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In this paper, a new stator-permanent magnet (PM) bearingless machine (SPMBM) is proposed. Its suspending windings, armature windings, and PMs are in the stator, while no PMs or windings are in the rotor. However, it is the focus in establishing an accurate mathematical model of radial suspension force to levitate the rotor stably by directly and effectively controlling the rotor eccentric displacement. First, operating principle and air-gap flux density distributions of the SPMBM are analyzed in detail. Then, an accurate mathematical model of radial suspension force is deduced by the Maxwell stress tensor method, and it is verified by the 2-D finite-element method (FEM). Results are consistent both by the radial suspension force mathematical models of the SPMBM and FEM. [ABSTRACT FROM AUTHOR]

In this paper, a new linear wound-field flux reversal (LWFFR) machine for low-cost linear direct-drive applications is proposed. Similar to the conventional LWFFR machine, the proposed machine possesses the merit of a simple and compact long stator structure, a low cost, and a high flux adjustment ability. The novelty of the proposed machine is to be designed based on the magnetic gear effect. Hence, its force capability can be significantly improved without increasing the structural complexity and manufacturing cost. Meanwhile, the feasible combinations of mover pole and stator pole numbers for the LWFFR machines are extended, and thus provide a more flexible design choice. The operation principle and electromagnetic characteristic of a new optimal LWFFR machine are analyzed by means of the time-stepping finite-element method, verifying the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

A permanent-magnet dual-rotor motor is particularly suitable for constructing the power split device in hybrid electric vehicle application. This paper proposes a new magnetic-geared dual-rotor motor (MGDRM) design with complementary structure, in which both the inner and outer rotors are divided into three modules with a proper angular displacement for each other along the axis direction. This complementary design makes the flux linkage symmetrical and total cogging torque significantly reduced, without impairing the torque production. A simplified magnetic circuit model is developed to illustrate the complementary principle. By finite-element analysis (FEA), the effectiveness of such complementary structure is verified through the comparison with the conventional design. A prototype motor has been manufactured, and experiments have been carried out. Both FEA and experiments show that this new MGDRM offers symmetrical back-EMF waveforms, smaller cogging torque, and lower torque ripple. [ABSTRACT FROM PUBLISHER]

Phase inductance is a key parameter in the design of switched reluctance machines (SRMs) because the torque, torque ripple, losses, and the dynamics of phase voltages and currents are related to the phase inductance. Therefore, accurate calculation of the inductance profile of an SRM is important in determining the SRM behavior. Instead of using the time-consuming finite element analyses (FEAs), or the analytical methods that require prior knowledge of flux linkage from either an FEA simulation or an experimental test such as the curve fitting and flux path based methods, this paper proposes a fast and accurate analytical approach to determine the phase inductance of an SRM with any common topologies, dimensions, and phase currents at any rotor position. In the proposed approach, the magnetic field distribution and the permeance parameters in the air region are first determined by solving the partial differential equations of magnetic potentials based on Maxwell's equations. The air-region permeance parameters are then substituted into a magnetic circuit network to include the impact of the saturation effects of steel on the phase inductance profile. The agreement between the results of the proposed analytical method and two/three-dimensional FEAs and experimental results validates the analysis. [ABSTRACT FROM AUTHOR]

Brushless dual-electrical-port dual-mecha-nical-port (BLDD) machine has become a good candidate to replace the traditional mechanical continuously variable transmission owing to its high compactness, reliability, and torque transmission capability. However, the mutual coupling between two sets of windings fed by different frequency currents leads to strong interference during both health and fault conditions, whereas the coupling effect is difficult to be reduced in the regular BLDD machine due to its operation principle. This paper presents a systematic analysis on a novel spoke-type BLDD (STBLDD) machine, aiming to eliminate coupling of windings. Using the winding function theory, the decoupling principle is analyzed in detail, and corresponding slot/pole combinations are derived. Through finite-element analysis, parameter influences on the performance of this STBLDD machine are then studied. A prototype and test bed have been designed and manufactured, and the experimental results verify the analysis results. [ABSTRACT FROM AUTHOR]

This paper presents the design characterization, optimization, and experimental validation of a multilayer ac winding that provides a high quality rotating MMF with reduced end-turn length. Harmonics in the airgap MMF have been characterized with standard winding functions and verified using finite element analysis (FEA). The multilayer winding design is optimized for a commercial premium efficiency/IE3 benchmark machine using grid multiobjective genetic algorithm (GMGA) and a prototype has been built. Performance of the designed motor has been verified with both FEA and experiments. Evaluation under IEEE 112 test standard demonstrates that by only updating its stator winding design, the designed motor can achieve IE4 class efficiency under the same frame size and cooling type as its IE3 class benchmark. [ABSTRACT FROM AUTHOR]

In an electrical machine design, thermal management plays a key role in improving the performance and reducing size. End-windings are commonly identified as the machine hot-spot. Hence, lowering and predicting end-windings temperature are crucial tasks in thermal management of electrical machines. This paper proposes and investigates a noninvasive but effective cooling method that aims for a uniform cooling of a machine's winding by implementing direct cooling on its end-windings. Modeling and experimental results show that a 25% hot-spot temperature reduction on a particular application can be achieved. To analyze the proposed technique in detail, an accurate but computationally economic lumped parameter thermal network is developed. Comparison between a “standard” thermal network and its simplified equivalent (with less nodes) is presented where the models are developed and fine-tuned based on experimental data. All the above is used to investigate the potential of the proposed end-winding cooling method with different configurations of the methodology. [ABSTRACT FROM AUTHOR]

