Search Results (708)

Driven by the rapid development of automotive fuel cells, compact and lightweight system demands require upgraded centrifugal air compressors, as conventional high speed motors at 50,000–80,000 rpm within 15 kW fail to meet current specifications. Since motor size and weight are dominated by torque, raising the rotational speed to improve power density has become the mainstream direction for ultra high speed permanent magnet synchronous motors (HSPMSMs), targeting over 100,000 rpm and 30 kW for fuel cell air compressor applications. This paper presents an 18-slot 2-pole HSPMSM with parallel magnetization, which achieves 35 kW rated power at 100,000 rpm. Electromagnetic performance, rotor mechanical strength, thermal behavior and rotor dynamics are systematically optimized by simulations and experiments. Full article

This paper presents the integrated design and experimental verification of a ferrite spoke permanent magnet motor with rib core skew for semiconductor process pump drives. Conventional induction motors are widely used in industrial pump systems because of their robustness and cost-effectiveness; however, rotor copper loss and limited output capability under a restricted installation envelope remain practical limitations. To address these issues without rare-earth magnets, a flux-concentrating ferrite spoke rotor is applied. The proposed design procedure considers the baseline induction motor envelope, electric and magnetic loadings, manufacturable winding specifications, voltage and current density limits, irreversible demagnetization, and post-assembly magnetization feasibility. An 8-pole/12-slot topology is selected because it enables one-shot post-assembly magnetization, unlike the 10-pole/12-slot alternative requiring segmented magnetization. Rib core skew and stator tooth shoe chamfer geometries are then applied to reduce cogging torque and load torque ripple. A prototype is fabricated and tested. At 1000 rpm, the measured no-load line-to-line voltage is 21.6 V_rms. At 7000 rpm, the prototype achieves 4.028 kW output power and 93.1% efficiency. The measured post-assembly magnetization ratio is 98.7%, and the maximum winding temperature recorded during an approximately 50 min water-cooled test at 6.68 A/mm² is 57.4 °C. These results confirm the feasibility of the proposed design procedure. Full article

Variable-speed induction motor drives spend most of their service life at partial load, where rated-flux field-oriented control (FOC) is inefficient and where loss-minimizing control (LMC) recovers a large part of the loss. LMC, however, is brittle in two ways that matter in industry: it is tuned isothermally, so as the windings heat, the rotor-resistance drift detunes the field orientation and corrupts torque; and it treats the loss-optimal flux as a quasi-static set-point, so an abrupt load rise from a light-load, low-flux condition forces a slow flux rebuild that throttles torque. This paper proposes a thermally adaptive economic model predictive controller (TA-EMPC) that retains the energy optimum of LMC while removing both weaknesses. A temperature-coupled total-loss model (machine copper and core loss plus inverter conduction and switching loss) is minimized over a finite horizon subject to a torque-delivery constraint; a reduced-order two-node thermal observer updates the loss-defining resistances online without a temperature sensor; and a load-demand-aware flux-reservation term pre-magnetizes the machine ahead of anticipated torque rises. In simulations on a representative 7.5 kW drive, TA-EMPC matched the energy of static LMC to within 0.3% across pump, conveyor, and fast-cycling duty profiles—both saving 1.4–2.3% of cycle energy relative to rated-flux FOC, and up to about 14.7 efficiency points at very light load—while, unlike LMC, holding the steady torque error below 0.5% when the winding temperature rose by about 95 °C, to a hot steady state near 115 °C (a stator-resistance increase of roughly 37%) (against an 8% error for the non-adaptive scheme) and reducing the torque undershoot during a light-to-heavy load step from about 23% to near zero. All quantitative results reported in this work are obtained entirely in simulation. A per-step operation-count analysis—not an on-target timing measurement—indicates that the condensed quadratic-program formulation with move blocking is executable within the 100 µs sampling interval on a production digital signal controller for the chosen control horizon; experimental validation on a loaded dynamometer bench, together with on-target timing measurement, is identified as future work. The contribution is thus energy-efficient operation delivered with the torque robustness that loss minimization alone does not provide. Full article

