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

This article proposes a simple method to calculate a current vector trajectory for the enhanced operation of the electric power generation system based on a synchronous reluctance machine (SynRM). Owing to magnetic saturation and cross magnetization, the performance and the torque capability of a SynRM vary according to the position and the value of the stator current. State-of-the-art control methods usually assume parameters with constant values, especially the inductance, neglecting saturation, leading to possible uncertainty in the machine operation. Therefore, a current vector trajectory to operate this type of machine, as a generator, in an extended speed range, with enhanced performance and considering magnetic saturation is proposed. A straightforward algorithm based on the inductance characteristic of the machine is used to calculate the trajectory of the stator current vector. This trajectory is evaluated via the numerical simulation of an experimentally validated finite-element model of a SynRM. The results show that the proposed current vector trajectory can improve the torque capability to 5% concerning the estimated trajectory without considering saturation. Experimental results are also provided to demonstrate the enhanced operation of the generator. [ABSTRACT FROM AUTHOR]

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

Thanks to the absence of rotor windings and permanent magnets, switched reluctance motors have a small weight construction. The integration of a modular power converter in a switched reluctance motor leads to a highly compact and fault-tolerant motor drive with small weight and high power density. In this article, a polygon-retrofitted integration topology is proposed for switched reluctance motors. Both the switched reluctance motor and the power converter are cooled with one shared cooling circuit. The power converter is designed and implemented using silicon carbide technology for its low losses and small thermal resistance. The proposed integration topology is extensively studied using multiphysics modeling and experimental measurements on a fully integrated rotating setup. A highly compact and power dense drive of 3.1 kW/L is obtained. [ABSTRACT FROM AUTHOR]

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

Rotor angle is essential in permanent-magnet (PM) brushless machines. Recently, an embedded magnetic encoder (EME) scheme, consisted of linear Hall sensors installing inside of the PM machines, has been proposed to sense the flux density and consequently provides rotor position. Compared with traditional optical encoder and resolver, the linear Hall sensor prevails over in both space and cost. The aforementioned scheme is employed successfully in rotor-PM machines, where a PM-excited field rotates at the synchronous speed. In this article, the feasibility of EME in stator-PM flux-switching machine is validated, where PMs are located in stator, resulting in a stationary PM field. The stator slots are selected as installation position of linear Hall sensors to avoid changing the existing structure of machines. The variation of linear Hall signal is due to the changing reluctance of rotor rather than rotating PMs. Then, a decoding algorithm is designed based on an add-up operation, a complex coefficient filter, and a synchronous reference frame phase-locked loop. Finally, experiments on a prototype machine are conducted to validate the effectiveness of EME scheme under both speed-varying and load-varying conditions. [ABSTRACT FROM AUTHOR]

Interturn short-circuit faults are one of the most (if not the most) harmful electrical machine failures, that if not detected and mitigated at a very incipient stage of development may involve serious consequences, both in terms of repair costs and safety. This article proposes a novel interturn fault diagnostic technique for synchronous reluctance machines based on the Luenberger state observer and current's second-order harmonic. The superiority of the proposed approach over the conventional model-based techniques is the ability to evaluate the severity of the fault as well as the efficiency in detecting faults in early stages and under various operating conditions. The effectiveness of the proposed method is demonstrated and validated through several experimental tests. [ABSTRACT FROM AUTHOR]

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

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

A generalized fault-tolerant control (FTC) strategy for the field-oriented control (FOC) and direct torque control (DTC) of five-phase fault-tolerant permanent magnet (FPFTPM) motors under various open-circuit faults is presented in this article. Most previous studies regarding FTC target a specific primary control algorithm and involve different reduced-order transformation matrices and additional current controllers, which increase the complexity of the entire drive system. In this study, a solution to the aforementioned problems is devised by developing optimal fault-tolerant voltages, which are derived from fault-tolerant mechanism analysis and steady-healthy design. Because the coordinate transformation need not be changed and additional voltage compensation is not required, a minimal control drive system reconfiguration under various open-circuit faults can be achieved to avoid accommodating the change of the primary control algorithm. The proposed control strategy not only improves the torque performance and dynamic response under healthy and fault conditions, but also adapts to both FOC and DTC. Experimental results for a 2 kW FPFTPM motor prototype are provided to evaluate the proposed strategy. [ABSTRACT FROM AUTHOR]

