Search

This paper comprehensively investigates the electromagnetic performance of 3-phase, 12-slot, and 8-pole switched reluctance machines (SRMs) with different winding configurations, i.e., double/single layer, short pitched (concentrated), and fully pitched (distributed). These SRMs are supplied by sinewave currents so that a conventional three-phase converter can be employed, leading to behavior which is akin to that of synchronous reluctance-type machines. Comparisons in terms of static and dynamic performances such as d- and q-axis inductances, on-load torque, torque–speed curve, and efficiency map have been carried out using two-dimensional finite-element method (2-D FEM). It is demonstrated for the given size of machine considered that for same copper loss and without heavy magnetic saturation, both single- and double-layer mutually coupled SRMs (MCSRMs) can produce higher on-load torque compared to conventional SRMs (CSRMs). Additionally, double-layer MCSRM achieved the highest efficiency compared to other counterparts. When it comes to single-layer SRMs, they are more suitable for middle-speed applications and capable of producing higher average torque while lower torque ripple than their double-layer counterparts at low phase current. Two prototype SRMs, both single layer and double layer, are built to validate the predictions. [ABSTRACT FROM PUBLISHER]

Novel stator slot permanent magnet (SSPM) machines with doubly salient structure have attractive features, such as a robust rotor and fail-safe capability during faults due to their peculiar PM excitation characteristics. In this paper, average electromagnetic torque production in SSPM machines is investigated using the frozen permeability analysis for the 12/10 stator/rotor pole machine. The single layer (SL) and double layer (DL) winding SSPM machines with 12/10 stator/rotor poles are further investigated, accounting for the influence of stator tooth-tips. The key findings include that the average electromagnetic torque can be enhanced by 9%–10% at the rated current for the DL and SL winding machines with stator tooth-tips. The influence of design parameters, open-circuit characteristics, inductances, electromagnetic torque, torque ripple, and losses is studied. Finally, the 2-D finite-element analysis is experimentally validated. [ABSTRACT FROM AUTHOR]

This paper first investigates the flux-weakening control performance of two types of partitioned stator-switched flux permanent-magnet (PM) (PS-SFPM) machines and then proposes a novel mechanical flux-weakening technique. The PS-SFPM machine topologies, operation principles, and flux-weakening control method are described. In addition, it is shown that by mechanically varying the relative position of two stators of the PS-SFPM machine, the PM flux linkage can also be varied, and hence, it can provide improvement in the speed range and torque capability. The optimal relative mechanical angle is derived to enable the maximum torque capability and reduce or even avoid the flux-weakening current injected by the inverter. The proposed technique is verified by three-dimensional (3-D) finite-element (FE) analyses and experiments on the prototype machines. [ABSTRACT FROM AUTHOR]

This paper presents a novel 6/5 segmental rotor-type switched reluctance motor (SRM) for cooling fan application. Unlike conventional structures, the rotor of the proposed structure is constructed from a series of discrete segments, and the stator is constructed from two types of stator poles: exciting and auxiliary poles. Meanwhile, the windings are only placed around the exciting poles, resulting in short flux paths and no flux reversal in the stator of the proposed SRM. Hence, the proposed structure may increase the electrical utilization and reduce magnetomotive force (MMF) requirement compared to conventional SRMs. To verify the proposed structure, the operation principle and the design rules of the proposed structure are illustrated and expounded. The finite-element method (FEM) is employed to get the static and dynamic characteristics of the conventional 12/8 and proposed SRMs. Furthermore, the prototype is manufactured and tested. Finally, the simulation and experimental results are presented and analyzed to verify the effectiveness of the proposed SRM. [ABSTRACT FROM AUTHOR]

This paper examines the effect of frame on the acoustic noise and vibration of a high-speed and high-power switched reluctance machine (SRM). Five types of frame/ribs are investigated, where different frame thicknesses, types of cooling ribs, and frame shapes have been analyzed. For this purpose, a 12/8 SRM has been designed at 22 000 r/min and 150 kW and two stages have been applied. In the first stage, a new equivalent stiffness of the frame is utilized in order to estimate the resonant frequencies for different frame shapes. The paper provides a mathematical calculation method and evaluates its effectiveness with finite-element simulations. The results indicate an improvement between 4% and 25% in the estimation natural frequencies. The second stage includes the vibration and acoustic noise analysis using 3-D finite-element method. Considerations for acoustic noise reduction in high-speed SRM using different frame types and cooling ribs are discussed. Particularly, radial and screw-type configurations represent a better solution to decrease the sound pressure level up to 12 dB. [ABSTRACT FROM PUBLISHER]

Direct-drive permanent magnet (PM) synchronous generators (DDPMSGs) are gaining more and more attention and application for wind power. This paper presents a comprehensive performance comparison of an external rotor surface-mounted PM synchronous generator equipped with three commonly used winding types, i.e., integral-slot distributed winding (ISDW), fractional-slot concentrated winding (FSCW), and fractional-slot distributed winding. The tradeoff between torque and the power factor, loss distribution, current, torque, and PM demagnetization characteristics under a short-circuit fault and the steady temperature rise are investigated and compared using finite-element analyses. It is found that, generally, FSCW PM generators exhibit high rotor losses compared with ISDWs, which will lead to an overly high temperature rise. Measures such as segment PMs and the adoption of lamination steel in the rotor can reduce the rotor loss and greatly improve the machine efficiency. However, the temperature rise of FSCW machines is still higher than that of ISDW machines. The conclusion is intended to help choose the proper winding types. [ABSTRACT FROM AUTHOR]

