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To reduce the influence of the permanent magnet (PM) installation error on the electromagnetic characteristics of the outer rotor permanent magnet synchronous motor (OPMSM), the rotor structure of the OPMSM is optimized in this paper. The optimization method of adding auxiliary teeth on the surface of the rotor core is studied, and the influence of different auxiliary teeth heights on the electromagnetic performance of OPMSM is analyzed. It is found that adding auxiliary teeth with suitable height can greatly reduce the installation error of the PM, increase the mechanical stability of the motor, and ensure that the electromagnetic characteristics of the motor remain at a good level. Firstly, the topology and parameters of the motor proposed in this paper are introduced and analyzed. Secondly, the influence of PM installation error on the electromagnetic performance of the motor is analyzed based on the finite element method (FEM), and the necessity of eliminating PM installation error is demonstrated. Then, the parametric scanning method is used to analyze the influence of auxiliary teeth height change on the electromagnetic performance of the motor, and the selection standard of the optimal auxiliary teeth height is determined. By comparing and analyzing OPMSM with different sizes and different pole–slot ratios, the universality of the conclusions is demonstrated. [ABSTRACT FROM AUTHOR]

In the last decade, permanent magnet (PM)-free or hybrid PM machines have been extensively researched to find an alternative for high cost rare-earth PM machines. Brushless wound rotor synchronous machines (BL-WRSMs) are one of the alternatives to these PM machines. BL-WRSMs have a lower torque density compared to PM machines. In this paper, a new topology is introduced to improve the torque producing capability of the existing BL-WRSM by utilizing the vacant spaces in the rotor slots. The new topology has two harmonic windings placed on the rotor which induce separate currents. A capacitor is used between the two harmonic windings to bring the currents in phase with each other. The harmonic winding currents are fed to the rectifier which is also placed on the rotor. Due to additional harmonic winding, the overall field current fed to the rotor field winding has been increased and hence the average torque has also increased. Finite element analysis (FEA)-based simulations are performed using ANSYS Maxwell to validate the proposed topology. The results show that the average torque of the machine has been significantly increased compared to the reference model. The detailed comparison results are provided in this paper. [ABSTRACT FROM AUTHOR]

The electrically excited homopolar inductor machine has a static excitation coil as well as a robust rotor, which makes it attractive in the field of high-speed superconducting machines. This paper designed and analyzed a megawatt class superconducting homopolar inductor machine for aerospace application. To improve the power density, a mass-reduced rotor structure is proposed. Firstly, the main structure parameters of the superconducting homopolar inductor machine are derived based on the required power and speed. Secondly, the electromagnetic performance of the superconducting homopolar inductor machine is analyzed based on the finite element method. Thirdly, a mass-reduced rotor is proposed to improve its power density. The structural performance of the rotor and the electromagnetic performance of the superconducting homopolar inductor machine before and after rotor-mass reduction are evaluated. Compared with the initial rotor, the mass of the mass-reduced rotor is reduced from 66.56 kg to 50.02 kg, which increases the power density by 14.3%. The result shows that a superconducting homopolar inductor machine with a mass-reduced rotor can effectively improve its power density without affecting its output power. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis, electromagnetic evaluation, and prototyping of a novel motor structure called the sinusoidal rotor switched reluctance motor. In this innovative design, a significant departure from the conventional switched reluctance motor is observed, as modifications are made to the rotor with the goal of reduction torque ripple and radial force characteristics. Importantly, despite these advancements, the proposed motor retains the weight and volume characteristics of the traditional, type. The key attributes of these motors have been thoroughly assessed using the three‐dimensional finite element method, complemented by a sensitivity analysis aimed at identifying the most optimal configuration within the proposed design. The findings reveal that the suggested structure successfully achieves a notable reduction in torque ripple and radial force when compared to the traditional counterpart, albeit with an expected reduction in average torque. These features render the new topology particularly well‐suited for applications that prioritise noise and vibration reduction. Furthermore, the effectiveness of the proposed topology is corroborated through experimental tests, providing empirical evidence of its advantages and potential for practical applications. [ABSTRACT FROM AUTHOR]

A study of a dual rotor radial flux, fractional slot concentrated wound permanent magnet synchronous machine is presented in this paper. The proposed structure is analyzed in two different magnetic polarity configurations of the opposing rotors poles, for performance evaluation. 2D and 3D Finite Element Method simulation results are presented along with experimental validation tests performed on physical prototype under different working conditions, for both considered configurations. The main goal was to achieve a higher power density for the machine. In addition to this, production cost reduction by modularity fabrication techniques, and increasing efficiency through the use of grainoriented electric steel were considered and studied. [ABSTRACT FROM AUTHOR]

