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Nowadays, research on electromagnetic devices increasingly focuses on multiphysics three‐dimensional complex systems. However, this kind of simulations require huge computational resources and consequently very high CPU time. Ristagno et al. proposed a level‐set based method allowing meshing step savings in any iterative processes (as movement modeling or optimization processes). The level‐set method lies in implicit description of moving fronts as described in the study by Osher et al. (1988). Inspired by Räisänen et al., all physical parameters (material properties, supply or armature movement) are implemented by projection of mathematical functions. In this paper, the authors proposes to study and design a new kind of mechanical commutator for DC machines thanks to this coupled method. Indeed, there is a renewed interest in DC machines because they can be suitable for small mobilities. To be noted, small mobility concerns all kind of vehicles (2 wheels–4 wheels–autonomous vehicles such as drones) that have speeds below 50 km/h. However, specifications for traction applications are difficult to achieve for such a rustic machine and requires some modifications. That is why, inspired by usual synchronous machine, the commutator has been redesigned to obtain expected theoretically signal waveform. Furthermore, numerical coupled simulations have been used to design both machine and supply simultaneously. This work has led to the manufacture of a proof of concept and preliminary results are very promising. [ABSTRACT FROM AUTHOR]

Hybrid excited machine (HEM) is a novel type of machine which has attracted much attention as it is able to adjust the flux linkage flexibly and ensure the wide speed range operation. In this paper, a novel brushless HEM with permanent magnet (PM) located in rotor is further researched. By supplying specific armature currents, the sub‐harmonic component magnetomotive force (MMF) in stator MMF would be generated and utilized to realize the brushless hybrid excited operation. Firstly, the generation principle of the sub‐harmonic component is derived analytically. Secondly, during the brushless hybrid excited operation, the influence of the stator current amplitude ratio m$$ m $$ is quantitatively studied. Thirdly, based on 2D finite element analysis (FEA), the electromagnetic performance of the brushless HEM is analyzed under different operation statuses over a wide speed range. At last, the experiment is performed based on a 6 kW brushless HEM prototype machine, and the correctness of the theoretical analysis and FEA results are validated by the test. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

To enhance the torque of short‐time duty permanent magnet (PM) dual‐redundancy brushless DC motors (DR‐BLDCM) and avoid the motor overheating under a fixed outer diameter and length, a design method based on the optimization of split ratio and stator magnetic density (Bm) considering thermal limitations is presented. The global thermal limitation of DR‐BLDCM is set by limiting loss density. The local thermal limitation of the winding is set by limiting current density. The thermal limitations are taken as the boundary of torque enhancement design optimization. Both the cold backup and hot backup DR‐BLDCM are studied in this paper. By researching the relationship between torque, split ratio, and Bm, the optimal combination of split ratio and Bm are calculated analytically. The influences of thermal limitations on the maximum torque and the optimal combination are analyzed, and the principle to determine the optimal combination is obtained. The analytically calculated results are verified by finite element simulation, and the error is less than 6.82%. A prototype is manufactured based on analytical design results. The error between the calculated and measured copper loss is 6.96%. The verification results show that the proposed optimization method can fully enhance the torque of DR‐BLDCM under the condition of fixed overall dimension and thermal limitations. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Summary: The switched reluctance motor (SRM) has the high level of vibration and noise, whose application is greatly limited in many fields. In this article, a novel stator for a SRM is designed to reduce torque ripple and is suitable for one‐directional or low‐speed reverse rotation. On the one hand, a shoe is added to the stator pole side in the rotating forward direction from the completely unaligned to the aligned position. On the other hand, a slot is set on the top of stator tooth. First, causes of vibration and torque ripple are analyzed. Second, it is indicated by the equivalent magnetic circuit (EMC) method that the air gap permeability of the model with the single‐sided pole shoe is larger than that of the conventional model in the nonoverlapping region between the stator and rotor. The influences of the angle and height of shoe on the air gap magnetic density, radial force, and torque ripple are analyzed. Third, the results from EMC method show that the radial force can be reduced by opening a slot at the top of stator pole arc. The width and depth of slot which has effect on the radial force and torque ripple are analyzed. Finally, finite element analysis results show that the decreases of 34.52% for the radial force wave peak and 43.39% for the torque ripple are achieved at the cost of a decrease of 8.54% for the average torque of the single‐sided pole and the slot model of the stator pole compared with the conventional model. Some experiments for the two prototypes verify that the torque ripple and radial force can be reduced by adopting the new model. [ABSTRACT FROM AUTHOR]

