Search

This aim of this paper is to assess the efficacy of mesh-based generated reluctance network (MGRN) modeling for the performance evaluation of a permanent magnet linear machine under load conditions. In the previous publications related to the use of this modeling technique, only approach implementation under an open-circuit performance has been assessed. The MGRN approach is based on the discretization of the geometry using elementary reluctance blocks (reluctance elements). This modeling technique has been implemented in a software tool that allows the automated processing of an arbitrary geometry providing a gain in model development durations. Validation of the MGRN model has been realized by comparison with a finite element analysis (FEA). Comparisons showed that both local and global quantities evaluated by MGRN and FEA are in excellent agreement. [ABSTRACT FROM AUTHOR]

This paper deals with the fault tolerance of a five-phase flux switching machine. Short-circuit currents calculation considering inductances variation is developed. Machine behavior (torque quality, copper losses, and homopolar current) under a single short-circuit phase fault, two consecutive and nonconsecutive phases short-circuited, is simulated with a two-dimensional finite elements (2-D FE) model and validated experimentally. Then, a new method is developed to improve its performances in faulty mode, by reconfiguring reference currents. In fact, an accurate torque model is established and then used in a genetic algorithm to optimize reference currents in faulty mode. In this approach of reference currents computation, the used algorithm has multiobjectives and multiconstraints, thereby allowing choosing the appropriate fault-tolerant current solution according to our application. The torque model is considered to be more accurate and closer to the 2-D FE results in both healthy and faulty modes. Then, a comparison of machine performances in healthy, degraded, and reconfigured modes is presented. Experimental results corroborate the analysis. [ABSTRACT FROM AUTHOR]

This paper presents two short-circuit fault models of a hybrid excitation flux switching permanent magnet machine, i.e., excitation phase short-circuit and interturn short-circuit in excitation windings. Two-dimensional finite element (FE) method is used to calculate the major parameters, such as armature and excitation inductances, which are not only functions of rotor position, but also of armature and excitation currents. Moreover, in case of short-circuits, the variations of armature and excitation currents are often significant. This in turn leads to an important change in winding inductances. Therefore, in order to precisely predict machine performance under short-circuit conditions, the use of inductances versus rotor position and RMS currents is essential. With the obtained FE results, two MATLAB/Simulink-based models are established. Then, the previously mentioned short-circuits have been studied and their influences on electromagnetic performances, such as armature and excitation currents, speed and torque, armature and excitation copper losses, stator and rotor core iron losses, as well as permanent magnet (PM) eddy current losses are analyzed. Experiments have been carried out to validate the simulations. [ABSTRACT FROM PUBLISHER]

The aviation industry is undergoing electrification due to the increased global focus on reducing emissions in air traffic. Regarding the volatility of raw material prices, one main objective is the increase in the specific power of the motor. This matches the ambitious targets of the CoE project (Center of Excellence) in Finland on high-speed electric motors. The targeted specific power is 20 kW/kg. In this work, motors are designed and optimized for a fully electric regional aircraft. motors with different slot/pole configurations and rotational speed values are studied to determine the advantage of increasing speed in terms of weight reduction. As increasing speed requires the use of a gearbox, the overall weight of the motor and the gearbox is evaluated in post-processing, which allows for determining the impact of high speed on the overall weight. An optimization tool coupled with an electromagnetic and mechanical analysis is used to optimize 1 MW surface mounted permanent magnet synchronous motors (S-PMSMs) for given specifications of regional electric aircraft. Optimization results indicate that there is considerable gain in terms of overall weight only when increasing the speed to the range of 10,000–15,000 rpm. [ABSTRACT FROM AUTHOR]

This paper presents a review of the most common power converters and torque ripple minimisation approaches for switched reluctance motors (SRMs). Unlike conventional three-phase AC motors, namely squirrel cage induction motors and permanent magnet synchronous motors, which require a typical three-phase inverter for operation, the switched reluctance motor requires a different topology power converter for reliable and efficient operation. In addition, due to the non-linear, discrete nature of SRM torque production, torque ripple is severely pronounced, which is undesirable in servo applications like electric vehicles. Hence, deploying a proper torque control function for smooth and quiet motor operation is crucial. This paper sheds light over the most popular SRM power converters as well as torque ripple minimisation methods, and it suggests an optimal SRM drive topology for EV applications. [ABSTRACT FROM AUTHOR]

Interior permanent magnet motors are widely used in applications requiring high power density and high efficiency due to their high torque-generating capabilities. Recently, given the price fluctuations and unstable supply of rare earth permanent magnets, alternative configurations with reduced use of permanent magnets are being sought. Among the various candidates related to this, the consequent-pole type rotor structure can halve the number of permanent magnets used compared with conventional structures. However, in a no-load analysis, the waveform of the back electromotive force becomes asymmetric, generating a harmonic component. As a result, there is a disadvantage that the torque ripple increases. To overcome these shortcomings, we propose a novel rotor structure that applies a consequent-pole structure to an embedded permanent-magnet motor structure, wherein a number of permanent magnets are arranged in a flared structure to constitute a single polarity. In the proposed flared-structured magnet arrangement, it is possible to adjust the angle of the permanent magnet and the polar angle to mitigate the asymmetry of the back-EMF waveform. The proposed structure was optimized with a genetic algorithm and a prototype of the optimal model was constructed and experimentally evaluated to verify its validity. Finally, the performance improvement and validity of the proposed structure were verified by comparing the analysis results of the optimal model with the experimental results. [ABSTRACT FROM AUTHOR]

