Design Of Permanent Magnet Machine Research Articles

Design and Analysis of Permanent Magnet Machines With Multiple Arc Pole Ratios in Stator Teeth

Design and Analysis of Permanent Magnet Machines With Multiple Arc Pole Ratios in Stator Teeth

Optimal Design of a Surface Permanent Magnet Machine for Electric Power Steering Systems in Electric Vehicle Applications Using a Gaussian Process-Based Approach

The efficient design optimization of electric machines for electric power steering (EPS) applications poses challenges in meeting demanding performance criteria, including high power density, efficiency, and low vibration. Traditional optimization approaches often fail to find a global solution or suffer from excessive computation time. In response to the limitations of traditional approaches, this paper introduces a novel methodology by incorporating a Gaussian process-based adaptive sampling technique into a surrogate-assisted optimization process using a metaheuristic algorithm. Validation on a 72-slot/8-pole interior permanent magnet (IPM) machine demonstrates the superiority of the proposed approach, showcasing improved exploitation–exploration balance, faster convergence, and enhanced repeatability compared to conventional optimization methods. The proposed design process is then applied to two surface PM (SPM) machine configurations with 9-slot/6-pole and 12-slot/10-pole combinations for EPS applications. The results indicate that the 12-slot/10-pole SPM design surpasses the alternative design in torque density, efficiency, cogging torque, torque ripple, and manufacturability.

Design and Analysis of a Novel Six-Phase Axial Switched-Flux Permanent Magnet Machine With Different Winding Configuration

In this paper, a novel six-phase axial switched-flux permanent magnet (PM) machine with stator-PM is proposed and designed. The topology and operating principle are analyzed in detail. Two different winding configurations, which are called the symmetric double-three-phase and asymmetric double-three-phase, are presented and studied. The electromagnetic performance of the machine with two winding configurations, including flux-linkage, back electromotive force, inductance, torque characteristics, and so on, is investigated. The behavior of the machine under the healthy and faulty conditions is analyzed and the fault-tolerant performance is researched. The prototype is manufactured and the experimental results are consistent with that of the finite element analysis. The results demonstrate that the performance of the machine with two winding configurations is excellent. The machine with asymmetric double-three-phase winding configuration has high quality PM flux-linkage and back-EMF, low cogging torque and torque ripple, and strong fault-tolerant capability. The machine with symmetric double-three-phase winding configuration has large torque capacity.

An efficient multi-objective optimization strategy for Halbach array permanent magnet synchronous machines based on nonlinear semi-analytical model

In this article, an efficient multi-objective optimization strategy for the Halbach array permanent magnet synchronous machine (PMSM) is developed by taking into consideration the nonlinear B-H behavior of soft magnetic materials. Based on the harmonic modeling (HM) technology, the electromagnetic performances (EPs) of the Halbach array PMSM can be computed. To specifically model the local magnetic saturation, the stator teeth are separated into several annular layers, and each tooth is further divided into several regions along the tangential direction. Then, the parameters of the Halbach array PMSM are optimized utilizing combined nonlinear semi-analytical model (SAM) and non-dominated sorting genetic algorithm II (NSGA-II). To validate the effectiveness and accuracy of the developed optimization scheme, a Halbach array prototype is then manufactured in accordance with the optimization results. The multi-objective rapid optimization strategy developed in this article, which includes but is not limited to Halbach array permanent magnet (PM) machines, serves as a reference for the design and optimization of various PM machines.

