Search

This paper employs an overhang structure for axial flux permanent magnet motor to enhance the torque density. However, the overhang structure requires a computationally expensive 3-D finite-element method (FEM) for analysis, because a quasi-3-D FEM cannot be applied to such a geometry. Thus, in order to reduce the computational cost of above-mentioned topology, this paper adopts a field reconstruction method (FRM). The conventional FRM is applicable only in the case, where the slot pitch to teeth length ratio is the same along radial direction. To address this problem, we introduce a virtual air gap concept so that it can take into account parallel slot effect as well as overhang effect. In this paper, the effectiveness of the proposed method is verified by the 3-D FEM and experimental results. [ABSTRACT FROM AUTHOR]

The shape of rotor bar is important in squirrel cage induction motor (SCIM) performance, such as starting torque, operating torque, and operating efficiency. Some designs of increasing starting torque of motor may decrease motor efficiency. Moreover, some designed shapes of bar are so complicated to be manufactured. In this paper, the design is focused on the simple inclination of conventional shape of bar with keeping the rotor bar area constant. The effects of rotor bar inclination on starting torque, operating torque, and operating efficiency in SCIM are analyzed. The results showed that there is optimum inclination of rotor bar to improve all the performances together. An application to the 3.4 kW SCIM showed that the starting torque is increased from 17.53 to 17.64 \text N\cdot \text m , the operating torque from 11.19 to 11.26~\text N\cdot \text m , and the operating efficiency from 94.18% to 94.81%. [ABSTRACT FROM AUTHOR]

A novel hybrid-flux permanent-magnet (PM) generator, which has both axial flux and radial flux, is proposed. An axial-flux PM generator is designed by a reluctance network method and the 3-D finite element method. Using these results, this paper proposes a radial-flux and hybrid-flux machine, whose main dimensions are chosen to the same values as a commercialized one. The proposed hybrid-flux machine has the largest output power per volume. The power density of the proposed generator is 9.4 times larger than that of the commercialized one. The efficiencies of the proposed hybrid generator and a radial generator are same as each other, and are larger than those of an axial and the commercialized generators. [ABSTRACT FROM AUTHOR]

This paper presents performance improvements of a double excitation synchronous motor by using a reluctance network (RN). The distinguishing feature of the double excitation principle is to use permanent magnets with high energy, while air-gap flux is flexibly controlled by field windings. Therefore, the first contribution of this paper focuses on maximizing air-gap flux range control. Second, an approach for torque ripple reduction is proposed by directly modifying air-gap flux according to the instantaneous torque profile. The achieved resultant torque stays almost constant for a case study. The validity of the RN method is examined by comparisons with 3-D finite element and experimental results for several machines. [ABSTRACT FROM AUTHOR]

For the purpose of saving energy resources, it is extremely expected to develop highly efficient electric motors. Different types of permanent magnet (PM) arrangement can significantly affect the performance of the motors. Conventionally, the arrangement of the PMs is determined by designer’s experience. This paper focuses on the optimal design of PM arrangement in PM synchronous motors (PMSMs). We present a general pattern of the PM arrangement in PMSM. By varying the parameters of the general pattern, it can produce different types of PM arrangement in the rotor. The employed approach combines the global optimization method with the finite-element method for solving the optimization of the PM structures. Based on the proposed general pattern and optimization methods, the best PM arrangement in the motor can be automatically determined. In order to reduce computing loading, this paper employs the response surface models for reducing the computing time of objective functions. In the end, numerical tests are designed to showcase the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper puts forward the design and analysis of an ironless permanent magnet machine for a micro wind power application. The proposed methodology includes comprehensive geometric, magnetic, and electrical dimensioning followed by detailed 2-D finite-element modeling of a synchronous generator. The configuration investigated in this paper shows the generators rotor fixed in the tip of the blades and illustrates the advantages of a large diameter for a microgeneration application. [ABSTRACT FROM AUTHOR]

Recently, dual-rotor motor (DRM) has emerged as an alternative for an induction motor (IM) or a permanent-magnet (PM) motor for electric vehicle application, due to its better drive performance and better torque density. This paper presents an analytical model for the hybrid IM-PM configuration of DRM. The analytical model can be used to predict induced bar currents, electromagnetic torque generated, and magnetic fields in various regions of the motor. The mentioned calculations are performed under steady-state conditions. The analytical method is developed using the subdomain model approach in 2-D polar coordinates. Appropriate governing equations along with boundary conditions across all the sub-domain regions of the DRM are employed to calculate the magnetic vector potential in all the regions. The developed analytical model has been validated with finite-element analysis for various operating conditions, and high accuracy has been achieved for all the results. [ABSTRACT FROM AUTHOR]