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

Due to the double-layer airgap configuration, the even-order harmonic components exist in the phase back electromotive force (EMF) of flux-modulation electrically excitation double-stator synchronous machine (FMEE-DSM), thus resulting in relatively high torque ripples. To promptly and effectively suppress these torque ripples, this article proposes and implements a second-order iterative learning control (ILC) strategy to minimize the main harmonic torque components based on the periodically repetitive characteristic of torque ripples in the FMEE-DSM. Via harmonic analysis on the torque ripples caused by the cogging torque and the nonsinusoidal induced EMFs, the dominative harmonic component, namely, the seventh-order component, can be precisely identified and then involved in the proposed ILC for torque ripple suppression. To verify the feasibility of proposed control strategy, a test bench of the FMEE-DSM control system was built based on dSPACE 1103. Accordingly, both the static and dynamic performances of the FMEE-DSM were investigated under the conditions of no-load and rated load. The theoretical analysis, computer simulation, and hardware experimentation are given to verify the proposed second-order ILC. [ABSTRACT FROM AUTHOR]

The interturn 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 article, a novel method for diagnosing the interturn 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 interturn 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 interturn short circuit conditions are conducted, and the results have verified the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

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

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. [ABSTRACT FROM AUTHOR]

In this article, based on flux modulation theory, an airgap-harmonic-based multilevel optimization design approach is proposed for a double-stator flux-modulated permanent-magnet (DS-FMPM) motor. The proposed DS-FMPM motor is purposefully designed, so as to realize the design requirements of driving cycle. In the proposed optimization approach, based on three fundamental elements of general flux modulation theory, motor optimization design is carried out from three levels. Furthermore, a response surface method, sensitivity analysis, and a genetic algorithm are purposely employed in different levels to obtain optimal motor design. In addition, electromagnetic performances of a DS-FMPM motor are demonstrated in detail. Finally, a prototype motor is manufactured and tested. Both simulation and experimental results verify the feasibility of the DS-FMPM motor and the effectiveness of the proposed airgap-harmonic-based multilevel optimization design approach. [ABSTRACT FROM AUTHOR]

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

In 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. [ABSTRACT FROM AUTHOR]

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]

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]

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]

Permanent magnets (PMs) have been widely used in different types of electrical machines to improve their performance. This article introduces a novel multi-tooth hybrid-excited switched reluctance motor (MT-HESRM) with PMs placed between the end teeth of the adjacent modules. Thanks to the innovative method of embedding PMs, a unique design is developed. First, the operating principle of the motor is explained, and the magnetic circuit model of the motor is analyzed. The magnetic characteristics in terms of flux density, flux linkage, inductance, and torque are obtained and compared with those of its PM-less counterpart. The mathematical model of the reluctance and PM torques is presented. The reluctance and PM torques are decoupled using the finite-element analysis, and the torque contribution of the PMs is discussed. The steady-state operations of both motors with both current chopping and single-pulse controls are analyzed and compared under different speeds. Finally, both motors are manufactured, the laboratory tests are done, and the experimental results are extracted. Both the simulation and test results elucidate that the MT-HESRM, which has only three small PMs as auxiliary flux sources, has unique features in terms of high output power and torque with a negligible cogging torque. [ABSTRACT FROM AUTHOR]

Synchronous reluctance machine (SynRM) has been studied widely in order to reduce its high torque ripple and improve its low power factor. This article proposes a torque ripple reduction method for SynRM by defining a novel parameter-torque function. With the help of torque function, the optimal currents aiming to compensate torque harmonics are obtained. The advantage of the proposed method is that torque function can be obtained easily and torque ripple reduction can be achieved by a simple control method. For the purpose of verifying the proposed method, both simulations and experiments are performed. Finally, the influence of power supply and parameter uncertainty on the proposed method has also been discussed. [ABSTRACT FROM AUTHOR]

In this article, we present a new configuration of bearingless slice motor that levitates and rotates a ring-shaped solid steel reluctance rotor. The rotor is 50 mm in diameter and has salient features on the outer surface. Symmetric sets of Halbach magnet arrays, mounted on the tips of stator teeth, establish a homopolar bias flux around the rotor. The bias flux passively stabilizes the rotor in the out-of-plane tilts and axial translation, whereas the rotor's radial translations are actively stabilized by feedback control. The rotor saliencies spatially modulate the air-gap bias flux such that the resulting torque-current relationship is similar to that of permanent-magnet synchronous machines. We have designed, built, and tested a prototype bearingless motor and control system. The prototype system achieves a torque constant of 14.9 mNm/A, maximum speed of 5500 r/min, and suspension bandwidth of 84 Hz with a phase margin of 11.3 $^{\circ }$. The rated torque and speed are 26.8 mNm and 3486 r/min, respectively, and the axial and tilting passive stiffnesses are 15.3 N/mm and 34.4 mNm/ $^{\circ }$ , respectively. [ABSTRACT FROM AUTHOR]