This paper presents a 3D multiphysic modeling based on the coupling between the nonlinear discrete energy‐averaged model and the finite element method for the design optimization of magnetoelectric laminar structures. The model is applied to investigate the influence of the layer width on the output voltage and power performances while taking into account the magnetic losses due to the eddy currents. [ABSTRACT FROM AUTHOR]

This study proposes a brushless hybrid excitation permanent magnet synchronous generator (HEPMSG) with rotor tooth harmonic winding. The rotor tooth harmonic electromotive force (EMF), induced by the inherent tooth harmonic magnetic field in the air gap, will provide the field current for the rotor field winding after the rectification. The structure and principle of the machine are introduced, and the generation mechanism of the rotor tooth harmonic EMF is analysed. The influence of design parameters on the rotor field current provided by the tooth harmonic excitation system is discussed. The performance of the tooth harmonic excitation is calculated and analysed for different design parameters including stator slot width, air‐gap length, tooth harmonic winding turns, skewed stator slot and magnetic saturation, and the optimal design parameters of the HEPMSG are obtained. One HEPMSG prototype with rotor tooth harmonic winding was developed, and five different working conditions of the tooth harmonic excitation system were tested. The maximum field current is obtained by comparing the connection mode of the tooth harmonic winding. [ABSTRACT FROM AUTHOR]

This study proposes a hybrid excited (HE) doubly salient machine with permanent magnets (PMs) located on stator slot openings. The HE machine inherits the high torque density of PM machines as well as flexible magnetic field regulation of wound field machines. Since the PMs are located at stator slot opening, the PM flux is shunted in the stator without DC excitation, and the machine exhibits high fault‐tolerant capability at high‐speed operation. The proposed machine is optimised, together with a comparison with a conventional stator slot PM HE machine. It is revealed that the proposed HE machine exhibits a significantly higher torque density under the same copper loss and PM usage. Finally, a prototype is fabricated, and experiments have been conducted to verify the accuracy of finite element simulation on the proposed machine topology. [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]

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]

This is a survey paper focusing on permanent magnet motors with variable field capability. The synchronous motors, which have been applied to somewhat limited fields, have garnered attention as attractive electric drives. Due to a connection with rare‐earth magnet and power electronics‐based flexible control, current permanent magnet synchronous motors have achieved the best position in terms of high power and torque densities, high efficiency and flexible control capability. In order to satisfy the diverse demands of users, a motor is requested to ensure high‐efficiency operation at multiple operating points on the speed–torque plane. It is well recognized that maximum efficiency is attained under the condition that the copper loss is equal to the fixed loss, mainly composed of iron loss, at a given operating point. This is why permanent magnet synchronous motors should have the capability of adjusting the field excitation, similar to the direct current shunt motors. In this paper, recent trends of research and development of variable field permanent magnet motors are overviewed from the standpoint of design and control. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This study proposes a new three‐phase dual‐rotor middle‐stator brushless flux switching generator for 400Hz diesel‐driven aircraft ground power units. For the proposed machine, both field and armature windings are hosted in the stator in such a way that not only fulfils brushless structure, but also realises the flux switching function. Moreover, both windings have non‐overlapping concentrated windings to shorten the end‐windings and reduce the copper losses. In the meantime, the rotor has only slots without any active parts. First, the machine detailed design is provided, and its performance is analysed using finite element method. Also, a selection topology of both stator and rotor pole arcs is carried out, targeting maximum generated electromotive force, minimum harmonic content, and minimum cogging torque. Then, a prototype is implemented and experimented to confirm the feasibility of the proposed machine. [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]

In this article, the driving characteristics of an electromagnet‐assisted ferrite magnet motor (EMaFM) are investigated using a 1.5‐kW prototype machine. The EMaFM is a new type of synchronous motor, which combines a ferrite magnet motor with an electromagnet motor. Finite element analysis and experimental results show the following. (1) A wide constant power range as well as high torque at low speeds can be achieved by assisting the torque with the built‐in electromagnet motor. (2) It is possible to reduce the losses and improve the efficiency by adjusting the field current according to the operating conditions. [ABSTRACT FROM AUTHOR]