The phasing out of high-GWP refrigerants and the growing diversity of working fluids used across heat pumps, refrigeration systems, and closed-cycle power applications have made drop-in fluid replacement a question of significant practical interest. Centrifugal compressors are designed around the thermophysical properties of a specific fluid, and the performance penalty is incurred when working fluid is replaced without redesigning the impeller. This study presents a CFD comparison of direct drop-in fluid replacement in a fixed geometry centrifugal compression system. Eight working fluids that span the property range relevant to current drop-in substitutions are evaluated: air, nitrogen, argon, carbon dioxide, R22, R134a, R1234yf, and R1234ze(E). A reference centrifugal impeller was reconstructed in ANSYS BladeGen, meshed in ANSYS TurboGrid using the Automatic Topology and Meshing method, and simulated in ANSYS CFX (2024 R2) as a single periodic passage with Frozen Rotor interfaces and Spalart–Allmaras turbulence closure. Performance maps were generated for each fluid across a range of rotational speeds and mass flow rates, with a common inlet reference condition applied across all cases to isolate the influence of fluid properties from an inlet state. The resulting dataset enables a like-for-like comparison of pressure ratio, efficiency, and shaft power requirement, providing a basis for assessing the aerodynamic implications of drop-in fluid substitution in centrifugal compression systems. Air, nitrogen, argon and carbon dioxide achieved similar peak efficiencies (~88%) and comparable pressure ratios (PR), indicating they can be used as drop-in substitutes without performance loss. Refrigerants R1234yf and R1234ze(E) matched R134a in efficiency (peak ~90%) while offering higher pressure ratios and significantly lower power requirements at peak efficiency. At 20,000 RPM and a mass flow rate of 2 kg/s, compared to a PR of 1.45 for air, nitrogen, carbon dioxide and argon achieved PRs of 1.4, 1.9 and 2.4, respectively. At the same settings, R134a and R1234 refrigerants reached PRs of 5 and 6, respectively. The power requirement was ~8 × 10⁴ W for air and similar fluids, and ~11 × 10⁴ W for refrigerants. Full article

We formulate and analyze a 26-dimensional nonlinear dynamical system governing a doubly-fed induction generator (DFIG) wind energy conversion system coupled to an infinite bus through a dynamic transmission line. Seven interacting subsystems—aerodynamics, a two-mass drivetrain, a fourth-order machine, rotor- and grid-side converter controllers, a phase-locked loop, and a pitch regulator—are assembled into a single vector field $\dot{\mathbf{x}}=\mathbf{f}(\mathbf{x},\mathbf{u})$ on ${\mathbb{R}}^{26}$, derived in dimensionless coordinates. Strict positivity of the determinant $\mathrm{\Delta }=L_s{L}_r-L_m^2=\sigma L_s{L}_r$ for every physically admissible machine renders the flux–current map invertible, so the right-hand side is well defined; the nodal Kirchhoff constraint forms a semi-explicit differential-algebraic relation that we eliminate to obtain an explicit ordinary differential equation. The central contribution is a constructive scheme for the equilibria: the 26 stationarity conditions $\mathbf{f}({\mathbf{x}}^{\star },\mathbf{u})=\mathbf{0}$ are solved by an iterative voltage-matching procedure converging to a residual below ${10}^{-11}$ per unit—essentially machine precision—which removes the spurious start-up transients common in reported simulations. Analytically chosen feedback gains induce a hierarchy of well-separated time scales, placing the closed loop in the multiple-time-scale class; the separation is made quantitative through explicit small parameters ${\epsilon }_i$ formed from the ratios of subsystem time constants. Numerical integration of a GE $3.6$ MW configuration confirms the construction: under stationary forcing, the rotor speed stays within $1.32\times {10}^{-5}$ pu of the equilibrium, and under a large-amplitude wind program ($11\to 14\to 9$ m/s) spanning the full operating envelope, it is regulated to within $0.065\%$, while the DC-link voltage deviation remains below $2.4\times {10}^{-5}$ pu and the power balance closes with residual below ${10}^{-3}$ pu, the ≈2% mechanical–electrical gap being the modeled losses. Linearization about the computed equilibrium yields a Jacobian whose spectrum lies entirely in the open left half-plane, establishing local asymptotic stability and exposing the individual electromagnetic, torsional, and control modes. The model furnishes a rigorously initialized, analytically transparent basis for linearization, spectral stability analysis, and bifurcation study. Its practical value is that a consistent equilibrium and a certified spectrum remove the start-up transients and undocumented tuning that otherwise let initialization artifacts masquerade as genuine dynamics, so that the model can serve as a trustworthy building block for weak-grid and wind-farm stability studies. Full article

