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

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

The position sensor is a major cost contributing factor of switched reluctance motor (SRM) drive and it is highly unreliable in case of submersible pumps. Therefore, this paper aims at the development of sliding mode observer (SMO) based position sensorless control for SRM drive for PV-battery standalone submersible pumps. Unlike look-up table-based methods or artificial intelligence-based algorithms, SMO-based algorithm offers simple and robust architecture and does not require any pre-stored magnetic data. In this paper, SMO algorithm employs instantaneous online calculation of phase inductance, constructed as a function of both rotor position and measured phase current and uses the derivative of the same to serve as an error function for the observer. Besides implementing SMO for position estimation, a two-phase excitation-based algorithm is integrated to SRM control to guarantee the unidirectional operation during starting. A laboratory-scale prototype is developed and the performance of the drive is discussed to justify its suitableness for submersible pumps.

Switched reluctance motors can be driven in a conventional or a modular way. In the conventional driving method, a number of stator coils are connected together and driven from one converter module. In the modular driving method, each stator coil is driven from one separate converter module. The conventional driving method provides better drive performance (i.e. efficiency, torque ripple, power density) but narrower speed range at rated torque and less fault tolerance-capability. The modular driving method provides wider speed range at rated torque and much better fault tolerance capability. Therefore, in low speed healthy operation, the conventional driving method is preferable while for high speed and faulty condition, the modular driving method should be used. In this paper, a converter topology that can be reconfigured to operate in conventional and modular driving ways is proposed and analysed. Using the proposed converter, the benefits of the conventional and the modular driving methods can be obtained by proper configuration of the converter. Also, a fault-tolerance strategy that results in symmetrical and high performance operation of the drive is proposed. The performance of the converter is assessed by simulations and experimental measurements.

This paper proposes a new position sensorless method for switched reluctance motor (SRM) drive control based on a sliding mode observer using nonlinear Fourier flux linkage model. First, to obtain an accurate mathematical model of SRM for establishment of sliding mode position observer (SMPO), an analytical method based on Fourier polynomial function is introduced to regress the nonlinear relationship between flux linkage, position and current. Then, a new SMPO is designed in detail to estimate the rotor position, including the establishment of SRM model of sliding mode observer, and analysis of estimation error and convergence conditions of SMPO. Finally, position sensorless control of SRM drive based on SMPO is carried out in terms of accuracy and robustness in simulation. Experiments are also given on a dynamic testing platform to verify the effectiveness of the proposed position sensorless scheme.

A multi-sensor data fusion method is investigated for bearing fault diagnosis of a switched reluctance motor (SRM) of an electric vehicle (EV) powertrain under varying speed conditions. The accumulative rotation angle of the SRM rotor is estimated by fusing the synchronous sampled current and vibration signals. The time-domain vibration signal is then resampled on an angular domain, and the bearing fault type is identified on the envelope spectrum of the resampled signal. An experimental setup is designed to validate the performance of the proposed method compared with the traditional ones. The practical EV working conditions including driving, coasting, and braking are considered in the experiments. Results indicated that the proposed method successfully diagnoses the SRM bearing faults under random and complex conditions. The method is promising for online SRM fault diagnosis under varying speed conditions as it requires no extra tachometer, specifically when the sensorless control strategy is adopted.

The inter-turn short-circuit fault of stator winding is a common failure mode in switched reluctance motors (SRMs), which can severely harm the operation of the motor. In this paper, a novel method for diagnosing the inter-turn short-circuit fault in the current chopping mode is proposed, which is suitable for online monitoring and protection of SRMs. The proposed method achieves a fast response and high sensitivity and can mitigate the interference of load conditions on detection reliability. Moreover, this method is based on phase currents, which does not require additional sensor or detection circuits. Meanwhile, the effects of inter-turn fault location in the stator winding on the motor flux and motor parameters are analyzed in detail through finite element analysis, which is helpful to establish a reliable diagnostics technique for various fault conditions. Experimentations based on an 8/6 four-phase SRM with special windings designed to simulate inter-turn short circuit conditions are conducted, and the results have verified the effectiveness of the proposed method.

In order to solve the coupling between torque and suspended force of the traditional bearingless switched reluctance motor (BSRM), a bearingless switched reluctance motor with hybrid-rotor (HBSRM) is proposed in this paper. The HBSRM discussed in the paper has a twelve-pole stator and an eight-pole hybrid-rotor composed of a cylindrical rotor and a salient rotor. The magnetic pulling force between cylindrical rotor and stator is used to independently levitate the shaft, and that between salient rotor and stator is used to separately rotate the rotor. So, the HBSRM not only breaks the restriction of the effective output region between torque and suspended force in the traditional BSRM, but also facilitates the decoupling algorithm design and simplifies the levitation control of this bearingless motor. Firstly, the topology, operating mechanism and mathematical model of the proposed HBSRM are introduced respectively. Then the no-load decoupling control and torque ripple of the traditional BSRM and HBSRM are compared. Moreover, the load decoupling control characteristics of HBSRM are presented and verified by simulation analysis.