Three-phase nonoverlapping stator wound-field synchronous (NSWFS) machines employing salient pole rotors are proposed in this paper. Based on the optimized design, the influence of rotor pole number on the proposed machine is investigated. According to 2-D finite-element analysis (FEA), it is found that the proposed machine shows higher torque density and lower torque ripple compared with the existing NSWFS machines. The operation principles of the proposed machine under different pole numbers are presented and compared in this paper. The FEA-predicted back electromotive force, cogging torque, and static torque of NSWFS machines are validated by experiments made on the prototypes. [ABSTRACT FROM AUTHOR]

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

This paper investigates the partial irreversible demagnetization characteristics of magnets in flux-switching permanent magnet (FSPM) machines. Two different partial demagnetization mechanisms in the FSPM machines are modeled and demonstrated. The 2-D finite-element analysis (FEA) results for a baseline 10 kW 15 kr/min ferrite FSPM machine verify the validity of the proposed partial demagnetization model. Performance degradation due to demagnetization is evaluated for the baseline machine based on the FEA results. This paper also proposes a novel design to enhance the demagnetization withstand capability. This research reveals the most vulnerable region of the magnet to irreversible demagnetization in the FSPM machines. It also provides a guideline for developing demagnetization withstand capability improvement techniques. [ABSTRACT FROM PUBLISHER]

This paper presents a novel flux-modulated type dual-axis motor that has two mechanical inputs/outputs, since it consists of a stator, a permanent magnet rotor, and a modulating rotor. Furthermore, since the dual-axis motor has a function the same as a planetary type magnetic gear, it can transmit torque with arbitrary gear ratio and divide mechanical input/output into two rotors without any mechanical contact. In this paper, first, conventional and proposed flux-modulated type dual-axis motors are optimized and compared using finite-element analysis. Next, the proposed dual-axis motor is prototyped and demonstrates the validity and availability by experiment. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid excitation vernier permanent magnet machine (HE-VPM). The characteristics of the proposed machine are: 1) the PMs are embedded in the stator teeth, which is helpful for the heat dissipation; 2) the rotor is salient structure without PMs and windings, which ensures the reliability of high-speed operation; 3) the nonoverlapping concentrated winding shortens the end-connection, and improves the torque density, 4) only half of the stator teeth possess PMs, and the total amount of PMs are decreased; and 5) the dc current are injected to the armature coils, therefore, the exciting field can be adjusted flexibly. In this paper, the electromagnetic performance, including back electromotive force, torque, etc. are analyzed with finite element analysis. The results show that the proposed machine exhibits flexible field adjustment capability, which may be suitable for applications requiring wide speed range operation. Besides, it is found that, compared with the existing pure sinusoidal phase current, higher torque density can be obtained with dc-biased phase current under constant stator copper loss. [ABSTRACT FROM AUTHOR]

Coreless axial flux machines are of interest because of the absence of stator core losses and cogging torque. These machines generally employ concentrated windings. One of the challenges with such a winding is that the torque producing MMF component that corresponds to the fundamental of the magnet excitation is accompanied by substantial asynchronous components. These harmonics cause losses in the rotor core and magnets, which can become significant at high speeds. This paper proposes a new multilayer winding arrangement to eliminate the non-torque producing MMF components. This winding is applied to a 12-coil 16-pole coreless axial flux machine. The efficacy of the winding is established by 3-D finite-element analysis. [ABSTRACT FROM AUTHOR]