This study overviews recent development of a new class of magnetically geared machine topologies, i.e. partitioned stator (PS) machines. They are developed from magnetic gears and magnetically geared machines, as well as stator permanent magnet (PM) machines (switched flux, flux reversal, and doubly saliency PM), wound field, or hybrid PM and field winding machines. Based on the operating principle, i.e. magnetic gearing effect/air-gap field modulation and flux switching by the salient rotor iron poles, various PS machine topologies are developed. All have features of two stators, two air-gaps, and one segmented ferromagnetic rotor identical to a magnetic gear's modulating rotor. Their inherent relationships are revealed, while their electromagnetic performance is compared. Both PM and wound field PS machines are discussed, together with hybrid excited PS-PM machines and Vernier machines. It shows that all of these PS machines share the same torque production principle and the differences are mainly in PM configurations and relative positions of two stators. All PS machines have higher torque density per copper loss compared with their counterparts of single-stator machines. PS switched flux PM machines can produce the highest torque density per copper loss. [ABSTRACT FROM AUTHOR]

This study overviews recent development of a new class of magnetically geared machine topologies, i.e. partitioned stator (PS) machines. They are developed from magnetic gears and magnetically geared machines, as well as stator permanent magnet (PM) machines (switched flux, flux reversal, and doubly saliency PM), wound field, or hybrid PM and field winding machines. Based on the operating principle, i.e. magnetic gearing effect/air‐gap field modulation and flux switching by the salient rotor iron poles, various PS machine topologies are developed. All have features of two stators, two air‐gaps, and one segmented ferromagnetic rotor identical to a magnetic gear's modulating rotor. Their inherent relationships are revealed, while their electromagnetic performance is compared. Both PM and wound field PS machines are discussed, together with hybrid excited PS‐PM machines and Vernier machines. It shows that all of these PS machines share the same torque production principle and the differences are mainly in PM configurations and relative positions of two stators. All PS machines have higher torque density per copper loss compared with their counterparts of single‐stator machines. PS switched flux PM machines can produce the highest torque density per copper loss. [ABSTRACT FROM AUTHOR]

Abstract: This paper compares different energy‐based magneto‐mechanical models, which describe the magnetization changes that a magnetostrictive and anisotropic material undergoes when subjected to a quasi‐static H‐field excitation and tensile or compressive external stress. The magnetic behavior is either characterized by considering the phenomenological energy‐based Hauser hysteresis model or by the recently introduced hysteresis energy. The effect of mechanical stress is included naturally in the energy summation of the multiscale models. Properties of the different models, such as accuracy and parameter identification, are illustrated by comparison with experimental data for a nonoriented FeSi3% electrical steel grade. [ABSTRACT FROM AUTHOR]

For electric vehicles (EVs) with severe acceleration requirement, the selected motor would be inevitably overdesigned to meet the acceleration requirement. To address this, the motor constant power speed ratio (CPSR) should be increased to remove part of the overdesign. There are different flux weakening techniques that are used to increase motor maximum speed (and increase the CPSR). Among them, hybrid excitation synchronous motor (HESM) advantages have been benefited in this study. CPSR depends on hybridisation ratio (HR) of the excitation system, and the motor inductance. The relation is analytically derived in this study. In addition to increasing CPSR, HR can control the place of motor high‐efficient area over the efficiency map, which can increase EV total efficiency. A search algorithm has been developed, here, to find the optimal HR of a non‐optimal HESM. The final design gives an efficient motor performance with less overdesign in drivetrain. Compared with the original permanent magnet synchronous motor, 4.1% improvement in total efficiency for an average city‐highway driving cycle has been achieved, and 16% decrease in rated values of drivetrain elements is obtained. [ABSTRACT FROM AUTHOR]

This study presents magnetic equivalent circuit (MEC) model of ring winding axial flux machine (AFM). The ring winding AFM is a new permanent magnet topology that presents many advantages like reliability, simple construction, low cost and ease of increasing pole and phase numbers. For optimal design of this new type of machine, a fast and accurate performance analysis tool is needed. In this regard, MEC model of the ring winding AFM is proposed. It is shown that the developed MEC model of the ring winding AFM provides very fast solution, yet accurate results compared with three‐dimensional finite‐element model (3D FEM). The proposed MEC model considers 3D geometry, magnetic saturation, leakage fluxes and rotor position. Furthermore, this study provides equations to consider fringing flux between arc segmented surface mounted permanent magnets and stator teeth. Experimental and 3D FEM results are employed to show the validity of the proposed MEC model. [ABSTRACT FROM AUTHOR]