This article presents a method to reduce the torque ripple in an 8/6 four-phase switched reluctance motor (SRM). The proposed scheme introduces a nonlinear modulating factor dependent on the rotor position and magnitude of the phase currents. This factor manipulates the currents in two adjacent phases during commutation and reduces the torque ripple effectively. Unlike the conventionally available torque-sharing functions, the proposed method instantaneously modulates every phase current obtained mathematically based on the other phase current in order to maintain the net torque constant. The proposed method requires minimal offline analysis and offers maximum possible torque with a minimal ripple. The method is simple and easy to implement due to a low computational burden. The proposed algorithm is implemented using MATLAB/Simulink software and is also validated experimentally on a 0.6-hp 8/6 SRM using a field-programmable-gate-arrays-based hardware setup developed in the laboratory. Typical results are presented and compared with the existing techniques. A torque ripple of $\approx 8\%$ has been achieved.

High-speed position-sensorless control of switched reluctance motor (SRM) drives is often realized by searching a priori flux linkage lookup table. However, obtaining the nonlinear flux linkage characteristic requires time-consuming offline measurement and occupies large memory storage. To deal with this problem, this article proposes a new position estimation scheme for SRM drives without using any magnetic characteristics. This feature is achieved by using a quadrature flux estimator (QFE) that can extract the fundamental flux and its quadrature signal from the real-time calculated flux linkage. The flux bias and flux harmonics can also be suppressed by the QFE’s adaptive bandpass capability. Therefore, the proposed method can reduce the nonlinearity in SRM flux linkage and derive simple sine-cos position signals. Afterward, the rotor position and speed can be estimated from the orthogonal flux signals using a three-phase phase-locked loop. To baseline the advantages, comparative experimental validation with the conventional method is conducted on a three-phase 12/8 SRM test bench. The results show that the proposed scheme can achieve the same estimation accuracy as the conventional method even though no magnetic characteristics are used.

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

Fault diagnosis technique is necessary for high reliability system. For switched reluctance motor, asymmetric half bridge converter is the most commonly used. The transistor is the most fragile component in converters. To the transistor in asymmetric half bridge converter, a fault diagnosis method is proposed in this paper. When faults of transistors occur, the conducting loop will be changed. The current slope can reflect the change of the conducting loop. Through reconfiguring current sensors, the sign of the measurements will reverse with the change of the conducting loop. By the current slope and the sign of the measurements, present conducting loop is determined. The changes and the fault types are one-to-one correspondence. Therefore, the fault type is known. Conditions that may lead to misdiagnosis are illustrated and avoided in online execution. Comparisons of the proposed fault diagnosis method and relevant existing methods are made according to the cost, the response speed, the application scope and so on. The proposed fault diagnosis method is demonstrated under all possible fault types of the transistor by simulations and experiments, which validates effectiveness of it.

In this letter, a transformed unsaturated inductance characteristic-based method is proposed for the rotor position of the switched reluctance machine. Due to the magnetic saturation effect, the phase inductance characteristics have a narrow linear region, which increases the difficulty of their analytical expression. To reduce the complexity of the analytical expression, the unsaturated inductance characteristic is transformed from the phase inductance characteristics. Then, a linear model is presented to explicitly describe the relationship between the rotor position and unsaturated phase inductance. Experimental verification is carried out to verify the effectiveness and accuracy of the proposed method. The proposed method can serve as a low-effort way to provide the accurate rotor position for the industry application at medium and high-speed ranges.

In this paper, a novel electric machine, Induction Switched Reluctance Machine (US patent-US20170370296A1) is introduced, and its preliminary performance is evaluated. The innovation is based on placing windings on the rotor, in order to create short magnetic flux paths in the rotor and stator core of the electric machine. As a result, a higher torque with lower copper and iron losses is generated. Like other ideas, there are unknown aspects of this electric machine, such as thermal and mechanical properties, that should be studied. A comprehensive research program is required to analyze and design an Induction Switched Reluctance Machine with an optimized configuration. This electric machine could be designed with different pole numbers and various winding strategies, and it is not possible to consider all configurations and aspects of it in this paper. Moreover, the size and the rated power of the machine can affect its properties. The purpose of this paper is to introduce, simulate and prototype a simple Induction Switched Reluctance Machine. This electric machine has an excellent potential to be implemented in the propulsion system of electric vehicles.

For traditional 12/8 bearingless switched reluctance motors (BSRMs), the coupling between torque and levitation increases the complexity of control. For the turbomachinery application, 2 degrees of freedom (DOF) BSRMs stabilized by extra 3-DOF active magnetic bearings are required. In this article, an improved BSRM with 4 rotor poles and 12 stator poles is proposed to realize 4-DOF radial levitation, and the torque dead zone is compensated because that two rotors and these poles are assemble with 15 mechanical degree shifted. The decoupling of torque and radial levitation is realized simultaneously. Moreover, the operation principle of axial reluctance force is analyzed for passive levitation in the axial direction. Various experiments were completed to verify the performance of the proposed BSRM, and the prototype achieved stable levitation of the rotor in 10 000 r/min.

