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This paper proposes a simple position observer based on the instantaneous power and a tuning procedure for the proposed observer in driving the surface-mounted permanent magnet synchronous motor. In the instantaneous power of a three-phase system, the imaginary and real powers have the information related to the position and velocity. Using the instantaneous power, the difference between real rotor position and estimated rotor position is calculated. For easy design, gain parameters are described as a bandwidth of position observer. The proper bandwidth is expressed in terms of the desired load transient response, system inertia, and permitted acceleration range. Also, the sensitivity of phase resistance and inductance is analyzed. The described mathematical results show the necessity of accurate parameter information. Simulation and experimental results show the validity of the proposed design method and analysis. [ABSTRACT FROM AUTHOR]

In this paper, the core losses that occur in a 4-kVA flux-modulating synchronous machine (SM) (FMSM) are investigated using 2-D finite-element analysis, and the results are supported by experiments. A method for reducing the core losses is also presented. The FMSM is a new type of multipole SM in which the stator field magnetomotive force is modulated by the air-gap permeance to generate the rotating field. A 2pa-pole three-phase armature winding and a 2pf-pole field winding are centrally wound around individual stator teeth, and a reluctance rotor with 2pr\ (= pa + pf) saliencies is used to provide a magnetic coupling between these windings. As a result of the investigation, it was found that, although the core losses occur in the rotor as well as in the stator, the rotor core loss can be effectively reduced by decreasing the height of the rotor poles. [ABSTRACT FROM AUTHOR]

Fractional-slot permanent-magnet (PM) machines have several advantages, but they suffer from the high content of space harmonics in the air-gap magnetomotive force (MMF) distribution. The MMF space harmonic amplitude and frequency depend on the particular combination of numbers of slots and poles. Such harmonics induce losses in the rotor since they are not synchronous with the rotor speed. This paper compares several kinds of machines with the same stator lamination but with different numbers of phases; three-, five-, and seven-phase PM machines are considered. Several winding configurations are compared, changing the number of poles but maintaining the same number of slots. Although in each case there is a reduction in terms of harmonic content, it is shown that rotor loss reduction is lower than expected. Some considerations about the harmonic impact are given. Although no experimental results are given, this paper refers to previous works in which rotor losses have been investigated and measured experimentally. [ABSTRACT FROM PUBLISHER]

This paper analyzes a 90-kW brushless doubly fed three-phase induction machine in which a wound rotor circuit is connected to a rotary transformer. It presents the advantages of substituting brushes and slip rings by a rotary transformer. In addition, it shows the rotary transformer design and presents the doubly fed induction machine operation. The steady-state model considers electrical circuit techniques to provide information about current, power factor, and efficiency on load. Equivalent circuit parameters are obtained through laboratory tests under a prototype. Comparisons between simulation and measurement results attest the good performance of the adopted model. [ABSTRACT FROM PUBLISHER]

A recently proposed shaft position sensorless method for torque and reactive power control of the brushless doubly fed reluctance machine has proven successful in simulation studies. In this paper, its real-time performance has been evaluated on a custom-designed machine prototype. The preliminary experimental results have confirmed the viability of the scheme and represent a serious step toward the development of a generic virtually parameter independent controller for doubly excited machines. A wide range of applications is possible, including drive and generator systems with limited speed ranges (e.g., large pumps and wind turbines), where the cost savings of using a partially rated power electronic converter are significant. [ABSTRACT FROM PUBLISHER]

This paper presents a new type of multipole synchronous machine (SM) in which 2pa-pole armature and 2pf-pole field windings are centrally wound around individual stator teeth. The proposed machine operates as a (2pa + 2pf)-pole SM by providing a magnetic coupling between the armature and field windings through a 2pr-pole reluctance rotor. A 4-kVA (32 + 48)-pole prototype machine was designed and built to validate the principle of this structure. Performance characteristics of the prototype machine were simulated using 2-D finite-element analysis (FEA) and were supported by experiments. In addition, the effects of the rotor pole shape on the performance characteristics were studied through 2-D FEA simulations. The results presented provide guidelines for the optimum design of the proposed machine. [ABSTRACT FROM PUBLISHER]