This paper proposes a new yokeless linear flux-switching permanent magnet (LFSPM) machine topology with double magnets per mover module for maximizing thrust density. The optimization and analysis for the proposed yokeless LFSPM machine are carried out by the finite-element method. The comparison between the proposed yokeless LFSPM machine and the optimized conventional yokeless machine under the same constraints is conducted, showing that the proposed machine exhibits higher thrust density and low force ripple, while the product of power factor and efficiency of the new machine is marginally higher than that of the conventional yokeless machine. [ABSTRACT FROM AUTHOR]

The transverse-flux linear switched-flux permanent magnet machine is investigated by 3-D finite-element analysis in this paper. The topology of the machine, as well as the machine operation principle, is introduced first. In order to improve the thrust force performance of the machine, two aspects are analyzed. One is the average thrust force, which is maximized by optimizing the mover stack length and the stator pole stack length. Not only does the average thrust force increase, but the force ripple slightly decreases as well. The other side is further lowering the force ripple. The segment group shift method is introduced and employed. After using this method, the force ripple has been reduced to an acceptable value, though the average thrust force will be slightly reduced. The analysis is the guidance for better understanding this novel machine. [ABSTRACT FROM AUTHOR]

This paper first presents a novel dual-layer permanent-magnet (PM)-excited (DPME) synchronous motor in which an extra set of iron teeth is employed in an inner stator between the PM rotor and the shaft. It can provide additional variation of magnetic reluctance along the circumferential direction of the air gap, and the strength of the flux modulation among the magnetic fields produced by the armature windings and the PMs is improved. The proposed motor has tactfully integrated the two pairs of flux-modulated motors inside one frame with one shared set of armature windings. The advantage of the proposed DPME motor is that it offers much higher torque capability than its conventional counterparts, making it more competitive for low-speed high-torque applications. In this paper, a novel triple-layer PM-excited (TPME) synchronous motor is further presented with the similar operating principle of the DPME, and it has three PM layers inside the frame. Finite-element method of magnetic field with mechanical motion coupled computation is employed to evaluate the electromagnetic torque precisely, showcasing that the proposed DPME motor can output an extra 37.5% more torque compared with a conventional synchronous motor, and the proposed TPME motor can output an additional 70% more torque with a similar power efficiency compared with the conventional PM synchronous motor. [ABSTRACT FROM AUTHOR]

A novel asymmetric interior permanent magnet (AIPM) machine is proposed in this paper for electric vehicle application. It has a skewed V-shape permanent magnet (PM) cavity, two PMs with different dimensions and an additional flux barrier outside the V-shape cavity in each pole. This asymmetric rotor topology can inherently utilize the magnetic-field-shifting (MFS) effect to reduce the current angle difference between the maximum PM and reluctance torque components, thereby enhancing the maximum synthetic torque with the same PM usage. The influences of cavity positions in the proposed AIPM and an existing AIPM with extra flux barrier inside the V-shape cavity are investigated and compared using finite element analysis. It is found that the proposed structure with outside flux barrier has higher average torque than the one with inside flux barrier. Both AIPM topologies are designed with the same stator, rotor diameter, and PM usage as the conventional V-shape IPM benchmark for Prius 2010. Electromagnetic, mechanical and steady-state thermal performance of three machines are compared. The results confirm that the proposed AIPM machine can achieve significant torque enhancement due to utilizing MFS effect, compared with the existing AIPM and the IPM benchmark. Finally, a small prototype of the proposed AIPM machine is designed, manufactured and tested to validate the FE analysis. [ABSTRACT FROM AUTHOR]

Low-speed flux-modulated permanent-magnet (PM) machines do not need to conform to the conventional design rule which requires identical number of pole-pairs in both stator and rotor. In flux-modulated machines, special ferromagnetic segments in the airgap are used to modulate the magnetic field. In this paper, a general rule to compare different types of electric machines as well as measures to improve the torque density in these machines are presented. In this paper, the energy conversion capacity of different machines with the same physical size and the same operating temperature-rise are compared. An adaptive-order method for modeling the load—temperature-rise relationship is presented to reduce the computing time for this inverse problem. Three power-electronic-driven PM electric machines, which are, namely, a traditional PM machine, a radial-flux-modulated machine (RFMM), and an axial-flux-modulated machine (AFMM), are analyzed and compared based on their temperature distribution and electromagnetic torque density using magnetic field and thermal field computation. Experimental results of an AFMM prototype are used to validate the temperature-rise which is computed using 3-D finite-element method (3-D FEM). [ABSTRACT FROM PUBLISHER]