The contactless transmission between the conductor rotor and the permanent magnet (PM) rotor of an adjustable permanent magnet coupler (APMC) provides the device with significant tolerance for alignment errors, making the performance estimation complicated and inaccurate. The first proposal of an edge coefficient in this paper helps to describe the edge effect with better accuracy. Accurate equivalent magnetic circuit (EMC) models of the APMC are established for each region. Models of magnetic flux, magnetic resistance, and eddy current density are established by defining the equivalent dimensional parameters of the eddy current circuit. Furthermore, the concept of magnetic inductance is proposed for the first time, parameterizing eddy currents that are difficult to describe with physical models and achieving the modeling of the dynamic eddy current circuit. The magnetic resistance is subdivided into two parts corresponding to the output and slip according to the power relationship. Furthermore, eddy current loss and dynamic torque models are further derived. The method proposed in this paper enables the APMC to be modeled and calculated in a completely new way. The correctness and accuracy of the model have been fully demonstrated using finite element simulation and an experimental prototype. In addition, the limitations of the proposed method and the reasons are fully discussed and investigated. [ABSTRACT FROM AUTHOR]

In this study, a generalized torque estimation method is proposed for synchronous motors, including surface permanent magnet synchronous motors (SPMSMs), synchronous reluctance motors (SynRMs), and interior permanent magnet synchronous motors (IPMSMs) for building the analytical motor model. The average motor torque is estimated using the Lorentz force by the generated flux density in the air gap to determine the relationships among torque, flux density, and injected current. In the proposed method, the generated flux density is derived step by step by considering the effects of magnetic flux saturation, the stator slot, the rotor barrier, and permanent magnets (PMs) to ensure that the generated average torque complies with the operating condition of the motor. To verify the proposed method, the output torque of finite element analysis (FEA), Maxwell 2D, is compared to the proposed method in a SPMSM. Moreover, a phasor diagram is plotted to determine the mechanism through which torque is generated in SynRMs and IPMSMs. A SynRM and an IPMSM with ferrites PMs are analyzed using the proposed method, FEA, and the experimental results of this study indicate the effectiveness. [ABSTRACT FROM AUTHOR]

In this contribution, a tool developed for the study of the efficiency maps of shifted inductances axes permanent magnet synchronous motors (SIAPMSMs) is presented and made available to the readers. The research builds upon a shared foundation that has already been established in previous works focused on the power capability of synchronous machines. This contribution is an extension of previous works dedicated to the power capabilities of shifted inductances axes synchronous motors where the losses were not considered. In this new contribution, the SIAPMSM models, which include the electromagnetic losses (joule and iron losses), are discussed. The mechanical losses are not included. The classical permanent magnet synchronous machines can be considered a particular case of a SIAPMSM. They will be used to validate the developed tools. The validation study is conducted by comparing the power capabilities and the efficiency maps of SIAPMSMs and classical PMSMs obtained by the newly developed modeling tool and a previously developed modeling tool. [ABSTRACT FROM AUTHOR]

The use of electric motors, and particularly, Permanent Magnet Synchronous Motors, is increasing in recent years, and their vibration response is one of the most crucial aspects regarding their behaviour. Thus, the reduction in vibrations is one of the key objectives when optimizing electric motors. In an initial design state, the influence of the main design parameters on the behaviour of the machines is not always clear. For that reason, this work presents a global sensitivity analysis procedure that allows identifying the most influential design parameters and determining guidelines to optimize the design of Permanent Magnet Synchronous Motors. First, the analytical calculations employed to estimate the electromagnetic torque and the vibration response of the machine are described. Then, the sensitivity analysis procedure, based on the Monte Carlo method, is presented, and the conditions to apply the method successfully and accurately are analysed. Finally, the sensitivity analysis is performed for a particular electric motor design, and some general design guidelines are deduced, which can be extrapolated to similar machines. [ABSTRACT FROM AUTHOR]

The PMSM (Permanent Magnet Synchronous Motor) is being studied a lot in traction motors for high efficiency and high performance. Usually, magnets containing rare earth elements are used. However, since rare earth elements are not suitable for future industries due to their limited reserves, many studies on magnets excluding rare earth elements are being conducted. Magnets excluding rare earth elements have a low coercive force and are vulnerable to irreversible demagnetization, so their design must be robust. Additionally, the design used for reducing the cogging torque, which is a major variable of traction motors, is also important. Therefore, in this study, a design process for reducing irreversible demagnetization and cogging torque is proposed. There are three methods for this process. The first one is the application of the tapering structure, and the second one is the tapering skew structure. The third one is the application of an asymmetric air hole. As a result of these methods, the target irreversible demagnetization ratio was satisfied and the cogging torque was reduced. This was proven through FEA (Finite Element Analysis) and verified by comparing and analyzing the experimental results and simulation results of actual manufacturing. [ABSTRACT FROM AUTHOR]