A simple offline method for measuring the magnetizing inductance of an asymmetrical six-phase induction machine is presented in this paper. The measurement procedure is based on dc excitation and it is performed at standstill. As opposed to the standard no load test, the magnetizing inductance is measured solely with the stator leakage influence significantly diminished. Additionally, the iron losses in the machine and their influence on the measurement are reduced considerably. The proposed method is applicable regardless of whether the neutral point of the machine is accessible or not. The method is verified through finite element analysis and experimentally. The obtained test results confirm the accuracy of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a novel consequent-pole permanent magnet (PM) (CPM) machine featuring N-S-iron sequences. In order to enhance the output torque and efficiency, the flux barriers are employed to improve the magnetic symmetry and reduce the saturation of the stator yoke. The tangential magnetized PMs are embedded in the flux barriers to form the hybrid-pole PM (HPM) machine, which further improves the output torque and efficiency. The rotor of the proposed CPM and HPM machines, as well as its conventional counterpart which employing N-iron sequences, are optimized by finite element analysis. Furthermore, the electromagnetic performances of the proposed machines, including the open-circuit airgap flux density, back EMF, average torque, torque ripple, efficiency, flux-weakening capability, unbalanced magnetic force, and unipolar leakage flux, are compared with the conventional CPM machine. It is demonstrated that the proposed HPM machine can obtain almost equivalent torque, efficiency, and better flux-weakening capability when compared to the conventional one. Moreover, the proposed HPM machine has no unipolar leakage flux in the end region, and thus the magnetization of the mechanical components can be effectively reduced. Finally, a 9-slot/8-pole HPM machine is prototyped and measured to validate the analyses. [ABSTRACT FROM AUTHOR]

Accurate position estimation is an integral part of any motion control system. Besides, instantaneous position of poles plays an important role in electronic drive system of modern PM machines. Resolvers, due to their structure, are the most reliable position sensors in harsh environments. However, resolvers are not as accurate as optical encoders in normal conditions. To increase the accuracy of these sensors, various solutions are used, such as optimization in winding arrangement, rotor and stator contour, slot–pole combinations, and improvements in resolver-to-digital converter. In this paper, fractional slot concentrated winding is used in an axial flux resolver. By the aid of winding function approach, it is shown that increasing the coil pitch improves the estimated position accuracy. The theory is tested for double-layer and four-layer windings with different displacement angles. A new double-stage resolver is also introduced. The proposed structure, in which a meta-heuristic algorithm determines the slot dimensions, the number of turns, and the displacement angle between the stages, results in lower total harmonic distortion of output voltage and, consequently, lower estimated position error. The theoretical and analytical expressions are verified by a three-dimensional time stepping finite element analysis and experimental results. Good agreement between simulation and experimental results validate the advantages of the optimized resolver. [ABSTRACT FROM AUTHOR]

This paper investigates a special tubular staggered-teeth transverse-flux permanent-magnet linear machine (TST-TFPMLM) for a free-piston Stirling power generating system. With the complicated flux leakage characteristic of the TST-TFPMLM considered, the general forms and evaluation method of the flux leakage are investigated by finite-element analysis, and the distribution law and reduction method of the flux leakage are obtained. To help the initial design of the TST-TFPMLM, both back electromotive force (EMF) and thrust are taken as the main concerned aims, and the influence of some primary structural parameters on both back EMF and thrust is studied. To improve the key performances of the TST-TFPMLM, the power factor is investigated with respect to the dimensions of permanent magnets (PMs), winding turns, armature current, internal power factor angle, and tooth tip dimensions. Furthermore, the methods of improving both efficiency and thrust density are explored. A prototype machine is manufactured and tested, and satisfactory experimental results are obtained, showing the feasibility of the TST-TFPMLM for the free-piston Stirling power generating system. This investigation provides a new idea to solve the drawbacks of conventional transverse-flux PM linear machines, which include complicated structure, poor manufacturability, high flux leakage, and low power factor. [ABSTRACT FROM AUTHOR]

This paper models a huge family of electrical machines featuring simple salient poles in a unified way based on the general airgap field modulation theory. The modulation principle is analyzed by introducing the magnetomotive force (MMF) modulation operator, which characterizes the influence of a variable reluctance block on the primitive magnetizing MMF distribution established by field winding. Popular machine topologies are investigated in detail from the perspective of an airgap field modulation mechanism. The iron core magnetic potential drop due to the finite slot opening depth and the impact of iron saturation on the parameters are considered by proper theoretical indication. In addition, the modulation effect of salient poles highly depends on the slot-opening-width-to-pole-pitch ratioϵ. The effect can be neglected whenϵ< 0.3 and the best modulation results will be achieved whenϵ= 0.5. It is also found that mainly three different harmonics parts modulated by salient poles contribute to airgap flux density and torque production. Straightforward relations between the frequency-domain or amplitude information of performances indexes and topological parameters can be obtained obviously by certain analytical expressions without heavy finite-element analysis (FEA). Analytical results are verified by two-dimensional FEA and experiments measurements. [ABSTRACT FROM AUTHOR]