This article develops a modified dynamic reluctance mesh (DRM) method that can be utilized to calculate and analyze the magnetic field of the iron-cored tiered-type permanent magnet spherical motor (T-PMSpM) effectively and efficiently, with the multi-degree-of-freedom (multi-DOF) movements taken into account. According to the structural characteristic of the iron-cored T-PMSpM, the tilting function part, including the tilting stator and rotor, is equivalent to a dynamic lumped-parameter magnetic network model. Besides, the magnetic saturation phenomenon of the iron materials is also considered. The DRM results of magnetic field distribution, flux linkage and back electromotive force (EMF) show a good agreement with the three-dimensional finite-element method results. For further verification, a prototype motor of the iron-cored T-PMSpM has been manufactured. The back EMF curves with different rotor tilting positions are measured by experiments and compared with the calculated results. [ABSTRACT FROM AUTHOR]

This article proposes a new five-phase flux-intensifying fault-tolerant interior-permanent-magnet (FIFT-IPM) motor to realize high fault tolerance and sensroless operating capacity of the motor drive system for electric vehicles (EVs). By employing the new concept of flux intensifying, the proposed motor owns the outstanding characteristic of Ld > Lq, which can contribute the sensorless operation significantly. By integrating the special design of the stator tooth, using the masterly permanent-magnet (PM) placement and increasing the length of air gap in the q-axis, the high fault tolerance and high reliability can be obtained, which is essential for EV applications. The static performances of the proposed motor are investigated by using finite-element analysis. And the corresponding sensorless operation experiments are implemented based on the prototyped motor. Both theoretical analysis and the experimental results verify the validity of the proposed five-phase FIFT- IPM motor design. [ABSTRACT FROM AUTHOR]

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

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

The 2-degree-of-freedom direct drive induction motor (2DoFDDIM) is capable of implementing rotary linear or helical motion, which has the definite advantages of integrated structure, high material utilization, and so on. In this paper, the characteristics analysis of the three kinds of motions is presented. The air-gap magnetic field distributions and mechanical characteristics of the 2DoFDDIM with three motions are derived respectively. The results show that there is super synchronous speed or velocity phenomenon for rotary or linear motion. Moreover, the coupling effects between the rotating and travelling wave magnetic fields and that between the two mechanical motions will deteriorate the performance of the three-dimensional (3-D) helical motion compared with the two-dimensional (2-D) motion (rotary or linear). The expressions of the resistant torque and force caused by the coupling effect are derived, which are verified by 3-D finite-element models (FEMs). The results regarding the weakening of the output torque of helical motion and interacting magnetic field obtained from FEMs are then verified by experimental tests. Finally, the skewed slot method is applied to 2DoFDDIM, which successfully improves the performance of helical motion aiming to compensate the coupling resistant torque and force. [ABSTRACT FROM AUTHOR]

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

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

This paper presents an improved asymmetric half-bridge converter (AHBC) to enhance the output performance of a segmented-stator hybrid-excitation switched reluctance motor (SSHE-SRM) drive. Differences from conventional AHBC include an additional boost capacitor, a power switch, and two diodes added between the dc-bus and the AHBC. The static torque characteristic of a 12/8 SSHE-SRM is briefly analyzed and compared with a conventional SRM (CSRM). Based on the magnetic characteristic, the SSHE-SRM appears to have higher torque production capability. The improved AHBC is employed in order to increase the dc-bus voltage under dynamic operation. Higher voltage can be applied to phase windings and faster excitation and demagnetization currents can be obtained owing to the addition of capacitor voltage. Detailed simulations of the SSHE-SRM drive with the improved AHBC are carried out as well as compared with conventional AHBC. Finally, a 12/8 SSHE-SRM is prototyped. The SSHE-SRM drive based on the improved AHBC and conventional AHBC are experimentally tested. The measured results of static magnetic characteristic and dynamic performances are presented to validate the analysis and effectiveness of the novel converter. [ABSTRACT FROM AUTHOR]

Linear switched reluctance motors (LSRMs) provide an alternative to linear induction motor and linear permanent magnet motor in both vertical and horizontal propulsion applications. This paper attempts to develop a unitized design method of a segmental secondary LSRM, which is characterized by a modular magnetic circuit structure and the independent operation of multimover units. The developed design method is directly performed in linear domain without transforming it to a rotary SRM, which complies with the essential natures of the segmental secondary LSRM, showing that it is capable of delivering more power at the same dimensions compared to the conventional tooth type LSRM. Further, the sensitivity analysis of the critical geometric parameters is performed, and the guidelines for selection of the best dimension parameters are given. Finally, the three-phase and four-phase LSRMs are designed and prototyped, respectively with a 1-m long stator. The experimental results validate the design procedures and analysis above. [ABSTRACT FROM AUTHOR]