Electric Machine Design by a Novel Fast Model Predictive Optimization Strategy Treating Dimension-Expensive Problem

As a crucial preprocessing for motor products, design optimization methodologies have been widely explored. However, existing studies always indicate some issues. Analytical model-based optimization involves complex mechanisms. The surrogate-based optimization can hardly satisfy the accuracy of multiple objectives or in scenarios with high dimensions. The numerical tool-based optimization is time-consuming even with the multi-level technique. Accordingly, a novel fast model predictive optimization (MPO) strategy is proposed. It follows a parametric analysis stage to quantify the intrinsic mechanisms between variable-objective pairs. The space-filling sampling technique and parameter correlation are applied. By searching in a library of machine learning algorithms, MPO constructs a trustable model with only limited case evaluations. To treat the objectives with different sensitivities, the proposed MPO strategy learns the algorithms, hyperparameters, and parameters. A novel ranking regularization is introduced to the ordinary loss function for examining the model accuracy or validity. Hence, finite element analysis can be avoided in the subsequent optimization. After performing the sensitivity analysis, the optimal design of permanent magnet machine is prototyped and tested to verify the proposed design methodology. In short, MPO finds a more complete Pareto frontier more efficiently than the FEA-based optimization.

Novel Multiphysics Design Methodology for Coreless Axial Flux Permanent Magnet Machines

This work is devoted to multiphysics design of coreless axial flux permanent magnet machines with concentrated coils. Recently, these machines have been proposed for the propulsion of civil miniature electric unmanned aerial vehicles, which need very high torque and power densities. Such requirements tend to be in contrast with other important features such as high efficiency and resilience, making the design quite challenging. Among the various geometrical parameters, the rotor poles to stator coils ratio plays a key role in their performance. The main contribution of this paper is the development of an original design method hinging upon the said ratio. The 2D electromagnetic model at the heart of the approach is derived at the average radius and accounts for multi-layer and axially thick stator coils. Additional contributions include the concurrent use of thermal modelling in the preliminary design stage and mechanical analyses in the design refinement stage aimed at optimizing torque density and guaranteeing rotor integrity at maximum speed. Comprehensive experimental tests on a full-scale prototype are reported and help build confidence in the proposed methodology.

An In-Phase Unit Slot-Opening Shift Method for Cogging Torque Reduction in Interior Permanent Magnet Machine

The cogging torque reduction methods in permanent magnet (PM) machines are more or less FEA trial and error-based and cause undesirable side effects, such as distorted back EMF, new harmonic components, and structure asymmetry. A slot-opening grouping method can address these issues. However, it needs to model all slots in FEA design validation during practical cogging torque optimization iterations, and also leads to back-EMF reduction. In this paper, a new grouping strategy, termed in-phase unit (IPU), is introduced, together with the slot-opening angle-shift method. The slot openings with the same cogging torque distribution pattern are grouped into an IPU, and the cogging torque peaks of the slot openings within an IPU can now be interleaved. Thereby, the major harmonic components of the cogging torque are cancelled out, instead of being summed up. The IPU grouping principle, the slot-opening shift angle computation, and the selection of the harmonic order to cancel are analyzed in detail. By comparison, the proposed method not only simplifies cogging torque optimization iterations by only modeling the slots in one IPU in FEA, but also compensates for the back-EMF constant reduction. The effectiveness of the proposed methods is validated by two typical interior PM machine design cases.

Design and Analysis of a Novel High-Speed Permanent Magnet Machine With Dual Semi-Cage Winding

This article proposes a novel high-speed permanent magnet synchronous machine (HSPMSM) topology. The characteristics of the proposed machine are: 1) The stator winding is divided into two parts and each part is connected by the end ring at one end, which is helpful to solve the existing shortage of overlong end length in traditional HSPMSM. 2) The stator of the machine is designed with closed slot, which can greatly weaken the eddy current loss and the cogging torque of the machine. 3) The machine is driven by two separate three phase converter, which can improve the fault tolerance. In this article, the topology, and the corresponding control system is analyzed firstly. After that the electromagnetic performance, including back electromotive force, cogging torque, torque, etc. are analyzed with finite element analysis (FEA). In addition, the losses, including the stator copper loss, the stator iron loss and the eddy current loss of the permanent magnet and sleeve of the rotor, are calculated by FEA. The mechanical strength and dynamic performance of rotor is also checked. Finally, a prototype was designed and manufactured. The experimental results the validity of the topology.