For electric vehicles (EVs) with severe acceleration requirement, the selected motor would be inevitably overdesigned to meet the acceleration requirement. To address this, the motor constant power speed ratio (CPSR) should be increased to remove part of the overdesign. There are different flux weakening techniques that are used to increase motor maximum speed (and increase the CPSR). Among them, hybrid excitation synchronous motor (HESM) advantages have been benefited in this study. CPSR depends on hybridisation ratio (HR) of the excitation system, and the motor inductance. The relation is analytically derived in this study. In addition to increasing CPSR, HR can control the place of motor high-efficient area over the efficiency map, which can increase EV total efficiency. A search algorithm has been developed, here, to find the optimal HR of a nonoptimal HESM. The final design gives an efficient motor performance with less overdesign in drivetrain. Compared with the original permanent magnet synchronous motor, 4.1% improvement in total efficiency for an average city-highway driving cycle has been achieved, and 16% decrease in rated values of drivetrain elements is obtained. [ABSTRACT FROM AUTHOR]

This study investigates the influence of rotor topologies and winding configurations on the electromagnetic performance of three‐phase synchronous reluctance machines (SynRM) with different slot/pole number combinations, e.g. 12‐slot/4‐pole and 12‐slot/8‐pole. Transversally laminated synchronous reluctance rotors with both round flux barrier and angled flux barrier have been considered, as well as the doubly salient (DS) rotor as that used in switched reluctance machines. Both concentrated and distributed winding configurations are accounted for, i.e. single‐layer and double‐layer conventional and mutually coupled windings, as well as fully pitched winding. The machine performance in terms of d‐ and q‐axis inductances, on‐load torque, copper loss, and iron loss have been investigated using 2D finite‐element analysis. With appropriate rotor topology, 12‐slot/4‐pole and 12‐slot/8‐pole machines with fully pitched and double‐layer mutually coupled windings can achieve similar torque capacity, which are higher than the machines with other winding configurations. In addition, the synchronous reluctance machine with round flux barrier can have lower iron loss than DS reluctance machine under different working conditions. The prototypes of 12‐slot/8‐pole single layer and double layer, DS SynRM have been built to validate the predictions in terms of inductances and torques. [ABSTRACT FROM AUTHOR]

Hybrid excitation synchronous machines (HESMs) are permanent magnet machines which allow the control of the air‐gap flux density. In this study, three new axial field HESM structures, each having two rotors and one stator, are proposed. The operation principles of these machines, considering weakening or supporting the air‐gap flux density, are described. The magnetostatic and transient analyses of the proposed models have been carried out by using finite element method. To have reliable analysis results, the stator length and input and output diameters of the models have been chosen to be identical. Results are compared in terms of efficiency, power density and range of flux control between each other and another axial field HESM in the literature. In conclusion, the proposed HESM models demonstrate satisfactory performance for the generator mode and they are suitable for wind energy applications. Furthermore, because of their field weakening operation ability they can be used as motors in the vehicle industry. [ABSTRACT FROM AUTHOR]

Radial vibration and torque ripple are the most two important factors to acoustic noise, especially when resonance is excited. This study focuses on radial vibration, which is composed of vibration impulse and fundamental vibration. The respective influence of the two components to resonance noise is analysed. It is experimentally demonstrated that fundamental vibration is more significant to resonance noise compared with vibration impulse. Accordingly, based on the already proposed randomising turn‐on angle method, the reduction effect of the method is analysed in detail using different control parameters like different variation range of turn‐on angle and different overlapping. The resonance noise is substantially reduced, which verifies the effectiveness of the randomising turn‐on angle. In addition, it is found that the reduction effect is almost the same by different control parameters, which shows the flexibility of the method. [ABSTRACT FROM AUTHOR]