This paper employs an overhang structure for axial flux permanent magnet motor to enhance the torque density. However, the overhang structure requires a computationally expensive 3-D finite-element method (FEM) for analysis, because a quasi-3-D FEM cannot be applied to such a geometry. Thus, in order to reduce the computational cost of above-mentioned topology, this paper adopts a field reconstruction method (FRM). The conventional FRM is applicable only in the case, where the slot pitch to teeth length ratio is the same along radial direction. To address this problem, we introduce a virtual air gap concept so that it can take into account parallel slot effect as well as overhang effect. In this paper, the effectiveness of the proposed method is verified by the 3-D FEM and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, the boundary discretization method is used to improve the traditional subdomain model. The improved model can be used to calculate the magnetic field distribution in the region containing non-orthogonal boundary, avoiding the influence of the simplified stator slot or permanent magnet shape on the results in calculating the motor magnetic field using the traditional subdomain model. In addition, the improved subdomain model can also be used to calculate the air-gap flux density when the rotor is eccentric, instead of segmenting the air-gap to an equivalent state without eccentricity. The calculation object of this paper is a surface-mount permanent magnet motor with a rectangular stator slot. The air-gap flux density under no-load and load conditions is calculated, respectively. Since the improved subdomain model does not need to simplify the stator slot shape, the magnetic potential in the stator slot is also calculated. Finally, the air-gap flux density under rotor eccentricity is calculated, and the influence of the calculating parameters on the results of the improved subdomain model is discussed. All the calculated results are compared with those obtained by the finite element method, which verifies the accuracy of the improved calculation model. [ABSTRACT FROM AUTHOR]

The development of high-temperature superconducting (HTS) electrical machines results in applications of various fields, as they have higher efficiency and power density. Numerical modeling of superconducting electrical machines is usually performed by finite element method based their electrical behavior, and H-Formulation of the Maxwell's equations is one of the models that are used tremendously due to its high flexibility and simplicity. Axial field machine (AFM) is a machine topology with higher efficiency and power density, but with more complexity when modeling. This paper proposed a new 2D model for the superconducting AFM, where the superconducting coil is simulated with a 2D infinitely long model, this model also divides the electrical machine into two parts: the superconducting parts (HTS coils, bulks, etc.) and non-superconducting parts (e.g., conventional conductors, machine structure). This paper compares the results of H-A Formulation and T-A Formulation with this approach, which requires appropriate boundary conditions and continuity between the two regions, along with correct modeling of fixed and moving parts of the electrical machine, where the geometry of this model is based on a linear synchronous machine, which means the rotor is moving linearly instead of rotation. [ABSTRACT FROM AUTHOR]

The shape of rotor bar is important in squirrel cage induction motor (SCIM) performance, such as starting torque, operating torque, and operating efficiency. Some designs of increasing starting torque of motor may decrease motor efficiency. Moreover, some designed shapes of bar are so complicated to be manufactured. In this paper, the design is focused on the simple inclination of conventional shape of bar with keeping the rotor bar area constant. The effects of rotor bar inclination on starting torque, operating torque, and operating efficiency in SCIM are analyzed. The results showed that there is optimum inclination of rotor bar to improve all the performances together. An application to the 3.4 kW SCIM showed that the starting torque is increased from 17.53 to 17.64 \text N\cdot \text m , the operating torque from 11.19 to 11.26~\text N\cdot \text m , and the operating efficiency from 94.18% to 94.81%. [ABSTRACT FROM AUTHOR]

This study employed two primary approaches to determine the optimum structure: the lightweight and sustainable models. The lightweight model considered various factors such as materials, geometry, and dimensions of the brake disc rotor and brake pads. On the other hand, the sustainable model considers the manufacturing process and aims to reduce the carbon footprint. To calculate the optimal lightweight structure, finite element analysis was conducted using two different materials to compare the resulting stresses and determine the most appropriate material. Subsequently, four different models were utilized in finite element analysis to evaluate the displacement and stress and establish the optimum structure. Regarding sustainability, two distinct processes were employed to assess the environmental impact and energy consumption to adopt an eco-friendly approach. This paper investigates the transition from the initial brake disc rotor to a lightweight model, employing finite element analysis, topology optimization, and sustainability considerations. The work is achieved by comparing the cost between conventional and 3D printing processes. [ABSTRACT FROM AUTHOR]

When the dual rotor system of the aircraft engine is operating, the mass eccentricity of the power turbine rotor and the misalignment of the shaft coupling or the bearing will cause too large vibration of the rotor; this vibration leads to the rub-impact between the rotor and the casing. The power turbine rotor from the dual rotor system is taken as the research object in this paper. Considering the misalignment, the resulting rub-impact faults, the imbalance of rotor and the disk offset, the equation of motion for the system is developed according to the Lagrangian Equation, and then the Range-Kutta Method is adopted to solve the equation. The influence of the key parameters such as the rotating speed, the misalignment angle and the rub-impact clearance on the dynamics of the system is studied; the finite element analysis was carried out to validate the correctness of the theoretical modeling method. The results show that the rub-impact increases the stiffness of the system; the Hopf bifurcation occurs in the misalignment and rub-impact coupling system; the vibrational stability near the half of the switching speed slumps with the increase of the misalignment angle; with increasing of the stiffness, the number of the chaotic zone increases, and the range of the chaos is widening; enlarging the rub-impact clearance is beneficial to reduce the degree of the rub-impact system and enhance the stability of the system. [ABSTRACT FROM AUTHOR]