An equivalent dq model of three-phase flux-switching synchronous motors employing a segmental rotor is constructed and tested for predicting steady-state performance. Both the wound-field and permanent-magnet excited motors are represented. The unconventional topologies of the two types of motors present significant departure from the basic assumptions of the dq theory, even though the motors may be operated from a drive incorporating generic dq control regimes. The equivalent dq inductances and flux linkages are calculated from finite-element simulation results and applied in predicting the steady-state performance of the motor. It is found that the credibility of the dq model to predict the performance of the motors over the operating range is assured and is enhanced by incorporating dq-coupling inductances in the model. [ABSTRACT FROM PUBLISHER]

This paper compares four analytical models for predicting the cogging torque in surface-mounted permanent-magnet machines, viz., lateral force (LF), complex permeance (CP), and exact subdomain (SD) models, together with an SD model based on a single slot/pole. The models are evaluated for the air-gap flux density, cogging torque, back electromotive force (EMF), electromagnetic torque, saturation effect, and computational complexity, with particular focus on the influence of design parameters, such as the slot-depth-to-slot-opening ratio and the optimal pole-arc-to-pole-pitch and slot-opening-to-slot-pitch ratios, on the cogging torque. It shows that all studied analytical models have similar high accuracy for the fundamental back EMF and average torque. However, their predictions are quite different for the ripples in the back EMF, cogging torque, and electromagnetic torque waveforms. Overall, the SD models have high accuracy, while the exact SD model is the most accurate among the studied models by accounting for mutual influence between slots, albeit with high computational complexity. The computation of the SD models is slower than that of the LF model but can be quicker than that of the CP model. The comparison is validated by the finite-element and experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents a metaheuristic algorithm inspired in evolutionary computation and swarm intelligence concepts and fundamentals of echolocation of micro bats. The aim is to optimize the mono and multiobjective optimization problems related to the brushless DC wheel motor problems, which has 5 design parameters and 6 constraints for the mono-objective problem and 2 objectives, 5 design parameters, and 5 constraints for multiobjective version. Furthermore, results are compared with other optimization approaches proposed in the recent literature, showing the feasibility of this newly introduced technique to high nonlinear problems in electromagnetics. [ABSTRACT FROM PUBLISHER]

This paper investigates different rotor topologies based on the spoke design as an alternative to the internal permanent magnet design currently used in the Toyota Prius 2004 design. Reference is made to the 2010 model where the magnet material and maximum torque are reduced, but the speed is doubled. A rare-earth spoke design is shown to be a viable alternative. The paper then goes further and investigates a ferrite alternative. While the torque density is reduced, it illustrates that the spoke magnet arrangement may a viable solution and may open up ferrite magnet use. To offset the reduction in torque density then the speed may be increased; this is the solution Toyota used in the 2010 machine for rare-earth magnet material reduction. [ABSTRACT FROM PUBLISHER]

This paper deals with the ac–dc interface conversion in grid-connected wind energy conversion systems based on modular permanent-magnet synchronous generators. In particular, some solutions based on diode rectifiers are extensively analyzed as for the waveforms, the efficiency, and the torque ripple, by considering several connections, which are allowed by the inherent modularity of the considered generators. Rectifier schemes with a high number of pulses can be easily realized without using special shifter transformers so that these solutions can be attractive for low- and medium-power applications. [ABSTRACT FROM PUBLISHER]

Directly coupled electromagnetic field-electric circuit modeling approach for coupling an electrical machine to its associated external circuit and power electronics has been widely reported in the literature. However, the inclusion of a closed-loop control system, such as conventional vector (field-oriented) control, within a directly coupled electromagnetic field-electric circuit model has not been widely studied. This is partly because it is a rather complex task. This paper introduces a directly coupled electromagnetic field-electric circuit computational model in which a conventional vector control system has been incorporated for detail simulation of vector-controlled electric machinery drive systems. The model has been successfully applied in the design and analysis of a vector-controlled wound field brushless starter-generator system prototype. Comparison between the simulation and test results for both motor and generator modes show excellent correlation that validates the efficacy and computational soundness of the modeling approach. [ABSTRACT FROM AUTHOR]