This paper presents a surrogate-model-based optimization of a doubly-fed induction generator (DFIG) machine winding design for maximizing power yield. Based on site-specific wind profile data and the machine's previous operational performance, the DFIG's stator and rotor windings are optimized to match the maximum efficiency with operating conditions for rewinding purposes. The particle swarm optimization-based surrogate optimization techniques are used in conjunction with the finite element method to optimize the machine design utilizing the limited available information for the site-specific wind profile and generator operating conditions. A response surface method in the surrogate model is developed to formulate the design objectives and constraints. Besides, the machine tests and efficiency calculations follow IEEE standard 112-B. Numerical and experimental results validate the effectiveness of the proposed technologies. [ABSTRACT FROM AUTHOR]

This paper presents a simple analytical model for two types of three-phase surface-mounted permanent magnet machines: modular and unequal tooth (UNET) width machines with different slot/pole number combinations. It is based on the slotless open-circuit air-gap flux density and the slotted air-gap relative permeance calculations. This model allows calculating the opencircuit air-gap flux density, phase flux linkage, back electromotive force, and average torque of both the modular and UNET machines. Its accuracy has been validated by the 2-D finite-element (FE) method. A flux focusing/defocusing factor has also been introduced to analyze the influence of flux gaps in alternate stator teeth of modular machines on the machine electromagnetic performances. It has been found that by properly choosing the slot/pole number combination and flux gap width, the open-circuit air-gap flux density, the winding factor, and the flux focusing effect can all be improved. As a result, the performance of the modular machine can be significantly boosted. The analytical and FE models have been validated by experiments. [ABSTRACT FROM AUTHOR]

In this paper, a linear permanent-magnet vernier machine is proposed, in which both magnets and armature windings are placed in the short mover, while the long stator consists of an iron core only. Hence, it is suitable for long-stroke applications such as urban rail transit. The proposed machine integrates two magnetization directions of magnets together, which can reduce leakage flux and enhance flux density. Meanwhile, since different topologies and different slot/pole number combinations have an effect on the winding factor, several general rules are established. It is revealed that the thrust force ripple of the proposed machine is lower than its cogging force ripple, which is explained by a built analytical model. Both the analytical model and the finite-element results are validated by experiments based on a prototype machine. [ABSTRACT FROM AUTHOR]

The dual-stator spoke-array vernier permanent-magnet (DSSA VPM) machines proposed in the previous papers have been proven to be with high torque density and high power factor. However, the design procedure on the DSSA VPM machines has not been well established, and there is little design experience to be followed, which makes the DSSA VPM machine design quite difficult. This paper presents the detailed DSSA VPM machine design procedure including decision of design parameter initial values, analytical sizing equation, geometric size relationship, and so on. In order to get reasonable design parameter initial values which can reduce the number of design iteration loop, the influence of the key parameters, such as rotor/stator pole combination, slot opening, magnet thickness, etc., on the performances is analyzed based on the finite-element algorithm (FEA) in this paper, and the analysis results can be regarded as design experience during the selection process of the initial values. After that, the analytical sizing equation and geometric relationship formulas are derived and can be used to obtain and optimize the size data of the DSSA VPM machines with little time consumption. The combination of the analytical and FEA methods makes the design procedure time-effective and reliable. Finally, the design procedure is validated by experiments on a DSSA VPM prototype with 2000 \N\cdot\m. [ABSTRACT FROM PUBLISHER]

Removing some sections of the stator yoke in a permanent-magnet brushless machine can be beneficial for reducing punching waste and simplifying motor manufacture. However, in some cases, restricting the possible flux paths, in this way, will have a detrimental impact on the torque and air-gap harmonics. This paper discusses the potential implications of modular stator core arrangements and presents the air-gap flux density harmonics and winding factors for potential slot/pole combinations. Finite-element analysis (FEA) simulations are presented to support the analytical calculations. The analysis indicates that the performance reduction from using a modular stator is minimal when the number of slots and poles are similar but drops off substantially when this is not the case. A modular core stator will increase the MMF subharmonics due to the magnet field but can reduce the subharmonics due to the armature if a single-layer winding is used. The effect of slotting is very similar for a modular and conventional core machine, and FEA results match previously published analytical analyses. [ABSTRACT FROM PUBLISHER]

This paper presents a method to approximately take account of the rotor excitation field of a synchronous machine under maximum aperiodic short-circuit condition using an impressed current vector potential in a 3-D transient finite-element analysis. The method is applied to compute end-region phenomena like end-winding forces or eddy current losses in conducting machine parts where the effects of the rotor excitation field cannot be neglected. A complex 3-D geometry model, the numerical method, and the computation results like end-winding forces are presented. The transient analysis of the electromagnetic field has been performed using the T, $\Phi $ - $\Phi $ formulation solved with an in-house software. [ABSTRACT FROM PUBLISHER]

This paper proposes a strategy for the optimal design of a synchronous motor with permanent magnets on the rotor surface. The proposed strategy includes several steps during which the general parameters of the rotor arrangements, currents in the stator windings, and the parameters of the slot tooth in the stator are consequently defined. The motor with the optimized cross section demonstrates significantly better performance than its initial prototype. All calculations are performed using industry-standard finite element method software. [ABSTRACT FROM PUBLISHER]