The application of multiphase machines in high-power applications is now a recognized alternative, thanks to their higher fault-tolerance when compared with standard three-phase systems. Although multiphase machines with multiples of three-phase winding sets have been favored in many applications, literature has shown that machines with a prime number of phases, such as five-phase machines, generally outperform other phase orders, especially in terms of machine torque density. One of the major problems when dealing with a prime number of phases either in academic research or industrial applications is the special stator design. This paper provides a general technique to rewind standard off-the-shelf three-phase stator frames with any general prime phase order while preserving the same copper volume. The proposed winding layout is derived using the star of slots theory and the concept of stator winding shifting. Finite-element simulations are used to investigate examples with different phase orders, while experimental investigation is carried out to corroborate the proposed concept by rewinding a standard three-phase stator as a five-phase machine. [ABSTRACT FROM AUTHOR]

In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

A two degrees of freedom (2-DOF) actuator capable of producing linear translation, rotary motion, or helical motion would be a desirable asset to the fields of machine tools, robotics, and various apparatuses. In this paper, a novel 2-DOF split-stator induction motor was proposed and electromagnetic structure parameters of the motor were designed and optimized. The feature of the direct-drive 2-DOF induction motor lies in its solid mover arrangement. In order to study the complex distribution of the eddy current field on the ferromagnetic cylinder mover and the motor's operating characteristics, the mathematical model of the proposed motor was established, and characteristics of the motor were analyzed by adopting the permeation depth method (PDM) and finite element method (FEM). The analytical and numerical results from motor simulation clearly show a correlation between the PDM and FEM models. This may be considered as a fair justification for the proposed machine and design tools. [ABSTRACT FROM AUTHOR]

A new type of electric machine with two free rotating rotors [dual mechanical port (DMP)] is investigated in this paper. Since this DMP machine has a squirrel-cage outer rotor, it is named as SCDMP machine. First, the electromagnetic characteristic of the SCDMP machine is analyzed. Then, the transient model and steady-state model of the SCDMP machine are derived. The proposed machine models are verified by finite element method and simulation. The results show that the proposed models accurately represent the unique electromagnetic characteristics of the SCDMP machine. [ABSTRACT FROM AUTHOR]

In this paper, based on 2-D finite-element analysis (FEA), the hybrid-excitation principle of a hybrid-excitation flux-switching (HEFS) machine is analyzed, and consequently, an improved topology is proposed to enhance the flux-regulation capability. These two machines are termed as the basic HEFS machine and the improved HEFS machine, respectively. In the basic HEFS machine, each permanent magnet (PM) is located at the middle of the corresponding slot and wound by a field winding coil. When field excitation is applied, it is found that the currents in the two field slots adjoining each PM exhibit reversal excitation functions, thus reversal flux-regulation functions. Hence, to improve the flux-regulation performances, an improved HEFS topology is proposed based on the basic one by reversing current direction in one of the field slots. Therefore, the improved topology shares identical structure with the basic one but has different field current directions in some field slots and thus different field winding accommodations. Comparisons of the FEA predictions indicated that both armature no-load flux-regulation capability and armature load torque capability in the improved HEFS machine are much better than those in the basic one. Finally, the FEA results are validated by experimental measurements on two prototyped HEFS machines. [ABSTRACT FROM PUBLISHER]

Motor current signal analysis (MCSA) provides an alternative nonintrusive approach to detect mechanical faults by using the fault signature transmitted along the torsional direction through the rotor. In existing fault detection methods based on MCSA, the gearbox health condition is monitored through the amplitude of the fault-related sidebands in the lower frequency range of the motor current spectra. However, their practical implementation is challenged by the harmonics resulting from the structural properties of the electrical machines and the inherent system imperfections. This effect is even more severe in case of a drivetrain containing planetary gearboxes due to its more complex assembly. In this paper, the resonance residual technique, which investigates the spectrum region around the resonance frequency where rich fault information may occur, is applied for the first time to MCSA to detect planetary gearbox faults. This proposed approach is verified through both simulation and experiments. A lumped parameter model for an electromechanical drive train with an annulus gear tooth crack is simulated to investigate its effect on the stator current. For experimental verification, a similar 4-kW motor-planetary gearbox–generator test rig is used. The robustness of the proposed method is demonstrated through simulations of a nonlinear finite-element model and experiments under different operating conditions. Furthermore, the effectiveness of the proposed method to extract fault information over the existing methods is also shown. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis and design of a two-pole dc brushless limited-angle torque-motor (LATM) with a toroidally wound armature using magnetic equivalent circuit modeling. A variety of design concepts is considered based on several defined criteria, and then, the most worthy alternative is chosen. To select the best design concept, an efficient decision-making tool called analytical hierarchy process is employed. A new segmented rotor pole tip structure of the LATM is introduced. The results obtained from finite-element simulation of the proposed machine conform well with the analysis. The selected design is prototyped, and the experimental results are presented. [ABSTRACT FROM PUBLISHER]

