Search Results (417)

To further satisfy the extreme operating conditions of electric tractors, a pole-changing double-sided excitation permanent magnet vernier motor (PC-DPMVM) is proposed evolving from the existing PC-SPMVM in this paper. Half of the rotor PMs are transferred to the stator small slots, while a consequent-pole rotor structure and stator PM structure can be obtained. Firstly, the simulation and experiments of the existing PC-SPMVM are introduced, which shows the deficiency of the maximum torque output. Then, the evolution process of the proposed PC-DPMVM is illustrated. The rotor modulation and stator modulation behaviors of the PC-DPMVM are introduced based on airgap field modulation theory. The main working PM flux density harmonics are deduced further. Next, electromagnetic performance comparisons are made between two PC-PMVMs by using finite element method, and the results reveal that the proposed PC-DPMVM has superior torque output compared with the PC-SPMVM, while the speed regulation abilities of the two motors are similar. It can be concluded that two extra operation regions can be obtained for the PC-DPMVM according to the comparison of torque-speed curve of the two motors. Full article

The paper presents the development of analytical and finite element models, focusing on both magnetostatics and thermal solutions, of axial classical and hybrid active magnetic bearings (AMBs). An improved hybrid axial AMB design is proposed, combining permanent magnets and an electromagnet, where the bias magnetic flux is provided by the permanent magnets. This configuration significantly reduces the power consumption and heat generation. Numerical modeling is conducted using 2D magnetostatic and both 2D and 3D thermal finite element analysis. The study focuses on the system’s mass reduction, electrical power consumption, and heat flow output while maintaining the bearing’s load capacity. Digital control systems and algorithms have been developed and fabricated for both axial classical and hybrid axial AMBs, using an ESP32 microcontroller. Two experimental setups have been designed, fabricated, and tested. Full article

It is well-established in the literature that surface-mounted permanent-magnet synchronous motors (SPMSMs) have a high torque density due to an elevated interaction between magnetic flux and windings. For this reason, SPMSMs are extensively studied. This paper investigated the mechanical interactions and strains that develop in the main components of the rotor of an SPMSM, with particular focus on the behavior of the adhesive layer used for magnet bonding. An iterative methodology was proposed to improve both the amount and distribution of the adhesive to reduce stress, from 182 to 9 MPa, and deformation, from 0.182 to 0.008 mm, in critical components such as permanent magnets (PMs). SPMSM rotors are particularly sensitive to centrifugal forces, which tend to expel the PMs radially toward the stator. This effect leads to deformations in the rotor, PMs, and adhesive layer, resulting in a reduction of 16% from the original airgap without adhesive and in the generation of stresses that must remain within acceptable limits, stresses which go beyond 170 MPa in the layout without adhesive. Several fastening configurations of the PMs were analyzed, each incorporating a mechanical retaining element, primarily for safety purposes, combined with different adhesive distribution strategies. Full article

An efficient and reliable heat dissipation system is essential for the safe and stable operation of high-power water-cooled couplers. However, thermal analysis methods accounting for the centrifugal effects on coolant flow remain limited. This paper presents a high-accuracy equivalent thermal network model (ETNM) for analyzing the temperature distribution in water-cooled permanent magnet couplers (WPMCs), based on fluid–structure interaction and rotational centrifugal flow-field inversion. First, the ETNM is established based on key assumptions. Subsequently, an eddy current loss calculation method based on permanent magnet mapping is proposed to accurately determine the heat source distribution. The convective heat transfer coefficient of the coolant is then precisely derived by inverting the flow field obtained from fluid–structure coupling simulations under rotational centrifugal conditions. Finally, the model is applied for temperature analysis, and its accuracy is verified through both finite element simulations and experimental tests. The calculated results show errors of only 3.2% compared to numerical simulation and 5.6% compared to experimental data, indicating strong agreement of the proposed thermal analysis method. The accuracy of copper conductor (CC) temperature prediction is improved by 32.73%, and that of permanent magnet (PM) prediction by 33.33%. Furthermore, this method enables accurate estimation of individual component temperatures, effectively preventing operational failures such as PM demagnetization, CC softening, and severe vibrations caused by overheating. Full article