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

This paper analyzes the flux characteristics and normal force of the double-sided switched reluctance linear machine (SRLM) under the asymmetric air gap. The magnetic equivalent circuit (MEC) of the machine and the details of the flux paths configuration at six distinct mover positions under the asymmetric air gap are included. Then, six special mover position magnetization curves are calculated by solving the MEC with the method of Gauss–Seidel. The magnetic flux-linkage model and thrust model based on six distinct mover positions are established by analytical polynomial. Three-dimensional (3-D) finite-element method (FEM) simulation and the experimental study with the prototype hardware are carried out to validate the accuracy of the MEC model calculated for the flux linkage and normal force. The six distinct mover positions flux linkage and normal force calculated by the MEC are consistent with the 3-D FEM calculated data and experimental data. It indicates that the proposed method to calculate the flux linkage and the normal force is feasible and effective. The dynamic analysis is also conducted. The simulated phase current waveforms are also consistent with the experimental results. It indicates that the presented method can be used to simulate the phase current under the asymmetry air gap effectively. The normal force under different asymmetry rates is analyzed, which provides the theoretical basis for reducing the unbalanced force of the double-sided SRLM. [ABSTRACT FROM AUTHOR]

The experimental comparison of two different global learning position controls (namely, “adaptive learning” and “repetitive learning” controls) for hybrid step motors performing repetitive tasks has been recently presented in the literature. Related benefits and drawbacks have been successfully analyzed on the same robotic application. However, the design of the two aforementioned learning controls—though relying on a rigorous stability analysis—are based on a simplified current-fed model of the motor. They cannot achieve precise current tracking due to the mere presence of proportional-integral (PI) control actions in the outer current control loops. The aim of this paper is to enrich and update the results of the aforementioned comparison in the light of the latest contributions that generalize the theoretical design to the full-order voltage-fed motor models of hybrid step motors. Learning actions are now included in the outer current control loops: They generalize the corresponding PI actions to the periodic scenario and allow to solve a control problem whose solution was seeming very difficult to be obtained. [ABSTRACT FROM PUBLISHER]

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

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

The objective of this paper is to investigate the design and optimization of a novel dual-rotor hybrid permanent magnet machine for traction application. The proposed dual-rotor hybrid synchronous PM machine synthesizes the synchronous reluctance and surface permanent magnet rotors into a single machine with the common shaft by using “inner-out” configuration. One feature of this hybrid machine is to explicitly separate the magnet torque and reluctance torque components so that the two rotors can be designed individually with more flexibility. Instead of using expensive rare-earth magnets, the hybrid machine is demonstrated to achieve similar performance as the Toyota Prius motor with only ferrite magnets arranged in a Halbach array structure. Design principles including structure configuration, sizing equation, and alternative topologies using N-N and N-S types are elaborated. Multi-objective optimization is implemented in the electromagnetic finite element analysis for the traction motor design, and Pareto line of the results is identified. Structural analysis is also used to validate the mechanical integrity at high-speed conditions. The optimized machine demonstrates almost the same torque profile as the Prius motor. [ABSTRACT FROM PUBLISHER]

Linear switched-reluctance motor (LSRM) is investigated and proved to be an alternative for direct linear driving systems, especially for long-distance transportation applications, such as vertical elevator driving motor. This paper presents the design, sensitivity analysis, and optimization of a toroidally wound mover LSRM with segmental stator. The presented LSRM has much higher copper utilization ratio and flux carrying capability than the conventional LSRM for vertical linear propulsion application. The features of motor performance influenced by various geometrical parameters are described using magnetic circuit and finite element analysis to give the guidelines for selecting the reasonable range of those parameters of this kind of machine. Furthermore, an optimization procedure is performed to obtain the optimal machine dimensions considering active payload ratio and force ripples. Finally, the experimental results from the prototype validate the design procedures and analysis above. [ABSTRACT FROM PUBLISHER]

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

Because single-phase dc-excited flux switching machines (DCFSMs) consist of only copper windings and iron cores, they have great potential in low-cost and high-speed applications, such as home appliances. However, similar to other types of single-phase ac machines, single-phase DCFSMs have insufficient initial torque at some rotor positions. A novel single-phase, eight-slot, four-pole DCFSM design is presented in this paper. The key feature of this design is the enhancement of reluctance torque at positions where the machine cannot deliver sufficient initial torque output. This is accomplished by modifying the outline of a section of the rotor. Consequently, the machine has a two-layer rotor structure along the axial direction. The proposed design is validated experimentally using a prototype. The results show that the machine can start from any rotor positions with initial torque higher than 50% of the rated output torque. [ABSTRACT FROM AUTHOR]