This paper investigates an original solution that can be used in the design of axial-flux permanent-magnet (AFPM) machines whenever a constrained shaft height requirement penalizes a standard design. A machine is tailored for electrical traction, but the ideas that are set forth are valid for any application with a constrained shaft height. Two design solutions that comply with a constrained shaft height are investigated, i.e., a standard Torus AFPM machine and an asymmetrically wound Torus machine, which is named “Ω AFPM” due to the shape of the stator winding. It is shown that the Ω AFPM machine has lower losses and higher efficiency. Finite-element simulations and experimental tests on a full-scale prototype confirm the validity of the proposed solution. [ABSTRACT FROM PUBLISHER]

Referring to the analysis of the impact of the eccentricity on a synchronous reluctance motor presented in the companion paper (Part I), a comparison is carried out between rotors with symmetric and asymmetric flux-barriers. As an example, a four-pole machine with one or two flux-barriers per pole is used. In addition, the analysis is also applied to motors with fractional-slot coil windings. Both single- and double-layer windings are considered. As an example, a six-slot four-pole machine with concentrated windings and 36-slot four-pole machine with distributed windings are compared. The analytical model which is proposed in Part I is used to predict the machine performance. A finite-element analysis confirms the results achieved by means of the analytical model. [ABSTRACT FROM AUTHOR]

This paper presents for the first time the analysis and experimental validation of a six-slot four-pole synchronous reluctance motor with nonoverlapping fractional slot-concentrated windings. The machine exhibits high torque density and efficiency due to its high fill factor coils with very short end windings, facilitated by a segmented stator and bobbin winding of the coils. These advantages are coupled with its inherent robustness and low cost. The topology is presented as a logical step forward in advancing synchronous reluctance machines that have been universally wound with a sinusoidally distributed winding. The paper presents the motor design, performance evaluation through finite element studies and validation of the electromagnetic model, and thermal specification through empirical testing. It is shown that high performance synchronous reluctance motors can be constructed with single tooth wound coils, but considerations must be given regarding torque quality and the d-q axis inductances. [ABSTRACT FROM AUTHOR]

A novel variable reluctance (VR) resolver with nonoverlapping tooth–coil windings is proposed in this paper. It significantly simplifies the manufacturing process of multilayer windings in conventional products. Finite element (FE) analysis is used to illustrate the basic operating principle, followed by analytical derivation of main parameters and optimization of major dimensions, including air-gap length and slot opening width. Based on winding distributions and FE results, it is shown that identical stator and winding can be employed for a resolver with three different numbers of rotor poles. Further, other stator slot/rotor pole combinations based on the nonoverlapping tooth–coil windings are generalized. In addition, the influence of eccentricity and end-winding leakage on the proposed topology is investigated. Finally, a prototype is fabricated and tested to verify the analysis, including main parameters and electrical angle error. [ABSTRACT FROM AUTHOR]

One of the main drawbacks of nonoverlapped coils in fractional slot concentrated winding permanent magnet (PM) machines are the high eddy current losses in both rotor core and permanent magnets induced by the asynchronous harmonics of the armature reaction field. It has been shown in the literature that the reduction of low space harmonics can effectively reduce the rotor eddy current losses. This paper shows that employing a combined star-delta winding to a three-phase PM machine with fractional slot windings and with a number of slots equal to 12, or its multiples, yields a complete cancellation to the fundamental magneto-motive force (MMF) component, which significantly reduces the induced rotor eddy current. Besides, it offers a slight increase in machine torque density. A case study on the well-known 12-slot/10-pole PM machine is conducted to explore the proposed approach. With the same concept, the general $n$ -phase PM machine occupying $4n$ slots and with a dual $n$ -phase winding is then proposed. This configuration offers a complete cancelation of all harmonics below the torque producing MMF component. Hence, the induced eddy currents in both rotor core and magnets are significantly reduced. The winding connection and the required number of turns for both winding groups are also given. The concept is applied to a 20-slot/18-pole stator with a dual five-phase winding, where the stator winding is connected as a combined star/pentagon connection. The proposed concept is assessed through a simulation study based on 2-D finite element analysis. [ABSTRACT FROM AUTHOR]

This paper introduces a method for the drive cycle performance analysis of a permanent-magnet traction motor based on a fast magnetostatic finite-element analysis (FEA). The flux linkage and torque behavior of the permanent-magnet synchronous machine is studied by a nonlinear magnetostatic FEA as a function of direct- and quadrature-axis stator current components. In the analytical machine performance analysis, the current combinations producing the desired torque and minimizing the losses are determined. The iron loss is calculated with the time-transient FEA at no load. The maximum stator flux linkage, limited by the battery voltage, is taken into account. The drive cycle analysis, based on optimal current component surfaces, is carried out for a traction motor of an electric sports car. The results are compared with values measured for the drive cycle on a racetrack. [ABSTRACT FROM PUBLISHER]