In this paper, a 10 kW/500 r/min nine-phase flux-switching permanent magnet (FSPM) machine for wind power generation system is proposed, analyzed, and designed. First, different topologies with alternative stator slots and rotor poles combinations are compared. Then, both the split ratio and rotor pole width, which have major influences on electromagnetic performance, are optimized, whereas static characteristics, viz., the phase PM flux linkage and electromotive force, cogging torque, inductance, and electromagnetic torque, are predicted by 2-D finite-element analysis (FEA). In addition, the unbalance magnetic force is investigated. Finally, a prototype of a 10 kW 36-stator-slots/34-rotor-poles nine-phase FSPM generator is manufactured and the experimental tests is carried out to verify the theoretical analysis and FEA-based predictions. [ABSTRACT FROM PUBLISHER]

In this paper, a novel three-phase bipolar stator surface-mounted permanent magnet (B-SSPM) machine with different magnetizations is proposed. The topologies and operation principles of a 6-stator-slots/8-rotor-poles B-SSPM machine are first introduced briefly, and an optimization on the key dimensions is explored to improve the characteristics of phase electromotive force and to reduce cogging torque. In addition, the influences of different magnetizations of magnets on the static characteristic of B-SSPM machines are comprehensively investigated. Finally, the predicted results are confirmed by both finite-element analysis and experiments. [ABSTRACT FROM PUBLISHER]

Flux-switching permanent magnet (FSPM) machines exhibit high torque density, high efficiency, and robust rotor structure. In this paper, a prototype of a high-power three-phase 12-stator-slot/10-rotor-pole FSPM motor used for hybrid electric vehicles (HEVs) is designed by finite-element analysis (FEA). First, the initial FEA model is improved by gradually taking into account lamination B – H curves due to different electrical frequencies, operation temperatures, 3-D end effect, and rotor eccentric. Thereafter, a modular manufacture method of the FSPM motor is discussed with the improved FEA model and validated by experimental measurements. Then, the measured overload capability of the FSPM motor is compared with that of an interior permanent magnet (IPM) motor used in Honda Civic, and the results indicate that the IPM motor exhibits significantly stronger overload capability, which is analyzed in depth from soft-iron materials, cooling conditions, and and so on. Finally, both the merits and demerits of FSPM motor employed for low-voltage and high-current HEV applications are highlighted. [ABSTRACT FROM PUBLISHER]

Axial magnetic fields leaking out at the ends of a conventional rotating synchronous machine cause losses. Therefore, it is important to be able to predict the axial magnetic fields. A linear steady-state model for the axial magnetic flux density phasor in the end regions of non-salient synchronous generators has previously been verified experimentally. This paper describes an extension of the model to salient pole synchronous generators and a method for calculating the coefficients. Experiments and 3-D finite element simulations justify a distinction between axial flux density contributions from the d and q components of the stator current. How the coefficients and the axial magnetic fields in the ends of a small synchronous generator change with steady-state operation conditions is here shown with measurements and to some extent with 3-D finite element simulations. [ABSTRACT FROM PUBLISHER]

An optimum electromagnetic design of a nonsalient magnetic-cored superconducting synchronous machine (SSM) is presented in this paper. First, self- and mutual inductances of a nonsalient magnetic-cored SSM are calculated using the magnetic energy method and analytical equations of magnetic vector potential. Then, a design approach for an SSM machine is proposed based on the inductances of the machine. An optimal design is finally performed using a genetic algorithm, considering the machine efficiency as an objective function. The finite-element method is utilized in each step to verify the analytical results. [ABSTRACT FROM PUBLISHER]

A novel dual-stator bidirectional-flux modulated permanent magnet (PM) machine is presented in this paper. The key of the design is to locate consequent PM poles in both stator and rotor sides and the merit is that the magnetic flux produced by either the rotating or stationary PMs and dual-stator windings can be modulated by the stator teeth and rotor iron segments. It is shown that with this flux modulation effect and improved reluctance torque effect, the torque density of the machine can be increased. The bidirectional flux modulation theory and operation principle of the machine are explained and analyzed using time-stepping finite element method. [ABSTRACT FROM AUTHOR]

The fault tolerant capability of electrical machine-based driving systems is extremely important in many applications. Hence, in this paper, two fault tolerant current control strategies for a nine-phase flux-switching permanent magnet (FSPM) machine are proposed and implemented when one or two phases meet the open-circuit fault. The basic concepts of the two control strategies are to keep the rotating magnetomotive force unchanged under both healthy and faulty conditions. Based on the principle, an optimal solution is derived through comparing the magnitudes of fault tolerant currents, average output torque, and torque ripple. The finite element analysis-based predictions of the nine-phase FSPM machine verify the effectiveness and difference of the two fault tolerant control strategies. [ABSTRACT FROM AUTHOR]