This paper presents work completed in order to investigate the importance of magnetic shunts in transverse flux machines. Two types of transverse flux machines with different configurations were designed and tested in the laboratory. The first type of machine is a transverse flux generator with inner rotor. This machine was designed according to one of the patents. The second type of the machine is a transfer flux generator with double coil. Both types of the generators were designed in such a way so that it was possible to implement magnetic shunts inside the machines. Finite-element method analysis and experimental results showed that transverse flux machines without magnetic shunts had a number of disadvantages compared to those with magnetic shunts. These disadvantages are: higher flux leakage in the stator cores, partial cancelation of flux linkage in the coils, higher cogging torque, and increased torque ripple. This paper showed that magnetic shunts played a significant role in the performance of transverse flux machines. As study showed, magnetic shunts complicate a manufacturing process and increase the weight of the machine. However, power to weight ratio of the machines with magnetic shunts is higher than that of the machines without magnetic shunts. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of mutual fluxes (inductances) on the resultant torque in three-phase conventional switched-reluctance machine (CSRM) and mutually coupled SRM (MCSRM) using the frozen permeability (FP) method. Under saturation conditions, the FP method allows accurately separating the torques due to self-flux and mutual flux, hence quantifying their contributions to torque generation. Then, appropriate current waveforms (unipolar or bipolar, square wave or sinewave) can be established to maximize the output torques. It is well known that the mutual torque of CSRM can be negligible. However, this paper has shown that when sinewave current is employed and under full or overload conditions, the torque will be significantly reduced due to non-negligible negative mutual torques. Different from CSRM, the self-torque and the mutual torque of MCSRM can be added if current waveform is properly chosen, e.g., sinewave currents. This can significantly boost the resultant torque. The predictions have been validated by experiments. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling and simulation of the effect of rotor eccentricity in permanent magnet synchronous machines. Static eccentricity is analyzed in a 2-D setting. The 3-D effect of an inclined rotor shaft is accounted by considering 2-D slices and interpolating on a grid constructed from finite-element simulations [response surface model (RSM)]. Common tools of uncertainty quantification, i.e., generalized polynomial chaos and Monte Carlo, are used to study the effect on the electromotive force. The novelty of this paper is the twofold use of the RSM: 1) to speed up the calculations in the 2-D setting and 2) to mimic a multislice model for inclined eccentricity. [ABSTRACT FROM AUTHOR]

This paper presents a study of the effects that the shoe shape of the teeth of electrical machines has on the performance and losses. This is done by considering a concentrated wound, high-speed permanent magnet generator. The paper investigates the influence of the tooth shoe shape on the machine magnetic circuit and the losses distribution based on analytical and finite-element analysis (FEA). A shape coefficient K {t} is proposed to provide an optimized design reference. A comprehensive analytical tool able to study the variations of the machine performance parameters is proposed. The deduced optimization function is normalized using the non-equilibrium relative weighting method, and then, it is processed via a genetic algorithm to achieve the optimized design. FEA is used to validate the proposed analytical tool and the optimum design. [ABSTRACT FROM AUTHOR]

This paper investigates the rotor losses of coaxial magnetic gears (CMGs) with surface-mounted permanent magnets. The iron losses and PM eddy current losses that occurred in the two rotors of an existing gear are calculated and analyzed by the finite-element method. Using magnetic flux barriers in the outer rotor, a novel rotor structure for CMGs is proposed to reduce the rotor losses, in which subharmonics are considered. A 1-D magnetic permeability model is also introduced to understand the principle of reducing the main subharmonics. Then the outer rotor losses of the existing gear and proposed gear are compared. The proposed model and the results presented in this paper will give useful guidelines for a reliable design and design optimization of the CMGs. [ABSTRACT FROM AUTHOR]

This paper presents a methodology that allows taking advantage of the geometrical periodicity of electrical machines together with the modeling of rotor motion. It enables by means of the discrete Fourier transform (DFT) to reduce the large-scale system obtained from the finite-element model to several smaller independent subsystems, allowing a shortening of the computational time. Due to DFT properties, the computational time can be more reduced especially when we consider the inter-dependence of the spectral components under either balanced or unbalanced supply condition. In addition, a further reduction is possible in the case of balanced regimes where the distribution of the eventual numerical solution is governed by a limited number of prevailing harmonics. [ABSTRACT FROM AUTHOR]

An analytical method for calculating the no-load magnetic field of external rotor permanent magnet brushless direct current motor (PMBLDCM) used as in-wheel motor of electric vehicle in the stator static coordinate and the rotor motion coordinate is presented in this paper. First, the analytic formulas of slotless permanent magnetic field in both coordinate systems are derived, respectively. Then, the complex relative permeance of external rotor PMBLDCM in both coordinate systems is calculated. Finally, the analytical solution of the no-load magnetic field in both coordinate systems is derived by applying the magnetic potential multiplied by the complex relative permeance. In this paper, a 46-pole-51-slot external rotor PMBLDCM is taken as an example, and the accuracy of the proposed analytical model is verified by the finite-element results. Based on the analytical model, the influences of the stator slotting effect on the no-load magnetic field of the external rotor and the inner stator are analyzed. The spatial order characteristics and frequency characteristics of the no-load magnetic field of the external rotor PMBLDCM in both coordinate systems are revealed, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a new hybrid permanent magnet (PM) synchronous motor with two-part rotor is proposed. The new motor is composed of surface mounted and interior magnet rotor segments on a stepped skewed shaft. The hybrid topology has wider constant power speed ratio than conventional surface mounted PM motors with relatively the same torque density. No-load and on-load finite-element analyses (FEA) are performed independently for both surface PM and interior PM synchronous motor. Superposition of the results is gathered to obtain the actual performance of the hybrid motor. The 2-D FEA results with skewed models are also performed at the final stage of the design. A prototype motor is manufactured and experimental results are obtained. Good agreement is observed between the simulations and test data for the proposed motor. [ABSTRACT FROM AUTHOR]

