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Abstract The contra‐rotating machine (CRM) has been a preferable selection of the contra‐rotating propulsion system (CRPS) owing to its high efficiency, high compactness, and low noise. However, the conventional CRM with rotating stator has the problem of brush and slip ring, and the conventional brushless CRM has the problem of coordinated control of equal and opposite torque. Aiming at the above problems, this article proposes a transverse‐dislocated magnetic‐field modulated brushless contra‐rotating machine (TDMFM‐BCRM). The proposed TDMFM‐BCRM has some advantages of no rotating winding, no associated brushes and slip rings, and equal and opposite torques at any time, therefore it has good potential for the CRPS. The working principle of the TDMFM‐BCRM including three dimensional magnetic‐field modulated theory, back electromotive force (EMF) generation, and torque relation is studied. Then, the influences of main parameters including magnetic block parameters and PM sizes on torques are investigated. The critical electromagnetic performances of the TDMFM‐BCRM are analysed. A prototype of TDMFM‐BCRM is manufactured and measured to validate the above analysis. Finally, the comparison of the TDMFM‐BCRM and the existing schemes are analysed.

The contra‐rotating machine (CRM) has been a preferable selection of the contra‐rotating propulsion system (CRPS) owing to its high efficiency, high compactness, and low noise. However, the conventional CRM with rotating stator has the problem of brush and slip ring, and the conventional brushless CRM has the problem of coordinated control of equal and opposite torque. Aiming at the above problems, this article proposes a transverse‐dislocated magnetic‐field modulated brushless contra‐rotating machine (TDMFM‐BCRM). The proposed TDMFM‐BCRM has some advantages of no rotating winding, no associated brushes and slip rings, and equal and opposite torques at any time, therefore it has good potential for the CRPS. The working principle of the TDMFM‐BCRM including three dimensional magnetic‐field modulated theory, back electromotive force (EMF) generation, and torque relation is studied. Then, the influences of main parameters including magnetic block parameters and PM sizes on torques are investigated. The critical electromagnetic performances of the TDMFM‐BCRM are analysed. A prototype of TDMFM‐BCRM is manufactured and measured to validate the above analysis. Finally, the comparison of the TDMFM‐BCRM and the existing schemes are analysed. [ABSTRACT FROM AUTHOR]

Permanent Magnet Linear Flux Switching Machines (PMLFSMs) are potential candidates when higher thrust force ( $\boldsymbol {T}_{ \boldsymbol {F}}$ ) and low cost are the primal requirements. However, conventional PMLFSMs shows flux leakages and utilizes high Permanent Magnet (PM) volume ( $\boldsymbol {V}_{ \boldsymbol {PM}}$ ) that increase overall expense. Therefore, this paper proposed novel Segmented PM Consequent Pole Linear Flux Switching Machine (SPMCPLFSM) with flux bridges. In comparison with PMLFSM, the proposed SPMCPLFSM diminish detent force by $\boldsymbol {20.41\%}$ , suppress thrust force ripples by 27.68%, reduces ripple ratio by 1.77 times, improve $\boldsymbol {T}_{ \boldsymbol {F}}$ to 2 times and boost $\boldsymbol {T}_{ \boldsymbol {F}}$ density to 2.64 times utilizing 75% PM volume and reducing PM cost by 24.16%. Moreover, to overcome computational complexity and computation time, analytical model uniting Lumped Parametric Magnetic Equivalent Circuits, vector potential and Maxwell Stress Tensor method are utilized for open circuit flux linkages, magnetic flux density, detent force and thrust force. Finally, analytical model is validated with finite element analysis (FEA) that show good agreement with FEA. Thus, authors are assured to suggest analytical techniques for early design purpose and proposed SPMCPLFSM for roller coaster application.