The 3-D finite element method (FEM) has been widely used for accurate analysis of winding loss with winding axial transposition angle considered. However, its application is limited due to long computation time and complex modeling processes. To address these problems, this article proposed a 2-D equivalent permeability modeling method (EMM). First, according to the proposed method, the 3-D winding model with axial transposition angle could be equivalent to several segmented 2-D models. Through equivalent axial length coefficients, 2-D models with different axial lengths could be solved in one project. Using appropriate segment and equivalent coefficients, to a great extent, the inherent error of the 2-D model could be reduced. Second, with equivalent permeability and conductivity, current density distribution and winding ac loss could be calculated. To verify the correctness and robustness of the proposed method, the study was conducted in the five-parallel-strand model. Single-tooth models with concentrated windings were built to verify the evaluated winding loss. In addition, a 20-kW 12/8 high-speed switched reluctance motor was manufactured, and the temperature rise was tested to verify the effect of winding loss on the temperature rise. Through the comparison of experiments and FEM, the EMM is verified to be with high accuracy and computational efficiency to analyze the ac loss and current distribution.

Implementation of fault diagnosis for power converter is critical to improve the reliability of electric vehicle (EV) with switched reluctance motor (SRM) drive. Conventional fault diagnosis methods are usually suitable for a single chopping mode or a certain control strategy. To avoid the problem, a virtual current coefficient-based diagnosis method for power transistors is proposed considering different chopping modes, control strategies, and fault cases simultaneously. The multipoint current detection method is proposed to obtain more current information, which is capable of providing remarkable fault features. The sensor current variations under various fault conditions are analyzed. The fault is first detected by identifying the error between the real sensor current and the value calculated with the mixed logic model. Three virtual current coefficients are introduced to obtain the fault location principles. The fault types and fault power transistors are recognized according to the difference between the real current coefficients and the virtual current coefficients. The applications of the fault diagnosis method are extended with the proposed scheme. The method does not require complex calculation, and thus has a good dynamic performance. Experiments on a three-phase 12/8 SRM drive validate the effectiveness of the proposed fault diagnosis method.

Considerable vibration and acoustic noise limit the further application of Switched Reluctance Machine (SRM) due to its structural characteristics and working principle. An improved SRM model with double auxiliary slots (DAS) was proposed, in which the direction of the magnetic line of force was adjusted, and the radial magnetic density in the air gap was reduced by changing the local tooth profiles of the stator and the rotor. The effects of initial rotor position and turn-on angle and turn-off angle on radial Electromagnetic Force (EMF) and maximum torque were investigated. The results indicate the radial EMF and torque increase significantly with the advancement of the turn-on angle or the delay of the turn-off angle. In the orthogonal experimental design, initial rotor position, turn-on angle, and turn-off angle were taken as the factors, and the optimal set of parameters that minimized radial EMF was determined according to a greater output torque. In contrast to conventional SRM, the radial EMF of the SRM with DAS significantly reduces when the optimal set is applied.

The performance of an electric machine depends on its ability to resist rising internal temperature and ambient temperature. In particular when it is a combination with a heat engine, it is essential to know the thermal characteristics of the electric machine in connection with its operating environment to decide which type of machine for a better result. This work will make a comparative thermal study of three types of generators namely: the permanent magnet generator (PMSG), the squirrel cage asynchronous generator (SCIG) and the switched reluctance generator (SRG), all driven by Stirling engine. The method involves solving the heat propagation equation to determine the thermal resistance network for each machine. The resolution of the network combined with the finite element method will allow a comparison of the temperature rise and its effect on the performance of each machine. The simulation results show that the temperature of the PMSG windings stabilizes at 430 K while that of the others stabilizes at 373 K and 346 K respectively. However, when comparing the performances for the specifications of this work (i.e., produce minimum electric power of 2kW at low speed generated by the Stirling engine), PMSG is the one that fulfil all the requirements. For the use of this machine for the generator set, it will be necessary to use magnets of types GNS-39EH whose operating temperature is approximately 473K (200 ° C) with magnetic induction of 1.22 T. Keywords: choice of machines, thermal network, Finite Element Method, machine’s performances, Stirling engine.

Purpose This paper aims to establish a piecewise Maxwell stress analytical model of bearingless switched reluctance motor (BSRM) for the full rotor angular positions. The proposed model varies from the existing models, which are only applicable to the partial-overlapping positions of stator and rotor poles. By extending the applicable rotor angular positions, this model provides a basic analytical model for the multi-phase excitation control of BSRM. Design/methodology/approach The full rotor angular positions are classified into the partial-overlapping positions and the non-overlapping positions. At first, two different air gap subdividing methods are proposed, respectively, for the two-position ranges. Then, different integration paths are selected accordingly. Furthermore, two approximate methods are presented to calculate the average flux density of each air gap subdivision. Finally, considering the mutual coupling between the two perpendicular radial suspension forces, a piecewise Maxwell stress analytical model is derived for the full rotor angular positions of BSRM. Findings A piecewise Maxwell stress analytical model of BSRM is built for the full rotor angular positions, and applicable to the multi-phase excitation mode of BSRM. For the partial-overlapping positions and the non-overlapping positions, two sets of air gap subdividing methods, integration paths and approximate calculation methods of air gap flux densities are proposed, respectively. The accuracy and reliability of the proposed model are verified by the finite element method. Originality/value The piecewise Maxwell stress analytical model of BSRM for the full rotor angular positions is proposed for the first time. The novel air gap subdividing methods, integration paths, approximate calculation methods of air gap flux densities and the coupling between the two radial suspension forces are adopted to improve the modeling accuracy. As the applicable range of rotor angular position is extended, this model overcomes the limitation of the existing models only for single-phase excitation mode and contributes to the accurate control of BSRM multi-phase excitation mode.