This paper presents an improved magnetic circuit (MC) model considering the leakage, cross coupling, and saturation effects for the performance analysis of an integrated 3 degrees of freedom magnetic bearing (3-DOF MB). Compared with the conventional MC model, this paper analyzes the permanent-magnet bias field, radial and axial control current fields together. By using this improved MC model, it reveals the cross-coupling effect between radial and axial directions in such an integrated 3-DOF MB. The stiffnesses of radial force are significantly influenced by the axial control current, while the stiffnesses of the axial force are independent of the radial control current. Its accuracy is verified by the 3-D finite-element method. [ABSTRACT FROM AUTHOR]

This paper proposes a novel transmission system supporting multi-path power flows for electric vehicles (EVs). It mainly consists of a coaxial magnetic gear (CMG), a lock, a clutch, and two electric machines (EMs). The key feature of the CMG is that its modulating ring can rotate freely. One of the EMs is integrated with the CMG, which constitutes an integrated magnetic gear permanent magnet machine. And the other is connected to the inner rotor of the CMG through a clutch and a shaft with a lock. By toggling the clutch, controlling the states of the lock and the two EMs, the proposed transmission system can achieve flexible power splits. It is very interesting that one of the EM can play the role of a flywheel storage device when necessary, which is capable of buffering the energy from regenerative braking, so as to protect the battery. In this paper, the configuration of the transmission system is illustrated; its operating principle is elaborated. Then, the electromagnetic design is conducted to meet the demands arising from EVs. Finally, the electromagnetic performances are analyzed by using finite-element method, which verifies the rationality of the electromagnetic design. [ABSTRACT FROM AUTHOR]

This paper investigates the interaction of the zero sequence component into both permanent magnet (PM) shape and phase current to improve the output torque in dual three-phase surface-mounted PM (SPM) machines. The optimal zero sequence components are analytically derived and validated by finite element (FE) analyses. It is found that the optimal zero sequence components into both PM shape and current waveform are dependent on the fundamental and zero sequence harmonic winding factors. For the dual three-phase SPM machines having rotors without shaping, Sine shape, Sine shape with the zero sequence components, the electromagnetic performances including the back electromotive force (EMF) waveform, cogging torque, average torque, and torque ripple are compared. It is demonstrated that the average torque with the optimal zero sequence component in PM shaping and current waveform can be improved by >30% while the torque ripple remains similar to that of the one with Sine shaping. Finally, the experiments are given to verify both the analytical and FE analysis. [ABSTRACT FROM AUTHOR]

From a new stator-flux perspective, a comparative study between the series and parallel hybrid excitation machine (PHEM) is conducted and it is revealed that in PHEMs there still exist distinct stator-flux harmonic components during high-speed flux weakening operation, which could be further utilized to improve the torque capability at high-speed range. Inspired by this idea, an auxiliary winding is creatively introduced into PHEMs to recycle and utilize the magnetic field energy generated during the field regulation. A new design case is presented in this paper, in which two sets of armature windings with different pole pair numbers are arranged to realize the function of flux weakening operation and energy recycling, respectively. The feasibility of this new hybrid solution is evaluated by using the finite-element analysis. Furthermore, a prototype is manufactured and relevant experiments are performed. The experimental results agree well with the theoretical analysis and simulation results, which verify that the recycled energy can be effectively used to boost the output torque and power of PHEMs in the high-speed region. [ABSTRACT FROM AUTHOR]