This paper proposes a novel double-stator axial-flux spoke-type permanent magnet vernier machine, which has a high torque density feature as well as a high-power factor at low speed for direct-drive systems. The operation principle and basic design procedure of the proposed machine are presented and discussed. The 3-D finite element method (3-D-FEM) is utilized to analyze its magnetic field and transient output performance. Furthermore, the analytical method and a simplified 2-D-FEM are also developed for the machine basic design and performance evaluation, which can effectively reduce the modeling and simulation time of the 3-D-FEM and achieve an adequate accuracy. [ABSTRACT FROM AUTHOR]

In this paper, the concept of dc-field excitation is newly incorporated into the axial-flux doubly salient (AF-DS) machine, leading to create the new magnetless AF-DSDC machine. With the external field excitation, the proposed machine not only can enjoy its improved torque density, but also the flux-weakening capability for the wide-speed range operation. With these characteristics, the AF-DSDC is favorable for the in-wheel direct drive application. In particular, the proposed machine is designed and compared based on the requirement of a typical passenger electric vehicle. To have a better illustration, a radial-flux DSDC machine is also designed under the fair environment. The corresponding performances of both machines are analyzed by using the 2-D and 3-D finite element method. [ABSTRACT FROM AUTHOR]

This paper presents an analytical method that integrates the equivalent circuit (EC) and magnetic circuit (MC) in order to analyze and design a brushless doubly fed reluctance generator (BDFRG). The proposed method is capable of evaluating the BDFRG performance at the design stage because the terminal voltage can be predicted through the MC and the torque can be calculated from the EC. The MC is used to calculate the air gap flux density so that the flux linkage can be further obtained for the calculation of the machine performance using the EC and a set of particular operating conditions. The integration of the EC and MC provides a rapid analysis for a direct connection between the physical dimensions and the machine performances, including torque, mechanical power, electric power, and efficiency. The proposed analytical method is applied to two BDFRG designs. One is a manufactured prototype. Finite element analysis and experiments are used to verify the analytical results. [ABSTRACT FROM AUTHOR]

DC-biased sinusoidal current vernier reluctance machines (dc-biased VRMs) have a doubly salient structure, and their phase currents contain an alternating current (ac) component and a direct current (dc) component. Hence, their main features are one set of concentrated windings compared with variable flux reluctance machines, low vibration and noise due to smooth current, compared with switched reluctance machines, and robust rotor structure. Besides, its achievable high slot fill factor can improve the torque density further. In this paper, based on the flux modulation principles, the torque production mechanism of dc-biased VRMs is analyzed, and two slot combinations of 12/8 and 12/10 are proposed. First, the machine topology and inverter main circuit are illustrated. Second, the torque production mechanism is explained. Furthermore, the inductance characteristic, optimal current configuration for maximum torque and lowest torque ripple are analyzed theoretically and by the finite-element analysis. Finally, one prototype was designed and built, and the proposed analysis is validated by the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a new topology of a spherical machine, denominated as a shell-like spherical induction machine, which was initially studied in recent published papers, is now designed and optimized for a powered-wheel application. The main objective is to perform an optimization design for the power/volume ratio maximization. The multiobjective/multiconstraint evolutionary algorithm NSGA-II (elitist nondominated sorting genetic algorithm) was used as the optimization tool. This optimization tool provides us a first design and physical insight to be further used in more complex 3-D finite-element analysis (FEA) tools. Thus, the shell-like spherical induction machine electromagnetic and thermal analytical models are first developed. To validate the thermal model, a small-scale prototype was built using a new soft magnetic material as the stator and rotor magnetic core. Tests to the prototype were carried out in our laboratory, measuring its electromagnetic torque and temperature, comparing them with the FEA and analytical results. Then, the optimization problem is defined by describing the objective functions, decision variables, and constraints for the powered-wheel application. Finally, the optimization results are analyzed using the Pareto front approach, showing the evolution of each objective function and decision variable. [ABSTRACT FROM AUTHOR]

The electromagnetic and heat issue is the core of the key problems for large synchronous generators. This paper presents a new method to account for the rotary excitation field of a large synchronous generator using a new 3-D static frequency-domain finite element to solve the end magnetic field and electromagnetic losses via phase transformation. The solution time is significantly reduced. Both magnetic flux leakage and temperature testing of the end structures are conducted. There is good consistency between the theoretical simulation and the experimental results for both magnetic and thermal fields. The regularity of the magnetic and thermal field distributions is studied drawing on the electromagnetic and heat transfer theories. [ABSTRACT FROM PUBLISHER]

In this paper, novel dual-stator switched-flux hybrid magnet machines (DS-SF-HMMMs) are proposed. Two sets of armature winding are employed so as to improve the space utilization and torque density. Meanwhile, two kinds of permanent magnets (PMs), i.e., neodymium–iron–boron and low-coercive-force magnets, are placed on either a common stator or separate stators. The proposed machines can provide the merits of high torque density in DS machines, and excellent flux adjusting capability in memory machines. The topologies and operating principle of the DS-SF-HMMMs having different PM arrangements are introduced and highlighted, respectively. In order to overcome the drawbacks of the original “U”-shaped PM type, two alternate designs are presented to increase the copper area in the inner stator and facilitate the manufacturability. In addition, the equivalent magnetic circuits for various machine models are formulated to reveal the field regulation principle. Then, the electromagnetic characteristics of various available DS-SF-HMMMs are evaluated and compared by the finite-element (FE) method. The stator/rotor pole combinations of the selected machine are analytically optimized in order to maximize the torque density. Finally, two prototypes are manufactured and tested to verify the FE analyses. [ABSTRACT FROM PUBLISHER]