Permanent magnet drives have frequently been used as a generator for a variety of applications. This is mainly due to their high-power density, reliability, robustness, and wide speed range. However, these systems often use expensive position sensors as well as complex controllers with high computational and memory capacity in order to control the drive at desired performance and operating range. This paper presents the concept of a simple digital control strategy for brushless dc generators. This technique is easy to implement and can be used for variety of applications including renewable energy systems, automotive systems, and flywheels. The control strategy shows satisfying performance, reliability, and robustness for both speed and voltage regulation, which are frequently used for industrial generator applications. Fundamental principles of the control technique have been presented with detailed simulation results. This scheme has been implemented and tested on a laboratory prototype generator to demonstrate feasibility and experimentally verify performance under various operating conditions. [ABSTRACT FROM AUTHOR]

The split ratio is one of the most important design parameters for permanent-magnet (PM) brushless machines. It has been optimized for maximum torque density with both internal rotor and tubular PM brushless machines in existing papers. This paper proposes an analytical model to determine the optimal split ratio for external rotor PM brushless machine having nonoverlapping winding. The influence of winding factor, tooth tip, and end winding on the split ratio is considered. The theoretical analyses are verified by finite element analysis and validated with experimental measurement. [ABSTRACT FROM AUTHOR]

This paper presents a new flux-mnemonic dual-magnet brushless machine which incorporates both the neodymium-iron-boron (NdFeB) and aluminum-nickel-cobalt (AlNiCo) permanent magnets (PMs) for hybrid excitation. By applying a temporary current pulse in a small magnetizing winding to online tune the magnetization of AlNiCo PMs, the proposed machine can provide flexible air-gap flux control, thus achieving high efficiency at different speeds and loads. By newly using a parallelogram to model the AlNiCo PM hysteresis loop and then incorporating into the finite element field equation, the performance of the proposed machine is analyzed. Finally, experimental results are given to verify the simulation, confirming the validity of the proposed machine and its analysis. [ABSTRACT FROM AUTHOR]

A predictive control of a brushless DC generator is presented in this paper. The tracking characteristic of the prime-mover is considered for setting the reference value of the electromagnetic torque developed by the generator. This reference is assumed in order to determine the switching pattern of the AC/DC converter, at each sampling period, under minimum Joule losses and minimum torque ripple constraints. In order to highlight the improved performances achievable by means of the proposed predictive control algorithm, two cases are considered: in the first one, the generator supplies a resistive load as in standalone applications, whereas, in the second one, it is connected to a constant voltage DC grid. Hence, the respective conversion systems are computer simulated in the Matlab Simulink environment and the results are compared to those of the traditional systems. The comparison reveals that, in both cases, the torque ripple minimization is achieved and more power can be delivered by using the proposed control technique with respect to those of traditional systems. [ABSTRACT FROM AUTHOR]

A flux-switching permanent-magnet (PM) (FSPM) machine is a new class of stator-PM brushless machines, which offers the advantages of high reliability, high power density, and high efficiency. In this paper, by employing redundant winding in the existing FSPM machine topology, a new redundant FSPM (R-FSPM) machine is proposed for a fault-tolerant operation of critical applications. The redundant winding configuration is analyzed, and the corresponding suitable control strategy for the postfault operation is proposed. The electromagnetic performance of the R-FSPM motor drive under normal and fault conditions is analyzed by using a cosimulation method coupling magnetic and electrical circuit solvers. Finally, a 12-stator-tooth/10-rotor-pole R-FSPM machine is prototyped for verification. Both simulation and experimental results are presented, verifying the fault-tolerant characteristic of the proposed motor drive. [ABSTRACT FROM AUTHOR]

Toroidally wound brushless dc (BLDC) machines are compact, economical, and can operate across large air gaps. In this paper, we provide analytical design equations for a radial-flux toroidally wound BLDC machine. The validity of the design equations is checked against finite-element analyses (FEAs) and experiments. It is found that the motor constant calculated by the design equations is off only by 5% from the results by the FEAs or experiments. We also provide an optimization metric that corresponds to the maximization of machine torque while maintaining minimum power loss. Two optimal design cases are presented. [ABSTRACT FROM AUTHOR]