In this paper, a new hybrid excitation drive motor (HEDM) was proposed to solve the problem of an uncontrollable magnetic field of a permanent magnet motor. The rotor part of the motor was composed of a combined magnetic pole permanent magnet rotor and a brushless electric claw rotor, in which the combined magnetic pole permanent magnet rotor has a parallel magnetic circuit structure. According to the characteristics of the parallel rotor structure, the equivalent magnetic circuit model was established, and the no-load leakage flux coefficient of the claw pole rotor was calculated. The Taguchi method was used for objective optimization of the permanent magnet rotor structure. The distortion rate of no-load back electromotive force (EMF) was taken as the first optimization goal; the cogging torque and the average torque were taken as the second optimization goal; and the torque fluctuation coefficient was a constraint condition. The optimal parameter matching under the mixed horizontal matrix was obtained. The parameters of the claw pole were optimized by using the method of uniform variables, and the dimension parameters of the motor were obtained. Finite element analysis and prototype tests were carried out for the optimized motor structure. The rationality and feasibility of the new HEDM as a vehicle motor were verified, which provided a possibility for the application of the new energy vehicle drive motor field. [ABSTRACT FROM AUTHOR]

Finally, in contribution [[8]], the authors presented an interesting overview of the recent advances in multi-phase permanent magnet synchronous machines (PMSMs) and drive control techniques, with a focus on dual-three-phase PMSMs. The authors analyzed different single-phase tubular linear permanent magnet machines, and compared different original structures with partitioned stators, and a passive mover was sandwiched between two stators. The authors highlighted that the proposed machines possess the merits of lighter mover mass and much lower magnet eddy current loss compared with the conventional single-phase short-stroke surface-mounted PM tubular machines (SPSS-SPMTM). [Extracted from the article]

This paper introduces a novel technique to maintain the operation of the five-phase permanent magnet synchronous motor post the failure in two phases of the motor and post the failure of the speed sensor occurs simultaneously. To achieve that, firstly, a fault-tolerant control (FTC) technique is implemented. The FTC is based on implementing two new space vector pulse width modulation (SVPWM) besides using field-oriented control to minimize the torque ripple and to maintain the performance post the two-phase failure. Secondly, algorithms are proposed to obtain the saliency position post the failure of the two phases. The technique is based on measuring the transient response of the motor's remaining healthy currents due to the inverter switching actions. These switching actions are related to the PWM signals obtained from the new SVPWM techniques implemented post the two-phase failure. The whole control technique post the failures is very simple to implement. Simulation results are provided to verify the reliability of the proposed control technique to maintain the performance of the five-phase motor drive post the failure in the two phases and the failure of the speed sensor occurred simultaneously without compromising the preperformance (maintain the torque ripple less than 3.6% and 3.4% post the failure). Moreover, the results have demonstrated the ability for the whole system to work effectively over a wide speed range and load conditions post the failure. [ABSTRACT FROM AUTHOR]

Eddy current losses in magnets are a major consideration in the rotor design of permanent magnet synchronous motors (PMSMs). Stator design choices and the use of modern inverters with high switching frequency introduce harmonics that can contribute to significant losses in the magnets, causing the rotor to heat up. In typical PMSMs, the lack of rotor cooling can cause the magnet's performance to degrade at high temperatures and eventually demagnetize. This review examines a large number of studies analyzing magnet eddy current losses using analytical methods and finite-element analysis. In some of these studies, magnet segmentation is carried out to reduce the losses; however, their loss-reduction effects depend highly on the type of PMSM and the mix of stator harmonics. Magnet segmentation without considering these effects can, in fact, increase the magnet losses, in addition to the extra manufacturing efforts. Multiple design analysis show the influence of rotor–stator geometric features on magnet losses. Although measuring magnet eddy current losses for these motor designs is a tedious task, authors have proposed calorimetric and loss segregation-based techniques to provide validation. This paper addresses magnet loss modeling techniques, PM material considerations, magnet segmentation effectiveness, motor and stator design effects, and experimental validation to inform motor designers about the costs and benefits of rotor designs that minimize rotor losses. [ABSTRACT FROM AUTHOR]

The present article proposes a nonlinear optimal control approach for permanent magnet AC machines with non-sinusoidal back electromotive force being fed by three-phase inverters. Such AC machines are also known as permanent magnet brushless DC motors (PMBLDC) and find use in several traction and actuation systems. First, by applying an extended park transformation, the dynamic model of the electric motor is expressed in the dq rotating reference frame. Next, the nonlinear dynamic model of the electric motor undergoes approximate linearization around a temporary operating point which is recomputed at each iteration of the control method. This temporary operating point is defined by the present value of the electric motor's state vector and by the last sampled value of the machine's control inputs vector. The linearization relies on Taylor series expansion and on the calculation of the system's Jacobian matrices. For the approximately linearized model of the electric motor, an H-infinity feedback controller is designed. This controller stands for the solution of the nonlinear optimal control problem for the considered type of electric motor under model uncertainty and external perturbations. For the computation of the controller's feedback gains, an algebraic Riccati equation is iteratively solved at each time-step of the control scheme. The global asymptotic stability properties of the control scheme are proven through Lyapunov analysis. Finally, the nonlinear optimal control method is compared against flatness-based control and sliding-mode control. [ABSTRACT FROM AUTHOR]