This paper investigates the rotor design optimization of synchronous reluctance machines (SynRMs) by using electromagnetic and structural finite-element simulations. Three conflicting objectives, i.e., average torque, torque ripple, and sound pressure level, were considered using a surrogate-based multi-objective approach. While the stator is fixed, the rotor flux barriers of a 33-slot 8-pole SynRM were geometrically varied to extract optimal design regions. These regions or constraints help decrease the computational time during the sampling procedure of a multiple-barrier design. Different numbers of flux barriers were studied and related to each other. Adding the sound pressure level was observed to affect previous results by spreading the Pareto front solutions across the design space. [ABSTRACT FROM AUTHOR]

In recent decades, bearingless switched reluctance motors (BSRMs) have been proposed. However, few researchers focused on the optimal design of the BSRMs. In this paper, the multi-objective optimal design of BSRMs is investigated. At first, an analytical design model is derived from the mathematical model of the BSRMs. An initial design is calculated by the analytical design model. The electromagnetic performance is compared with calculation results from the finite-element method (FEM). Then, the objective functions, constraints, and decision variables are also determined. Corresponding sensitivity analysis of the decision variables is implemented. Besides, aiming at solving the optimization problem with disconnected, non-uniformly distributed Pareto front and multiple local optimums, a novel multi-objective genetic particle swarm optimizer (MOGPSO) is presented. The algorithm performance of the proposed MOGPSO is validated by solving the standard test functions. Then the proposed MOGPSO is applied for the optimal design of BSRMs. Optimization results solved by MOGPSO, conventional multi-objective particle swarm optimizer, and non-dominated sorting genetic algorithm II are compared and analyzed. Comparison results reveal that the proposed MOGPSO can achieve more non-dominated solutions in Pareto front and is particularly suitable for optimization of BSRMs. The final optimal design is selected from the obtained Pareto front. The electromagnetic performance is compared with the initial design and verified by the FEM. Verification results show that the optimal design of BSRMs based on the analytical design model and the proposed MOGPSO is feasible and effective. [ABSTRACT FROM PUBLISHER]

A novel hybrid excitation flux reversal machine (HEFRM) is developed for application in electric vehicle propulsion. The proposed machine has a simple reluctance rotor and a stator with conventional ac armature windings and concentrated dc field windings. Besides, there are also permanent magnets (PMs) on the stator teeth. The PMs on each tooth have the same polarity, and the PMs on the adjacent two teeth have different polarities. In this paper, the feasible slot–pole combinations and equivalent circuits of the HEFRM are introduced, and the influences of several key design parameters such as rotor slot number, ratio of field winding to total winding, ferromagnetic pole arc, stator slot opening ratio, and rotor slot opening ratio on torque density and power factor are investigated by finite-element algorithm. Moreover, to verity the advantages of the hybrid excitation, the torque–speed envelop and power factor–speed envelop of the proposed HEFRM are compared to that of its solely PM excited counterpart. Finally, an HEFRM prototype is built and tested to validate the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel high-temperature superconducting stator-excited axial-flux magnetic gear (HTS-SEAFMG) for the high-torque transmitting system. The proposed magnetic gear combines the merits of both HTS-excitation and stator-excitation. By using the HTS-excitation, a high air-gap flux density can be easily obtained, thus achieving the high torque density. The HTS-excitation windings are placed on the stator with a static seal of cooling Dewar which greatly reduces the manufacturing difficulty and the cost of refrigeration system compared with the dynamic seal. Thanks to the stator-excitation pattern, both the high-speed rotor and the low-speed rotor comprise only iron, thus contributing to the high mechanical reliability. The axially sandwich structure can also simplify its assembly in the high torque transmission applications. The dimensional parameter optimization and the electromagnetic performance evaluation are conducted by using the finite element method, respectively. The results show that the torque density of the proposed HTS-SEAFMG can reach 123 kNm/m3. Theoretical analysis and results are both given to verify the feasibility of the proposed HTS magnetic gear design. [ABSTRACT FROM AUTHOR]

This paper proposes and analyzes a novel radial partitioned stator HTS-excitation flux-switching (RPS-HTSFS) machine. The key is that the single ring-shaped HTS-excitation coil is independently placed in the coaxial claw-pole outer stator while the armature windings are wound around the U-shaped iron core on the inner flux-switching armature stator without permanent magnets. This solution has been explored to realize the physical isolation of armature winding and excitation winding, relieving the influence of armature field on the HTS-excitation coil. Moreover, only a single ring-shaped HTS-excitation coil is employed, therefore, reducing the HTS wires and the bending strain of the HTS-excitation coil. Also, the special refrigeration system can realize stationary seals of the double-layer ring-shaped cooling Dewar pattern, improving the cooling performance. By using the three-dimensional finite element analysis (3D-FEA), the machine performances are investigated and the validity of the proposed machine is verified. [ABSTRACT FROM AUTHOR]