This study presents the design, manufacturing, and prototype-level evaluation of a high-efficiency interior permanent magnet synchronous motor (IPMSM) developed for compact electric vehicle traction applications. The proposed motor employs a 12-slot/10-pole spoke-type rotor topology and was evaluated in terms of electromagnetic performance, mechanical integrity, and thermal behavior. The slot–pole and winding configuration was assessed as part of the design evaluation, and the manufactured prototype was experimentally tested under different operating conditions. The experimental results were compared with numerical simulations using line-to-line back-EMF, efficiency maps, phase current–torque characteristics, and output power variation. At the nominal operating point of 7000 rpm and 3.5 Nm, the prototype delivered 2.5 kW output power with an experimental efficiency of 90.7%. The deviations between experimental and simulation results were 1.17% for phase current, 0.48% for line-to-line back-EMF, 1.18% for input power, and 1.20% for efficiency. Mechanical static structural finite element analysis indicated a rotor safety factor of 3.61 under the maximum centrifugal loading condition, while the resulting structural deformation remained sufficiently low to avoid adverse effects on air-gap alignment. In addition, the rotor incorporated an adhesive-free, mechanically disassemblable magnet-retention structure, which was mechanically evaluated under centrifugal loading and showed no magnet displacement, structural damage, or bolt-preload loss after testing. Thermal analysis and continuous-load experimental testing showed that the winding temperature remained around 80 °C under passive cooling conditions. Overall, the results demonstrate that the manufactured IPMSM prototype provides consistent electromagnetic performance, adequate mechanical reliability, and thermally safe operation for compact electric vehicle applications. Full article

Synchronous Reluctance Machines (SynRMs) have emerged as a strong candidate for electric vehicle (EV) traction owing to their rare-earth-free construction, robust rotor structure, and competitive efficiency relative to permanent magnet (PM) and induction machines (IMs). Their performance, however, is governed by complex electromagnetic and thermal phenomena—saliency, magnetic saturation, flux-barrier geometry, and temperature-dependent losses—that demand accurate yet computationally tractable modelling. This paper reviews the modelling and design landscape for SynRMs in EV traction, covering analytical approaches (d–q models, magnetic equivalent circuits), numerical methods (finite element analysis), and recent hybrid techniques such as the Enhanced Hybrid Subdomain Method (EHSDM). Rotor geometry optimization, including flux-barrier shaping and saliency-ratio enhancement, is examined alongside coupled magnetic–thermal analysis, an aspect typically treated in isolation in earlier surveys. The review compares the trade-offs of competing techniques across the design workflow—from initial sizing to final verification—and identifies open challenges in reducing computational cost while preserving accuracy. The synthesis is intended to guide motor designers toward modelling choices appropriate to each design stage and to highlight directions for future research in high-performance, rare-earth-free traction motors. Full article