This paper presents a new topology of parallel hybrid excitation machine (PHEM), which integrates permanent-magnet synchronous motor (PMSM) and variable-reluctance machine, namely, doubly salient electromagnetic machine (DSEM), and provides a solution to better field-regulating capability. The configuration and the operation principle of the proposed PHEM are introduced. The combination criterion and design consideration are discussed. The performances of the two axial sections (PMSM and DSEM) are studied by 2-D finite-element analysis (FEA), respectively, to achieve reasonable integration. The field and voltage regulation capability of the PHEM is further investigated by 3-D FEA. A prototype PHEM is designed, manufactured, and tested. The measured results verify structural validity and finite-element predictions. The loss is predicted, and the measurement of short-circuit current illustrates the capacity of deexcitation at fault. The results confirm that the PHEM achieves effective power superposition of two different brushless machines. Bidirectional field-regulating capability facilitates a wide field regulating range of 6.5:1 under no load. [ABSTRACT FROM PUBLISHER]

This paper presents a comprehensive analysis and comparison of air-cored axial-flux permanent-magnet machines with different types of coil configurations. Although coil factor is particularly more sensitive to coil-band width and coil pitch in air-cored machines than conventional slotted machines, remarkably no comprehensive analytical equations exist. Here, new formulas are derived to compare the coil factor of two common concentrated-coil stator winding types. Then, respective coil factors for the winding types are used to determine the torque characteristics and, from that, the optimized coil configurations. Three-dimensional finite-element analysis (FEA) models are built to verify the analytical models. Furthermore, overlapping and wave windings are investigated and compared with the concentrated-coil types. Finally, a prototype machine is designed and built for experimental validations. The results show that the concentrated-coil type with constant coil pitch is superior to all other coil types under study. [ABSTRACT FROM PUBLISHER]

A model of permanent-magnet synchronous machine (PMSM), including the electromagnetically originated torque ripple, is presented in this paper. This unique representation of such equivalent circuit is highly critical to understand the torque ripple content and to develop an appropriate mitigation scheme for low torque ripple applications requiring four quadrant operations. This research proposes a method to quantify the various sources of torque ripple and modifies the existing dq-model to enhance the modeling capabilities for both surface-mount and interior PMSMs. Finite-element (FE) analysis is used for modeling various PMSMs to verify the lumped circuit model proposed in this research. The theoretical results obtained from analytical and FE analysis are validated using experimental test. [ABSTRACT FROM AUTHOR]

In this paper, a global fault-tolerant control (FTC) technique is proposed for multiphase permanent-magnet (PM) machine drives. The goal of the proposed FTC is to find a general closed-form solution for healthy phase currents under steady-state postfault conditions. Healthy phase currents are found through an optimization problem to produce ripple-free output torque with minimum ohmic losses. A comprehensive FTC approach should be able to provide fault-tolerant currents for multiphase machines with any number of phases. In addition, it needs to find currents based on fault type (open-circuit/short-circuit), fault locations [phase(s) and/or line(s)], connection of stator windings, and even different control objectives. An important feature of the proposed method is its flexibility and simplicity in dealing with all possible fault conditions. The proposed method is a great tool to evaluate fault-tolerant capability of different drive systems in terms of maximum available ripple-free torque and copper losses. Due to its simplicity and flexibility, it is also well-suited for real-time implementation. A five-phase PM machine is used as an example to investigate the validity of the proposed solutions through finite-element analysis and experimental tests. [ABSTRACT FROM AUTHOR]

This paper proposes a new hybrid permanent magnet synchronous reluctance machine (HPM-SynRM) with axially sandwiched magnets for improving machine performance including airgap flux density, back electromotive force, torque, torque ripple, efficiency, and power factor. The significant feature of the proposed machine is the configuration of axially integrating two kinds of independent and symmetrical rotors with a specific assembling angle, such that it can make full use of the magnetic torque and the reluctance torque for efficient production of the total torque. Meanwhile, the proposed machine greatly improves the PM utilization for high magnetic torque, and releases the stress condition of SynRM rotors for more proper design of ribs, thus to further improve the torque, efficiency, and power factor, especially when compared to the conventional PM-SynRM with the same machine specifications and operating conditions. The design of the proposed machine, including the PM optimization using the Kriging method and genetic algorithm, rib width and assembling angle design using the finite element method (FEM), has been first discussed in detail. Then, the advantages of the proposed machine are highlighted by quantitatively comparing to a conventional PM-SynRM by the FEM. Finally, the proposed machine is manufactured to validate its high performance by experiments. [ABSTRACT FROM AUTHOR]

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

Fractional-slot concentrated-winding (FSCW) permanent magnet (PM) machines have been widely studied in recent years. This is mainly due to the several advantages, including high power density, high efficiency, short end turns, high fill factor, low cogging torque, good flux-weakening and fault-tolerant performance. However, the key challenges of utilizing FSCW-PM machines are the abundant stator magnetomotive force (MMF) harmonics. In this paper, the multiphase star–delta hybrid connection (SDHC) windings configuration that can eliminate some stator MMF harmonics is systematically studied. First, the general relationship between the number of slots and phases which are appropriate for the SDHC windings configuration is derived. In addition, the particular principle of the MMF harmonics elimination by the SDHC windings configuration is researched. In order to verify the analysis results, four three-phase SDHC FSCW-PM machines with different slot–pole combinations are built and calculated by the finite-element method. Finally, experiments on a prototype three-phase 12-slot ten-pole FSCW-PM machine are carried out for validation. [ABSTRACT FROM AUTHOR]