Severe leakage flux is a long-existed drawback in the transverse-flux permanent magnet machines (TFPMs), which results in a low permanent magnet (PM) utilization rate and prominent cogging torque in TFPMs. Aiming to solve this problem, this paper presents a novel consequent-pole transverse-flux machine (CP-TFM). The key is to artificially shift the upper and lower salient-pole rotors with a half-pole pitch and connect them with a ring-shaped core. Therefore, a complementary magnetic circuit is constructed to reduce the flux leakage between the adjacent poles as well as improve the PM utilization rate. To verify the feasibility of design, a 3-D finite-element model is established and its electromagnetic performance is evaluated. With the same peripheral dimension and copper loss, a quantitative comparison is carried out between the proposed CP-TFM and conventional TFPM. Finite-element simulation results reveal that compared to its contrast, the proposed solution can almost double the PM utilization ratio and effectively reduce the cogging torque. [ABSTRACT FROM AUTHOR]

In this paper, three partitioned-stator (PS) machines, namely the PS flux-switching permanent-magnet (PS-FSPM) machine, the PS-FS hybrid-excitation machine, and the flux adjuster PS-FSPM (FA-PS-FSPM) machine are proposed for the hybrid electric vehicles (HEVs). Owing to the installation of additional inner-stators, all three proposed machines can offer satisfactory power and torque densities. In particular, the FA-PS-FSPM machine artfully utilizes its inner space to accommodate the mechanical FAs, such that outstanding flux-weakening capability for wide-speed range operation can be achieved. To verify the proposed concept, the established machines are purposely compared with the profound Prius HEV machine based on finite-element method. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid-excited vernier permanent magnet (PM) machine is proposed. Two excitation sources, namely, the PM excitation and the electrical excitation are artfully combined together based on the homopolar topology, resulting in a parallel hybrid excitation. The flux regulation capability of the proposed machine is discussed and analyzed. Unlike other hybrid-excited machines, the flux regulation is realized based on the variation of the armature flux linkage rather than directly adjusting the air-gap flux. Performances of the bi-directional flux regulation are evaluated by the 3-D finite-element method. In order to verify the analytical results, the proposed machine is prototyped and tested as a generator. Both no-load and on-load performances are assessed. The experimental results agree well with the analytical ones. [ABSTRACT FROM AUTHOR]

The noise of electrical machines has drawn more attention in recent years due to their harm to people and the environment. Normal skewed slot has proven to be an effective method to reduce vibration and noise of squirrel-cage induction motor. Double skewed slot is superior to normal skewed slot on reducing vibration and noise. However, it is still difficult to meet the requirements of noise standards in some occasions. In this paper, based on double skewed slot, a new skewed slot type is proposed, which can offer a better effect on reducing vibration and noise. 2-D fast Fourier transform and 3-D finite-element method are adopted to analyze and compare the performance of the three types of skewed slots. [ABSTRACT FROM AUTHOR]

This paper presents a new switched reluctance motor (SRM) with wide speed range for the application of electric vehicles. It has an in-wheel structure for direct drive and multiple teeth per stator pole to enhance output torque. Also, the number of rotor poles is more than that of stator teeth. A 6/16 three-phase in-wheel SRM with the concepts of multi-teeth per stator pole and more rotor poles than stator teeth has been proposed for analysis. The torque performance of the topology with multi-teeth per stator pole is proven by theoretical analysis. Moreover, a new design formula is introduced for a novel combination of stator and rotor poles. The parameters of the motor are optimized by genetic algorithm method for the maximum torque output. Then the torque performance is computed by finite-element method (FEM) and compared with its counterparts, including three-phase 6/8 and 6/10 SRMs. The FEM results exhibit higher torque density for the proposed topology. [ABSTRACT FROM AUTHOR]

In this paper, a double-stator linear-rotary permanent magnet motor (DSLRPMM) for linear and/or rotary movement is presented. Since the two types of permanent magnets are orthogonally arrayed on the inner and outer surfaces of the mover core, respectively, the influences of the orthogonal magnetic field (OMF) on the motor electromagnetic characteristics cannot be ignored. Based on the 3-D finite-element method (FEM), the OMF in the motor and the iron core magnetization characteristics are investigated, and a test device is constructed to verify the results obtained by the theoretical analysis and 3-D finite-element analysis (FEA). On the basis of the measured data, the 2-D FEM is employed to analyze the electromagnetic characteristics of the DSLRPMM, including flux density, flux linkage, back-electromotive force, detent force, and cogging torque. The results are compared with that obtained by the 3-D FEA, and they are in agreement. Moreover, a prototype is built and tested. The experimental results verify the correctness of the predictions. [ABSTRACT FROM AUTHOR]