Spoke-type interior permanent magnet (IPM) machines are an attractive topology for high-performance electric motors, especially designed for vehicle traction applications. In this paper, a special design for a spoke-type IPM motor is presented to enhance motor flux-weakening capability in the operation over a wide speed range. The proposed design consists of a simple and robust mechanical device that includes radially displaceable rotor yokes, connected to the shaft by means of springs. At high speed, the centrifugal force prevails over the elastic one due to springs, causing the mobile yokes to displace radially and establish a partial magnetic short circuit between PMs. This increases PM leakage flux and consequently reduces the air-gap field. As a result, a mechanical flux weakening effect is achieved at high speed, which helps significantly to reduce the demagnetizing \boldsymbol d -axis current to be injected by the inverter, along with the related copper losses and demagnetization issues. The proposed design is investigated in this paper using an analytical model whose parameters are computed by finite-element analysis. The effectiveness of the solution being set forth is successfully proven by some testing on a laboratory prototype. Experimental results are compared with analytical predictions showing a satisfactory accordance. [ABSTRACT FROM AUTHOR]

This paper discusses the analysis and simulation method and the test method for a two-degree-of-freedom (2-DOF) actuator torque. The previous studies on the analysis of 2-DOF motor’s tilting torque were carried out only by finite element method (FEM), not by analytic method. This paper describes the operating principles of and the processes of inducing a tilting torque and a holding torque both of which exist only in special purpose electric machines. This allowed us to establish a design process. By overcoming the limits of the 3-D FEM, this paper introduced the 2-D model analysis by considering a real coil shape. Finally, this paper manufactured and tested the 2-DOF actuator to verify the introduced analytic analysis method. [ABSTRACT FROM PUBLISHER]

This paper deals with an effective reduction method of torque ripple by adopting novel asymmetric pole structure of wound-field synchronous motor. In general, skewed pole structure of a rotor is used to reduce torque ripple despite decreasing an average torque. This paper introduces the design parameter of shift angle of an asymmetric pole-plate for effective elimination of torque ripple. In addition, the design can maintain the length of field winding compared with skewed pole structure, which means low copper loss in field winding and low material cost. In addition, average torque can be increased at the same input voltage over the driving region as well. The 2-D finite element method is used for the analysis of proposed model and skewed model. For the comparison of characteristics between the skewed model and proposed model, skewed pole with three steps is introduced with low torque ripple. [ABSTRACT FROM PUBLISHER]

In the numerical analysis of electrical machines, accurate computation of the electromagnetic torque is desired. Maxwell stress tensor method and Coulomb’s method are the most commonly used methods for computing torque numerically. However, several other methods have also been developed and are being used. These methods are observed to have several accuracy issues related to the finite element discretization used in the air gap of the machine. In this paper, the effect of various finite element meshes in the air gap of the machine and the effect of the shape of the elements used to compute the torque are studied and discussed. This paper carefully compares the torques obtained from a direct method and a method based on the power balance of the machine. [ABSTRACT FROM AUTHOR]

This paper investigates the iron loss calculation of permanent magnet (PM) machines undertaking unconventional operations, where the high-frequency alternating armature field is only a fraction of the constant PM field. It is found that the iron loss of PM machines undertaking such unconventional operations cannot be calculated reliably as the conventional summation of all the iron loss harmonics predicted by finite-element (FE) methods due to fake iron loss harmonics. Further investigation is conducted on the influence of current frequency and magnitude, FE mesh, and convergence tolerance on the FE predicted iron loss under unconventional operations. It is then proposed in this paper that the iron loss of PM machines undertaking unconventional operations can be calculated as the summation of only the iron loss harmonics, which are insensitive to the convergence tolerance. The analyses are validated by the experimental results. [ABSTRACT FROM AUTHOR]

Non-skewed asymmetrical rotors bars can be used to eliminate the slot harmonic fields and the resulting noise and vibration in cage induction motors. However, it is difficult to determine the spatial distribution of the asymmetrical rotor bars and the slot combinations, which can affect the loss and the air gap force significantly. With a 5.5 kW, 4-pole induction motor as an example, this paper studies the influence of the above factors on the loss and the air gap force by time-stepping finite element method, and the experiments are performed to validate the calculations. [ABSTRACT FROM AUTHOR]

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, a methodology using the 3-D finite-element (FE) modeling approach and a posteriori loss calculation is presented for the estimation of the stray load losses. The case of a cage induction motor is investigated, and results are compared with the experiment. The simulation is performed at different load conditions using a 3-D FE model with external circuit coupling. [ABSTRACT FROM AUTHOR]