A three-phase, segmental-rotor, flux-switching synchronous motor is presented for the first time, with both field and armature windings placed on the stator. Mutual coupling of the circuits is through segments whose motion causes switching of flux in the armature circuit. The magnetic geometry is substantially different to that of other flux-switching machines (FSMs), and may offer advantages in terms of torque density and controllability. This paper describes the principles and the evaluation of a three-phase design, based on a 12-tooth stator with an eight-segment rotor, before introducing a prototype machine and test results. The prototype has been found to have torque density and profile comparable to that of a switched reluctance motor (SRM) of the same size. [ABSTRACT FROM PUBLISHER]

The roots of swarm intelligence are deeply embedded in the biological study of self-organized behaviors in social insects. Particle swarm optimization (PSO) is one of the modern metaheuristics of swarm intelligence, which can be effectively used to solve nonlinear and non-continuous optimization problems. The basic principle of PSO algorithm is formed on the assumption that potential solutions (particles) will be flown through hyperspace with acceleration towards more optimum solutions. Each particle adjusts its flying according to the flying experiences of both itself and its companions using equations of position and velocity. During the process, the coordinates in hyperspace associated with its previous best fitness solution and the overall best value attained so far by other particles within the group are kept track and recorded in the memory. In recent years, PSO approaches have been successfully implemented to different problem domains with multiple objectives. In this paper, a multiobjective PSO approach, based on concepts of Pareto optimality, dominance, archiving external with elite particles and truncated Cauchy distribution, is proposed and applied in the design with the constraints presence of a brushless DC (Direct Current) wheel motor. Promising results in terms of convergence and spacing performance metrics indicate that the proposed multiobjective PSO scheme is capable of producing good solutions. [ABSTRACT FROM AUTHOR]

In this paper, a low-time-consuming and low-cost sensorless-control algorithm for high-dynamic performance permanent-magnet synchronous motors, both surface and internal permanent-magnet mounted for position and speed estimation, is introduced, discussed, and experimentally validated. This control algorithm is based on the estimation of rotor speed and angular position starting from the back electromotive force space-vector determination without voltage sensors by using the reference voltages given by the current controllers instead of the actual ones. This choice obviously introduces some errors that must be vanished by means of a compensating function. The novelties of the proposed estimation algorithm are the position-estimation equation and the process of compensation of the inverter phase lag that also suggests the final mathematical form of the estimation. The mathematical structure of the estimation guarantees a high degree of robustness against parameter variation as shown by the sensitivity analysis reported in this paper. Experimental verifications of the proposed sensorless-control system have been made with the aid of a flexible test bench for brushless motor electrical drives. The test results presented in this paper show the validity of the proposed low-cost sensorless-control algorithm and, above all, underline the high dynamic performances of the sensorless-control system also with a reduced equipment. [ABSTRACT FROM AUTHOR]

An axial-flux permanent-magnet brushless motor is designed with variable stator alignment of independent stators, thus allowing field weakening via a controllable and variable generated-voltage constant. This feature is particularly valuable in vehicle traction motors with large constant-power speed ratio, where there is also a strong desire to eliminate the need for gear changes and keep the overall size of the motor drive as small as possible. The advantage of high pole count as applied to this technique is discussed, and the simulation impact on motor drive kilovoltampere, efficiency, gradability, acceleration, and maximum speed over typical driving cycles is shown. [ABSTRACT FROM AUTHOR]

Solar-powered aircraft require electric drives for the main propulsion system. It is critical that these drives provide both very high efficiency and low mass. This paper discusses the relative merits of different machine topologies based upon maximizing efficiency, taking into account power-electronic losses, motor losses, mass, and size penalties. Laminated machines are usually limited in their efficiency at light load because of their iron losses. This paper shows how, by combining a high pole number with an ultralow loss lamination material, these machines can be more efficient than other more complex arrangements which have been adopted by others. A demonstrator machine has been built and predicted efficiencies have been validated by test. It has then been used to propel a solar plane to over 60 000 feet and extend the aircraft flight-endurance world record from 30 to 84 h. [ABSTRACT FROM AUTHOR]

This paper presents the design, analysis, control, and experimental evaluation of an innovative field-controlled axial-flux surface-mounted permanent-magnet machine. Topology and design equations, as well as an optimized design study, are attained. The machine is investigated in detail using finite-element analysis, and a prototype machine is built. In order to evaluate the new axialfiux machine topology, an experimental system setup is devised and discussed. The experimental results of the prototype machine and a comparison between the analysis and test results are also presented. [ABSTRACT FROM AUTHOR]