In this paper, a novel direct drive, bilateral planar switched reluctance generator (BPSRG) is developed for 2-D wave energy conversion with a mixed type of flux circulation. The proposed BPSRG has longitudinal flux type of the magnetic circuit on one direction and transverse flux-type magnetic circulation for the other perpendicular direction. The characteristics of the magnetic flux and static inductance are calculated for the BPSRG based on the 3-D finite-element method, in order to ensure negligible coupling effect between any phases. Theoretical model of the BPSRG is derived, and parameters that impact the open-loop operation performance of the power generation are analyzed, optimized, and supported by experimental results. [ABSTRACT FROM AUTHOR]

This paper deals with an analytical model of reluctance synchronous motor, able to consider both stator slotting effect and magnetic saturation in the stator and rotor iron paths. It joints the field distribution at the air gap to a lumped-parameter magnetic network. Local saturation factors are defined so as to adjust the flux-density distribution. The analytical approach exhibits great potentiality, since it is a formulation based on an harmonic study, and it is easily adaptable to any motor geometries. As an example, 36-slot 4-pole machine is analyzed, considering three flux barriers per pole. Finite element analysis confirms the results achieved by means of the analytical model. [ABSTRACT FROM PUBLISHER]

A new partitioned stator (PS) hybrid excitation (HE) machine with slot Halbach permanent magnet (PM) arrays is proposed in this paper. Due to the adoption of PS structure, its armature winding (AW) is located in the outer stator, and the PMs and the field winding (FW) are housed in the inner stator, thus the space utilization is significantly enhanced. The key difference of proposed machine is that Halbach PM arrays are employed in the inner stator slot openings, so that the parallel magnetic circuit between PM field and wound field is performed and the ratio of PM field short-circuited in the inner stator is effectively reduced. Thus a wider speed regulation region and a higher torque/power density can be achieved. Firstly, the configuration of proposed machine is described, based on which its operating principle is discussed. Then the electromagnetic performances are calculated and compared based on 2-dimensional finite element analysis (FEA). The results show that the torque can be improved by 76% with a similar magnetic field regulation ratio compared with an existing PS-HE machine with slot PMs. Finally, a prototype machine is built and tested to verify the analysis and FEA results. [ABSTRACT FROM AUTHOR]

Nowadays, finite element analysis represents the most accurate tool to analyse electrical machines. However, the time domain resolution of electromagnetic problem, in some cases, requires long simulation time due to the induced nature of the currents. The computational burden increases when the machine features a skewed layout on the stator or rotor structures, since this requires 2D multi-slices approximated analysis or even a full 3D model. In this paper, a general analytical method to model electromagnetic devices is applied to a squirrel cage induction motor featuring a skewed rotor structure. The modelling approach is wisely implemented and adapted to pursue a fair balance between accuracy of the analysis and computational burden, taking advantage of all the symmetries existing in the rotor cage of the machine, aiming to minimize the model complexity. A comparative analysis in term of the inductances between analytical and finite element is proposed. The results provided by the model developed are compared with respect to the corresponding values provided by both finite element and experimental test performed on the reference machine. Such comparisons show that the proposed model is actually able to achieve a pretty good balance between accuracy and computational efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of short circuit fault (SCF) in wound rotor (WR) resolvers. For this purpose, an analytical model based on winding function (WF) method is developed considering the stator and rotor windings’ fault, the severity of the fault, the phase of the stator faulty winding, and the tooth of shorted turns. The proposed model leads to a comprehensive understanding of the SCF behavior of WR resolvers and also leads to define proper fault detecting signatures. All the predictions are verified by time stepping finite element analysis as well as the experimental tests on two prototyped resolvers. [ABSTRACT FROM AUTHOR]

The fault-tolerant capability is a prerequisite for electrical safety-critical applications. In this regard, multi-phase induction motors are well-known actuators used to provide this feature. Compared to conventional three-phase machines with distributed windings, induction machines having concentrated windings could be more fault-tolerant because of increasing the number of phases. In addition, concentrated windings have shorter end-winding and less required copper weight which makes it a lower cost solution compared to distributed windings. However, concentrated windings adversely increase the distortion of the air gap flux density which affects motor performances. In this paper, a pseudo-concentrated winding layout has been proposed for six-phase squirrel-cage induction motors to improve performances compared to conventional concentrated windings. Winding function and equivalent circuit methods are used to analytically calculate performances. Finally, time-stepping finite element method and experimental measurements have been presented to confirm obtained analytical results. [ABSTRACT FROM AUTHOR]

Inverter driven electrical machines need resolver for position estimation and efficient electronic commutations. In this paper, the resolver signals are also used for the purpose of mechanical fault diagnosis. Therefore, a comprehensive procedure based on winding function (WF) method is presented to propose a noninvasive index to identify the mechanical fault's type (static/dynamic eccentricity) and even its percentage. In this regard, once the resolver signals are measured and saved in health condition. Then, during the operation of the motor, calculating the proposed index using the healthy and faulty signals leads to predict the fault type and its percentage. The success of the proposed index is verified using transient finite element analysis and experimental measurements on the prototype resolver. [ABSTRACT FROM AUTHOR]