This article reports design and testing of silicon carbide) devices-based three-phase asymmetric H-bridge converter capable of switching at 50 kHz and intended to drive high-speed switched reluctance machine. Electromagnetic designs of a 7.5-kW, 30 000-r/min and a 20-kW, 50 000-r/min Switched reluctance machine are presented. The 30 000-r/min machine is fabricated and characterized. A machine model is obtained from the measured characteristics. Based on the machine model, as well as drive operating variables and device data-sheet parameters, two methods are proposed for evaluating the losses in the power devices. The first method relies on machine model to obtain machine current and converter duty ratio, and thereby estimate the device losses. A second simplified method provides closed-form expressions for device losses. The proposed analytical expressions relate the machine characteristics such as inductance and saturation current with converter losses. The estimated loss is further used to predict device junction temperature. The power converter and device ratings are chosen so that the converter is suitable for both machines. The capacitor selection and sizing are discussed. Further, the power converter architecture and other subsystems of the converter are described. Test results are presented for the asymmetric H-bridge converter at 800 V dc bus voltage, 50 A of load current, and 50 kHz of switching frequency. Thermal image is presented for validation of estimated heat-sink temperature. The predicted heat-sink temperature is found to agree well with the measured temperature. The power converter is used to operate the 30 000-r/min machine at various speeds.

A novel U-shape dual-stator switched reluctance motor (DS-SRM) is presented in this paper. The structure and initial geometry dimensions are given. The fundamental torque equation of average electromagnetic torque is established. The sensitivity analysis on key structure parameters is carried out to obtain the final geometry dimensions. The optimization results are verified by simulation and experimental test. The research of this paper has great influence on the DS-SRM design and optimization.

This paper proposes a novel dual three-phase flux-modulated switched reluctance motor (SRM) drive with maximum torque per ampere (MTPA) capability. Different from the existing open-winding structure, the stator winding is in dual three-phase connection, which effectively eliminates the side effects of the zero-sequence harmonic voltage component. Hence, the modulating region of the space vector pulse width modulation (SVPWM) can be enhanced together with the increase of the dc-link voltage utilization ratio. The mathematical models of the dual three-phase flux-modulated SRM in the stationary reference frame and synchronous rotating reference frame are analyzed in detail. By considering the inductance nonlinearity, the MTPA control strategy is proposed based on the polynomial fitting method, which not only improves the torque capability but also simplifies the calculation of the current control system. The contributions of fundamental and harmonic currents to the electromagnetic torque are considered. By online adjusting the ratio of the dc-biased current component to the ac current component, the torque capacity can be improved. Besides, the effectiveness of the proposed MTPA control strategy can be enhanced by suppressing the harmonic current components caused by distorted back-EMF. Experimental validations are provided to verify the effectiveness of the proposed SRM drive.

Measuring and quantifying the electromagnetic characteristics of switched reluctance motors (SRMs) are indispensable for advanced motor control and performance enhancement. This article reports on a novel method in obtaining the flux-linkage characteristics of an SRM without rotor clamping devices and position sensors. This approach combines measurement with data reconstruction. For the measuring step, flux-linkage samples at four torque-balanced positions were measured indirectly. Considering the magnetic coupling among phases, two different excitation forms were adopted to further increase accuracy. Then, for the reconstructing step, a fuzzy logic-based approach was applied to reconstruct the complete flux-linkage characteristics with measurement results. The construction results were compared to measurements results from the traditional rotor clamping method, and good agreements can be found, demonstrating the effectiveness of the proposed method. Furthermore, based on reconstructed electromagnetic characteristics, dynamic simulation of an SRM prototype under different control modes was carried out and analyzed in MATLAB. Comparison with dynamic experiments further verifies the accuracy and effectiveness of the proposed method.

This paper mainly takes a 6/4 switched reluctance motor (SRM) as an example to analyze the temperature of the motor. In order to establish the equivalent thermal circuit model (ETCM) conveniently, the mechanical structure of the motor is simplified to a certain extent, and the characteristic nodes are divided. Then the heat transfer process in the rotor region, the stator region and the whole motor during the operation of the motor is analyzed, and the ETCM of those regions are established respectively. This method of establishing ETCM is also applicable to superconducting motors. Based on the basic principles of heat transfer, the calculation method of thermal resistance in each ETCM is given in this paper. Then, the three-dimensional (3-D) finite element (FE) temperature field model of the motor is built and compared with the ETCM. Finally, the accuracy of the ETCM is verified by experiments.