Vernier permanent-magnet machines have been attracted more and more attention because of their high torque density. In this paper, the sensorless control strategy of the novel axially magnetized Vernier permanent-magnet (AMVPM) machine is presented. First, the inductance non-linearity is investigated under different load conditions. Second, the mathematical model is established in cooperation with the finite element method. After that, the back electromotive force based sensorless control strategy is developed according to the state equation of the motor. In the sensorless drive, the model reference adaptive system (MRAS) technique incorporated with the inductance non-linearity is used for the speed estimation. The modified control strategy not only increases the stability but also improves the dynamic response of the system. Finally, the simulation results show that the modified MRAS is of high estimation precision, and the AMVPM machine can be well controlled, and the experimental results validated the theoretical design process. [ABSTRACT FROM AUTHOR]

Permanent Magnet Synchronous Motors (PMSMs) are increasingly being used and are required to satisfy noise and vibration specifications. Thus, it is necessary to develop design guidelines for electric motors that consider vibration response as a key output of the design. This work shows the influence of the main design parameters regarding PMSMs: the number of slots and the number of poles. First, the influence of the number of slots in the natural frequencies is analysed by Finite Element calculations, which are experimentally verified. Then, the analytical calculation of the vibration response is explained. This is applied for several combinations of the number of slots and the number of poles, and the results are compared. Considering the analytical development, a procedure to choose the most adequate combination of the number of slots and poles is proposed. The analytical predictions are validated according to experimental measurements in two machines. [ABSTRACT FROM AUTHOR]

The load capacity of the permanent magnet synchronous motor is limited by the rotor temperature, and the excessive temperature of the rotor will bring potential thermal safety problems of the system. Therefore, the accurate prediction of the rotor temperature of the permanent magnet synchronous motor for the electric vehicle is crucial to improve the motor performance and system operation safety. This paper studied the heating mechanism and the energy flow path of the motor and built the heat energy conversion model of the stator and rotor. The real-time algorithm to predict the rotor temperature was constructed based on the dissipative energy conservation of the stator of the motor rotor temperature. And the prediction method of the initial rotor temperature is fitted using the experimental results when the system is powered on. Finally, the test platform was set up to validate the rotor temperature accuracy. The results show that the motor rotor temperature estimation error under the dynamic operating condition is within ±5. The research provides a solution to improve the performance and thermal safety of the permanent magnet synchronous motor for electric vehicles. [ABSTRACT FROM AUTHOR]

Some key features to be satisfied by electric motors catering a wide range of applications are high specific power, lower manufacturing cost, rugged construction, and fault‐tolerant operation. Switched reluctance motor is one such motor technology satisfying all the above requirements and is an emerging competitor to the induction and permanent magnet motors in domestic, industrial and electric vehicle applications. The present‐day research on this motor is moving towards improving efficiency at lower speeds, power density, and the torque density. Certain challenges in achieving the same are (a) minimising the losses, (b) mitigation of torque ripple, noise, and vibration, and (c) material advancements. A review based on the estimation and mitigation techniques of each of these over the past three to four decades has been dealt with in this study. The salient features and results in each section provide a clear understanding of how each of these challenges can be overcome in the aspect of design and control strategies. [ABSTRACT FROM AUTHOR]

This study presents a hybrid excitation permanent magnet synchronous generator (HEPMSG) with a stator third harmonic winding to solve the problems of adjusting the air‐gap magnetic field of the permanent magnet synchronous machine (PMSM) and simplify the excitation system structure. The electromotive force (EMF) of the stator third harmonic winding, induced by the inherent third harmonic magnetic field in the air gap, provides the adjustable field current for the rotor field winding via the controllable rectification. The proposed machine structure is described, and the generation mechanism and the excitation principle of the stator third harmonic EMF are analysed. The conditions for maximum excitation current output are discussed, and the integrated design methods of the stator third harmonic winding and the rotor excitation winding are described. Based on the finite element method, the performances of the third harmonic excitation system are numerically compared for different stator third harmonic windings, and the open‐circuit voltage regulation characteristics under different control angles are analysed. A 2.5 kW HEPMSG prototype with a stator third harmonic winding is manufactured and tested. The predicted and experimental results are in good agreement, which verifies the correctness of the excitation principle of the proposed HEPMSG. [ABSTRACT FROM AUTHOR]

Permanent magnet flux switching machines (FSPMs) have attracted considerable attention in recent years, due to their outstanding characteristics to operate as brushless AC drives. Since they are relatively new, there are particular challenges not only for their design procedure but also for their operating principle comprehension. This study highlights several issues on FSPMs from the basic operation description to their key design points. After a comprehensive description of FSPMs working principles, a detailed discussion is presented on their armature winding design. In addition, this study reviews various methods for their performance modification, including torque profile, electromotive force, and loss characteristics. This study also surveys field regulation technologies, modelling and design optimisation methods applied to FSPMs along with their fabrication and cost issues. [ABSTRACT FROM AUTHOR]