During the launch phase of a carrier rocket, the spacecraft carried by the rocket will be subjected to strong vibrations from the rocket body. Therefore, based on the special working conditions during the rocket launch phase, a passive-tuned magnetorheological (PT-MR) damper using the magnetorheological (MR) composite was proposed, which achieves stable and efficient operational performance using permanent magnets (PMs). Firstly, the influence of squeeze mode on the performances of the MR composite was analyzed for different vibration conditions. Then, by analyzing the squeeze strengthening effect of the MR composite and the influence of non-uniform radial gap size on the damping force, the mechanical model of the proposed damper was derived. Furthermore, the damper prototype was fabricated and its mechanical properties were tested, and the test results showed that the proposed damper can generate a damping force exceeding 800 N. Finally, the vibration isolation effectiveness of the proposed damper was verified from a system perspective by building the simulation model of whole-spacecraft vibration isolation. Full article

In this paper, the effect of eddy-current losses of permanent magnets (PMs) is studied by conducting analyses and experiments. PM segmentation is used to reduce eddy-current losses. Nowadays, many researchers are focusing on improving the efficiency and torque of permanent magnet synchronous motors (PMSMs), particularly in electric vehicle applications. This study evaluates PM eddy-current losses of an in-wheel-type PMSM designed for light electric vehicle (LEV) propulsion. Improving output torque and efficiency is essential in this type of direct-drive application. The eddy-current losses of PMs can be reduced by forming PMs as electrically isolated magnet segments. PM segmentation leads to shorter paths and reduces the values of eddy-currents, creating reduced magnetic losses. The improvement in torque production capability also implies an improvement in efficiency. To investigate the validity of PM segmentation, a three-dimensional (3D) finite element analysis (FEA) software is used for non-segmented (monolithic) and segmented cases. The experimental study is conducted using monolithic PM and segmented PM rotor assemblies. This study demonstrates the contribution of PM segmentation to torque production. Full article

Presented here is a 2-D analytical model for predicting the magnetic field distribution in a surface-mounted permanent magnet (SPM) rotor with multi-layered segmented permanent magnets (PMs). Each layer is treated independently, enabling the linear superposition of magnetic fields across all layers. The model employs subdomain modeling combined with the separation of variables, with the magnetic vector potential expressed as a Fourier series to derive the airgap magnetic field. The formulation is generalizable to five regions in each layer: outer airgap, optional outer inactive magnetic layer, active magnetic layer(s), optional inner inactive magnetic layer, and inner airgap. Validation against finite element analysis (FEA) shows a prediction difference of around 0.5% in airgap flux density. The model’s design utility is demonstrated through a genetic algorithm (GA) optimization, which maximizes static flux linkage and confirms performance improvements from the multi-layered configuration. Full article

This paper presents a novel Sensitivity-Guided Two-Stage Optimization (SGTSO) framework for magnetic gear (MG) design, introducing two fundamental methodological advances: (1) the adoption of global Sobol sensitivity analysis, which transcends conventional local sensitivity techniques by holistically quantifying both individual parameter effects and the interactions across the complete design space, and (2) the establishment of a mathematically guaranteed convergent two-stage optimization methodology that strategically decomposes high-dimensional problems into sequential subproblems. Unlike traditional one-factor-at-a-time sensitivity approaches that overlook parameter interdependencies, Sobol indices deliver quantitative evaluation of individual parameter contributions and coupling effects. The two-stage optimization architecture is rigorously proven to converge to near-optimal solutions under weak parameter coupling assumptions, with mathematically derived error bounds The optimized configuration achieves remarkable performance features: 65.4% suppression of inner rotor torque ripple, 27.2% reduction in outer rotor torque ripple, and 19.2% decrease in Permanent Magnet (PM) utilization, while preserving average torque output within a marginal 4.03% reduction. The proposed framework achieves a 5.25-fold enhancement in computational efficiency while maintaining mathematical convergence assurance, marking a substantial progression beyond conventional heuristic optimization paradigms. Full article