This paper introduces a technique aimed at improving the performance of an interior permanent magnet synchronous machine (IPMSM) by reducing torque ripple and radial force harmonics. Unlike conventional IPMSMs, the proposed method employs a variable airgap length that is defined by a mathematical function. Two distinct rotor shapes are investigated to determine the most efficient design. Finite Element Analysis is employed to assess both the electromagnetic and mechanical attributes of the proposed motors. It compares the results for three operating points of the shaped motor with those of a conventional one. The investigation delves into the influence of rotor geometry on key output parameters, including Back Electromotive Force (back‐EMF) harmonics, average torque, cogging torque, torque ripple, efficiency, power factor, and radial force harmonics. The findings indicate that optimising rotor shape can significantly enhance IPMSM performance by reducing torque ripples and radial force harmonics, while simultaneously increasing average torque and efficiency at different operating points. [ABSTRACT FROM AUTHOR]

In this paper, counter rotating dual rotor wound field flux switching wind power generator is revisited to study the generating characteristics of the AC output power curves based on finite element analysis (FEA) and experimental study. Analysis are performed under dynamic conditions, such as variable resistance, field excitation and speed. Also, electromagnetic performance is studied under variation of the field and armature currents. Analysis reveals that outer port machines with higher power capability and better electromagnetic performance compared to the inner port counterparts, although with higher fluctuations exhibited on the torque profiles of the former due to higher slotting effects. From the power generation characteristics curves, it is clear that the developed wind generator is able to produce reliable performance over a wide operating range. The accuracy of the FEA predicted results are validated, experimentally. The cover image is based on the Research Article Generating characteristics and experimentation of counter rotating dual rotor wound field flux switching wind generator by Wasiq Ullah et al., https://doi.org/10.1049/elp2.12374. [ABSTRACT FROM AUTHOR]

In order to reduce the x-direction and Y-direction displacement disturbance of the barrel and improve the firing accuracy, based on Bernoulli Euler's theoretical assumption of beam and taking M134 barrel machine gun as the calculation model, the pre-stress modal analysis and optimization of cantilever supported rotor under unbalanced force and moving mass are carried out in this paper. The main work of this paper is as follows: (1) M134 physical model is established, and the unbalanced force in the motion process of projectile in bore is solved by interior ballistic theory; (2) Based on the unbalanced rotor theory, the barrel vibration model considering the projectile weight and acceleration is established; (3) The critical speed model of high-speed rotating system is established, and the critical speed is determined by finite element modal analysis to determine the rigid/flexible state of barrel components in different speed regions; (4) Based on the above model, take the x-direction and Y-direction displacement of the barrel as the output value, and take the elastic modulus of the barrel, the relative position between the barrel hoop and the fuselage components and the cross-sectional area as the variable values, carry out the optimization design, and verify the firing accuracy before and after optimization through experiments. [ABSTRACT FROM AUTHOR]

Variable leakage flux (VLF) interior permanent-magnet synchronous machines (IPMSMs), which use intentional magnet leakage flux paths cross-coupled with the q-axis flux paths to reduce losses over driving cycles, have been introduced recently, but self-sensing has not been discussed for these machines. This paper focuses on the saliency angular offset attributes that are the primary metric for the well-established injection-based self-sensing methods. This paper begins by evaluating the effect of the intentionally designed cross-coupling in the VLF-IPMSM with rotor surface bridges on the saliency angular offset. This paper then proposes alternate rotor designs with side-loop structure that cause relatively linear and well-behaved cross-coupling that improves the load-dependent saliency angular offset characteristics. The effect of VLF properties on power conversion and driving cycle loss reduction capability is evaluated for the proposed designs. This paper also applies the concept of VLF design to conventional flux-weakening interior permanent-magnet machine rotor design and presents the loss reduction capability of such designs. [ABSTRACT FROM AUTHOR]

In this paper, the design of the concentrated flux-type synchronous motor (CFSM) using ferrite permanent magnets to improve torque is proposed for an automotive chassis actuator. The thin pancake type CFSM of this paper has considerable axial magnetic leakage flux due to structural reasons. It is, therefore, necessary to improve the torque. In order to meet the required specifications in a constrained installation space, this paper proposes two methods for torque improvement. The first method is the alternate-stacking core as this structure removes the magnetic leakage flux path. The second method is the rotor overhang that increases the air-gap flux density. Furthermore, the structures require a three-dimensional (3-D) finite element method (FEM) analysis for accuracy. However, to analyze the characteristics easily and quickly, the 3-D structure is made into the equivalent 2-D FEM through an analytical method using an equivalent magnetic circuit. Finally, in this paper, the validity of the design process and the effectiveness for torque improvement is verified through experiments. [ABSTRACT FROM AUTHOR]

This paper deals with electromagnetic torque and current characteristics of an induction motor with rotor bar breakage, and electromagnetic field analysis based on finite element method and motor current signal analysis is performed according to various load conditions. Although various monitoring techniques of rotor bar breakages were dealt with in previous studies using MCSA, they cannot be, in fact, applied to every case. Therefore, in this paper, electromagnetic field analysis of induction motor with various rotor bar fault conditions is performed to establish fault monitoring criteria in MCSA method. This study employs 0.4(kW) squirrel cage induction motor, and experimentally measured torque and current supports the analysis results. [ABSTRACT FROM AUTHOR]