This paper proposes to apply optimal multiphysic models to the design of highly constrained electrical machines, such as interior permanent-magnet (IPM) machine intended for an automotive integrated starter generators. One of the main problems in the use of such optimal approaches remains the accuracy of the models used by the optimizer. In a recent study, we proposed a design model linked to three strong hypotheses: 1) Iron losses are calculated according to the flux density fundamental (sinusoidal approach); 2) flux densities are estimated with a saturated but decoupled d,q reluctant circuit model neglecting the cross saturation effect; and 3) thermal states are indirectly treated with a current density limit. This paper improves these models by using first the finite element method for the determination of flux and iron losses in the machine and then an equivalent thermal steady-state lumped-parameter network. These models are included in the optimization loop and so are evaluated at each iteration. The optimization method uses standard sequential quadratic programming algorithm and Sequential Simplex algorithm. A comparison between the design of an IPM machine with the previous model and the new one will be performed. [ABSTRACT FROM AUTHOR]

Slim pump for cooling devices play an important role for cooling the electronics apparatus. This paper develops an axial-flux internal rotor type motor for the low-profile vortex pump. The integrated motor-pump structure is composed of an internal permanent magnet (PM) disc rotor and double-sided external coreless stators with windings piled up on the printed circuit board (PCB). The impeller is disposed on the periphery of the magnet and a fluid dynamic bearing (FDB) is set in the centre of the magnet to rotate relative to the centre shaft. A prototype of the axial-flux motor pump and drive circuit has been made and tested. Both simulated and experimental results show that the proposed motor would be an acceptable solution for the slim notebook (NB) applications. [ABSTRACT FROM AUTHOR]

The ever-increasing necessity to miniaturize smooth torque rotary actuators has placed severe constraints on the current slotless permanent-magnet technology. These constraints are mainly the consequence of the relatively large effective magnetic airgap which limits the achievable magnetic loading and, therefore, the torque density of slotless permanent-magnet rotary actuators. Further, the miniaturization has to be achieved at ever-decreasing costs and, therefore, it would be advantageous to implement solid back irons. However this, even at reduced magnetic loading, still results in considerable eddy-current losses. Therefore, a careful selection of the various actuator dimensions and most appropriate soft magnetic laminated or solid material is a prerequisite for applications that require smooth speed and torque characteristic. This paper will identify the influence of various parameters of the slotless permanent-magnet actuator on the eddy-current loss in the back iron using both 2-D and 3-D finite-element analysis. [ABSTRACT FROM AUTHOR]

The paper investigates the influence of stator asymmetry on the cogging torque of permanent magnet brushless motors. It shows that high localized magnetic saturation due to such asymmetry can significantly increase the magnitude of the cogging torque and introduces cogging components which have an order lower than the least common multiple between the stator slot number and the rotor pole number. The findings are confirmed by both finite element analyses and measurements on an 18-slot, 6-pole prototype motor. [ABSTRACT FROM AUTHOR]

In this paper, a phase-locked-loop (PLL)-assisted internal model (IM) adjustable-speed controller for brushless dc (BLDC) motors is proposed. Major contributions include proposing a new adjustable-speed module structure of PLL controllers for BLDC motor drives and integrating an IM control strategy and a novel complete motor current sensing scheme. By employing the proposed PLL-assisted IM control method, the controller can be made more robust and accurate. In addition, due to properly integrating the motor current sensing scheme with the pulsewidth modulation control, the hardware implementation of the BLDC motor drive can be made rather compact and enable further integration into chips to reduce the cost and enhance the current regulation performance. Finally, a prototype of the proposed controller is also constructed and applied to an industrial blower to verify the feasibility of the proposed control. Experimental results show that both accurate steady state and fast transient speed responses can be achieved. Moreover, compared with the conventional induction motor drives for industrial blowers, the proposed PMBLDC drives can achieve much higher efficiency with less volume and weight. [ABSTRACT FROM AUTHOR]