Electrical machines are widely used in home appliances, the performance of which is mostly related to the quality function of the electrical machines. What has been used so far in home appliances brought with themselves a wide assortment of advantages and disadvantages. With the aim to overcome the drawbacks of the previously implemented electrical motors in washing machines, a new configuration of flux switching permanent magnet motor (FSPM) with the segmented outer rotor (SOR‐FSPM) is proposed benefitting from a direct driven drum. To reduce the cogging torque as well as torque ripple and to improve the total harmonic distortion, cutting the stator in a way to lower overlapping between the rotor and stator pole, inserting notches into the poles of the rotor to modify the air gap between the stator teeth and the rotor segments are proposed. The Taguchi method and sensitivity analysis are further applied to find the best combination set of changes in such a way to smoothen the chart showing reluctance between stator and rotor and fix the zero‐point crossing of the flux linkages in different rotor positions. Finally, the proposed SOR‐FSPM is prototyped, and experimental results along with the finite element method results are discussed and compared in order to verify the design process. [ABSTRACT FROM AUTHOR]

Rotor position sensor signal is a critical signal in a permanent magnet synchronous machine drive system. The alignment between the position sensor zero and the rotor quadrature axis must be accurately quantified for optimal torque generation under field-oriented control. However, the mechanical interfaces used for mounting the sensors are susceptible to failure due to environmental, manufacturing, and operational conditions resulting the position alignment to change from the previously calibrated value. In this article, a theoretical framework is presented that demonstrates the influence of the faulty static offset error in a position sensor of a permanent magnet synchronous machine and accordingly a diagnostic strategy is proposed to detect such failure mode. Both simulation and experimental results are provided to validate the theory and the diagnostic strategy. Theoretical analysis and simulations closely correlate with the experimental results. Furthermore, false positive prevention strategies for the fault diagnostic strategy are also discussed. [ABSTRACT FROM AUTHOR]

Permanent Magnet Flux Switching Machines (PMFSMs) enclose unique features of permanent magnet (PM) synchronous machine, direct current machine, and switch reluctance machine therefore, applicable for high speed brushless AC applications. However, conventional PMFSMs exhibits demerits of high PM volume VPM, high torque ripples Trip, low average torque Tavg, lower torque density Tden, power density Pden and leakage flux. In this paper, a new topology of 12S‐13P and 6S‐13P E‐Core PM Consequent Pole Flux Switching Machines (PMCPFSM) with flux barrier and partitioned PM is proposed that eliminate leakage flux, enhanced flux modulation effects through flux barriers and reduces the PM volume up to 46.53%. Moreover, due to non‐linear behaviour of PM and complex stator structure alternate analytical sub‐domain model is utilized for initial design and Multi‐Variable Geometric Optimization (MVGO) is opted to investigate influence of design parameters on electromagnetic performances such as Tavg, Trip, Tden and Pden. Analysis and comparison with the existing 12S‐10P E‐Core PMFSM, 6S‐10P E‐Core PMFSM, 6S‐10P C‐Core PMFSM and 12S‐14P C‐Core PMCPFSM reveals that proposed 6S‐13P PMCPFSM produced Tavg higher up to 88.8%, suppress Trip maximum up to 14.72% and offer 2.45 times Tden and Pden capabilities, when compared with the aforesaid state of the art.[AQ ID=Q1] [ABSTRACT FROM AUTHOR]

In this study, a new flux‐switching permanent‐magnet (FSPM) motor with two rotors and toroidal coil are introduced. First, the proposed FSPM (PFSPM) motor structure and performance principles are presented. Then, the performance parameters of the PFSPM motor, including flux linkage, back‐electromotive force, air‐gap flux distribution, inductance, eddy current loss, cogging torque and the output electromagnetic torque are compared with a conventional FSPM motor based on finite‐element analysis. Then, the effect of the angle between the two‐rotor poles on the performance parameters of the PFSPM motor is indicated. Finally, the PFSPM motor model is manufactured and the results of the finite‐element test are compared with the results of the experimental test and the accuracy of the finite‐element model is confirmed. [ABSTRACT FROM AUTHOR]

In recent years, consequent‐pole permanent magnet (CPM) machines draw much attention due to their high utilisation ratio of permanent magnet (PM) material. However, they have some disadvantages, such as the even‐order harmonics of airgap flux density, which may cause asymmetric phase back‐EMF and the increase of torque ripple. In this study, a novel hybrid‐pole PM (HPM) machine is proposed, in which the rotor combines consequent‐pole and spoke‐type PM rotors. The working principle of the proposed HPM machine is analysed based on the equivalent magnetic circuit, and validated by the finite‐element method. Then, the electromagnetic performance of the HPM machine is compared with those of the existing CPM and spoke‐type PM machines. It is shown that the HPM machine obtains similar average torque, PM utilisation ratio, torque ripple and efficiency to the spoke‐type PM machine, whilst it has a higher PM utilisation ratio and much lower torque ripple than the conventional CPM machines. Finally, these analyses are validated by the tested results of a 9‐slot/6‐pole HPM machine. [ABSTRACT FROM AUTHOR]