A novel hybrid-flux permanent-magnet (PM) generator, which has both axial flux and radial flux, is proposed. An axial-flux PM generator is designed by a reluctance network method and the 3-D finite element method. Using these results, this paper proposes a radial-flux and hybrid-flux machine, whose main dimensions are chosen to the same values as a commercialized one. The proposed hybrid-flux machine has the largest output power per volume. The power density of the proposed generator is 9.4 times larger than that of the commercialized one. The efficiencies of the proposed hybrid generator and a radial generator are same as each other, and are larger than those of an axial and the commercialized generators. [ABSTRACT FROM AUTHOR]

This paper presents performance improvements of a double excitation synchronous motor by using a reluctance network (RN). The distinguishing feature of the double excitation principle is to use permanent magnets with high energy, while air-gap flux is flexibly controlled by field windings. Therefore, the first contribution of this paper focuses on maximizing air-gap flux range control. Second, an approach for torque ripple reduction is proposed by directly modifying air-gap flux according to the instantaneous torque profile. The achieved resultant torque stays almost constant for a case study. The validity of the RN method is examined by comparisons with 3-D finite element and experimental results for several machines. [ABSTRACT FROM AUTHOR]

In this paper, a new field-modulated permanent magnet (FMPM) machine with an improved rotor is proposed and analyzed. The proposed FMPM machine enjoys the advantages of high PM utilization and better heat dissipation. For a fair comparison, the proposed FMPM machine is designed with the same geometrical parameters based on the existing FMPM machine. The electromagnetic performances of existing FMPM (E-FMPM) machine and proposed FMPM (P-FMPM) are compared and analyzed by using finite element method, verifying that the proposed FMPM machine with an improved rotor can obtain high torque density and high PM utilization. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical model for the prediction of air gap magnetic field distribution for axial flux permanent magnet (AFPM) machine with various types of misalignments. The AFPM machine geometry is first transformed to a polar representation. Consequently, the subdomain model based on current sheet technique is developed. Then the stator coordinate system is chosen as reference coordinate to consider both static/dynamic angular and axis misalignments. The back electromagnetic forces and cogging torque are obtained accordingly based on Maxwell's equations. The results show that the proposed approach agrees with the finite-element method. The model is further validated by experiments under healthy, dynamic angular and axis misalignment conditions, which can validate the proposed approach. It turns out that the proposed approach can predict the performance of AFPM machines with types of misalignment quickly and effectively, which is greatly significant for further fault detection. [ABSTRACT FROM AUTHOR]

This paper presents a fast analytical model for estimating the components of the PM flux density distribution in the air-gap for a number of interior permanent magnet synchronous machines (IPMSMs). Deriving the two-dimensional (2-D) analytical model for IPMSMs is more challenging compared to that of surface-mounted permanent magnet synchronous machines (SPMSMs) due to the inconsistent geometry of the rotor in polar coordinates. IPMSMs are usually modeled by using 0-D or 1-D methods such as the magnetic equivalent circuit (MEC); however, the MEC method is unable to take into account the tangential component of the magnetic flux density vector. In this paper, a 2-D analytical no-load electromagnetic model for five rotor topologies of IPMSMs is proposed. The effects of the stator slots on the radial component of the PM flux density distribution in the air-gap are then included by defining an air-gap function. The effects of the stator slots on the tangential components of the PM flux density distribution in the air-gap are also considered by injecting virtual surface currents (VSCs) or virtual permanent magnets (VPMs). For verification purposes, the analytical results are compared with those of the finite element method (FEM) and the experimental results of one of the cases. [ABSTRACT FROM AUTHOR]

The estimation of armature reaction is of great importance in the design and operation of synchronous machines. This paper proposes a new method to reduce quadrature armature reaction in salient-pole synchronous generators. The proposed method is to reduce the quadrature axis synchronous reactance of a salient-pole synchronous generator by novel flux barrier to the rotor poles. Finite element analysis by Maxwell software was used to evaluate the nonlinearity of the synchronous reactances and to obtain the result that the quadrature axis synchronous reactance decreases when the flux barrier is introduced into the rotor pole of a salient-pole synchronous generator. As part of the study, a new flux barrier was introduced and experimented on the rotor pole of a 50 kW, 4-pole salient-pole synchronous generator without damper winding used for diesel generator. [ABSTRACT FROM AUTHOR]

Interior permanent magnet (IPM) motors in traction applications often employ discrete rotor skewing constructions to reduce torsional excitations and back-EMF harmonics. Although skewing is very effective in reducing cogging torque, the impact on torque ripple is not well understood and can vary significantly over the operating envelope of a motor. Skewing also leads to the creation of a non-zero axial force that may compromise the bearing life if not considered. This paper introduces a holistic methodology for analyzing the effect of skewing, aiming to minimize torsional excitations, axial forces and back-EMF harmonics whilst mitigating the impact on performance and costs. Firstly, analytical models are employed for calculating cogging torque, torque ripple and axial forces. Then, 2D and 3D finite element analysis are used to incorporate the influence of non-linear material behavior. A detailed structural model of the powertrain is employed to calculate the radiated noise and identify key areas allowing a motor designer to reduce noise, vibration and harshness (NVH). A meticulous selection process for the skewing angle, the number of skew stacks and the orientation of skew stacks is developed, giving particular attention to the effect of the selected pattern on NVH in both forward and reverse rotating directions. [ABSTRACT FROM AUTHOR]