In this paper, a general analytical model is proposed to calculate the back electromotive forces of various manufacturing imperfections in the double-rotor axial flux permanent magnet machine. First, the axial and circumferential flux density in the air gap under healthy condition is developed by Maxwell’s equations and Schwarz–Christoffel mapping. Second, the equations of air gap length and radii are introduced to calculate the flux density with manufacturing imperfections. The back EMFs of each case are calculated. For each case, finite-element (FE) method models are developed to validate the analytical model, and the results show that the analytical model predictions match well with the FE results. Finally, the analytical model is verified by experimental results. [ABSTRACT FROM AUTHOR]

The brushless doubly fed induction machine (DFIM) is a special machine type that is of interest as a generator in wind turbine drive trains. The brushless DFIM has a significant space-harmonic content compared with conventional machine types, due to its construction. This results in additional harmonic distortions, such as torque-ripple and time harmonics. This paper studies the causes and origins of harmonic distortions in the brushless DFIM. Using time- and space-harmonic analysis, an analytical evaluation method is derived to predict the torque ripple frequencies and time-harmonic frequencies in stator and rotor voltages and currents. The evaluation method is applied to a prototype brushless DFIM to demonstrate the severity of harmonic related distortions that can be present in the brushless DFIMs. The evaluation is validated by additional finite-element analysis and measurements. Furthermore, measures are proposed to reduce harmonic distortions. The insight into harmonic distortions in the brushless DFIM and the ability to predict and prevent them must lead to the improved brushless DFIM designs in the future. [ABSTRACT FROM PUBLISHER]

Electric continuously variable transmission (e-CVT) device is a key component in hybrid electric vehicles (HEVs), which serves to perform the energy transmission among the initial combustion engine, battery, and output shaft. This paper presents a novel consequent-pole PM magnetic-geared double-rotor machine (CPDRM) that utilizes the magnetic gearing effect to transmit the power with a high efficiency. The artistry of CPDRM is to insert a dc winding within the center of the stator on the circumferential direction. Therefore, the machine can extend the constant-power region by changing the current direction and amplitude of dc windings. Meanwhile, the flux density within the air gap is changed accordingly. Then, the working principle of CPDRM and the flux change process are illustrated by employing the magnetic circuit method. Finally, a finite-element method model is constructed to verify the performances of the CPDRM under different operating modes. The result shows that the proposed machine has an excellent flux-weakening ability, and it can serve as a suitable candidate as an e-CVT component for HEVs. [ABSTRACT FROM AUTHOR]

Overhang is a useful structure for increasing the torque and power densities of permanent-magnet (PM) machines without expansion of the machine space. A 3-D finite-element method (FEM) is needed to evaluate the performances of PM machines with an overhang structure because the overhang structure results in non-uniform magnetic flux distributions in the axial direction. However, it is computationally expensive, especially in the early design stage. In this paper, we propose a magnetic equivalent circuit (MEC) model considering the overhang effects of interior PM (IPM) machines. With the proposed MEC, the performances of IPM machines with an overhang structure were precisely calculated and the computational time was significantly reduced. The proposed MEC was verified by the 3-D FEM. [ABSTRACT FROM AUTHOR]

A new type of three-phase stator hybrid excited machine with permanent magnets (PMs) located at the slot openings of field winding slots is presented in this paper. It has the advantage of good flux regulation capability due to the field excitation. The machines with different stator/rotor pole combinations, i.e., 6-stator pole and 7-/8-/10-/11-/13-/14-rotor poles, have been comparatively investigated in terms of the open-circuit and on-load characteristics, as well as the influence of dc current and the unbalanced magnetic forces. The 2-D finite element analysis (FEA) has been employed for analysis and optimization of the machines together with experimental validation. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis and optimization of radial, coaxial magnetic gears. Multi-objective optimizations of the modulator shape of two magnetic gear configurations, one with and one without back iron on the outer rotor, are presented and discussed. The focus of this publication is to show that a magnetic gear with the same total volume and output torque can provide a much higher efficiency when the outer rotor is built with no back iron. To guarantee comparable results, equal start geometries, objectives, and appropriate optimization parameters are considered. After the optimization process, the geometries of the two gear configurations show different optimal modulator shapes and, therefore, different flux distributions. The gear configuration without back iron achieves a comparable torque capability in comparison with the gear configuration with iron yoke. However, 2-D finite elements calculations estimate for the latter design a loss reduction of 70%. [ABSTRACT FROM AUTHOR]