A fault‐tolerant field‐oriented control (FOC) is proposed for five‐phase surface‐mounted permanent magnet synchronous motor (SPMSM) with non‐sinusoidal back electromotive force under single‐phase open‐circuit fault. On the basis of the concept of preserving the circular rotation of fundamental magnetic motive force and PM flux linkage, the decoupled model of five‐phase SPMSM under single‐phase open‐circuit fault is derived. To suppress the torque ripples caused by third‐harmonic content of PM flux linkage, the closed‐form solution of current references with zero‐torque pulsation in the synchronous coordinate is presented. Then, the presented solution is used for obtaining optimum current references to achieve minimum stator winding losses and maximum available torque while satisfying the zero‐torque‐pulsation constraint. The optimal current references generation method is simple and is suitable for real‐time implementation. The experimental results confirm that the proposed method can effectively suppress the torque ripples and produce lower stator winding losses as well as wider‐torque operation range compared with traditional fault‐tolerant FOC method. [ABSTRACT FROM AUTHOR]

Here, machines having permanent magnets (PM) mounted in the stator are compared during fault operations such as armature winding short circuits. The magnet potential irreversible demagnetisation is also investigated due to the fact that the PMs are placed close to the armature coils (heat sources) and hence are prone to temperature-related demagnetisations. It is found that the doubly salient and flux reversal machines have inherently higher fault tolerant capabilities when compared with the switched-flux one. To the point of view of demagnetisation withstand capability, the doubly salient topology stands out as the most robust one while the switched flux is the weakest one. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSM) have been used in a lot of industrial fields. In this paper, a review of faults and diagnosis methods of PMSM is presented. Firstly, the electrical, mechanical and magnetic faults of the permanent magnet synchronous motor are introduced. Next, common fault diagnosis methods, such as model-based fault diagnosis, different signal processing methods, and data-driven diagnostic algorithms are enumerated. The research summarized in this paper mainly includes fault performance, harmonic characteristics, different time-frequency analysis techniques, intelligent diagnosis algorithms proposed recently and so on. [ABSTRACT FROM AUTHOR]

In this study, a new sensitivity analysis based on non‐linear varying‐network magnetic circuit (VNMC) method is proposed for an outer‐rotor I‐shaped permanent magnet flux‐switching motor. By integrating concept of sensitivity analysis into the non‐linear VNMC method, the whole design efficiency can be improved effectively by using the comprehensive sensitivity method and sequential non‐linear programming algorithm. In the optimisation process, two design objectives are selected, including machine output torque and torque ripple. Based on the sensitivity analysis, the parameters possessing the significant influence on the design objectives can be selected purposely, thus the overall amount of calculation is obviously reduced. After the determination of the sensitive parameters, the rest of optimisation can be realised efficiently by the non‐linear VNMC method. Finally, a prototype motor is manufactured and tested. Both theoretical analysis and experimental results confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

IPM (Interior Permanent Magnet) motors produce torque based on two different mechanisms. The first of them is permanent-magnet torque, which is generated by the flux linkage between the PM (Permanent Magnet) rotor field and the electro-magnetic field of the stator. It is the same torque as produced by SPM (Surface Permanent Magnet) motors, however, IPM designs produce another force known as reluctance torque. The second one, the shape and location of the slots in the rotor laminations are designed to channel magnetic flux so that even if the slots were left as air gaps, the rotor would experience a force to align the magnetic flux lines with those generated by the stator coils. IPM motors are now very popular in industrial and military applications by providing high power density and high efficiency compared to other types of motors. This paper presents the use of finite element method harmonic analysis for investigation of IPM motor acoustics noise. This method is useful for DC (Direct Current) motor designs in many industrial and military applications. [ABSTRACT FROM AUTHOR]

This paper suggests a possible design of variable flux motor for adjustable speed operation. A method to calculate electrical parameters to meet variable speed conditions is suggested, and the basic motor shape is decided using the relationships between the calculated electrical parameters and motor geometry. The difference between coercivity of two types of magnet is used to control the flux. To prevent irreversible demagnetization of low-coercivity magnet, the approximate shape of magnet is decided by calculating the operating point of the magnet using an equivalent magnetic circuit. The optimum shape of magnet considering the nonlinear characteristics is suggested using a finite-element method. To validate the design, magnetizing/demagnetizing, and load operation tests are conducted. [ABSTRACT FROM PUBLISHER]

Hybrid-excited permanent magnet (PM) machines utilise the coordinated operation between the PM and the field excitation current. To enhance the effectiveness of the field excitation current, iron flux bridges are applied to hybridexcited switched-flux PM machines. This study proposes a new control strategy in which the d-axis current is utilised, while the field excitation current is controlled towards zero rather than negative in the flux-weakening mode. These reference currents are determined by the voltage error regulation method. The special magnetic circuit can effectively reduce the d-axis flux-linkage by either partially short-circuiting the PM flux via the iron bridge or removing the field excitation current. The proposed method exhibits advantages, such as highly enhanced torque response in the constant torque region, extended speed range, robustness against machine parameters, and higher efficiency in fluxweakening region. The feasibility of the proposed method is verified by detailed experimental results. [ABSTRACT FROM AUTHOR]