This paper presents a new three-phase 12/8-pole brushless doubly fed doubly salient (BDFDS) machine for application to electric vehicles. It consists of two types of stator windings-polyphase armature winding and dc field winding. The key is to design, model, and analyze the proposed BDFDS machine. The output power equation is derived analytically, and the initial calculation of machine dimensions and parameters are also discussed. When we use finite-element analysis, the field distributions of the BDFDS machine at different loads and field currents are obtained, in which magnetic saturation and armature reaction are considered. Static characteristics of the proposed machine are also obtained. Based on these characteristics, the system mathematical model can be established. Hence, the evaluation of system performance is conducted by computer simulation. A 12/8-pole BDFDS machine is designed and built for experimentation. Experimental results are given to verify the theoretical analysis and simulation. [ABSTRACT FROM AUTHOR]

This paper describes a novel solution for the active locomotion of a miniaturized endoscopic capsule in the gastrointestinal (GI) tract. In particular, the authors present the design, development, and testing of a legged locomotion system embedded in a capsule (with a volume of about 4-5 cm3) and actuated by a brushless minimotor. The actuation mechanism and transmission mechanism are described in detail in order to highlight the compactness of the overall design. This device is provided with four superelastic legs, allowing large stroke advancement in the GI tract, and a CMOS frontal camera, for diagnostic purposes. A dedicated electronic board for controlling the opening angle of the legs and adjusting their speed has been developed. In order to investigate the motion ability of the device, a set of experiments has been carried out. Four different types of superelastic legs have been designed and tested with the objective to identify the best leg configuration for capsule locomotion. Experimental results demonstrate that the device can travel in the digestive tract with a typical speed ranging between 10 and 40 mm/min. [ABSTRACT FROM PUBLISHER]

This paper examines two methods-magnet shifting and optimizing the magnet pole arc-for reducing cogging torque in permanent magnet machines. The methods were applied to existing machine designs and their performance was calculated using finite-element analysis (FEA). Prototypes of the machine designs were constructed and experimental results obtained. It is shown that the FEA predicted the cogging torque to be nearly eliminated using the two methods. However, there was some residual cogging in the prototypes due to manufacturing difficulties. In both methods, the back electromotive force was improved by reducing harmonics while preserving the magnitude. [ABSTRACT FROM AUTHOR]

A general analytical model, formulated in 2-D polar coordinates, is developed to predict the unbalanced magnetic force, which results in permanent-magnet brushless ac and dc machines having a diametrically asymmetric disposition of slots and phase windings. It is shown that the unbalanced magnetic force can be significant in machines having a fractional ratio of slot number to pole number, particularly when the electric loading is high. The developed model is validated by finite-element calculations on 9-slot/8-pole and 3-slot/2-pole machines. In addition, the unbalanced magnetic force has been measured on a prototype 3-slot/2-pole machine and shown to be in excellent agreement with predicted results. [ABSTRACT FROM AUTHOR]

This paper presents a factorization method for the generation and use of several kinds of transformation matrices in specific structures of phase modulation polyphase motors. The method can be applied to an arbitrary phase number. It avoids complex trigonometric manipulations. Several examples illustrate its application to a seven-phase machine. [ABSTRACT FROM AUTHOR]

We evaluate the superposition method for calculating the cogging torque in permanent-magnet brushless machines, the resultant torque being synthesized from cogging torque components associated with a pair of magnets. Although finite-element analyses and measurements show that the resultant cogging torque cannot be synthesized directly from the torque components due to a single magnet, we use the concept of a fictitious single magnet to analytically establish the relationship between the cogging torque and key design parameters. The method is particularly useful in assessing the influence of the slot number and pole number combination. [ABSTRACT FROM AUTHOR]

A simple analytical technique is proposed to synthesize the cogging-torque waveform of a permanent-magnet brushless machine from the cogging torque, which is associated with a single stator slot. An analytical expression is derived, which reveals the relationship between the two. It is then applied to two motors, which have a fractional number of slots per pole. It is shown that the resultant cogging-torque waveform can be synthesized to a high accuracy, as confirmed by both finite-element analysis and measurements. It is also shown that not all the cogging-torque harmonics that exist in the cogging-torque waveform due to a single slot will be present in the resultant cogging torque, and that the most significant components can be identified analytically. [ABSTRACT FROM AUTHOR]