The irreversible magnet demagnetisation phenomena are investigated, under both healthy and short‐circuit conditions for a switched flux permanent magnet (SFPM) machine. The temperature effects on permanent magnet material are taken into account and the influence of short‐circuit current over demagnetisation is evaluated. To calculate the short‐circuit current (mainly inter‐turn short circuit), the MATLAB/Simulink model has been employed. The aforementioned short‐circuit current is then fed to the finite‐element model, so the demagnetisation analysis can be carried out. Various fault scenarios are investigated, including a high speed and high fault severity. It is found that the short‐circuit current has limited effect on the magnet demagnetisation due to particular features of the SFPM machines. The mechanism of demagnetisation has been revealed and found out to be mainly due to temperature rise and poor PM materials utilisation. Experiments have been carried out to validate the MATLAB/Simulink model for short‐circuit current predictions. [ABSTRACT FROM AUTHOR]

In this paper a 1.5 kW flux switching permanent magnet (FSPM) generator is presented for direct drive small scale wind turbine applications. For maximizing induced voltage and the output torque while minimizing cogging torque and unbalanced radial magnetic force (UMF), the proposed machine exhibits a new 6/19 stator pole/rotor teeth number and an outer rotor configuration. At first, in the paper an analytical design has been developed, then a finite element method (FEM) analysis is carried out for validating the analytical procedure and for design improvement. The simulation results extracted by FEM confirm the theoretical analysis procedure and help in the understanding of the performance analysis of the machine against the variations of the design variables. Furthermore, an experimental laboratory prototype of the proposed FSPM is implemented to confirm the analytical design and FEM modelling approaches. A comparison of induced voltage, torque, UMF and cogging torque produced by different FSPM configurations present in literature respect to the proposed generator has been developed. The results show the goodness of the adopted methodology and prove that, because of suitable electromagnetic performance of the proposed FSPM generator, it could be counted as a proper candidate for small scale wind turbine applications. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The present work investigates the influence of small geometrical defects on the behavior of slender rigid blocks. A comprehensive experimental campaign was carried out on one of the shake tables of CEA/Saclay in France. The tested model was a massive steel block with standard manufacturing quality. Release, free oscillations tests as well as shake table tests revealed a non-negligible out-of-plane motion even in the case of apparently plane initial conditions or excitations. This motion exhibits a highly reproducible part for a short duration that was used to calibrate a numerical geometrically asymmetrical model. The stability of this model when subjected to 2000 artificial seismic horizontal bidirectional signals was compared with the stability of a symmetrical one. This study showed that the geometrical imperfections slightly increase the rocking and overturning probabilities for earthquake signals in a narrow range of peak ground acceleration. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study presents a design methodology for a newly emerged switched‐flux memory machine with low‐cost non‐rare‐earth. The adoption of aluminium–nickel–cobalt magnet with low‐coercive force enables the flexible air‐gap flux control without unnecessary excitation loss. Hence, the excellent flux variability and high‐efficiency sustainability within a wide‐speed range can be achieved. Since geometric constraints exist among major parameters, a design trade‐off should be established to facilitate the feasible design. Therefore, a simplified magnetic circuit is modelled to analytically determine the relationships among various parameters, and the generic design considerations including magnet grade selection and stator/rotor‐pole combination are addressed, respectively. The influences of design parameters on back‐electromotive force and torque capability are evaluated to aid the performance optimisation. A machine prototype is then fabricated to experimentally validate the theoretical analyses. [ABSTRACT FROM AUTHOR]

In this paper, a correction method is introduced to make a more accurate calculation of winding eddy‐current losses of high‐voltage direct current (HVDC) converter transformer. The assumption that winding eddy‐current losses of HVDC converter transformers follow the frequency with the exponent 2 proposed by IEC 61378‐2 Std. is thought to be inappropriate and the skin effect should be taken into consideration. The frequency characteristic of winding eddy‐current losses is proposed by analysing the distribution of magnetic flux in conductors, in which skin effect is taken into consideration. The correction method with a correction factor is then introduced to correct the assumption. To verify the validity of the correction method, a two‐dimension axisymmetric finite element analysis of a HVDC converter transformer is conducted. The geometrical complexity of windings and electrical connection are fully taken into account, it is shown that the correction method shows a significant advantage. Influence of different methods is revealed by applying the actual non‐sinusoidal load current and it is shown that the error of correction method is the least. At last, harmonic losses measurements are conducted on three coils to investigate the limits of the correction method. [ABSTRACT FROM AUTHOR]