This study investigates the electromagnetic performance of a hybrid excited switched flux permanent magnet (SFPM) machine using the frozen permeability (FP) method. The flux components due to PMs, field excitation windings and armature windings have been separated using the FP method. It has been used to separate the torque components due to the PMs and excitations, providing a powerful insight into the torque generation mechanism of hybrid excited SFPM machines. It also allows the accurate calculation of d- and q-axis inductances, which will then be used to calculate the torque, power and power factor against rotor speed to compare the relative merits of hybrid excited SFPM machines with different types of PMs (i.e. NdFeB, SmCo and Ferrite). This offers the possibility of choosing appropriate PMs for different applications (maximum torque or maximum speed). Although only one type of hybrid excited PM machine has been employed to carry out the investigations, the method used in this study can also be extended to other hybrid excited PM machines. The predicted results have been validated by tests. [ABSTRACT FROM AUTHOR]

The flux-switching permanent-magnet (FSPM) motor has been viewed as a highly reliable machine with both armature windings and magnets on the stator. Owing to the high torque-production capability with low torque ripple, FSPM motors with a higher number of phases are potential candidates for traction applications in hybrid electric vehicles (HEVs). However, existing research has mostly focused on the principles and static performance of multiphase FSPM motors, and little attention has been paid to advanced control strategies. In this paper, the fully decoupled current control of a 36/34-pole nine-phase FSPM (NP-FSPM) motor is developed and the performance under different operating conditions is investigated. The aim of the design is to alleviate cross coupling effects and unwanted low-order stator harmonic currents, to guarantee fast transient response and small steady-state error. In addition, its fault-tolerance is further elaborated. These features are very important in automotive applications where low torque pulsation, high fault-tolerant capability and high dynamic performance are of major importance. Firstly, the research status of multiphase FSPM motors is briefly reviewed. Secondly, the mathematical model in the dq reference frames and control strategies are presented. Then, the control and performance of the NP-FSPM motor are evaluated by using MATLAB/Simulink. Finally, experiments on an NP-FSPM motor prototype are carried out to validate the study. [ABSTRACT FROM AUTHOR]

The hybrid excitation synchronous machine (HESM) with magnetic shunting rotor is a new topology of brushless HESM. To optimize the excitation construction, improve the flux control capability, and decrease the magnet consumption as well, two types of HESMs with different air-gap features are further proposed and investigated in this paper. First, configuration of the HESM with axial auxiliary air-gaps is presented. The comparative study of axial auxiliary air-gap scheme with respect to radial one is carried out. Three-dimensional (3-D) finite-element analysis (FEA) of the HESM is performed to achieve the field distribution, air-gap flux density and flux control characteristic, which indicates the HESM with axial auxiliary air-gaps also has good flux control capability and moreover enlarged excitation housing. Afterwards, construction and flux control principle of the new HESM with axial non-uniform air-gaps are introduced. A prototype HESM is developed, and the experimental results of open-circuit characteristic and terminal characteristic, which agree with the 3-D FEA results, verify the satisfactory field control performance, desirable power output capability, and the improved flux control capability of the HESM at negative excitation current as well. [ABSTRACT FROM PUBLISHER]

Switched-flux permanent magnet (PM) (SFPM) machines have attracted considerable interest in recent years, since the flux focusing can be utilized, both armature windings and PM excitation sources are on the stator, while the salient pole rotor is very simple and robust. In SFPM machines, the high variable flux densities throughout the stator core result in iron loss being a significant proportion of the total losses. This paper presents a novel modular-rotor SFPM machine that facilitates a reduction in iron loss for a marginal reduction in output torque. The modular rotor also offers a reduction in rotor mass over the conventional-rotor topology. The electromagnetic performance of both conventional- and modular-rotor SFPM machines is analyzed by 2-D finite element analyses and is verified by measurements on small-scaled prototype SFPM machines. [ABSTRACT FROM AUTHOR]

This paper proposes a novel permanent-magnet (PM) flux switching (PMFS) machine with an outer-rotor configuration for in-wheel light traction applications. The geometric topology of the outer-rotor PMFS machine is introduced, and the analytical sizing equations are derived to determine the main design parameters of the machine. Two-dimensional finite-element analysis (FEA) models are developed to investigate and optimize the machine performance. Furthermore, the flux-weakening capability of the machine is analyzed and further improved by segmental PMs with iron bridges. The machine performance predictions by 2-D FEA models are validated by experimental tests on the prototype machine. The suitability of the proposed outer-rotor PMFS machine for in-wheel light traction application is demonstrated. [ABSTRACT FROM PUBLISHER]

In this paper, a proposal for a field weakening method for a permanent-magnet synchronous motor is evaluated. The method consists in inserting giant magnetostrictive elements between permanent magnets. The magnetic permeability of these magnetostrictive parts is modified when the speed increases. The field leakages around the permanent magnets are consequently increased, thus reducing the electromotive forces in the armature windings. An original modeling approach, based on the concept of equivalent stress, is proposed in order to evaluate this field weakening solution. [ABSTRACT FROM PUBLISHER]