Design and analysis of a new field-modulated permanent magnet machine with an improved rotor

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.

Flux-Leakage Design Principle and Multiple-Operating Conditions Modeling of Flux Leakage Controllable PM Machine Considering Driving Cycles

This article reveals the flux leakage design and modeling principle of a flux leakage controllable permanent magnet (FLC-PM) machine by considering driving cycles. The key is to obtain the relationship between flux leakage characteristics and multiple operating conditions. Based on the flux leakage controllable concept, an FLC-PM machine with an artfully designed flux leakage region is proposed. The design principle of the machine is investigated by analyzing the magnetic circuit of the machine in multiple operating conditions. The flux leakage factor is introduced to characterize the variable magnetic field in multiple operating conditions. On this basis, the mathematical model of the FLC-PM machine is deduced, and the driving characteristics of the machine are studied in detail. In order to evaluate the presented principle of the FLC-PM machine, a prototype is manufactured for experiments. Through the theoretical analysis and experimental testing, it is verified that the proposed principle is feasible and effective.

Design and Optimization Technologies of Permanent Magnet Machines and Drive Systems Based on Digital Twin Model

One of the keys to the success of the fourth industrial revolution (Industry 4.0) is to empower machinery with cyber–physical systems connectivity. The digital twin (DT) offers a promising solution to tackle the challenges for realizing digital and smart manufacturing which has been successfully projected in many scenes. Electrical machines and drive systems, as the core power providers in many appliances and industrial equipment, are supposed to be reinforced on the verge of Industry 4.0 in the fields of design optimization, fault prognostic and coordinated control. Therefore, this paper aims to investigate the DT modelling method and the applications in electrical drive systems. Firstly, taking the high-speed permanent-magnet machine drive system as an example, multi-disciplinary design fundamentals and technologies, aiming at building initial mechanism and simulation models, are reviewed. The state-of-the-art of DT technologies is figured out to serve for high-precision and multi-scale dynamic modelling, by which a framework for DT models of electrical drive systems is presented. More importantly, fault diagnosis and optimization strategies of electrical drive systems in the decision and application layer are also discussed for the DT models, followed by the conclusions presenting open questions and possible directions.

Analytical Design and Optimization of Axial Flux Permanent Magnet Machines With Slotless Structure

The three-dimensional (3-D) finite element (FE) analysis is an extremely time-consuming task in the design and optimization of axial flux permanent magnet (AFPM) machines. The aim of this article is to present a fast and accurate design model of slotless AFPM machines. Thanks to the separation of active- and end-winding parts, the overhang structure, which has widely been used in the air gap winding, can be handled by the proposed method. The winding eddy current loss, a primary source of losses in the air-core structure, is incorporated into the analytical model. In addition to the high accuracy, this approach makes it possible to evaluate machine performances only once without needing to rotate the rotor position. As a result, the proposed analytical model can significantly reduce the computational time, preferred in applying an optimization algorithm. Finally, the accuracy of the proposed method is verified by both FE and experimental results.

Design and Performance Analysis of Axial Flux Permanent Magnet Machines with Double-Stator Dislocation Using a Combined Wye-Delta Connection

Conventional fractional slot concentrated winding three-phase axial flux permanent magnet machines have an abundance of armature reaction magnetic field harmonics which deteriorate the torque performance of the machine. This paper presents a double-stator dislocated axial flux permanent magnet machine with combined wye-delta winding. A wye-delta (Y-△) winding connection method is designed to eliminate the 6th ripple torque generated by air gap magnetic field harmonics. Then, the accurate subdomain method is adopted to acquire the no-load and armature magnetic fields of the machine, respectively, and the magnetic field harmonics and torque performance of the designed machine are analyzed. Finally, a 6kW, 4000r/min, 18-slot/16-pole axial flux permanent magnet machine is designed. The finite element simulation results show that the proposed machine can effectively eliminate the 6th ripple torque and greatly reduce the torque ripple while the average torque is essentially identical to that of the conventional three-phase machines with wye-winding connection.