The operation of a brushless permanent-magnet machine requires rotor-position information, which is used to control the frequency and phase angle of the machine's winding currents. Sensorless techniques for estimating rotor position from measurements of voltage and current have been the subject of intensive research. This paper reviews the state of the art in these sensorless techniques, which are broadly classified into three types: motional electromotive force, inductance, and flux linkage. [ABSTRACT FROM AUTHOR]

In this paper, a rotor position estimator for the sensorless permanent magnet synchronous motor (PMSM) is developed. The proposed approach exploits the time-scale separation between the electrical and mechanical time constant of the PMSM to formulate a linear observer. The observer produces accurate rotor angle estimates in steady-state and transient, and is attractive for electric propulsion applications due to its independence from mechanical parameters such as load torque, inertia, and friction. The sensorless strategy is well-suited to the nonsaturating slotless PMSM, but the demonstrated robustness of the observer to modeling uncertainties allows for application to slotted construction as well. Experiments are conducted to confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux- switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also investigated, and optimal design parameters, such as the rotor pole width, the stator tooth width, and the ratio of the inner to outer diameter of the stator, are discussed. [ABSTRACT FROM AUTHOR]

This paper deals with the design of a 1-kW permanent-magnet (PM) brushless motor operating in the speed range of 20-40 k r/min. The design procedure involves a parametrical investigation of the most adequate motor configuration by means of a coupled thermal and electromagnetic analysis. The design procedure takes advantage of an analytical study based on Maxwell's equations and is refined by finite-element analysis. Both slotted and slotless motor configurations have been taken into account, with different PM materials for an overall comparison of the motor performance. [ABSTRACT FROM AUTHOR]

There has recently been considerable interest in using the sensorless permanent magnet synchronous motor (PMSM) for vehicle propulsion systems. While many sensorless PMSM techniques have been presented in the literature, few have discussed in detail the underlying hardware and implementation issues. This work focuses on the implementation and application of a sensorless PMSM strategy that is particularly well suited for vehicle propulsion systems. The selected sensorless PMSM technique is implemented in a real-time motor control system to form a sensorless electric drive prototype. The hardware, strategy and implementation issues associated with the development of the sensorless drive are discussed. Experimental results are included in order to demonstrate the robustness of the implementation and the effectiveness of the sensorless drive under transient operating conditions such as startup and speed reversal. [ABSTRACT FROM AUTHOR]

We develop an analytical model for predicting the eddy-current loss in the rotor magnets of permanent-magnet brushless machines that have a fractional number of slots per pole, when either all the teeth or only alternate teeth are wound, and in which the unwound teeth may be narrower than the wound teeth. The model enables the magnetic field distribution in the air gap and magnet regions to be determined, by neglecting the eddy-current redistribution effect and assuming that the eddy currents are resistance limited. It can account for space-harmonic magnetomotive forces (MMFs) resulting from the winding distribution and time-harmonic MMFs due to nonsinusoidal phase currents, as well as for the effect of curvature and circumferential segmentation of the magnets. We have validated the model by finite-element analysis, and used it to investigate the eddy-current loss in the magnets of three surface-mounted magnet brushless motors that have similar slot and pole numbers, and employ identical rotors but different stators, when they are operated in brushless ac (BLAC) and dc (BLDC) modes. We show that the stator winding configuration, as well as the operational mode, significantly influence the resultant eddy-current loss. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for the magnetic field inside an unconventional ironless brushless (ILBL) dc motor design. We discuss the unique characteristics of the design, which adopts an "inside-out" construction with an internal ironless stator. With the intention of obtaining an analytical solution for the magnetic field, we propose a model based on a magnetic pole concept for representing the magnetic circuit. The magnetic field inside the motor, which has no iron for guiding magnetic flux paths, is obtained by solving Laplace's equation for magnetic scalar potential. We present both analytical and numerical solutions for the magnetic field and compare them with measured results of a 20-pole prototype IL design to show the validity of the model. The IL design is simple, easy to manufacture and, as indicated by the results, has an optimum number of magnets, for which its performance becomes maximum. [ABSTRACT FROM AUTHOR]