The dual-rotor system is the core component of advanced aero-engine. Establishing a reasonable, accurate, and efficient dynamics model is the key to studying the dynamics and vibration of the rotor system for aero-engine. This manuscript takes a representative aircraft engine dual-rotor system as a prototype, considers the rig-id-flexible coupling characteristics of different stiffness elastic supports and rotor structures, and establishes an analytical dynamic model of the dual-rotor system. Based on the established dynamic model, the natural char-acteristics of the dual-rotor system are analyzed. The model was validated using two different research methods: the rigid-flexible coupling multi-body system dynamics simulation platform ADAMS, and finite element analy-sis. The dynamic model of the dual-rotor system established in this paper can meet the requirements of hierar-chical rigid-flexible coupling of system and structure, overall mass distribution, and stiffness distribution. In particular, it can also effectively realize the simulation of multi-facet and multi-phase unbalanced vibration of the rotor system. The research methods of this paper can further enrich the basic theory of dynamics and vibration of the aero-engine rotor system. [ABSTRACT FROM AUTHOR]

This paper presents the performance analysis of a three-phase squirrel cage induction motor (SCIM) with a double–triple-layer (DTL) stator winding configuration operating with broken rotor bar (BRB) faults. The effects of BRB faults on the performance of specific parameters are analyzed under a steady-state regime. The SCIM is modeled using the two-dimensional finite element method (FEM) to study electromagnetic performance under healthy and BRB faulty conditions. To validate the finite element analysis (FEA) results, a prototype of an SCIM with a DTL stator winding configuration is tested for performance evaluation under healthy and BRB faulty conditions. The FEA and experimental (EXP) results of the SCIM with a DTL stator winding arrangement are compared with the results of the SCIM with a conventional double-layer (CDL) stator winding configuration. FEA and EXP results evidenced that the SCIM with a DTL stator winding configuration mitigates some of the adverse effects introduced by the BRB faults compared to the SCIM with a CDL stator winding of the exact specifications. Under loaded conditions, the SCIM with a DTL stator winding configuration reduced the magnitudes of the twice slip frequency sidebands caused by BRB faults from ±1.2 Hz for the SCIM with a CDL stator winding arrangement down to ±0.2 Hz and ±0.36 Hz when operating with 3BRB and 6BRB faults, respectively. The results also indicate that the SCIM with a DTL stator winding configuration has reduced the decibel sideband magnitude by 7.5 dB and 8 dB for unloaded and loaded conditions, respectively. This premise has positioned the SCIM with a DTL stator winding configuration as a strong candidate in applications where BRB faults are frequent, and the motor may be required to continue operating with a BRB fault until scheduled maintenance is in effect. [ABSTRACT FROM AUTHOR]

For the purpose of saving energy resources, it is extremely expected to develop highly efficient electric motors. Different types of permanent magnet (PM) arrangement can significantly affect the performance of the motors. Conventionally, the arrangement of the PMs is determined by designer’s experience. This paper focuses on the optimal design of PM arrangement in PM synchronous motors (PMSMs). We present a general pattern of the PM arrangement in PMSM. By varying the parameters of the general pattern, it can produce different types of PM arrangement in the rotor. The employed approach combines the global optimization method with the finite-element method for solving the optimization of the PM structures. Based on the proposed general pattern and optimization methods, the best PM arrangement in the motor can be automatically determined. In order to reduce computing loading, this paper employs the response surface models for reducing the computing time of objective functions. In the end, numerical tests are designed to showcase the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper puts forward the design and analysis of an ironless permanent magnet machine for a micro wind power application. The proposed methodology includes comprehensive geometric, magnetic, and electrical dimensioning followed by detailed 2-D finite-element modeling of a synchronous generator. The configuration investigated in this paper shows the generators rotor fixed in the tip of the blades and illustrates the advantages of a large diameter for a microgeneration application. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic thermal model which predicts the winding temperature of electrical machines at steady-state and transient conditions where windings are used in integrated battery chargers (IBCs) for DC charging in a stationary position. Using winding in high current charging process causes rising winding temperature which affects insulation life. Switched reluctance machines are a proper choice for using in electric vehicles (EVs) because of their advantages such as simple and sturdy structures. IBCs can reduce volume and weight of EVs and total cost is diminished because of integration. The analytical thermal model proposed in this paper can calculates the winding temperature in balanced and unbalanced currents injection because of the phase inductance in each rotor angle is distinct, so current excitation in each phase should be different for obtaining zero total torque and keeping rotor in a stationary position, also a reduced-order model is proposed with minor impact on the accuracy of the model. Special attention has been paid to monitor the winding temperature with considering the motor lifetime in DC charging mode, this view has not been addressed in IBCs before. The proposed model is then validated against experimental results and 3D finite element method. [ABSTRACT FROM AUTHOR]