Switched reluctance (SR) machines are attractive because they present relatively high efficiency and torque density in spite of lacking permanent magnets. This paper focuses on a two-objective optimization of an external rotor SR motor with a stator that has concentrated coils and a rotor with magnetically isolated modules. The objectives are minimum loss and mass, and 11 independent dimensionless geometric variables are considered as inputs that affect them. A combined design of experiments (DOE) and differential evolution (DE) approach is proposed. The DOE methodology is used to reduce the search space by eliminating from consideration input variable values, leading to poor-performing designs. Following this initial DOE study, an optimization study based on DE is run over the reduced search space, which leads to significant savings in computation time. Furthermore, a directed graph-based method for comparing different designs on the Pareto front to rank the best compromise designs is proposed. [ABSTRACT FROM AUTHOR]

This paper introduces a novel hybrid-excited stator slot opening permanent magnet (PM) machine (HSSPMM). The operation principle of the machine is described and the effects of rotor eccentricity and magnetic saturation due to PMs on electromagnetic performance, with particular emphasis on back electromotive force (EMF), are analyzed by finite element method (FEM). It shows that different from the conventional PM machines, the open-circuit back EMF in this novel HSSPMM should be zero but may become non-zero if significant magnetic saturation exists, and furthermore, the rotor eccentricity has a detrimental effect on the waveforms, amplitudes, and symmetries of three-phase back EMFs, as confirmed by FEM and tests. [ABSTRACT FROM AUTHOR]

This paper presents a design of a new line-start synchronous reluctance motor (LSSynRM) that has a markedly robust structure, vibrates little, and is lighter in weight. These advantages stem from the combination of flux barriers with a 3-D net structure achieved by the 3-D printing technology. In addition, the lamination and the 3-D printing performance of the induction motors, SynRMs, and LSSynRMs, respectively, are compared. The characteristics are investigated experimentally and analytically by using a prototype and a finite element analysis tool. [ABSTRACT FROM AUTHOR]

In this paper, each component of the no-load loss of interior permanent magnet motors under the conditions of both sinusoidal supply and converter supply is investigated by the finite-element method and experimental method. The no-load loss is calculated at different rotation speeds, two different slot and pole combinations and different converter parameters. The wireless temperature sensor embedded in the interior rotor is used to test the temperature of the permanent magnet under no-load condition, and the permanent magnet loss is calculated according to the slope of the initial temperature–time curve. Then, the mechanical loss of the prototype is measured by dragging a nonmagnetic rotor. The total tested losses are subtracted from the copper loss, the mechanical loss, and the permanent magnet loss to obtain the test results of core loss, and the experimental results of each loss and permanent magnet temperature rise are compared with the corresponding calculated results to verify the correctness of the simulation results. [ABSTRACT FROM AUTHOR]

Magnetic gears with dual-mechanical port have several attractive features, such as reduced maintenance requirements and inherent overload protection, as compared with mechanical gears. However, it is difficult to obtain an intuitive analytical model because of its complicated magnetic flux interaction, and the dual-port transmission of this magnetic gear is rarely discussed. These difficulties actually limit the practical applications and increase the control difficulty. Therefore, this paper develops a modeling approach based on the block diagram. Both of the kinematic and dynamic characteristics for a dual-port transmission can be obtained in one unified description. This control-based approach also provides more flexibility and convenience, facilitating further control applications. The feasibility will be verified by finite element analysis simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a novel consequent-pole hybrid brushless wound-rotor synchronous machine (CPH-BL-WRSM). The proposed machine employs permanent magnets (PMs) on the alternate poles of the salient pole rotor, which has considerably less magnet usage compared to the regular (PM) assisted synchronous machine. The proposed CPH-BL-WRSM offered the advantages of high starting torque, high torque density, and better performance under full-load conditions. The BL operation for the proposed machine is achieved by generating a composite magneto motive force (MMF) with a fundamental component and sub-harmonic component. The sub-harmonic component of the stator MMF is used for BL excitation of the rotor. The finite-element method was used to analyze the performance of the CPH-BL-WRSM in comparison with the performance of the existing BL-WRSM and regular PM-assisted BL-WRSM. Finally, a prototype of the CPH-BL-WRSM was manufactured and the experiment was conducted to demonstrate the performance of the proposed CPH-BL-WRSM. [ABSTRACT FROM AUTHOR]