Flux‐reversal permanent magnet (PM) machines can be considered as stator‐surface‐mounted PM (SSPM) machines, where normally a pair of magnets with reversal magnetization polarities is mounted on the surface of each stator tooth. Hence, the SSPM machines and the conventional rotor surface‐mounted PM (RSPM) machines are rather similar since both machines house the PMs in the air‐gap, and the only difference is the location of magnets in the stator side and rotor side, respectively. In this study, a comparative study between SSPM and RSPM machines is conducted to investigate the difference including topology, operation principle and performance. First of all, the topology of both machines is compared. Then, the operation principle in both machines is analysed based on the air‐gap field modulation theory. Correspondingly, the characteristics of flux density harmonics either due to PMs or armature reaction are obtained. Therefore, the harmonics that make contribution to back‐electromotive force and rated torque are quantified. Besides, other electromagnetic performances, e.g. overload capability, flux weakening ability and loss distribution are also evaluated. Finally, a 12/14 prototyped SSPM machine is manufactured and tested to verify analytical and finite element method‐based prediction. [ABSTRACT FROM AUTHOR]

This study presents a comparative study of different modular brushless wound rotor synchronous machines (MB-WRSM) using non-overlapping fractional slot double-layer concentrated windings. The goal of the study is to highlight the structure which offers the best fault-tolerance capability and the highest output performance. The fundamental winding factor is calculated by using the method based on voltage phasors as a significant criterion to select the preferred numbers of phases, stator slots, and poles. With the limited number of poles for a small machine (3.67 kW/7000 rpm), 15 different machines for different phase/slot/pole combinations are analysed using two- dimensional (2D) finite element method and compared according to three criteria: torque density, torque ripple, and machine efficiency. The seven-phase/seven-slot/six-pole machine is chosen with the best compromise of high torque density, small torque ripple (3.89%), and high nominal efficiency (95%). This machine is then compared with a reference design surface-mounted permanent magnet synchronous machine (SM-PMSM). The simulation results are discussed and demonstrate that the MB-WRSM presents interesting performance features, such as extended field weakening range, with overall performance closely matching that of an equivalent SM-PMSM.

In this study, a novel partitioned stator hybrid excited machine is proposed, in which the excitation sources including both permanent magnets (PMs) and field windings are allocated on the secondary stator that is separated from the original stator having armature windings. As a result, the available space is boosted to improve the torque density and flux regulation capability. Meanwhile, the rotor is simple without coil or PM. The PMs on the stator is placed on the slot openings between the two neighbour tooth tips, with which the uncontrolled voltage of the proposed machine is limited and it is favoured for safety-critical applications. The machine topology and operating principle are introduced in detail, and the basic electromagnetic performance is evaluated based on finite element method to validate the analysis.

This paper focuses on the comparative analysis of modular spoke-type permanent magnet machines with two magnetization modes, which are referred to as M-I and M-II types. The analytical models of the proposed machines are built based on the simple magneto-motive-force-permeance method. With the help of finite element analysis and the analytical models, magnetic fields in machines with different magnetization modes are compared. Then, taking as a base an existing commercial in-wheel machine used in an electric motorcycle, two proposed machines with different magnetization modes are designed as in-wheel traction machines and compared with respect to electromagnetic torque, flux-weakening performance, over-load capability, etc. The machines are prototyped and experimentally tested to verify the prediction that the M-II machines exhibit a higher torque output whereas the M-I machines have a wider speed range. [ABSTRACT FROM AUTHOR]

This study presents a comparative study of different modular brushless wound rotor synchronous machines (MB-WRSM) using non-overlapping fractional slot double-layer concentrated windings. The goal of the study is to highlight the structure which offers the best fault-tolerance capability and the highest output performance. The fundamental winding factor is calculated by using the method based on voltage phasors as a significant criterion to select the preferred numbers of phases, stator slots, and poles. With the limited number of poles for a small machine (3.67 kW/7000 rpm), 15 different machines for different phase/slot/pole combinations are analysed using two- dimensional (2D) finite element method and compared according to three criteria: torque density, torque ripple, and machine efficiency. The seven-phase/seven-slot/six-pole machine is chosen with the best compromise of high torque density, small torque ripple (3.89%), and high nominal efficiency (95%). This machine is then compared with a reference design surface-mounted permanent magnet synchronous machine (SM-PMSM). The simulation results are discussed and demonstrate that the MB-WRSM presents interesting performance features, such as extended field weakening range, with overall performance closely matching that of an equivalent SM-PMSM. [ABSTRACT FROM AUTHOR]