Meat extract is a product with a high aggregated value obtained by concentrating cooking broth from meat products. To optimize project design and processing, we determined experimental values of the density and rheological behaviour of meat extract. We evaluated the influences of temperature and solids concentration on the studied parameters. Different concentrations and temperatures were selected based on the main processing steps, ranging from 0-60 gsoluble solids/100 gsolution and 2-98 °C. The model best fitted to density was derived and a thermodynamic relation was applied to calculate the thermal expansion coefficient. Meat extract density had a linear dependence on temperature and quadratic dependence on solids content, while the thermal expansion coefficient remained approximately constant at 5.33 x 10-4m³ x m-3 x K-1. Concerning rheological analyses, meat extract had Newtonian behaviour from 1.5-20 gsoluble solids/100 gsolution at the temperature range studied. From 30-60 gsoluble solids/100 gsolution, the Power-Law model was better fitted to the data and the consistency coefficient and flow behaviour index could be calculated. Both parameters were sensitive to changes in temperature and concentration. Apparent viscosity increased with increasing the meat extract concentration and lowering the temperature. The dependence of rheological parameters on temperature was expressed through an Arrhenius-type equation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel integrated brushless excitation method (IBEM) for a rotor‐excited generator. IBEM is applied to a rotor‐excited hybrid excitation synchronous generator (HESG) to realise brushless excitation while the key features of the rotor‐excited generator are maintained. The new generator is referred as IBE HESG here. The stator excitation windings are buried in the stator slots. The static excitation field is established in the air gap when there is dc excitation current in the stator excitation windings. The three‐phase armature coils of the rotor induce the static excitation field and provide the dc excitation current for the rotor excitation windings via a rotating rectifier. The operating principles are discussed theoretically. The magnetic field distribution and the operating characteristics are studied by finite‐element analysis. The no‐load, external, regulation and excitation characteristics are analysed. Compared with the brush excitation HESG, the rotor excitation current is able to meet the requirement and the output voltage is conveniently regulated by the stator excitation current. Finally, a 1.5 kVA prototype is fabricated to test the operating characteristics of IBE HESG. It demonstrates that the brushless excitation is realised and the output voltage is regulated by the stator excitation current. [ABSTRACT FROM AUTHOR]

This paper presents a finite simulation model of the hybrid excitation synchronous machine taking into consideration the saturation effect, the iron losses and including higher‐order electromagnetic force harmonics. Simulation and experimental testing prove that the advanced model represents more accurately the machine especially when compared with the basic Park model built with sinusoidal waveform assumption. The main contribution of the work is that only few experimental measurements are needed in order to implement the advanced model. [ABSTRACT FROM AUTHOR]

Hybrid excited axial field flux‐switching machine (HEAFFSM) with permanent magnets (PMs) and excitation windings in its stator is a novel hybrid excited flux‐switching PM machine. The HEAFFSM combines the advantages of the hybrid excited synchronous machine and flux‐switching PM machine. In this study, the topology and operating principles of the HEAFFSM are analysed, and the electromagnetic characteristics (including the winding inductances, flux, and cogging torque) are obtained by the three‐dimensional finite‐element method. On the basis of the vector control method, the mathematical model of the HEAFFSM is deduced, and the operating performance of the HEAFFSM across its entire operating range is investigated. A new minimum‐copper‐loss (MCL) control strategy for the HEAFFSM drive system, which can operate in both flux‐enhancing and flux‐weakening conditions, is proposed and compared with the traditional control. The experimental results demonstrate that the MCL strategy maximises the range of speed regulation while minimises the copper loss of the HEAFFSM drive system. Moreover, the flux‐regulation capability and high power/torque density of the HEAFFSM are validated. [ABSTRACT FROM AUTHOR]