In order to improve the reliability of the traditional doubly salient electro‐magnetic generators (DSEG) and realize the isolation of interphase magnetic circuit, a U‐shaped rotor stator excitation generator (UR‐SEG) for vehicle applications is proposed in this paper. The machine has the interphase physical isolation and short flux path structure because of the U‐shaped rotors. According to the theoretical analysis of the fault‐tolerant characteristics of this UR‐SEG, the characteristic of the phase electromotive force (EMF) of the UR‐SEG completely overlaps with the EMF of front and rear phase in the entire power generation stage is revealed. Then the flux linkage, EMF, output voltage of both normal and faulty states are comparative investigated using the two‐dimensional finite element method (FEM). The output characteristics of the normal state and four faulty states of the machine with different exciting currents are researched, and the influence rules of fault on output characteristics are obtained. Finally, the outstanding fault‐tolerant characteristics of the UR‐SEG were verified by the experimental results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Recently, dual-rotor motor (DRM) has emerged as an alternative for an induction motor (IM) or a permanent-magnet (PM) motor for electric vehicle application, due to its better drive performance and better torque density. This paper presents an analytical model for the hybrid IM-PM configuration of DRM. The analytical model can be used to predict induced bar currents, electromagnetic torque generated, and magnetic fields in various regions of the motor. The mentioned calculations are performed under steady-state conditions. The analytical method is developed using the subdomain model approach in 2-D polar coordinates. Appropriate governing equations along with boundary conditions across all the sub-domain regions of the DRM are employed to calculate the magnetic vector potential in all the regions. The developed analytical model has been validated with finite-element analysis for various operating conditions, and high accuracy has been achieved for all the results. [ABSTRACT FROM AUTHOR]

This paper presents the design of a switched reluctance machine (SRM) for off-road hybrid electric vehicle applications. SRMs are ideally suited for this application for their low cost, fault tolerance, and reliable operations. A multistage fast design methodology for SRM is presented in this paper. The process aims to determine the best speed at which the SRM would start single-pulse mode operation. This ensures the best efficiencies over the specified operating range. The machine is initially designed at that operating point using analytical design tools and then further optimized through finite-element analysis (FEA). The designed machine has been prototyped and then experimentally tested. [ABSTRACT FROM PUBLISHER]

Three-phase nonoverlapping stator wound-field synchronous (NSWFS) machines employing salient pole rotors are proposed in this paper. Based on the optimized design, the influence of rotor pole number on the proposed machine is investigated. According to 2-D finite-element analysis (FEA), it is found that the proposed machine shows higher torque density and lower torque ripple compared with the existing NSWFS machines. The operation principles of the proposed machine under different pole numbers are presented and compared in this paper. The FEA-predicted back electromotive force, cogging torque, and static torque of NSWFS machines are validated by experiments made on the prototypes. [ABSTRACT FROM AUTHOR]

This paper presents the harmonic torque reduction by the different rotor pole angles of a three-phase 12/8 switched reluctance motor via an analytical model and simulation method. Improving torque performance by stator and rotor angles was applied for three-phase switched reluctance motor at stator pole/rotor pole ratios of 6/4, 8/12, 18/12, and 24/18. The average torque and the torque ripple effect by stator and rotor pole embrace have been recently studied in many projects. Due to the fact that leakage flux, flux density, and inductance are affected by the stator and rotor pole angles non-linear and linear leakage flux curves occur. Many stator and rotor pole angle combinations for the three-phase switched reluctance motor have already been done via a finite element method. In this paper, turn-on and turnoff angles will be figured based on stator and rotor pole embraces. [ABSTRACT FROM AUTHOR]

A hybrid analytical and lumped-parameter thermal model is proposed in this paper to estimate the transient and steady-state two- and three-dimensional (2/3-D) spatial magnet temperature distributions for an interior permanent magnet synchronous machine (IPMSM). On the basis of a lumped-parameter thermal model (LPTM), the magnet analytical thermal models (ATMs) are synergized to establish the hybrid thermal model. By utilizing the transient or steady-state boundary conditions calculated by the LPTM, the ATMs are obtained by solving the heat conduction equations to estimate the spatial magnet temperature distributions in the 2-D horizontal-vertical and axial-vertical planes, which can also be extended to the 3-D temperature distribution by utilizing the multi-slice method. Meanwhile, the non-uniform magnet eddy current loss is also considered. Finally, both electromagnetic-thermal coupled finite element analysis method and experiments are used for verification based on a totally enclosed IPMSM. [ABSTRACT FROM AUTHOR]

The vibration characteristics of stator system of the interior permanent magnet synchronous motor for EV are deeply studied in this paper, the effectiveness of reducing the vibration by optimizing the vibro-inertance (acceleration admittance) of the stator system is validated. Firstly, the theory of the vibro-inertance matrix of stator system with single-point excitation and multi-point response is proposed, and the mathematical theory model of vibro-inertance matrix of prototype motor stator system is established. Secondly, a new method of 3D finite element method (FEM) be used to simulate and analysis the vibro-inertance's characteristics for the prototype's stator system. Then, the correctness of the theory and the FEM simulation is verified by the prototype source-path-contribution (SPC) experiment. And it is found that near some non-natural frequencies with large vibro-inertance amplitudes, although the amplitude of operating force is relatively small at these frequencies, the prototype still produces large vibrations. Finally, three methods for optimizing the vibro-inertance matrix of the stator system are further studied. These methods can effectively shift the inertance frequency band of the stator system and change the average value of the inertance's amplitude of the motor stator system in different frequency bands, thereby changing the vibration characteristics of the whole motor. [ABSTRACT FROM AUTHOR]