In this study, a novel partitioned stator hybrid excited machine is proposed, in which the excitation sources including both permanent magnets (PMs) and field windings are allocated on the secondary stator that is separated from the original stator having armature windings. As a result, the available space is boosted to improve the torque density and flux regulation capability. Meanwhile, the rotor is simple without coil or PM. The PMs on the stator is placed on the slot openings between the two neighbour tooth tips, with which the uncontrolled voltage of the proposed machine is limited and it is favoured for safety-critical applications. The machine topology and operating principle are introduced in detail, and the basic electromagnetic performance is evaluated based on finite element method to validate the analysis. [ABSTRACT FROM AUTHOR]

Due to the doubly salient structure, high magnetic flux density in the air gap and low pole number, cogging torque of 6/4 pole flux‐switching permanent magnet (FSPM) machine is seriously high. In some cases, it may cause this machine hard to start up and serious torque ripple. So, reducing the cogging torque of 6/4 pole FSPM machine to a certain low extent is important to keep it work properly. To reduce cogging torque, a chamfering and flange rotor pole shape is proposed to reduce the cogging torque of 6/4 pole FSPM machine without skewing teeth. The key dimensions of the proposed rotor pole shape have been optimised by analytical methods and simulation based on finite‐element analysis. The effectiveness of the proposed method has been verified by experimental results. The effect of the proposed rotor pole shape method on back‐electromagnetic force and average electromagnetic torque has also been investigated. [ABSTRACT FROM AUTHOR]

The split ratio of rotor outer diameter to stator outer diameter is one of the most important design parameters due to its significant impact on machine torque density and efficiency. It has been optimised analytically in existing papers with due account given only for the thermal limitations. Here, the optimised split ratio for high‐speed permanent magnet machines (HSPMM) with consideration of the mechanical constraints is investigated analytically. In addition, the influences of flux density ratio, maximum operating speed and sleeve material on the optimised split ratio are discussed in detail. The analytical results are verified by finite‐element analyses. It is demonstrated that the optimised split ratio as well as the achievable torque of HSPMM is significantly reduced when the mechanical constraints are taken into consideration. The experimental results on a 6/slot‐4pole HSPMM confirm the validity of previous analyses. [ABSTRACT FROM AUTHOR]

Spring-assisted oscillating actuators allow the overall energy consumption of a system to be reduced. The concept relies on springs that store and release energy into the system when required. Conventional mechanical springs impose some limitations on a system, mainly in terms of compactness, friction, material fatigue, and failure. Magnetic springs have the potential to overcome these issues, especially for long-stroke high-frequency operation. We report here on the investigation of a magnetic spring into a linear oscillatory motor without any changes to the permanent magnet arrangement on the mover. We focus on a compact and highly integrated design with maximum energy storage capacity. Our analytic equations define the relevant geometrical parameters that exploit the potential of the system best and are on a par with a finite-element-based optimization. We also investigated the expected losses and demonstrate the importance of correct choice of materials to efficient operation. We validated our results using measurements from a prototype linear oscillatory motor featuring the proposed integrated magnetic spring. [ABSTRACT FROM PUBLISHER]

The torque ripple is a main source of the noise and vibration which has a considerable effect on the performance of the machine. A design technique, tooth notching, which was extensively used in permanent magnet machines, has been innovatively applied to a wound‐rotor brushless doubly‐fed machine (BDFM) to reduce the torque ripple. First of all, the winding structure, the winding space harmonics and magnetic fields of the stator and the rotor were studied. Then, general analytical expressions of the electromagnetic torque (EMT) for the BDFM were deduced. Finally, prediction of the results was verified by several models which were calculated by the finite‐element analysis method, meanwhile, the influences of different tooth‐notching structures and the notch depth on the EMT were investigated. It is shown that the torque ripple can be reduced by the suggested design with small increment of the magnetic field saturation and the currents of the control winding and the rotor winding. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous machines (PMSMs) are popular due to their high efficiency and favorable dynamic properties. In practice, these machines often have a back-electromotive force (EMF) waveform, which deviates from a theoretically ideal sinusoid or trapezoid. In the past, current waveform shaping techniques were developed for these machines to calculate nonconventional current waveforms to reduce the torque ripple. However, in the light of global warming, energy efficiency has become more important than torque ripple in many applications. Therefore, current waveform shaping techniques can be used to focus on maximum efficiency. In this paper, a technique is presented that maximizes the efficiency of both the PMSM and the drive simultaneously. A time domain approach is used instead of the classical frequency domain approach, which allows us to include many machine aspects that had to be neglected previously, i.e., armature reaction, reluctance, zero-sequence components, and iron losses. [ABSTRACT FROM AUTHOR]