Interior permanent magnet synchronous motors have high torque density and a high salient pole effect, combine low-speed high torque with constant-power wide speed regulation, and are increasingly favored by more and more car companies and widely used in electric vehicles. With the development of interior permanent magnet synchronous motors for electric vehicle towards high speed and large capacity, the eddy current loss generated inside the permanent magnet increases rapidly when the magnetic field alternates. Simulation results show that the excessive eddy current loss can raise the permanent magnet temperature of the I2V-type rotor up to 112 °C under rated operating conditions. Such a high temperature far exceeds the stable working temperature range of conventional NdFeB materials and greatly increases the risk of irreversible demagnetization. NdFeB permanent magnet materials have high electrical conductivity but weak heat-resistant capacity, so the temperature rise of permanent magnet is more serious, and even irreversible demagnetization occurs, which is fatal for the safe operation of motors. Therefore, it is necessary to analyze and study the eddy current loss of permanent magnets, explore methods to reduce magnet loss, and design reasonable and efficient cooling systems. Firstly, this paper selects three different rotor topologies as research objects, establishes two-dimensional parameterized finite element analysis models, and analyzes and compares magnet loss and the hysteresis loss, eddy loss, and copper loss of the stator. Secondly, to solve the problem that the I2V-type rotor generates higher magnet loss than the other two structures under all working conditions, magnetic isolation holes are arranged on each rotor pole to optimize the internal magnetic circuit. Simulation analysis results show that this method can effectively reduce magnet loss and stator hysteresis losses. Finally, the temperature of the shaft, magnet and stator winding are studied; aiming at characteristics of high torque density with small size, large torque, and high magnet temperature, a cooling method combining housing cooling and shaft cooling is proposed. Simulation results indicate that the new cooling method can greatly suppress the magnet temperature rise, which reduces the maximum permanent magnet temperature from 112 °C to 80 °C under rated operating conditions and can further improve the torque density and operating reliability of interior permanent magnet synchronous motors. This provides a feasible design reference for high-reliability vehicle interior permanent magnet synchronous motors. Full article

High-speed electric machines enhance power density and eliminate the need for a gearbox in waste heat recovery microturbine systems. However, existing designs often suffer from high manufacturing costs and complex cooling requirements. This study presents the development, experimental validation, and comparative analysis of three high-speed machine designs. First, a lower-speed induction machine prototype, constructed using standardized components, was tested at an operating speed of 13,000 rpm. This prototype enabled experimental validation of the numerical model used for loss calculations. Experimental results showed total losses of 7.89 kW, closely matching the simulated value of 7.75 kW at an output power of 93.1 kW, i.e., an efficiency of 92.19%. Building on these findings, two smaller machine prototypes were developed: one featuring an induction squirrel-cage rotor and the other employing a surface-mounted permanent magnet rotor topology. Both machines were designed and evaluated using finite element analysis and conjugate heat transfer simulations. Their performance was analyzed under both sinusoidal and pulse-width-modulated voltage supply conditions. At an operating speed of 14,000 rpm, the permanent magnet machine outperformed the induction machine, achieving 63.2 kW of mechanical power and an efficiency of 96.21%, while operating at lower temperatures. In comparison, the induction machine delivered 52.4 kW of mechanical power with an efficiency of 94.64%. The primary novelty and contribution of this work lie in the implementation of a two-pole machine architecture capable of achieving an output power of 100 kW at operating speeds between 20,000 and 25,000 rpm. Compared with similar solutions reported in the literature, the proposed machines feature a simplified bearing arrangement and a more straightforward liquid-cooling system. These characteristics have the potential to reduce manufacturing costs and simplify maintenance during operation. Full article

This study presents an extended Blade Element Momentum Theory (BEMT) framework for predicting the hover performance of an EC135-class light-twin helicopter rotor while quantifying the impact of sectional aerodynamic uncertainty on global rotor metrics. Because the proprietary EC135 airfoils are not publicly available, a reproducible surrogate blade based on the ONERA OA213 and OA209 airfoils is adopted. The airfoil substitution is explicitly treated as an epistemic modelling assumption, and its effect on rotor-level hover predictions is assessed through a dedicated geometric comparison and bounded sensitivity analysis. The classical BEMT formulation is enhanced with Prandtl tip-loss corrections, Mach-dependent sectional aerodynamics, and an iterative non-uniform inflow model. Aerodynamic coefficients are obtained from Gaussian Process (GP) surrogate models trained on XFOIL-generated databases and calibrated using cross-validation techniques. The calibrated GP models are coupled with the rotor solver and their predictive uncertainty is propagated through Monte Carlo simulations. For the nominal hover trim condition, the rotor was trimmed to $C_T=0.00607$, while the model predicted a power coefficient of 0.00041 and a figure of merit of 0.819. The propagated GP/XFOIL-conditioned uncertainty yields a 95% confidence interval of 0.8074–0.8285 for the figure of merit, indicating limited sensitivity of rotor performance to sectional aerodynamic uncertainty. The influence of compressibility and tip-loss effects is also quantified. In a separate Caradonna–Tung solver-verification case, the thrust-coefficient error is reduced from 32.57% to 7.78% when finite-aspect-ratio corrections are included. The proposed framework provides a fast, reproducible, and uncertainty-aware approach for helicopter rotor hover analysis suitable for preliminary design and performance assessment. Full article