Two motors are studied and optimized for transportation applications. The objective is to design motors whose external model is well suited for conventional vector control. Hence, in the design procedure, the emphasis is on the back-electromotive force (EMF) waveforms and external parameters. The first topology is a surface-mounted (nonsalient pole) motor with segmented magnets reducing significantly selected harmonics. The second is an inset magnet type (salient pole) motor with surface poles particularly shaped to reduce the harmonic content of the air gap flux density. For both motors, the principle of pulse width modulation is used for the harmonic reduction in the design process. The interest of these motors lies in the sinusoidal waveform of their back EMF allowing a simple vector control even at field-weakening region for high speeds. [ABSTRACT FROM PUBLISHER]

Permanent magnet (PM) brushless machines having magnets and windings in stator (the so-called stator-PM machines) have attracted more and more attention in the past decade due to its definite advantages of robust structure, high power density, high efficiency, etc. In this paper, an overview of the stator-PM machine is presented, with particular emphasis on concepts, operation principles, machine topologies, electromagnetic performance, and control strategies. Both brushless ac and dc operation modes are described. The key features of the machines, including the merits and drawbacks of the machines, are summarized. Moreover, the latest development of the machines is also discussed. [ABSTRACT FROM PUBLISHER]

Flux-switching permanent magnet (FSPM) machine is a relatively novel brushless machine, which exhibits inherently sinusoidal PM flux-linkage, back-EMF waveforms and high torque capability. However, the air-gap field density is difficult to be regulated since it is produced by the stator magnets alone. Hence, hybrid-excited flux-switching (HEFS) machine is proposed by introducing a set of field windings into an original FSPM machine. However, in HEFS machines the flux linkages of armature windings vary in inverse proportion to the air-gap flux density when significantly saturated, which is different from the conventional machines. So in this paper, the oversaturated phenomenon in HEFS machines is explained and the effect of saturation, especially due to magnet material, on the relationship between air-gap flux density and armature flux linkage is investigated based on 2-D finite element analysis. Also, an effective stator-tooth-width coefficient (kstw) is defined to evaluate the oversaturated effect quantitatively. [ABSTRACT FROM AUTHOR]

A novel E-core switched-flux permanent-magnet (SFPM) brushless machine is proposed, and its electromagnetic performance is compared with that of the conventional SFPM brushless machine. The operation principle of the E-core SFPM machine will be first described, and the influence of stator and rotor pole number combinations is investigated, while the electromagnetic performance of the optimized E-core SFPM machine is predicted by finite-element analyses and validated by experiment. It is shown that the number and volume of magnets in the E-core SFPM machine is significantly reduced, only half of that in the conventional machine, while the phase back electromotive force and torque of the E-core machine are \sim 15% larger than those of the conventional machine. [ABSTRACT FROM AUTHOR]

A Hybrid Exciting Synchronous Generator (HESG) is analyzed in this paper, including its particular structure and operation principle. A permanent magnet generator is used for providing the main output and a homopolar inductor alternator is used for regulating the terminal voltage. The electromagnetic field computation and the performance analysis of the HESG are carried out by using three-dimensional finite element method. A 1.5 KW, 2000 rpm to 9000 rpm, 8-pole and 9-slot HESG is tested to verify the flux control capability. Experimental results show that it is possible to obtain a voltage from 64% to 126% of the voltage generated only by PM with the adjustment of the exciting current. And the variation range of the output voltage can be narrowed greatly while the speed of the generator varies from 2000 mm to 9000 rpm. [ABSTRACT FROM AUTHOR]

This paper proposes new practical optimal current control methods for a newly emerging class of synchronous motors with hybrid rotor fields by both permanent magnet and winding. In a practical situation with limited voltage, the extensively used permanent-magnet synchronous motor hardly achieves an ideal performance in an energy-efficient manner due to its constant magnet field, which simultaneously allows both low-speed high-torque and wide speed-range operations. The hybrid-field synchronous motors (HFSMs) are potential candidates that can achieve the ideal performance as practical motors with control- lable hybrid rotor field. HFSMs can dynamically control the rotor flux according to the operation requirements by the low-speed, high-torque, and wide speed-range operations, etc. For the HFSMs, the same torque can be produced by a variety of stator and rotor currents due to the nonlinearity between the torque and the currents. Produced losses and required voltages depend upon the associated currents. Consequently, in the situation that current control systems are well constructed, appropriate determination of a set of stator and rotor current commands plays a key role to achieve the ideal performance in an energy-efficient manner. The proposed methods determine the current commands corresponding to a given torque command such that the total winding copper losses due to the stator and rotor currents can be minimized if the exact currents associated with the torque command exist; the best approximate torque can be produced if no exact associated currents exist, which is, of course, under the circumstance of a voltage limitation. The determined current commands are optimal in the sense of energy efficiency or degree of approximation under voltage limitation. New recursive algorithms searching the optimal current solution in real-time are also given as parts of the methods. The proposed methods are analytical but practical, whose usefulness is verified through experiments. [ABSTRACT FROM AUTHOR]