In this paper a unified approach for several synchronous machine current waveform optimization problems is presented. It is shown that the problems of ohmic losses minimization with and without the constraint of constant torque waveform admit solutions which can be described by the same equation in different vector spaces. The constraint of open-circuited neutral node is also investigated and it is shown that in the unified framework only a minor modification of the solution is needed irrespectively of the presence of the constant torque constraint. The ohmic losses and the torque ripple of the various waveforms are compared in the case of a permanent magnet synchronous generator used in a variable speed wind turbine. The optimal waveforms are also compared to non-optimal waveforms obtained using a diode rectifier. [ABSTRACT FROM AUTHOR]

In this paper, novel design of a flux-switching permanent magnet machine (FSPMM) with a yokeless stator and two rotors has been proposed. The proposed machine has been found to perform on par with a 6-slot/13-pole C-core conventional FSPMM in terms of torque output. Additionally, the proposed machine has no significant unbalanced magnetic forces, which is a major challenge in conventional FSPMM with odd number of rotor poles. Step-by-step parametric optimization has been performed using finite-element models of the machine in order to achieve the highest torque with the given magnetic and electrical constraints. [ABSTRACT FROM PUBLISHER]

The price fluctuations of rare-earth (RE) metals and the uncertainty in their availability have generated an increased interest in ferrite magnet machines. The influence of temperature on the $B$ – $H$ characteristics of the ferrite magnet differs considerably from that of the RE magnet, and hence, requires a different approach when deciding their operating point. In this paper, the laboratory measured $B$ – $H$ curves of a ferrite magnet are used for estimating the possibility of demagnetization in a segmented axial torus (SAT) permanent magnet brushless dc (PMBLDC) motor. The $B$ – $H$ characteristics for different temperatures have been used to study the performance variation of the ferrite magnet SAT PMBLDC motor with temperature. A detailed analysis is carried out to ensure that the designed ferrite magnet motor is capable of delivering the specified torque throughout the operating speed, without any irreversible demagnetization of magnets. It has been shown that the ferrite magnet PMBLDC motor operation is influenced by the magnet temperature, and the maximum motor speed for a given load torque decreases as the magnet temperature drops. [ABSTRACT FROM PUBLISHER]

This paper investigates the appropriate permanent magnet (PM) arrangement of novel flux-modulating synchronous machines (FMSMs) in which PMs are embedded in the stator back iron. Using finite element analysis (FEA), three types of FMSMs with different PM arrangements are designed, and their performance characteristics are compared. As a result of the investigation, it was found that the FMSM with a V-shaped PM arrangement has a higher torque capability than do other FMSMs. The accuracy of the FEA simulations was confirmed through experiments on a prototype machine. [ABSTRACT FROM AUTHOR]

By predicting future phase-current commutation instants of brushless dc (BLDC) machines, self-sensing control is achieved. Detection of the back electromotive force (EMF) zero-crossing moments is one of the methods used to predict the phase-current commutation instants. Most of the techniques based on back-EMF zero-crossing detection have the inherit disadvantage of an indirect prediction of commutation instants. This is the result of the commutation instant occurring at the 30^\circ electrical position after zero-crossing of the induced back-EMF in the unexcited phase. Often, the time difference between the zero-crossing of the back-EMF and the current commutation instant is assumed constant. This assumption can be valid for steady-state operation; however, a different time span should be taken into account during transient operation of the BLDC machine. To overcome this problem, an enhancement is proposed here, which improves the performance while keeping the simplicity of the back-EMF zero-crossing detection method. [ABSTRACT FROM PUBLISHER]