This paper introduces a novel double stator switched reluctance machine (DSSRM). U-shaped stator blocks are used for both internal and external stators. Each stator tooth is wound with a central winding, and the polarities of the two stator teeth on each U stator block are opposite. Firstly, the working principle and the geometric design of the proposed DSSRM are given. The methods of reducing torque ripple from machine structure of the proposed DSSRM are illustrated. Then, this paper makes the comprehensive comparison between conventional DSSRM and proposed DSSRM by finite element method (FEM). The simulation results indicate that this proposed DSSRM has lower torque ripple and higher torque density than the conventional DSSRM. Finally, a prototype motor is manufactured and the simulation analysis is validated by the experimental results.

The eddy-current loss of switched reluctance motor (SRM) is studied and analyzed in this paper. As a significant part of core loss, eddy-current loss has a great influence on motor performance. First, the average magnetic flux waveforms in every distributed region are derived from the magnetic equivalent circuit (MEC) model. Based on this, each harmonic of magnetic density is obtained by adopting the fast Fourier transform (FFT) method for further calculation. Then, each harmonic eddy-current loss is computed by sinusoidal magnetic density and the total eddy-current loss in different region of motor is derived by superposing of them. Therefore, the calculated results at different speed and conduction angles of each region are analyzed. Finally, the 3D finite element (FE) model is established in software FLUX and the experimental platform of the SRM prototype is built.

A new method to detect the initial rotor position of switched reluctance machine (SRM) is presented in this article. Unlike most conventional position estimation methods, the proposed method does not need any extra premeasurement and only the data with finite element method (FEM) are required. First, a linear regression model (LRM) is presented to describe the relationship between FEM and measured inductance characteristics. Then, to detect the position, the residual sum of squares of the proposed LRM is considered as an objective function, which is a convex function with rotor position. The rotor position can be estimated by minimizing the objective function with the golden-section search method. Finally, the accuracy of the proposed estimation algorithm is validated by the experimental results on a three-phase 12/8 pole SRM prototype. Compared with the existing position estimation methods, the proposed method has higher accuracy and less measurement effort. The proposed method can serve as a supplement to provide accurate initial position information for incremental position sensors.

Transverse-flux structure is a potential choice for switched reluctance linear machines (SRLMs) to enhance electromagnetic thrust density. A transverse-flux single-phase SRLM combined with tubular shape, which is a tubular SRLM (TSRLM), is proposed in this paper. There are four stator poles on the cross section of its stator for increasing effective flux path and maximizing flux linkage. To increase the advantage of this novel TSRLM in thrust density, the sensitivity relationships between the maximum electromagnetic thrust value and some key structure parameters are investigated via three-dimension finite element method (3-D FEM). The optimal structural dimensions of proposed TSRLM are determined finally according to a series of sensitivity analysis results. In addition, a new concentrated winding structure is applied in the proposed TSRLM. The analysis result demonstrates that the proposed TSRLM with new concentrated winding structure is superior in thrust density than before.

In this article, an improved direct instantaneous torque control (DITC) based on adaptive terminal sliding mode control (ATSMC) is proposed to suppress torque ripple and enhance the anti-interference ability for switched reluctance motors (SRMs). The proposed speed controller used in the outer loop of DITC is based on the rate of change in load torque. The state of the system converges quickly to the equilibrium point and realizes fast output of the given torque without known disturbance upper bound. Moreover, a novel reaching law is proposed to reduce torque ripple and startup time. The stability of the adaptive terminal sliding mode motion is verified by using the Lyapunov function. The improved DITC system is implemented on a 16/10 segmented-rotor SRM. Compared with sliding mode control and terminal sliding mode control, the proposed ATSMC in the DITC system behave with better performances in aspects of the speed and torque response, antiinterference ability, robustness, and torque ripple suppression. Simulation and experimental results are given to verify the effectiveness of the improved DITC.

Switched reluctance motors (SRMs) are a good choice for electric vehicle motors, because the rare-earth elements are not necessary. Planetary gear transmission (PGT) has a large transmission ratio, high power density, and compact structure. Therefore, the integrated electric driving system of the SRM-PGT is the development direction for electric vehicle power transmission. The integrated electric driving system of the SRM-PGT is proposed in this paper. Aiming at this system, the dynamic model of the mechanical system is constructed using the reduced-order finite-element method, which considers the flexibility of the gearbox, stator, ring gear, and carrier. A dynamic model of the SRM is simultaneously constructed to obtain the nonlinear spatio-temporal electromagnetic torque and radial force waves. Finally, a coupling dynamic model, including the mechanical, electric, and control systems, is built. The interaction between the PGT and SRM with and without coupling is investigated under steady-state conditions and impact load conditions. It is demonstrated that there is a strong coupling interaction between PGT and SRM. Under the impact load conditions, the free-vibration mode of the system is excited and the free-vibration modes produced by different components are different. The modal energy method and mode vector distribution are used to diagnose the potential dangerous components of the system. Coupling can effectively suppress the shock oscillation of the system, but it also can increase the interaction effect between the gear system and motor. Therefore, the coupling characteristic of the SRM-PGT system should be fully considered, which lays the foundation for the integration design method.