Oscillating water column wave energy converters require self-rectifying turbines capable of maintaining stable performance under bidirectional airflow. This study numerically investigates the aerodynamic performance and internal flow characteristics of an axial-flow impulse turbine using OpenFOAM under both uniform and reciprocating airflow conditions. Rotor motion was modeled using the Multiple Reference Frame approach, and the numerical model was validated against experimental data for one-way flow at an inlet velocity of 8.71 m s⁻¹ and rotational speeds ranging from 300 to 1300 rpm. The CFD results successfully reproduced the experimental efficiency trend, yielding a peak efficiency of η = 0.4269 at 700 rpm and ϕ ≈ 0.95, which closely aligns with the experimental peak efficiency of η = 0.4425. Validation metrics demonstrated a high degree of accuracy, with an RMSE of 0.0219, a mean absolute error of 0.0197, a maximum absolute error of 0.0399, a squared Pearson correlation coefficient of 0.826, and a peak-efficiency difference of 3.5%. Flow-field analysis revealed that low rotational speeds resulted in high outlet velocities and incomplete energy extraction, whereas excessive rotational speeds caused flow misalignment, downstream vortex formation, and additional aerodynamic losses. Under reciprocating flow conditions, characterized by a sinusoidal velocity amplitude of 8.71 m s⁻¹ and periods of 0.5–2.0 s at 700 rpm, both input and torque coefficients exhibited hysteresis, with the strongest loops observed at the shortest periods. Examinations of streamline, pressure, and velocity distributions indicated that residual flow during flow reversal alters the effective inlet direction in the subsequent half-cycle, resulting in flow memory and a phase-dependent turbine response. As the present computational domain excludes the OWC chamber, these findings characterize turbine-level aerodynamic performance rather than the complete system power coefficient. Full article

Coaxial magnetic gears (CMGs) have emerged as a promising alternative to conventional mechanical gear systems due to their contactless torque transmission, low maintenance requirements, and high reliability. However, under high-speed operation, conductivity-induced eddy current losses become dominant and significantly limit thermal performance. This study comparatively investigates the coupled electromagnetic and thermal behavior of two compact CMGs with identical torque capacity using M400-50A electrical steel and cobalt-based Hiperco 50A. Coupled electromagnetic–thermal finite element analyses are performed from 1000 to 12,000 rpm under worst-case natural convection conditions. The results demonstrate that the use of Hiperco 50A reduces core losses by up to 71% at high speeds and enables approximately 7.3% greater volumetric compactness owing to its higher saturation capability. Eddy-current-related losses remain the dominant loss mechanism at elevated speeds, causing inner-rotor permanent-magnet temperatures to exceed the allowable limits of NdFeB materials. Under natural convection, the outer permanent-magnet temperature remains below the critical threshold of 200 °C up to approximately 5800 rpm for the M400-50A design. With Hiperco 50A, this limit increases to approximately 6000 rpm under identical operating conditions, corresponding to an improvement of about 3%. These findings demonstrate the thermal benefits of high-saturation magnetic alloys; however, additional cooling strategies are required for operation at higher speeds. Full article

