenumbers and temporal harmonic frequencies of the flux density in the electromagnetic force. The proposed model enables the understanding of the spatial harmonic footprint on the temporal frequencies of the electromagnetic force ripple. The study is carried out through finite element simulations, which are verified by prototype measurements. [ABSTRACT FROM AUTHOR]