The advent of electrically powered actuation system (EPAS) promises improved reliability, controllability and efficiency as well as reduced maintenance in high‐power applications that have historically been serviced by hydraulic systems. Dual three‐phase permanent magnet brushless machine (DTPPMBLM) is the key subsystem in EPAS. The strong mutual coupling and nonlinearity of DTPPMBLM as well as its drive make it very difficult to obtain a comprehensive mathematical model. This paper proposes a new method to modelling the DTPPMBLM and drive based on the matrix and tensor approach (MTA). The magnetic equivalent circuit (MEC) is used to model the magnetic field of DTPPMBLM. The switching mode of the converter is analysed and modelled theoretically, based on which the DTPPMBLM and drive is coupled with MTA. Then, the MTA and two dimensional finite element analysis (2D‐FEA) model are used to simulate the various steady‐state and transient performances of the 2 × 1.8 kW DTPPMBLM. Comparison of the simulation results verifies the feasibility of MTA. The results suggest that MTA may be an efficient approach for the DTPPMBLM and drive. The experimental results are reported to show that the modelling scheme has good estimation performance under different operation conditions of the DTPPMBLM. [ABSTRACT FROM AUTHOR]

Two constant current models of Permanent Magnet Brushless Direct Current Motor (PM BLDC) are presented in the paper. In the first part of the paper principle of operation, basic properties and mathematical equations describing PM BLDC models are given. Then, two different constant current models of PM BLDC motor are considered: In the first model, PM BLDC motor is approximated with dc motor; in the second model, modified constant current model is applied with additional block, which is used to take into account the impact of inductance on torque-speed characteristics. In order to verify these models, torque-speed characteristics have been determined and compared for different motor supply voltages. After running a series of simulation and laboratory tests, we have found that this modified model (which makes allowance for the influence of inductance on torque-speed characteristics) ensures obtaining torque-speed characteristics identical to those of the real motor. Therefore, this model may be recommended for those simulation tests which do not consider effects occurring inside the electronic commutator-motor circuit. However, approximation of PM BLDC motor with dc motor is not recommended in computer tests. [ABSTRACT FROM AUTHOR]

Since a Halbach array exhibits a number of attractive features, it has been increasingly applied to different market sectors, including aerospace, industrial, domestic, renewable and healthcare and so on. The need of fast global optimisation, cost‐effective design and physical understanding of the relationship between parameters and performance requires a powerful analytical model. Hence, this study develops a general analytical model which is capable of predicting the electromagnetic performance of slotted/slotless permanent magnet (PM) brushless machines with both even‐ and odd‐segment Halbach array, having different magnet remanence, magnetisation angle and arc for each single magnet segment. The emphasis has been on the magnetisation which is the key in analytical modelling of PM machines having a segmented Halbach array and its investigation. The validity of proposed analytical model is extensively examined by finite‐element analyses, together with its applications for global optimisation and comparative study. [ABSTRACT FROM AUTHOR]

This study presents a novel direct torque control (DTC) of permanent magnet (PM) brushless AC (BLAC) drive under single‐phase open‐circuit fault (SOF) accounting for the influences of inverter voltage drop (IVD), together with novel current model‐based and voltage model‐based stator flux estimation schemes for post‐fault operation. It is demonstrated that for accurately elaborating the modified mathematical model, the voltage induced in the stator open phase winding and its relevant flux linkage should be taken into account although they do not contribute to torque production in the post‐fault operating mode. It is also proven that reconfiguration of the conventional six‐switch three‐phase inverter for the purpose of fault‐tolerant control results in a significant magnitude imbalance between the α‐ and β‐components of IVD. Thus, the influences of this unbalanced issue on performance of the two proposed stator flux estimation methods are investigated in details and a compensation method for the voltage model‐based stator flux estimator is proposed and experimentally verified. It is shown that fault‐tolerant control with high performance operation can be maintained for a DTC‐based PM BLAC drive under SOF using the proposed modified mathematical model. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

In this paper, a method for predicting the electromagnetic vibration of permanent magnet (PM) brushless motors is presented. It calculates the electromagnetic force on individual stator teeth by the Maxwell stress method, based on two-dimensional finite-element analysis of the electromagnetic field. The resulting radial force contour is then used in an analytical shell model to predict the stator vibration. The method is validated experimentally, and is used to investigate the vibration in various PM brushless motors with different fractional slotlpole number combinations. The relationship between the slot/pole number combination and the dominant vibration frequency and mode order is also established. [ABSTRACT FROM AUTHOR]