The electromagnetic structure of the resolvers makes them excellent for difficult applications. Among them, axial flux resolvers show better performance against mechanical faults. However, a complicated resolver-to-digital converter (RDC) overshadows the whole system's reliability. Both of the conventional software and hardware decoding methods suffer from deficiencies, such as difficulty to implement, poor performance against electromagnetic noise, expensive equipment, etc. To overcome these challenges any easy-to-implement software-based RDC is suggested in this paper that is used for rotational forth-and-back motions. In fact, instead of the conventional arc-tangent method to extract the position information from sine (SIN) and cosine (COS) signals, three transfer functions are proposed to estimate the position. Tylor's series are used to linearize the transfer functions over the zero position and a transfer function with minimum linearization error over the whole region is selected as opt one. The design process of axial flux resolvers is presented as well. 3-D time-stepping finite element method (FEM) is used to verify the success of the proposed analytical calculations. Finally, prototypes of the different configurations are tested for experimental measurements. [ABSTRACT FROM AUTHOR]

Integrated battery charging (IBC)—multiplexing the motor windings as line inductors for charging electric vehicle battery packs—can improve the onboard charging capability without increasing the weight and cost. However, during the charging operation, currents flowing in the stator winding definitely generate a magnetic field, which may demagnetize the permanent magnets (PMs) in the PM traction motors. In this paper, the demagnetization effects of IBC current on magnets in interior PM machines are compressively investigated. In this paper, a recursive algorithm to update the PM magnetization states by using a parallelogram hysteresis model at different demagnetization levels is applied. The PM temperature is also considered for establishing this model. By coupling this algorithm to the finite element analysis, the demagnetization transit at different demagnetization levels can be assessed. By decomposing the flux density of each node within the magnets along its magnetization direction, irreversible demagnetization can be accurately evaluated. Impacts from both the pulsating and rotating demagnetization magnetic fields during the IBC operation are assessed and compared. [ABSTRACT FROM AUTHOR]

A novel partitioned-primary hybrid-excited flux-switching linear machine with dual-PM excitation (DP-PPHEFSLM) is proposed and investigated in this paper. Unlike conventional single-primary hybrid-excited topologies, this proposed topology separates armature windings and field windings into two different parts of the partitioned-primary, with each part also having sandwiched or buried PMs. Due to greatly increased armature and field slot areas, it thus solves the problem of a crowded primary, which is typically encountered with conventional structures. Besides, the thrust density is further increased by skillfully positioning PMs on both primary parts. In this paper, first, the topology, operation principles, and viable primary/secondary pole-number combinations of the proposed machine are elaborately addressed. Based on 2D finite-element method (FEM), the proposed machines are globally optimized using genetic algorithms and their electromagnetic performances further investigated. Moreover, the proposed machine is compared with conventional topologies in terms of electromagnetic performances, which shows that the proposed machine exhibits multiple merits such as higher thrust density, improved space utilization, and more flexible flux control capability. Finally, a 6/7 DP-PPHEFSLM prototype machine is manufactured and tested to validate the 2D FEM-predicted results. [ABSTRACT FROM AUTHOR]

Fractional-slot concentrated-winding (FSCW) interior permanent magnet synchronous motors (IPMSMs) have been attracting considerable attention due to their high power density, high efficiency, short end winding, high slot fill factor, low cogging torque, excellent flux-weakening, and fault tolerance capability. However, compared to integral-slot distributed-winding (ISDW) IPMSMs, the key challenge of using FSCW configurations is the significant rotor losses, particularly at high speed. To figure out the IPMSM with which winding configuration is more suitable for electric vehicle (EV) application, the thermal behaviors of four IPMSMs with ISDW, single-, double-, and four-layer FSCWs are comprehensively and comparatively investigated in this paper. First, electromagnetic design and loss analysis of the four IPMSMs are investigated to meet the EV traction motor requirements. Second, finite-element method is employed to investigate the thermal performance of the IPMSMs under different rotational speeds and torque overload capacities. Thirdly, experiments implemented on an ISDW prototype are carried out to validate the presented analysis method. Finally, some conclusions are drawn for a suitable winding configuration selection and the PM traction motor design. [ABSTRACT FROM AUTHOR]

Rotary-linear switched reluctance motors (RLSRMs) have been introduced to realize simultaneous rotary and linear motions in one structure. This paper proposes the modeling of RLSRM in two manners: analytical and finite-element methods. In the first approach, a model is proposed based on position-wise functions which describe the governing equations of the motor. The derived equations are utilized in a block diagram to comprise the model. In the second approach, static FEA is utilized to improve the former model by obtaining the inductance profile of the motor. The models separate the rotary motion from the linear motion in order to calculate the torque and force. The analytical model is faster than the FEA-based model because of the independency to FEA. However, it is less accurate. The FEA-based model needs prior static FEA and considers the fringing and saturation effects more accurately. The FEA-based model is computationally more efficient than the 3-D transient FEA. The motor’s performance parameters obtained via the models versus the 3-D transient FEA as well as the experimental test results indicate the accuracy and efficiency of the proposed models. [ABSTRACT FROM AUTHOR]