An overview of thermal modelling techniques for permanent magnet machines

Permanent magnet (PM) machines have gained increasing attention from the industry because of their potential merits over conventional electrical machines. High-temperature level in electrical machines is a major factor that can adversely impact the performance and health conditions of these machines. These effects need to be minimized to make them competitive with currently operational machines in the industry. It can be done by performing a thorough thermal analysis of the prototype during the design process and proper online thermal monitoring of the machine during the operation stage. Thermal modelling is a powerful tool for achieving such goals in both cases. This paper aims to review the state-of-the-art of thermal modelling techniques and provide a detailed comparison of them in PM machines. The fundamental concepts of heat transfer and sources of heat in PM machines are first discussed. Then, different thermal modelling techniques, including thermal subdomain models (TSMs), lumped parameter thermal networks (LPTNs), finite element models (FEMs), computational fluid dynamics (CFD), reduced order models (ROMs), and hybrid thermal models (HTMs) are introduced and compared. Finally, the utilization of these models in the thermal design, control, and monitoring of PM machines is studied.

Low electromagnetic vibration design of double-layer interior permanent magnet machines for electric vehicle

Electromagnetic vibration and noise of driving motor affect the comfort for electric vehicles. Considering low harmonic component and pole design flexibility of double-layer interior permanent magnet (IPM) machines, in this paper, an improved analytical method of no-load air gap flux density for double-layer IPM machines is introduced, and the harmonic spectrum of electromagnetic force is analyzed. A commercial double-layer IPM machine is taken as benchmark, the electromagnetic–structure–sound coupling model is established. The main spatial and temporal order of electromagnetic force for benchmark motor is indicated. Based on this analytical model, a method to minimize the electromagnetic force of specific harmonic component is proposed to reduce electromagnetic vibration and noise, by optimizing parameters of double-layer IPM machine rotor pole without impairing the motor performance. The vibration and noise of the optimized motor under working condition and no-load are compared with the results of the benchmark motor by multi-physics simulation, and validate the proposed optimization approach.

Multi-objective optimization design of inset-surface permanent magnet machine considering deterministic and robust performances

The inset-surface permanent magnet (ISPM) machine can achieve the desired electromagnetic performance according to the traditional deterministic design. However, the reliability and quality of the machine may be affected by the essential manufacturing tolerances and unavoidable noise factors in mass production. To address this weakness, a comprehensive multi-objective optimization design method is proposed, in which robust optimization is performed after the deterministic design. The response surface method is first adopted to establish the optimization objective equation. Afterward, the sample points are obtained via Monte Carlo simulation considering the design-variable uncertainty. The Design for Six Sigma approach is adopted to ensure the robustness of the design model. Furthermore, the barebones multi-objective particle swarm optimization algorithm is used to obtain a compromise solution. A prototype is manufactured to evaluate the effectiveness of the proposed method. According to the finite-element analysis and experimental tests, the electromagnetic performance and reliability of the machine are significantly enhanced with the proposed method.

Fast model-based design of high performance permanent magnet machine for next generation electric propulsion for urban aerial vehicle application

Model order reduction (MOR) is considered as a good alternative to reduce the computational scale for electro-magnetic problems. The aim of this work is to introduce the use of dynamic mode decomposition (DMD) as a promising tool for MOR to analyze its effectiveness in creating a fast model-based design platform for the permanent magnet motor design for ur-ban aerial vehicles (UAVs). Using a singular value decomposition (SVD) based DMD, the design process is constructed and verified against different scenarios.