This article presents a multiphysics simulation methodology to predict the temperature-dependent demagnetization phenomenon of a 900 W permanent-magnet synchronous generator (PMSG). For the 2D electromagnetic model, a commercial finite element method (FEM) package was used to determine the power loss distribution under steady-state conditions, accounting for temperature-dependent demagnetization. The thermal analysis was carried out on a 3D model using computational fluid dynamics (CFD) software, where a polyhedral mesh, rotor rotation effects, and turbulent modeling were implemented. Two simulation cases were evaluated: Case 1, electromagnetic losses at constant temperature without FEM-CFD coupling; Case 2, bidirectional FEM-CFD coupling under steady-state conditions. The analysis confirms that in Cases 1 and 2, there is no risk of irreversible demagnetization, thus validating the selection of the permanent magnet (PM) and the design of the PMSG. Additionally, the methodology accurately captured the heat transfer effects resulting from natural convection and turbulent flow in the critical regions. The CFD modeling convergence criteria, based on residuals and flow monitors, demonstrated numerical stability and a satisfactory mesh discretization in both the FEM and CFD domains, providing valid feedback on the PM temperatures. The proposed methodology provides a robust and accurate tool for coupled electromagnetic–fluid–thermal analysis of the PMSG at rated operating conditions. Full article

Due to the limitations of traditional micropumps in terms of miniaturization and integration, ferrofluid micropumps, as emerging microfluidic driving devices, exhibit significant application potential due to their unique pumping mechanism. Research on ferrofluid micropumps can advance micro/nano technology, meet biomedical needs, and facilitate micro-electro-mechanical system (MEMS) integration. As traditional structural improvement methods struggle to meet increasingly stringent application conditions, under the action of the motion and mechanism of magnetic fluids, a new method of using neodymium magnetic ball plugs instead of traditional magnetic fluid plungers has been developed, aiming to enhance the pumping performance. In this study, the influence of the magnetic field (MF) generated by permanent magnets (PM) on the magnetic properties inside the micropump cavity was first determined. Furthermore, it was revealed in this research that the neodymium magnetic ball plug enhances the pumping flow rate and maximum pumping height of the ferrofluid plug and the pumping stability of the neodymium magnetic ball plug ferrofluid micropump is significantly improved. Additionally, the rotational speed (Rev) of the dynamic neodymium magnetic ball type magnetic fluid plug driven by the motor and the magnetic strength created by the PM are the main aspects influencing the result in this experiment. Full article

The line-start permanent-magnet (LSPM) motor combines the direct-on-line starting of induction motors with the high efficiency of permanent-magnet (PM) synchronous motors, but conventional interior PM designs are difficult to manufacture and surface PM (SPM) designs often suffer from limited starting torque and reduced efficiency. This paper investigates consequent-pole SPM designs, in which the number of magnets is reduced by half while maintaining equal magnet volume, enabling simple rotor construction and improved starting performance. A prototype is manufactured and tested, confirming smooth synchronization under load. Efficiency is constrained by the non-sinusoidal flux distribution of the consequent-pole structure. Rotor design strategies enlarging the air gap near the iron poles are analyzed, and a finite element method analysis shows improved torque and efficiency without loss of starting capability. Full article

The industrial motor systems account for 45% of global electricity consumption. A life cycle model is established to quantify the potential environmental benefits of typical adjustable permanent magnet drives (APMDs, 1250 kW) versus variable frequency drives (VFDs) in China. The model covers mining of metals, manufacturing, operation, and recycling phases of APMDs, incorporating empirical data from China’s 3232 coal-fired units. Four scenarios are set up: business-as-usual, moderate, aggressive, and full-retrofit. Key findings demonstrate that APMDs reduce operational energy consumption by 94.5% compared to VFDs through significantly declining frequency conversion losses and cooling requirements. The life cycle carbon emissions of APMDs (29.7 tonnes CO₂_eq) represent merely 5% of VFDs emissions (570 tonnes CO₂_eq), achieving a 95% reduction. Within APMDs’ footprint, recycling contributes a 45% emission offset (−13.3 tonnes CO₂-eq), while operational efficiency drives the majority of the reduction. Sensitivity analysis identifies electricity emission factors, NdFeB production emissions, and metal recycling rates as primary sensitivity drivers (sensitivity index ST = 0.80). Scenario simulations confirm that the aggressive retrofit strategy (covering high- and moderate-potential units) could reduce annual GHG emissions of 3.12 million tonnes CO₂_eq., with corresponding 89% decreases in particulate matter (PM). This research demonstrates that APMDs are an effective pathway for the low-carbon transition in coal power systems. Their large-scale implementation can potentially necessitate breakthroughs in tiered retrofit policies, thereby providing crucial technological support for industrial carbon neutrality. Full article