In this paper, an investigation into an alternative topology for reluctance synchronous machine rotor flux barriers is presented. The investigated topology employs a high number of flux barrier variables with an alternative asymmetric rotor structure. The focus in this paper is on maximizing average torque and minimizing torque ripple, using finite element-based design optimization, in order to study the possibility of achieving acceptably low torque ripple. A subsequent investigation into the effect of rotor skew on the proposed optimized design to reduce torque ripple even further is also conducted, as well as the manufacturing and testing of the proposed flux barrier prototype. [ABSTRACT FROM PUBLISHER]

This paper investigates the partial irreversible demagnetization characteristics of magnets in flux-switching permanent magnet (FSPM) machines. Two different partial demagnetization mechanisms in the FSPM machines are modeled and demonstrated. The 2-D finite-element analysis (FEA) results for a baseline 10 kW 15 kr/min ferrite FSPM machine verify the validity of the proposed partial demagnetization model. Performance degradation due to demagnetization is evaluated for the baseline machine based on the FEA results. This paper also proposes a novel design to enhance the demagnetization withstand capability. This research reveals the most vulnerable region of the magnet to irreversible demagnetization in the FSPM machines. It also provides a guideline for developing demagnetization withstand capability improvement techniques. [ABSTRACT FROM PUBLISHER]

This paper presents a novel flux-modulated type dual-axis motor that has two mechanical inputs/outputs, since it consists of a stator, a permanent magnet rotor, and a modulating rotor. Furthermore, since the dual-axis motor has a function the same as a planetary type magnetic gear, it can transmit torque with arbitrary gear ratio and divide mechanical input/output into two rotors without any mechanical contact. In this paper, first, conventional and proposed flux-modulated type dual-axis motors are optimized and compared using finite-element analysis. Next, the proposed dual-axis motor is prototyped and demonstrates the validity and availability by experiment. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid excitation vernier permanent magnet machine (HE-VPM). The characteristics of the proposed machine are: 1) the PMs are embedded in the stator teeth, which is helpful for the heat dissipation; 2) the rotor is salient structure without PMs and windings, which ensures the reliability of high-speed operation; 3) the nonoverlapping concentrated winding shortens the end-connection, and improves the torque density, 4) only half of the stator teeth possess PMs, and the total amount of PMs are decreased; and 5) the dc current are injected to the armature coils, therefore, the exciting field can be adjusted flexibly. In this paper, the electromagnetic performance, including back electromotive force, torque, etc. are analyzed with finite element analysis. The results show that the proposed machine exhibits flexible field adjustment capability, which may be suitable for applications requiring wide speed range operation. Besides, it is found that, compared with the existing pure sinusoidal phase current, higher torque density can be obtained with dc-biased phase current under constant stator copper loss. [ABSTRACT FROM AUTHOR]

Coreless axial flux machines are of interest because of the absence of stator core losses and cogging torque. These machines generally employ concentrated windings. One of the challenges with such a winding is that the torque producing MMF component that corresponds to the fundamental of the magnet excitation is accompanied by substantial asynchronous components. These harmonics cause losses in the rotor core and magnets, which can become significant at high speeds. This paper proposes a new multilayer winding arrangement to eliminate the non-torque producing MMF components. This winding is applied to a 12-coil 16-pole coreless axial flux machine. The efficacy of the winding is established by 3-D finite-element analysis. [ABSTRACT FROM AUTHOR]

This paper presents work completed in order to investigate the importance of magnetic shunts in transverse flux machines. Two types of transverse flux machines with different configurations were designed and tested in the laboratory. The first type of machine is a transverse flux generator with inner rotor. This machine was designed according to one of the patents. The second type of the machine is a transfer flux generator with double coil. Both types of the generators were designed in such a way so that it was possible to implement magnetic shunts inside the machines. Finite-element method analysis and experimental results showed that transverse flux machines without magnetic shunts had a number of disadvantages compared to those with magnetic shunts. These disadvantages are: higher flux leakage in the stator cores, partial cancelation of flux linkage in the coils, higher cogging torque, and increased torque ripple. This paper showed that magnetic shunts played a significant role in the performance of transverse flux machines. As study showed, magnetic shunts complicate a manufacturing process and increase the weight of the machine. However, power to weight ratio of the machines with magnetic shunts is higher than that of the machines without magnetic shunts. [ABSTRACT FROM AUTHOR]

A dynamic rotor interturn short circuit fault may occur during synchronous generator operation. However, there is no method to analyze the generator's characteristics under the dynamic rotor interturn short circuit fault and identify the fault. In order to solve this problem, a new dynamic rotor interturn short circuit fault analysis model is creatively proposed through mathematical derivation. Firstly, the rotor vibration characteristics and the mechanical response under magnetic pull excitation are theoretically analyzed. In addition, a finite element modeling method for the dynamic rotor interturn short circuit fault is proposed, and an experimental device is designed. The model of a synchronous generator under the dynamic rotor interturn short circuit fault is established to obtain the rotor's unbalanced magnetic pulls and mechanical responses by finite element calculation. Finally, the rotor vibrations are tested on a CS-5 prototype generator. The validity of the model is verified by finite element calculation and an experiment. This paper provides theoretical support for the diagnosis of a synchronous generator's dynamic rotor interturn short circuit fault. [ABSTRACT FROM AUTHOR]