In this paper, the electromagnetic performance and operating characteristics of magnetic-geared permanent-magnet machines (MGPMMs) are evaluated using the subdomain analytical method. We derive the governing equations for each region based on the electromagnetic theory and some assumptions. The undetermined coefficients of the governing equations are calculated using boundary conditions. Based on the analytical solutions, the electromagnetic performance is analyzed. The proposed analytical method is validated through the nonlinear finite-element method and an experiment. In particular, an analysis of the performance analysis of the slot combination, which is one of the design variables, suggests the increased power factor and operating range. The analytical method can be useful for the initial and optimal designs of MGPMMs. [ABSTRACT FROM AUTHOR]

This paper presents the design and experimental validation of a synchronous reluctance motor (SynRM) using a multilayer (ML) ac winding that meets the ultra-premium/IE5 class efficiency requirement. Compared to conventional double-layer ac windings, the ML winding yields a more sinusoidal stator magnetomotive force (MMF) with a shorter end-turn length. The ML winding is characterized using an analytical stator MMF model with verification against finite element analysis (FEA). The proposed winding configuration is optimized under a given design benchmark. The multi-barrier rotor design is also optimized based on FEA using a genetic algorithm. The performance of the designed ML-SynRM is compared against a commercial premium efficiency induction motor and a conventionally wound SynRM for the same standard frame and cooling type. Results show significant efficiency gain with SynRM designs, and also, the designed ML-SynRM yields lower torque ripple with an improved power factor compared to the conventional SynRM. The prototype ML-SynRM is built, and its simulation results are experimentally validated against the benchmark including their performances at a thermal steady state. [ABSTRACT FROM AUTHOR]

Axial flux permanent magnet (AFPM) motors are suitable options for solar-powered vehicles due to their compact structure and high torque density. Furthermore, certain types of AFPM machines may be configured without stator cores, which eliminates associated losses and cogging torque and simplifies the manufacturing and assembly. This paper examines two machine designs for use in the solar-powered vehicle of the challenger class—a single rotor, single stator conventional AFPM machine, and a coreless AFPM machine with multiple stator and rotor disks. The response surface methodology (RSM) is utilized for the systematic comparison of the conventional and coreless topologies and to select the optimum designs among several hundreds of candidates. Designs with minimum losses and mass producing required torque with larger air-gap are favored. The performance of the selected designs has been studied via three-dimensional finite element analysis (FEA). The FEA parametric modeling methodology is validated by measurements on three AFPM machines of the conventional and coreless type. [ABSTRACT FROM AUTHOR]

This paper proposed a varying magnetic network modeling method of dual-rotor permanent magnet reluctance (DRPMR) machines based on magnetic circuits considering possible saturation and nonlinearity according to the physical structure, which is put forward to obtain the accurate inductance characteristics of the proposed machine. The feasibility of this analytical model is confirmed by the finite element method. Moreover, experiments are designed to validate the analytical results. It indicates that the analytical inductance characteristics of the DRPMR machine have good agreements with the experimental results. [ABSTRACT FROM AUTHOR]

This paper describes a new brushless and magnet-less synchronous generator where an induction machine (IM) is embedded in a synchronous machine (SM) to provide the excitation. Hence, this machine is named as brushless induction excited synchronous generator (BINSYG). To avoid the magnetic interaction between both IM and SM, they are configured for different number of pole pairs. A rotating uncontrolled rectifier (mounted on the shaft) is proposed to be used to rectify the rotor voltage of the IM to provide the excitation to the SM. Thus, by controlling the IM from stator side, field current of the SM can be controlled smoothly. As an example, in this work, SM and IM are configured for two pole and six pole, respectively. Practical winding-design-challenges and mutual interaction between IM and SM fields are analyzed briefly for 2/6 (SM poles/IM poles) pole BINSYG. Extensive finite element simulations of the proposed machine have been conducted using Maxwell-2D and these simulated results are obeying the theoretical analysis. A 3 kVA laboratory prototype of 2/6 pole BINSYG has been developed to evaluate the performance when IM is operated in the plugging mode for definite advantages. While a brushless configuration is proposed, brushes and slip-rings are used for the experimental machine, such that, rotor side windings of SM and IM can be accessed for the better understanding of the performance. Experimental results from this prototype confirm the theoretical and finite element method predictions. [ABSTRACT FROM AUTHOR]

This paper explores the use of speed harmonic for accurate and fast maximum-torque-per-ampere (MTPA) control of interior permanent magnet synchronous machines (IPMSMs). A novel MTPA angle calculation approach is proposed, in which the MTPA angle is directly calculated from the phase angle of the speed harmonic that is induced by an injected harmonic current. At first, the relation between the speed harmonic and machine parameters is derived from the IPMSM model, which shows that the phase angle of the induced speed harmonic can be utilized to cancel the machine parameters in existing MTPA equation. Thus, a new MTPA equation is derived, which does not involve machine parameters for MTPA angle calculation. Compared with existing methods, the proposed approach is independent from the machine and drive nonlinearities. Moreover, the MTPA angle is directly calculated from the derived MTPA equation, so the proposed approach is fast and computationally efficient. Thus, the proposed approach is suitable for both on-line applications and building off-line lookup tables of MTPA angles for IPMSMs. The proposed approach is experimentally evaluated on a laboratory IPMSM drive system. [ABSTRACT FROM AUTHOR]