Three-phase trapezoidal back-EMF permanent magnet (PM) machines are used in many applications where the reliability and fault tolerance are important requirements. Knowledge of the machine transient processes under various fault conditions is the key issue in evaluating the impact of machine fault on the entire electromechanical system. The machine electrical and mechanical quantities whose transient behaviors are of importance under fault conditions include the voltages and currents of the coils and phases, the electromagnetic torque, and the rotor speed. Experimental test based on true machines for such a purpose is impractical for its high cost and difficulty to make. Computer simulation based on the finite element method has shown its effectiveness in fault study in this paper. Before the finite element model was used to perform simulations under fault conditions, it was validated by test data under normal conditions. Three types of fault conditions-single-phase open circuit fault, phase-to-phase terminal short-circuit, and internal turn-to-turn short-circuit have been studied. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of three-phase permanent-magnet brushless machines in which the slot and pole numbers are similar, with reference to conventional brushless dc machines in which the ratio of the slot number to pole number is usually 3:2. Three different motor designs are considered. Two have equal tooth widths, with one having a coil wound on every tooth and the other only having a coil wound on alternate teeth, while the third machine also has coils wound on alternate teeth but these are wider than the unwound teeth while the width of theft tooth tips is almost equal to the rotor pole pitch in order to maximize the flux linkage and torque. Analytical and finite-element methods are employed to predict the flux-linkage and back-electromotive-force waveforms, and the self- and mutual-inductances, and these are shown to be in good agreement with measured results. It is also shown that the third machine is eminently appropriate for brushless dc operation. [ABSTRACT FROM AUTHOR]

In this paper, nonlinear identification of the excitation system (EXS) in the gas unit #2 of Rajaee power plant in Iran is presented. Two methods of modeling, i.e., grey-box and black-box modeling are used and compared. In the grey-box (classical) approach, first a block-diagram for the EXS is suggested, then a test procedure for identification of its parameters is outlined. The input-output data corresponding to each block of the system is obtained through field tests. In this approach, the only nonlinearities considered in the block diagram are the limits. The other nonlinearities are reflected in the change of parameters in the linear transfer functions at different operating conditions. In the black-box approach, identification of the system is carried out using discrete wavelet transform. A variable structure wavelet was tried to cope with system changes at different operating conditions, but a wavelet with fixed number of scaling functions or wavelet functions proved to be quite adequate. The simulation results and their comparison, show the good accuracy of both derived models. Although the model obtained through the black-box approach shows a better fit when its output is compared with the measured variables, the model obtained through the grey-box approach reflects the physical properties of the system and may be more useful for power engineers. [ABSTRACT FROM AUTHOR]

This paper characterizes electromagnetic excitation forces in interior permanent-magnet (IPM) brushless direct current (BLDC) motors and investigates their effects on noise and vibration. First, the electromagnetic excitations are classified into three sources: 1) so-called cogging torque, for which we propose an efficient technique of computation that takes into account saturation effects as a function of rotor position; 2) ripples of mutual and reluctance torque, for which we develop an equation to characterize the combination of space harmonics of inductances and flux linkages related to permanent magnets and time harmonics of cur- rent; and 3) fluctuation of attractive forces in the radial direction between the stator and rotor, for which we analyze contributions of electric currents as well as permanent magnets by the finite-element method. Then, the paper reports on an experimental investigation of influences of structural dynamic characteristics such as natural frequencies and mode shapes, as well as electromagnetic excitation forces, on noise and vibration in an IPM motor used in washing machines. [ABSTRACT FROM AUTHOR]

Three-phase permanent magnet brushless dc motors are widely used. As a function of the rotor position, the torque produced by these machines has a pulsating component in addition to the de component. This pulsating torque has a fundamental frequency corresponding to six pulses per electrical revolution of the motor. The shape of the torque waveform and, thus, the frequency content of the waveform can be influenced by several factors in the motor design, and construction. This paper addresses the various factors that influence the torque waveshape. It is shown that in addition to the basic induced electromotive force (EMF) waveshape, the magnetic saturation in the stator core, and the accuracy in the skewing are also key factors in determining the torque waveshape. Computer simulation using finite element technique has been conducted to study the torque waveform. Simulation results successfully duplicated the torque waveforms measured in experiments under different excitation currents. [ABSTRACT FROM AUTHOR]