This paper proposes a solution to enhance the torque production capability of Permanent Magnet Synchronous Machine (PMSM), utilizing not only the unused space resulting from the stator end windings on the rotor side, but also the otherwise unused space around the winding on the yoke side. By implementing an additional axial rotor equipped with Permanent Magnets (PMs) in both rotor and yoke sides, the proposed design technique increases the PMSM torque output, taking advantage of the useless space on the yoke side. In the proposed configuration, one magnetic flux path circulates between the PMs on the rotor (rotor side) and the stator, while an additional flux path circulates between the PMs positioned on both sides of the stator end windings. These two flux paths contribute to generating a stronger and more effective magnetic field within the machine than conventional structure, resulting in increased torque density. A magnetic equivalent circuit (MEC) model of the proposed design is developed, and its accuracy is validated through Finite Element (FE) analysis. For a fair evaluation, the proposed structure is compared with a conventional configuration using the same volume of PM material. Furthermore, optimization of the proposed design is carried out to maximize Torque/PM. Full article

This paper investigates the impact of permanent magnet (PM) displacement and flux barrier extension on cogging torque in flux-intensifying permanent magnet-assisted synchronous reluctance machines (FI-PMa-SynRMs) with surface-inset PMs. Unlike prior work centred on average torque, torque ripple, or inductance, we focus on cogging torque, a key driver of noise and vibration. Four rotor configurations are evaluated via finite element analysis of ∼20,000 designs per configuration generated during NSGA-II multi-objective optimisation. To avoid bias from near-duplicate designs, we introduce Euclidean distance-based medoid filtering, which enforces a minimum separation of models within each configuration. The cross-configuration similarity is measured by Euclidean distance over common design variables. Results show that PM displacement alone does not substantially reduce cogging torque, while flux barrier extension alone yields reductions of up to ∼25%. Combining PM displacement with flux barrier extension achieves up to a ∼30% reduction in cogging torque, often maintaining average torque and lowering torque ripple. This study provides a comparative framework for mitigating cogging torque in FI-PMa-SynRMs and clarifies the trade-offs revealed by similarity-based analyses. Full article

Conventional permanent magnet-assisted synchronous reluctance machine (PMaSynRM) suffers from limited power factor and efficiency. To boost these, the use of sintered rare earth permanent magnets (PMs) is an option, with respect to sintered ferrite, resulting in a high-performance PMaSynRM (HP-PMaSynRM). However, the increasing price of rare earth PM can lead to an overall increase in machine cost. To overcome this issue, a novel HP-PMaSynRM is presented in this paper. Structurally, the proposed four-pole HP-PMaSynRM rotor is characterized by two fluid-shaped flux barriers filled with sintered ferrite, as well as a cut-off region. Based on the finite element analysis (FEA) results, the proposed HP-PMaSynRM exhibits higher performance compared with the conventional HP-PMaSynRM with rare earth PMs. It is shown that the proposed HP-PMaSynRM has higher power factor, efficiency, and better torque quality over a wide range of operating conditions. Moreover, the HP-PMaSynRM presented incurs lower cost. Finally, the proposed HP-PMaSynRM is manufactured, tested, and compared with the conventional benchmark HP-PMaSynRM, proving its advantages, including higher power factor, higher efficiency, lower torque oscillation, and lower cost. Full article