This paper proposes an improved transverse flux type permanent magnet reluctance generator (TFPMRG) for the purpose of reducing the leakage flux and improving the back EMF. This improved TFPMRG has auxiliary rotor poles with permanent magnet (PM) added between the main rotor poles. The auxiliary rotor pole is effective to obtain high-back EMF voltage source under no-load condition and to increase the amplitude and region of the generated current under load condition. To obtain these desired performances, PMs are inserted into both ends of auxiliary rotor pole. The auxiliary rotor and main rotor poles works at the same instance under load condition. Characteristics of the improved TFPMG are analyzed using the finite element analysis and it is verified that the improved TFPMRG has an excellent performance. [ABSTRACT FROM AUTHOR]

This paper presents a novel gearless and brushless power split transmission system for variable-speed constant-frequency wind power generation application. The core element of this system is a novel axial-flux doubly fed dual-rotor permanent magnet machine. The key of the design is to utilize the flux modulation principle to modulate the magnetic flux in an axial-flux machine and use doubly fed stator winding to control the rotor rotation. This design combines the merits of direct-drive machines and doubly fed generators. As the mechanical problems related to brushes, slip rings, and gear boxes are successfully overcome, the operational reliability of the system is improved. The stator winding of the proposed system can be directly connected to the power grid, and the power rating of its associated frequency converter is reduced. Time-stepping finite-element method is used to analyze the dynamic performance of the proposed system. [ABSTRACT FROM AUTHOR]

Switched reluctance machines (SRMs) have been comprehensively researched, and they play an important role in the modern industrial field. The topology of SRMs is quite simple and only one set of windings is employed. Consequently, the winding configuration has an essential impact on performance. In this paper, a new winding configuration for SRMs with only half-teeth wound (HT-SRM) is proposed, which is totally different from the conventional SRMs with full-teeth wound (FT-SRM). First, the basic topology and operating principle of HT-SRMs are presented by a three-phase 12/8 prototype. Then, based on the 2-D finite element analysis, an optimization of the original 12/8 HT-SRM is conducted and a series of static characteristics of three SRMs, namely, a conventional 12/8 FT-SRM, an original 12/8 HT-SRM with the same iron laminations, and an optimal HT-SRM with the optimized dimensions, are compared. Finally, three 12/8 SRM prototypes are fabricated and the experimental results verify the theoretical analysis and the corresponding finite element analysis-based predictions. [ABSTRACT FROM AUTHOR]

In this paper, stator/rotor pole combinations, winding configurations, and electromagnetic performance of novel variable flux reluctance machines (VFRMs), which employ a doubly salient structure similar to switched reluctance machines (SRMs) but with stator-located dc field windings, are investigated. VFRMs with 12 stator poles are taken as examples to illustrate the method for determining the winding connections and winding factors. The back-electromotive force (EMF), self- and mutual inductances, cogging torque, static torque, torque ripple, and unbalanced magnetic force (UMF) are investigated by finite-element analyses. It is found that many stator/rotor pole combinations, i.e., 12/8 (which may be derived from the conventional three-phase SRM), 12/10, 12/11, 12/13, and 12/14, are feasible for the 12-stator-pole VFRMs. Among these pole number combinations, the 10- and 14-rotor-pole VFRMs can eliminate the inherent UMF in 6/5 and 6/7 VFRMs and exhibit more sinusoidal back-EMF waveforms and have higher torque density than an 8-rotor-pole VFRM, whereas the 11- and 13-rotor-pole VFRMs exhibit similar torque density as the 10- and 14-rotor-pole VFRMs, but with negligible cogging torque and torque ripple, albeit with UMF. Five prototype VFRMs with 12 stator poles and different rotor poles have been designed, manufactured, and tested to verify the analyses. [ABSTRACT FROM AUTHOR]

Analytical calculation methods for all the major components of the synchronous inductance of tooth-coil permanent-magnet synchronous machines are reevaluated in this paper. The inductance estimation is different in the tooth-coil machine compared with the one in the traditional rotating field winding machine. The accuracy of the analytical torque calculation highly depends on the estimated synchronous inductance. Despite powerful finite element method (FEM) tools, an accurate and fast analytical method is required at an early design stage to find an initial machine design structure with the desired performance. The results of the analytical inductance calculation are verified and assessed in terms of accuracy with the FEM simulation results and with the prototype measurement results. [ABSTRACT FROM PUBLISHER]

A new vector-phasor combined with an analytic method for solving complex flux distributions is proposed. The flux leakage and losses in the end region of a 1266 MW scale generator are analyzed by both finite element simulation and an analytical method. The deviation of the calculated result between the analytical model and the finite element method is very small. The analytical model can acquire current data for fast prediction of the flux density. The analytical and numerical results of the flux distribution are found to be in a satisfactory agreement. In addition, the ability to reduce the eddy current losses in the end regions is also researched using various of structural solutions. [ABSTRACT FROM AUTHOR]