Switched reluctance machines (SRMs) are being researched extensively to function in generating mode for small capacity wind power generating systems (WPGSs) such as the ones installed on a roof top. By virtue of being installed in the middle of the inhabited portion of the land, the WPGS should have the capability to generate electricity over a wide range of speeds, inclusive of lower wind speeds. At lower wind speeds, the choice of capacitor for self-excitation becomes much more difficult because the reactive power offered by the capacitor becomes meagre due to reduced magnitude of the generated emf at lower rotational speed of the generator. This paper advocates a methodology for selecting the capacitor appropriately, by obtaining the generated voltage magnitude of the SRG at any operating condition, by plotting flux linkage variations with rotor position and current, and simultaneously evaluating the reactive power requirement and voltage ripple at the output of the generator. Analytically, the equations for the SRG are derived first; then, the capacitance value is determined based on the reactive power requirement and permissible voltage ripple. These are cross-verified by simulations and experimentation at various wind velocity conditions. Finally, a closed loop control to maximize the power harvested from SRG has been put-forth by adjusting the phase current reference value suitably so that the generator makes use of the full potential of the WPGS at any given wind velocity. Analytical results are corroborated by results obtained from simulation models and experimental implementation.

In order to combine the advantages of modularity and hybrid-excitation for motor torque and power density enhancement, this article proposes a 12/4 modular-topology, permanent magnet (PM) assist, hybrid-excitation switched reluctance machine (HESRM) with both segmented-stator and -rotor. The machine topology and basic operating principle are presented. Three key parameters of the machine are optimized for assessment on the torque production . The three-dimensional finite-element analysis is employed to consider the effects of end winding and core saturation. The static magnetic characteristics and dynamic performances are simulated and compared with a 12/4 segmented SRM (SSRM) without PM and a 12/10 segmented-stator HESRM. Two prototypes of the proposed 12/4 HESRM and a 12/10 segmented-stator HESRM with the same size are manufactured and developed for experimental verification. Both results show that the proposed motor can achieve higher dynamic average torque and higher power/torque density at high-speed operation. It also has a stronger starting capability, more rapid response for command changes, as well as better stability and tracking features.

A drive topology composed of a T-type single-phase three-level voltage source rectifier (VSR) and a four-level switched reluctance motor (SRM) converter is proposed in this article. The commonly used diode bridge rectifier presenting degraded power quality is replaced by the VSR to drive the SRM converter. Compared with the conventional split-dc converter, the four-level SRM converter of the proposed drive topology adopts one more switch and one more diode for each phase, but two more operation modes are formed. With the double-voltage demagnetization mode of the four-level SRM converter, the tailing time of demagnetization current is significantly reduced, which increases the utilization of inductance increasing region. All the operation modes of this converter can be implemented successfully, even in the multiphase excitation region. Moreover, a centralized control strategy is proposed to regulate the VSR and SRM together, within which the speed and grid-side power factor are regulated by the d -axis and q -axis component of grid-side current in VSR, respectively. Most importantly, the bidirectional energy flow is realized. An idea-proofed testbench is constructed. The results obtained from the comparative experiments confirm the validity of the proposed drive topology and its control strategy.

A variable reluctance electric machine with a two-degree of freedom rotor motion characterized by rotation around the center of the rotor and orbiting around the center of the stator is studied. One motivation for adopting such rotor motion would be to allow torque generation through both the radial and tangential components of the electromagnetic forces created in the airgap, as opposed to common rotary machines in which torque is a byproduct of only the tangential component of the airgap electromagnetic forces. Furthermore, the rotor motion provides a built-in gearing action similar to that of a cycloidal drive, which allows natural torque multiplication and the tight integration of the electromagnetic and mechanical systems. The two-degree of freedom rotor motion also results in a counter-intuitive inertia characteristic of this machine concept which is elaborated in this paper for the first time. Due to the reluctance nature of the torque, and because of the distinctive rotor motion profile which resembles the motion of a cycloid, the studied machine is called a cycloidal reluctance (CR) electric machine (CRM). In this paper, the principle of operation of the CRM is explained, and its performance is compared to a counterpart switched reluctance machine (SRM). A prototype is built, and the theoretical torque calculations are validated by experimental measurements.

Vibration characteristics of a solid-rotor switched reluctance machine (SRM) are measured in the static as well as dynamic conditions. A series of impulse hammer-based static measurements are carried out on the assembled machine. The impulse hammer tests identify the main resonant frequencies of the rotor assembly, bearing housing and enclosure. For the dynamic vibration tests, the SRM is run at different speeds using single-pulse control and current control. The measured currents are utilized to obtain the electromagnetic radial force on the stator through finite element analysis. The frequency components of the estimated radial force are observed in the vibration spectrum measured in the dynamic tests. The dynamic vibration spectrum also include the resonant frequencies of the SRM subassemblies. The natural frequencies of the rotor assembly are found to influence the vibration spectrum significantly. Harmonics of speed are the other significant components in the measured vibration spectrum at any given speed; the magnitudes of these components increase with rotor speed.