In this study, a mechanical flux adjusting technique for the switched flux permanent magnet (SFPM) machines is presented to improve the flux‐weakening capability by extending the speed range. The ferromagnetic material pieces, that is, flux adjusters (FAs), are located on the outside surface of the stator poles equipped with permanent magnet (PM) and used to weaken the PM flux via short‐circuit. To explore the most suitable machine topologies for such flux adjusting technique, the performance of conventional SFPM machines with different stator/rotor pole combinations, multi‐tooth, E‐core and C‐core SFPM machines is investigated and compared by employing the FAs. It shows that the maximum speed and flux‐weakening capability of the conventional SFPM machines can be significantly increased if the FAs are used. On the other hand, the multi‐tooth, E‐core and C‐core SFPM machines have inherently large inductance. Thus, the flux adjusting technique has less influence on their flux‐weakening performance. Besides two‐dimensional (2D) finite‐element analysis (FEA) and analytical methods, 3D FEA accounting for end‐effect is also used to predict the results. Finally, the analyses are validated by experiments. [ABSTRACT FROM AUTHOR]

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]

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 hybrid‐excited 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 flux‐weakening 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]

This paper presents two novel designs of magnetic flux‐modulated mnemonic (MFMM) machines which incorporate magnetic gearing effect and flux‐mnemonic concept together. Both of these two machines can perform large torque production at low‐speed because of the magnetic gearing effect, and can readily achieve flexible flux‐controllability by temporarily applying current pulses to magnetise/demagnetise aluminium‐nickel‐cobalt magnets so as to expand the constant‐power region operation effectively. One machine has permanent magnets (PMs) on its rotor and outer stator which is referred as the dual‐layer PM MFMM (DPM‐MFMM) machine; bi‐directional field modulating effect is artfully incorporated in this machine to guarantee effective coupling between the magnetic fields excited by the armature windings and those excited by the two sets of PMs. The second machine employs all the PMs on the outer stator and the rotor is only made up of ferromagnetic segments. In other words, it is a single‐layer PM‐MFMM (SPM‐MFMM) machine, and the rotor carries the flux modulating poles. The configurations and working principles of both machines are discussed. The electromagnetic performances are comprehensively studied and quantitatively compared using finite element method (FEM). [ABSTRACT FROM AUTHOR]

Synchronous machines with brushless excitation have the disadvantage that the field winding is not accessible for the de‐excitation of the machine. This means that, despite the proper operation of the protection system, the slow de‐excitation time constant may produce severe damage in the event of an internal short circuit. A high‐speed de‐excitation system for these machines was developed, and this study presents the continuation of a previously published study. This study presents the design by computer simulation and the results of the first commissioning of this de‐excitation system in a commercial 20 MVA hydro‐generator. The de‐excitation is achieved by inserting resistance in the field circuit, obtaining a dynamic response similar to that achieved in machines with static excitation. In this case, a non‐linear discharge resistor was used, making the dynamic response even better. [ABSTRACT FROM AUTHOR]

A novel switched flux permanent magnet machine (SFPMM) with both normal NdFeB and low coercive force (LCF) magnets has been developed in this paper. Outside a conventional SFPMM, the LCF magnets are mounted on the back of every U‐shaped stator lamination segment with parallel magnetisation direction and alternative polarities. A lamination ring yoke is placed around all the LCF magnets, while extra magnetisation coils are wound on each of them. By injecting different directions of current pulses into the magnetisation coils, the polarities of the LCF magnets can be rewritten in order to enhance or weaken the field generated by normal NdFeB magnets. Therefore the back EMF and torque capability could be adjusted in a wide range. In this paper, the operation principle and machine topology are introduced firstly. Then the stator/rotor pole combinations and design considerations of the machine have been discussed. With the help of two‐dimensional finite element software, a 6/5 stator/rotor pole machine has been globally optimised as an example to show the machine performances such as open‐circuit field and back EMF, dq‐axis inductances, torque capabilities and magnetisation. Finally, a prototype with the same dimensions has been manufactured and tested to validate the analysis results. [ABSTRACT FROM AUTHOR]

This paper presents an optimization analysis of an axial flux-switching hybrid excitation synchronous machine (AFHESM) to improve its no-load electromagnetic performances. The shapes of permanent magnet (PM), rotor-teeth and stator slot of AFHESM are investigated for a better design scheme by finite element analysis (FEA). Some optimal results under no-load are achieved, which mainly including the induced electromotive force (EMF), cogging torque and field control ability. Both FEA and experimental results show that the induced EMF can be improved when PM shape coefficient is 0.95 and the rotor-teeth bevel angle is 6°. [ABSTRACT FROM AUTHOR]