This paper describes a new method aiming at the multi-objective optimization of a transverse flux machine with a claw-pole and flux-concentrating structure (CPTFM). Considering the 3-D main magnetic flux in the CPTFM, the time-consuming 3-D finite-element method (FEM) should be used to accurately analyze the performance of the machine. In order to reduce the calculation time for the optimization of the complex CPTFM, the Taguchi method is first applied to evaluate the importance of all the design parameters in the consideration of the predefined five objectives. Subsequently, a mathematical model is developed to replace the 3-D FEM, so that the objectives depending on the selected four critical parameters can be analytically calculated. With its help, the four parameters are further optimized with the multi-objective particle swarm optimization method and nondominated sorting genetic algorithm 2. Finally, the optimal design of the CPTFM is selected from all the searched Pareto solutions with the help of fuzzy logic. It can be concluded that the developed method is effective and efficient, which can make an appropriate compromise between the calculation time and the improvement of the machine performance. [ABSTRACT FROM PUBLISHER]

Slotless permanent magnet machines are attractive in some modern drive and power generation fields, where the cogging torque and additional losses need to be minimized or removed. The stator slotless design can be combined with different surface permanent magnet (SPM) rotor topologies. In this paper, explicit analytical expressions are derived to analytically compute the slotless machine torque and no-load back Electro-Motive Force in the case of segmented SPM rotor with parallel, radial, or Halbach-array magnetization patterns. The expressions are found by solving the magnetic field due to the slotless stator winding and to the permanent magnet blocks; the latter modeled through equivalent surface current densities. The accuracy of the method is successfully assessed by comparison with the finite-element analysis (FEA). The proposed formulas are an effective alternative to the FEA to quickly compare different design solutions as well as to optimize them. Application examples are provided in which the presented method is adopted to define the machine cross section that maximizes the torque density. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis of a brushless doubly fed reluctance machine (BDFRM) for renewable energy applications with an emphasis on the rotor design. The BDFRM stator includes two sets of windings, i.e., the control winding (CW) and power winding (PW). The PW is connected to the grid, while the CW links the grid by a power converter of fractional rating to regulate the operating speed. This reduces the converter cost, and the brushless configuration enhances the reliability. In this paper, the reluctance rotor of the BDFRM, which is similar to that of a synchronous reluctance machine, is designed and analyzed in order to improve the performance. The influence of the total MMF and its allocation to the two stator windings are also discussed in relation to the machine performance. Finite-element analysis is used for performance simulation. The experimental study validates the proposed design for a small BDFRM. [ABSTRACT FROM PUBLISHER]

This paper presents an exact analytical subdomain model of slotted permanent-magnet (PM) machines, taking into account the diffusion effect. The model gives the magnetic fields, both the eddy currents and the power losses in the PM, the instantaneous and average torque. In the model, eddy currents are not assumed to be resistance limited, contrary to what is done in the conventional exact subdomain models of the slotted machines. The model is hence general and valid both at low and high frequencies. It shows that it is possible to calculate the power losses in the PMs, only knowing the fields in the air gap. The model takes into account the presence of tooth-tips. The comparison with conventional exact subdomain models shows that the model presented in this paper is more accurate. The model is validated using the finite-element methods. [ABSTRACT FROM AUTHOR]

Helical windings (or zigzag windings) are used in a number of applications, however, in electrical machines, mainly employed in low-power, high-speed permanent magnet (PM) brushless dc machines due to the cost effectiveness of the winding type while maintaining reasonable performance. Typically, helical windings are used for low-voltage applications due to their spiral form, which makes them most suitable for a small number of turns. In high-speed electrical machines, such a low number of turns are applicable. It is apparent that high-speed PM machines suffer from rotor eddy-current losses, which in some cases may lead to PM demagnetization due to overheating. The performance of the machine is compromised by these losses; hence, they have to be considered during the design procedure. There are many papers analyzing the magnetic field of these machines employing helical windings; however, none of them present a simple and precise electromagnetic model of a machine with the helical winding. This paper presents an analytical approach to model the resulting 3-D magnetic field of the helical winding, considering eddy currents in the conducting media of the rotor. The model is verified with the 3-D finite-element method by means of comparing magnetic field and rotor eddy-current losses. [ABSTRACT FROM AUTHOR]

This paper presents a fast method to compute wound rotor induction machines in steady state. Coupled time-harmonic finite-element (FE) circuit equation is used under a first space harmonic approximation for the air-gap magnetic field. It is shown that only four magnetostatic FE computations are necessary to determine the machine performances for any slip value. The performance comparison with a conventional complex magnetodynamic and time-stepping FE analyses show the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]