To overcome the disadvantages of traditional switched reluctance machine (SRM) with moderate power/torque density and high torque ripple, this article proposes a novel double-stator SRM (DSSRM) with the inner and outer stators both adopting U-shaped segmental stator structure. By optimizing the polarity distribution of the inner and outer stator magnetic fields, the inner and outer stator magnetic fields are decoupled. Then, the relationships of torque ripple coefficient with the mechanical offset angles of the inner and outer rotor teeth are investigated. To optimize the mechanical offset angle and reduce the torque ripple of the motor, the initial design method is proposed, and five main parameters of the machine are optimized by the finite-element analysis. Then, the static magnetic characteristics and dynamic performance of this novel machine are simulated and analyzed. Finally, a 16/18/18/16 DSSRM is prototyped to validate the above simulation and theoretical analysis.

This article proposes a topology of special axial split phase (ASP) bearingless switched reluctance (BSR) machine for flywheel applications named ASP-bearingless flywheel (ASP-BF) machine, which adopts hybrid-inner-stator permanent magnet (PM) structure and exhibits complete decoupling of torque and radial suspension force, four degrees-of-freedom (DOF) actively controlled suspension, high torque and radial force density. The topologies of conventional radial split phase (RSP)-BSR machines and the proposed ASP-BF machine are comparatively investigated. It is found that problems of conventional RSP-BSR machines, i.e., the radial suspension force generation dead zone and strong coupling of radial suspension force and torque, can be solved in ASP-BF machines and the suspension DOF can be doubled. Electromagnetic performances, including magnetic field distribution, inductance, torque, radial force are comprehensively investigated. Further, the concept of degree-of-coupling (DOC) is introduced, and the DOCs of the proposed machine and conventional machines are quantitatively analyzed and compared. It shows that the DOC of ASP-BF machine in two cases are 3.41% and 4.05%, less than a quarter of the conventional 8/10 pole machine (22% and 16%) and less than half of the 12/14 pole machine (8.57% and 11.3%). Finally, a 3 kW/100 Wh prototype is built and the experiments proved the validity.

This paper deals with an analytical method to effectively calculate the inductance of an exterior-rotor switched reluctance motor (SRM), which evaluates the winding inductance of both the active section and the end section, accounting for the influence of core saturation. According to the inductance calculated by the analytical model, the flux linkage table and torque table can be established, and the steady state performance such as phase current, flux linkage, copper loss and core loss can be predicted. Effectiveness of this method is verified by the finite element method as well as by experimental results of a 12/8 SRM prototype.

This paper presents a dynamic thermal model which predicts the winding temperature of electrical machines at steady-state and transient conditions where windings are used in integrated battery chargers (IBCs) for DC charging in a stationary position. Using winding in high current charging process causes rising winding temperature which affects insulation life. Switched reluctance machines are a proper choice for using in electric vehicles (EVs) because of their advantages such as simple and sturdy structures. IBCs can reduce volume and weight of EVs and total cost is diminished because of integration. The analytical thermal model proposed in this paper can calculates the winding temperature in balanced and unbalanced currents injection because of the phase inductance in each rotor angle is distinct, so current excitation in each phase should be different for obtaining zero total torque and keeping rotor in a stationary position, also a reduced-order model is proposed with minor impact on the accuracy of the model. Special attention has been paid to monitor the winding temperature with considering the motor lifetime in DC charging mode, this view has not been addressed in IBCs before. The proposed model is then validated against experimental results and 3D finite element method.

Combining the advantages of switched reluctance motors and magnetic bearings, bearingless switched reluctance motors (BSRMs) have the potential value for industrial applications, such as turbine generators and compressors, because of their high reliability and low friction. In order to ensure the axial levitation of a rotor coping with loading in the axial direction, the axial reluctance force is essential to be considered for the BSRM. In this article, the analytical model of the axial reluctance force is proposed for BSRMs to investigate the axial levitation ability of the studied BSRM. The operational characteristics of the axial reluctance force are revealed by electromagnetic analysis for the BSRM. The factors affecting the axial reluctance force are explained, and the principle of output characteristics with the change of parameters is obtained. The analytical model is applicable for the calculation of the axial reluctance force under different motor parameters, i.e., axial displacement, current, and some mechanical parameters. After that, the finite-element method is adopted to verify the proposed analytical model. Then, the torque and radial levitation control and corresponding power converters are implemented in experiments to test the performance of the studied BSRM on the axial levitation in practice.

Conventionally, the converter of switched reluctance motor (SRM) is fed by the uncontrollable diode bridge rectifier (DBR), which leads to a low grid-side power factor (PF) and high current total harmonic distortion (THD). In this paper, an alternative solution for the grid-connected high-speed SRM drive system with improved PF is proposed. In the proposed drive system, the three-level active front end (AFE) is connected in cascade with the midpoint converter for SRM operation. A centralized strategy, which controls the AFE and SRM together, is proposed to govern the motor speed and grid-side PF by regulating the real power and reactive power of the system, respectively. Specifically, the real power, reactive power, and the voltage balancing of split capacitors are controlled by the model predictive directed power control (MP-DPC) algorithm, which significantly reduces the control complexity and guarantees the fast dynamic response. Consequently, satisfying speed regulation, high PF, low current THD, and bi-directional power-transfer capability are achieved. An idea-proofed testbench is constructed in laboratory, and the applicability of the proposed drive system is verified by a series of experimental results.