This paper is to propose a new self-decelerating permanent-magnet (PM) in-wheel motor for low-speed and high-torque drive of electric vehicles (EVs). This motor uses sensorless control and integrates advantages of magnetic gear and those of PM machine together while gear inner rotor is removed. The key is the magnetic gear, which can reduce the size of the motor and achieve the similar torque amplification provided by a mechanical gearbox and does not require maintenance or cause breakdown issues. The topology and the operating principle of the proposed in-wheel motor are analyzed; the effects of flux modulated by the magnetic gear and the static characteristics are investigated by using the finite-element analysis. To solve the problems of mechanical sensors, an improved sliding model observer for sensorless control is studied. Then, the evaluation of the system performances is conducted by the simulation based on the MATLAB/Simulink and the experiment based on a prototype. Both the simulation and the experimental results show that the system can provide low-speed high-torque driving for EVs without mechanical gears and sensors. [ABSTRACT FROM PUBLISHER]

The significant losses in the end components due to leakage flux excited by the armature and field end windings can result in partial overheating, and are important for the design of large synchronous generators. This paper describes a method based on 3-D transient finite-element analysis (FEA) to determine the fields and losses in the generator end region. Taking the nonlinear and anisotropic properties and the induced in-plane eddy currents in stator into consideration, the electromagnetic field and loss distributions in the end region are calculated. The method is validated by the agreement between the temperatures predicted by a corresponding 3-D thermal FEA and the temperatures obtained from a physical measurement at different locations in the generator end region. Then, the field and loss distributions in the end components in the open-circuit test condition short-circuit test condition and rated apparent power with a 0.85 lagging power factor, a unity power factor, and a 0.95 leading power factor conditions are analyzed and compared using the proposed 3-D transient FEA method. [ABSTRACT FROM AUTHOR]

This paper presents research work on a 12-slot ten-pole tapered axial-flux permanent-magnet machine utilizing amorphous magnetic material in the stator core. Novel loss separation techniques are described, including mechanical loss and locked-rotor tests. Mechanical loss estimation is based on a combination of experimental tests and 3-D finite-element model analysis using an uncut stator. The locked-rotor test is introduced to separate the stator and rotor losses by eliminating the uncertainty associated with mechanical loss. High rotor yoke losses were identified in the baseline design. The rotor design was modified and a significant improvement in efficiency was demonstrated. [ABSTRACT FROM PUBLISHER]

Axial flux variable reluctance (AFVR) resolvers have substantial benefits that make them suitable for motion control drives. However, they suffer from insufficient accuracy, especially in high-accuracy applications. Hence, optimizing the AFVR resolver structure is necessary for improving its commercial usage. However, its accurate modelling needs three-dimensional (3-D) time stepping finite element analysis (TSFEA) that is computationally expensive and unsuitable for co-usage with optimization algorithms. The aim of this paper is to establish an accurate, yet computationally fast, model suitable for optimal design of AFVR resolvers. The working of the proposed model is based on magnetic equivalent circuit (MEC) and conformal mapping, which are in turn based on Schwarz–Christoffel mapping. The model uses conformal mapping to calculate reluctances that are used in MEC for calculating magnetic fluxes linkages, inductances, and induced voltages. Then, the induced voltages are used for calculating angular position. The results of the proposed model are compared with those of 3-D TSFEA. Finally, the experimental prototype is used to evaluate the developed analytical model. [ABSTRACT FROM PUBLISHER]

Induction motors are used in a variety of industrial applications where frequent startup cycles are required. In those cases, it is necessary to apply sophisticated signal processing analysis methods in order to reliably follow the time evolution of fault-related harmonics in the signal. In this paper, the zero-sequence current (ZSC) is analyzed using the high-resolution spectral method of multiple signal classification. The analysis of the ZSC signal has proved to have several advantages over the analysis of a single-phase current waveform. The method is validated through simulation and experimental results. The simulations are carried out for a 1.1-MW and a 4-kW induction motors under finite element analysis. Experimentation is performed on a healthy motor, a motor with one broken rotor bar, and a motor with two broken rotor bars. The analysis results are satisfactory since the proposed methodology reliably detects the broken rotor bar fault and its severity, both during transient and steady-state operation of the induction motor. [ABSTRACT FROM AUTHOR]

The premium induction motor has received worldwide attention in recent years due to its high efficiency. However, the high efficiency benefits from the high cost. In the paper, a multiphysical field collaborative optimization method of the premium induction motor based on the genetic algorithm (GA) is presented to improve the utilization of the materials and reduce the cost. First, the cost and efficiency are taken as bi-objective; the magnetic circuit optimization based on GA is established to get the initial electromagnetic scheme. Then, the parameters of the premium induction motor are automatically transferred to a 2-D transient electromagnetic field calculation model so that the operation performances of the premium motor can be determined. The results will be sent to the magnetic circuit optimization to compare with the optimization objectives. The electromagnetic scheme will adjust until the errors between the transient operation performances and optimization objectives are within the convergence errors. Based on the results above, the transient results will be transferred to the 2-D temperature field calculation model to determine the thermal distributions of the premium induction motor. The structures of the premium induction motor will also adjust until the thermal distributions meet the requirements. The presented multiphysical field collaborative optimization method is applied to optimize several premium motors, and the accuracy is validated by the experimental data. [ABSTRACT FROM PUBLISHER]