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

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

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

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

The half-teeth-wound switched reluctance machines (HT-SRMs) having single-layer concentrated windings, feature simpler structures since the coil number is half, and phase-to-phase insulations in slot are eliminated. To evaluate the effects of winding configurations, the electromagnetic performances of HT-SRMs and conventional full-teeth-wound SRMs (FT-SRMs), including air-gap flux density, coil and phase flux linkage, inductance, torque, volt–ampere, and radial magnetic force (RMF), are comprehensively compared. The results based on theoretical analysis and finite-element (FE) method reveal that HT-SRMs would exhibit higher torque per ampere when the magnetic saturations are not too severe, whereas require higher voltage supply and generate more significant RMF. Further, it is found that the fault-tolerant capabilities of HT-SRMs are superior to FT-SRMs. A pair of prototypes with identical laminations but different winding configurations are manufactured and the experimental results confirm the predictions. [ABSTRACT FROM PUBLISHER]

This paper presents a novel switched reluctance motor incorporating a new design methodology. The proposed structure is designed using distinct concepts including design considerations of salient poles and the motor energy conversion capacity. First, multiple techniques to increase the motor torque using these concepts are discussed. Then, the new design is introduced. Based on the concepts of maximum energy conversion and also providing a topology change process, a novel stator-segmented structure is proposed. The three-phase form of the proposed motor has six segments in the stator with four poles and a solid rotor with 22 poles. The novel motor's characteristics are initially obtained using finite-element analysis and shown to exhibit higher torque density when compared to the conventional structure. Finally, the performance of the new design and analysis methods described in the paper are verified by experimental results obtained by a built prototype. [ABSTRACT FROM PUBLISHER]

The position-sensorless control methods of dc+ac stator fed doubly salient electromagnetic motor (DSFDSEM) covered full speed range are presented in this paper. To implement these methods, the following procedures are done. First, the series self-inductance area difference method, in consideration of cogging torque produced by field current, is adopted for identifying the initial position. Second, the current pulse injection technique in the commutation point is proposed to detect the commutation moment at low speed. Finally, the terminal voltages are considered as vectors with a fixed phase difference, and the composed vector is rotated with varying rotor positions; the commutation point can be obtained by coordinate transformation of three terminal voltages at high speed. The filter with a low cutoff frequency is not required in this method. Moreover, the smooth-switch technology between startup and high-speed operations is researched to prevent the out-of-step fault. The sensorless control of a DSFDSEM from startup at standstill to high-speed operation can be easily implemented by the aforementioned methods. No additional hardware or complex computation is required. A 12/8 DSFDSEM prototype is built and tested to verify the feasibility of the proposed sensorless schemes. [ABSTRACT FROM PUBLISHER]

This paper presents a multiphysics modeling of a switched reluctance motor (SRM) to simulate the acoustic radiation of the electrical machine. The proposed method uses a 2-D finite-element model of the motor to simulate its magnetic properties and a multiphysics mechatronic model of the motor and controls to simulate operating conditions. Magnetic forces on the stator are calculated using finite-element analysis and are used as the excitation on a forced response analysis that contains a finite-element model of the motor stator structure. Finally, sound power levels are calculated using the boundary element method. Simulation results of the model are shown and compared with experimental measurements for a four-phase 8/6 SRM. [ABSTRACT FROM PUBLISHER]

Switched reluctance machine (SRM) has been viewed as a low-cost machine with concentrated windings on the stator and no magnetic source on the rotor. Owing to the higher torque-production capability with lower ripple, an SRM with a higher number of rotor poles is a potential candidate for traction applications in hybrid and plug-in hybrid electric vehicles. However, since external phase commutation and rotor-position detection are necessary to run the SRM, its control can be challenging. In case of an SRM with a higher number of rotor poles, each phase is energized more frequently in one revolution, and the current conduction time is shorter due to the smaller interpolar gap between rotor poles. This paper investigates potential control complexity owing to the higher number of rotor poles, self-starting, and fault tolerance of the machine. A 5-hp drivetrain with a three-phase 6/10 SRM has been developed for traction application. Conventional current and speed controls have been implemented to experimentally evaluate the dynamic performance of the new family of SRMs. It has been shown that the 6/10 SRM is capable of operating even if two of its phases develop a fault. Moreover, the 6/10 SRM is capable of starting by itself with an initial hard alignment when only two phases are operating. [ABSTRACT FROM PUBLISHER]