This paper investigates the impact of segmented permanent magnet (PM) configurations on torque production, eddy current loss, and demagnetization in spoke-type flux-intensifying interior permanent magnet (FI-IPM) motors. While PM segmentation has been explored in conventional interior permanent magnet synchronous motors (IPMSMs) for reducing losses, its effect in flux-intensifying (FI) motors, characterized by reverse saliency, remains underexplored. To address this, five rotor designs with segmented PMs are analyzed against a baseline model using finite element analysis, maintaining identical stator and PM volume. Results show that segmentation increases reluctance torque, compensating for reduced PM torque, while simultaneously lowering eddy current loss and enhancing demagnetization resistance. These improvements validate segmented PMs as a viable strategy to enhance the durability and efficiency of FI-IPM motors for electric vehicle applications. Full article

Cycloidal propellers are known for their omnidirectional vectored thrust, enabling smooth transitions between hovering and forward flight, making them ideal for unmanned aerial vehicles (UAVs) and electric vertical take-off and landing (eVTOL) aircraft. However, cycloidal propellers tend to have lower hovering efficiency than screw propellers at the unmanned aerial vehicle (UAV) scale. Adding end plates to the blade tips can improve hovering efficiency by suppressing blade tip vortices. But the impact of these end plates have not been thoroughly studied. This paper aims to seek the designs with enhanced hovering efficiency and develop design guidelines for cycloidal propellers with end plates. Comprehensive force measurement experiments are performed on designs with and without end plates, and designs with rotating and static end plates. Complementary high-fidelity numerical analysis is performed to gain deeper insights into the complex 3D flow structures and the role of end plates in suppressing induced power losses. Our study reveals that end plates can effectively suppress the efficiency degradation typically associated with low aspect ratio blades. We demonstrate that even with a blade aspect ratio of 1.5, a cycloidal propeller equipped with end plates can achieve high hovering efficiency, thereby establishing a new design guideline for lightweight, high-performance propulsion systems. The designs with stationary end plates are superior to those with rotating end plates because rotation introduces additional torque caused by the friction force. Designs featuring thick end plates (${\overline{t}}_e=0.056$) outperform those with thin end plates (${\overline{t}}_e=0.004$), as the rounded edges can eliminate end plate vortices. A comprehensive parametric study is conducted, evaluating blade chord-to-radius ratios from 0.26 to 0.65, aspect ratios from 0.5 to 3.0, pitching amplitudes from 10° to 50°, as well as end plate configurations (stationary vs. rotating, and thin vs. thick). From this parameter space, the best design was identified as featuring stationary thick end plates (${\overline{t}}_e=0.056$), a chord-to-radius ratio of 0.65, and a large pitching amplitude of 40 degrees. It achieves a hovering efficiency of 0.72 with a blade aspect ratio of 3, which is comparable to that of sub-scale rotors with similar Reynolds number. In contrast, for the cases without end plates, the highest hovering efficiency is lower than 0.6. Full article

This study presents the prototype manufacturing and experimental validation of a 1 kW, 750 rpm three-phase outer-rotor permanent magnet-assisted synchronous reluctance motor (PMASynRM) designed for in-wheel electric vehicle applications. The work is based on a previously reported electromagnetic design and finite element method (FEM)-based optimization framework and focuses on the physical implementation and experimental evaluation of the proposed motor. The prototype was manufactured using M470-50A grade electrical steel laminations and arc-shaped N35H NdFeB permanent magnets embedded within a three-barrier transversally laminated anisotropic rotor structure. A custom-built experimental test bench consisting of the PMASynRM prototype, a PMSM generator with a controllable resistive load bank, a torque transducer, and a precision power analyzer was developed to evaluate motor performance under controlled operating conditions. Experimental investigations were carried out under four steady-state load conditions—no-load, 13 Nm, 20 Nm, and 26 Nm—as well as during dynamic stepwise load transitions representative of in-wheel drive operation. The measured results show good agreement with FEM predictions, with a maximum efficiency of 90.55% at nominal load and efficiency values remaining above 87% under overload conditions up to 26 Nm. Minor differences between simulation and experimental results are mainly associated with mechanical friction, bearing losses, and manufacturing tolerances that are not fully captured in the numerical model. The study provides experimental validation of an outer-rotor PMASynRM prototype under multi-load steady-state and dynamic operating conditions for in-wheel electric vehicle applications. Full article