Switched reluctance generators (SRGs) come into prominence in other electrical machines with its simple structure, only stator winding, reliability, high fault tolerance and the possibility of working within wide speed range. These generators are used especially in wind power plants due to their ability to operate in variable speed range and applications of aviation and electric cars. In this study, the control of the SRG was performed. A simulation of SRG driver in Matlab/Simulink was performed and the real-time implementation control of SRG is carried out on DS1103 Ace kit digital signal processor to determine the performance of the SRG. The output voltage of the SRG is controlled by the proportional-integral (PI) voltage controller. As a result, the graphs of change in SRG phases currents and SRG output voltage were obtained according to different parameters. Simulation results compared with experimental results. Consequently, they overlap on experimental results.

The regulation of phase currents is bound by the voltage of power source for switched reluctance motor (SRM) drive with conventional asymmetric half-bridge (AHB) power converter in electric vehicle (EV). To avoid the drawback, an improved active boost power converter with self-balanced capacitor voltages is proposed. First, the problems existing in the AHB power converter are analyzed in different stages of each phase current. Then different working modes of the proposed converter are investigated. The corresponding control strategies are implemented in the light of two conduction sequences. The reference phase voltage is obtained with a new method. Then the control signals of the front-end topology are generated by comparing the reference phase voltage with the required value. One significant advantage of the proposed converter is that it can provide different voltages according to the operation condition of SRM dynamically. The other is that the maximum phase voltage the converter can boost is up to three times the supplied voltage. Comparative experiments on a three-phase 12/8 SRM drive validate the performance of the converter and the effectiveness of the control strategies.

In this paper, the researchers have described the development, design and characterization of a Switched Reluctance (SR) actuator, with a rotary motion, having a single-excitation activity. This SR actuator design consisted of a stator and rotor core and was based on the simplest SR actuator model design, with a Stator-to-Rotor pole ratio (S: R) of 6:4. In this design, the winding was coiled at Phase A, which enabled the single step motion characterization based on a single excitation. This SR actuator prototype showed a compact size, with a 36 mm stack length and a 60 mm outer diameter. This feature allowed small machine applications like the precision robotic machining, but required a low production cost, as it lacked a permanent magnet. On the other hand, the SR actuator consisted of highly non-linear characteristics and showed uncontrolled motion behavior. While achieving a very precise motion, it is important to suppress the non-linear characteristics of an actuator. Hence, the researchers designed the linearizer unit based on its characterization at Position 0°, which was related to the excitation current and the rotary angles for the various initial rotor positions. This initial position was chosen as it reflected the characteristics which indicated the self-starting characteristics. Thereafter, the researchers experimentally investigated the appropriate driving signal for this SR actuator as the normal step input signal showed a lower precision motion because of the discharging effect-related issues.

In this article, the integrated drive for three-phase switched reluctance motor (three-phase SRM) is proposed, and it combines a battery-powered bidirectional dc/dc converter to provide bidirectional power transfer in practice. In the proposed integrated drive, there is no relay to reconfigure and no need to add separate charging/discharging units and circuit components. Only one physical current sensor is used to sense the switch-bus current to provide all current signals not only for SRM driving, but also grid-to-vehicle/vehicle-to-grid functions at a standstill. The proposed integrated drive and its control are implemented and demonstrated by the provided results.

Noise, vibration, and harshness (NVH) issue in switched reluctance machines (SRMs), originating from their doubly salient structure and unique principle of operation, is addressed in this work by proposing a structural design modification in the stator, which increases stiffness to mass ratio of the structure. A 24-slot 16-pole (24s/16p) SRM designed with the aim of automotive application is studied here for the NVH optimization, at different target operating points, using stator pole bridges. Stator pole bridges link consecutive stator teeth to provide additional stiffness to the stator structure. Average torque reduction due to flux shorting in stator pole bridges is tackled by proposing a low-permeability material, with considerable stiffness, which has not yet seen its’ application in SRM NVH domain. Multiphysics aspects of stator pole bridge design encompassing electromagnetic radial force, mechanical stress, steady-state temperature distribution, and acoustic noise analyses are presented in this article. Possible manufacturing issues are considered during the design phase and appropriate measures are implemented to facilitate easier construction of two 100-kW prototypes. The final design with stator pole bridges and a baseline design without any stator pole bridges are prototyped, after rigorous multiphysics optimization, for extensive testing. Experimental results verify simulation outputs and report a maximum noise reduction of 12.52 dBA in the stator pole bridge model compared to the baseline SRM.

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).

This paper proposes a deflectable switched reluctance motor/generator, which can be used in wave energy conversion and underwater propulsion systems. When an underwater vehicle stops working, the ocean current drives the turbine blades connected to the motor to rotate, and the rotating turbine blades drive the deflectable generator shaft to generate electricity. The deflectable motor can complete multi-degree-of-freedom motion, so it can receive ocean current energy in multiple directions, thereby improving energy extraction efficiency. When the underwater vehicle starts to work, the deflectable motor can freely adjust the course of the vehicle, so that the vehicle can yaw freely under water. The finite element method is used to analyze the air gap flux density during rotation and deflection. The relationship between the flux, torque and current of a single coil under different rotor positions is obtained, and then the output current and voltage of the deflectable generator are obtained. Finally, a prototype was made for experimental verification.