Potentials and limits of the Hybrid-Excitation Permanent-Magnet (HEPM) synchronous machine are dealt with in this paper. A six-pole machine is taken into consideration, and both parallel and series configurations are analysed and compared. Taking advantage of the rotor excitation coils, the permanent magnet (PM) rotor flux can be adjusted according to the operating speed to improve its performance parameters. The electro-magnetic force is analysed in its first harmonic and in the complete shape. Moreover, a comparison between analytical and numerical formulation has been done for the rotor current control. In particular, the speed range is extended, and electro-mechanical torque and power are increased, as well as the efficiency. It will be shown that the rotor flux reduction by using the excitation winding yields an improvement of the motor performance. The main advantage will be obtained during the flux-weakening operations. In this paper, different rotor topologies will be analysed to highlight the advantages and drawbacks of each of them, and how it is possible to achieve higher speed with higher torque and without high saliency ratio. A magnetic network will be introduced to explain the different contribution of the excitation winding to the rotor flux. Furthermore, a comparison of the amount of the volume of PM, copper and iron in internal permanent magnet (IPM) motor and HEPM motor will be analysed. Actually, an analysis of the harmonic content in the electro-motive force even varying the excitation current and a mechanical stress analysis of each machine will be shown. Finally, it will be verified that the excitation losses represent a minimum component of the total losses. [ABSTRACT FROM AUTHOR]

This paper studies the torque production mechanism of the dual-stator axial-field flux-switching permanent magnet (DSAFFSPM) machine. Due to the double-sided slotting design of such topology, more resultant air-gap working harmonics in the air-gap flux density are responsible for the torque production and the stator air-gap permeance is especially considered in the investigation. Based on the magnetic force (MMF)-permeance model, the composition and difference of the air-gap working harmonics are demonstrated. The DSAFFSPM machine torque contributions of the main working harmonics are analyzed theoretically and quantified by finite element analysis (FEA). The influence laws of the parameters on the working harmonics are shown and this effectively improves the motor operation performance. Finally, some experiments on the DSAFFSPM machine are carried out to validate the analytical and FEA results. [ABSTRACT FROM AUTHOR]

This paper gives a comprehensive review of advanced cooling schemes and their applications to the permanent magnet synchronous motors (PMSMs), as well as investigating the electrical motor's topologies its thermal design issues, materials and performances. Particularly, the electromagnetic and electric performances, machine sizing, together with the structural design, are given. In addition, the work addresses the motor's material design and properties along with its insulation performance, which is the main goal of optimization. Mainly, thermal mapping with analysis is provided according to the different cooling methods, including air-cooling, water-cooling, oil-cooling, heat-pipe-cooling, potting silicon gelatin cooling, and as well as cooling strategies for tubes and microchannels. The most common special features and demands of the PMSMs are described in the appearance of the motor's failures caused by uncontrolled temperature rise. In addition, heat sources and energy losses, including copper loss, core loss versus motor speed, and output power, are analyzed. The review of the proposed cooling methods that will achieve the required heat transfer of the PMSM is presented with numerical simulations and measurements data. A review of numerical methods and results, including the finite element methods (FEM), such as the Ansys CFD software, to obtain a high-accuracy thermal mapping model of the PMSM system is given. The revived methods and design requirements due to PMSM temperature profile and cooling flow at different rotor speeds and torque loads are investigated. Finally, the motor design recommendations, including the newly developed cooling solutions, which enable it to effectively redistribute the temperature and heat transfer, increasing the efficiency of the PMSM machine, are laid out. [ABSTRACT FROM AUTHOR]

Contemporary research has shown impetus in the diagnostics of permanent magnet (PM) type machines. The manufacturers are now more interested in building diagnostics features in the control algorithms of machines to make them more salable and reliable. A compact structure, exclusive high-power density, high torque density, and efficiency make the PM machine an attractive option to use in industrial applications. The impact of a harsh operational environment most often leads to faults in PM machines. The diagnosis and nipping of such faults at an early stage have appeared as the prime concern of manufacturers and end users. This paper reviews the recent advances in fault diagnosis techniques of the two most frequently occurring faults, namely inter-turn short fault (ITSF) and irreversible demagnetization fault (IDF). ITSF is associated with a short circuit in stator winding turns in the same phase of the machine, while IDF is associated with the weakening strength of the PM in the rotor. A detailed literature review of different categories of fault indexes and their strengths and weaknesses is presented. The research trends in the fault diagnosis and the shortcomings of available literature are discussed. Moreover, potential research directions and techniques applicable for possible solutions are also extensively suggested. [ABSTRACT FROM AUTHOR]

Interior Permanent Magnet Synchronous Machine (IPMSM) are high torque density machines that usually work under heavy load conditions, becoming magnetically saturated. To obtain properly their performance, this paper presents a node mapping criterion that ensure accurate results when calculating the performance of a highly saturated IPMSM via a novel magnetic reluctance network approach. For this purpose, a Magnetic Circuit Model (MCM) with variable discretization levels for the different geometrical domains is developed. The proposed MCM caters to V-shaped IPMSMs with variable magnet depth and angle between magnets. Its structure allows static and dynamic time stepping simulations to be performed by taking into account complex phenomena such as magnetic saturation, cross-coupling saturation effect and stator slotting effect. The results of the proposed model are compared to those obtained by Finite Element Method (FEM) for a number of IPMSMs obtaining excellent results. Finally, its accuracy is validated comparing the calculated performance with experimental results on a real prototype. [ABSTRACT FROM AUTHOR]