Design and Analysis of Fractional Pole-Pair Linear Permanent Magnet Machine

A novel concept of fractional pole-pair linear permanent magnet machine (FP-LPM) has been proposed recently. It is found that using fractional pole-pair number in linear permanent magnet machine(LPM) could effectively reduce slot cogging force as well as back EMF unbalance. Thus thrust ripple is curtailed which improves its thrust quality and enhances its application potential. However, some issues of FP-LPM still remain unsolved, such as phase split, current phase adjustment, plus structure optimization is different from the traditional topology due to extra auxiliary tooth, etc. This paper contributes to giving a detailed designing methodology including winding arrangement, regulations of choosing slot/pole combination and effective end optimization method of FP-LPM. Thus, this paper can give helpful guidance in designing FP-LPM to satisfy different application demands. Finally, an 18slots/29poles fractional pole-pair linear permanent magnet vernier machine (FP-LPMVM) is designed and constructed using the proposed method and the test results verifies the research conclusions.

High-Frequency Core Loss Analysis of High-Speed Flux-Switching Permanent Magnet Machines

Accurate prediction of core losses plays an important role in the design and analysis of flux-switching permanent magnet (FSPM) machines, especially during high-speed and high-frequency operation. Firstly, based on the numerical method, a high-frequency core loss prediction method considering a DC-bias magnetization component and local hysteresis loops as well as the harmonic effect is proposed. Secondly, the magnetizing characteristics of the silicon steel sheet and, consequently, the core loss of the electrical steel used as the core lamination are measured. Then, the loss coefficient of each core loss component is obtained by the data fitting tool. Based on the proposed method, the stator and rotor core losses of a three-phase, 12-stator-slot, and 10-rotor-pole (12/10) FSPM machine with different soft iron materials and driving modes are calculated. Finally, the results of the numerical method are verified by conventional finite element analysis.

Design and Performance Analysis of a Novel Outer-Rotor Consequent Pole Permanent Magnet Machine With H-Type Modular Stator

In this paper a novel outer-rotor consequent pole permanent magnet machine (OR-CPPMM) with H-type modular stator core is proposed for higher average torque ( $T_{avg}$ ), flux linkage ( $\Phi$ ) and efficiency ( $\eta$ ) whereas low cogging torque ( $T_{cog}$ ), torque ripple ( $T_{rip}$ ) and harmonics content in flux linkage ( $\Phi _{THD}$ ) and back-EMF ( ${\mathrm {EMF}}_{THD}$ ). The proposed OR-CPPMM is investigated with different stator flux gaps width for static and dynamics electromagnetic performances. Analysis reveals that flux gaps in H-type stator core not only improve electromagnetic performance i.e., $\Phi $ is enhanced by 10.23%, $\Phi _{THD}$ is suppressed by 80.65%, diminished ${\mathrm {EMF}}_{THD}$ by 59.37%, truncate $T_{rip}$ by 44.37% and improve $T_{avg}$ by 15.99% but also exhibits better flux focusing effect to enhance flux linkage and diminish harmonic contents. In addition, H-type modular stator structure provide physical isolation of adjacent phase that de-couple the adjacent phase coupling flux which enhance self-inductance and weaken mutual-inductance and hence improve fault tolerant capability. In addition, to elaborate effectiveness of the proposed design and justification of OR-CPPMM novelty with H-type modular stator, electromagnetic performance is extensively compared with existing state of the art including E-core and C-core structure. Analysis and comparison with state-of-the-art reveals that proposed OR-CPPMM enhanced $\Phi $ by 65.35%, diminish $\Phi _{THD}$ by 67.24%, truncate $T_{cog}$ by 96.72%, suppresses ${EMF}_{THD}$ by 44.40%, diminish $T_{rip}$ by 77.23% whereas $T_{avg}$ is enhanced by 91.69%. Furthermore, the proposed design novelty is justified with comparison of OR-CPPMM with inner rotor and dual rotor permanent magnet flux switching machines. Comparison and analysis unveil that OR-CPPMM exhibits $T_{avg}$ higher up to 35.16%, truncate $T_{rip}$ up to 32.88%, enhanced $\Phi $ up to 22.13% and boost $T_{den}$ to 3.41 times at the cost of 2.58% increase in $T_{rip}$ .