Search Results (86)

Severe pressure pulsations caused by complex flow fields in pumped-storage power stations significantly threaten operational safety and stability. With advances in computational technology, fully three-dimensional simulations coupling pipelines and pump-turbine units have become feasible. In this study, a fully three-dimensional analysis model was developed, coupling the water conveyance system and a finely modeled prototype-scale pump-turbine with splitter blades, to numerically simulate the compressible flow field under the maximum head pump mode. The study reveals a strong bidirectional coupling between the flow in the long outlet pipe and the internal flow within the pump-turbine unit. Influenced by structural features such as bifurcations and flow impingement at the T-junction, complex three-dimensional vortices arise and cannot be neglected. Based on the flow field, the study further investigates the time-domain, frequency-domain, and spatial characteristics of pressure pulsations at various downstream hydraulic components, ranging from the vaneless space to the outlet of the long outlet pipe. The pressure pulsation frequencies are shown to be affected by both rotor–stator interactions and the complex vortical structures in the flow. These findings clearly demonstrate the necessity of fully three-dimensional simulations that incorporate both the water conveyance system and the pump-turbine unit. Full article

The global energy crisis demands efficient electricity production solutions, especially for isolated communities where hydraulic energy can be harnessed sustainably. This paper presents a case study analyzing the efficiency of a 13,330 kW hydrogenerator, consisting of a bulb-type hydro-aggregate using the calorimetric method—a viable alternative when testing at nominal load is not feasible due to technical limitations. The method involves measuring the thermal energy absorbed by the cooling water under three operating conditions: no-load unexcited, no-load excited, and symmetric three-phase short-circuit. Measurements followed IEC standards and were conducted with high-precision instruments for temperature, flow, voltage, and current. The results quantify mechanical, ventilation, iron, and copper losses, as well as additional losses via radiation and convection. Thermal analysis revealed significant heat accumulation in the rotor and stator windings, indicating the need for improved cooling solutions. The calorimetric method enables efficiency evaluation without interrupting generator operation, offering a valuable tool for diagnostics, predictive maintenance, and informed decisions on modernization. Furthermore, integrating an intelligent operational control system could enhance efficiency and improve the quality of the supplied energy, supporting long-term sustainability in hydroelectric power generation. Full article

The inchworm piezoelectric motor, with the advantages of long stroke and high resolution, is ideally suited for precise positioning in wafer-level electron beam inspection systems. However, the large number of piezoelectric actuators and the complex excitation signal sequences significantly increase the complexity of system assembly and temporal control. A flexure-based actuation stator structure, along with simplified excitation signal sequences of a high-precision inchworm piezoelectric motor, is proposed. The alternating actuation of upper/lower clamping mechanisms and the driving mechanism fundamentally mitigates backstep effects while generating stepping linear displacement. The inchworm piezoelectric motor achieves precision linear motion operation using only two piezoelectric actuators. The actuation stator is analyzed via the compliance matrix method to derive its output compliance, input stiffness, and displacement amplification ratio. Furthermore, a kinematic model and natural frequency expression incorporating the pseudo-rigid-body method and Lagrange’s equations are established. The actuation stator and inchworm piezoelectric motor are analyzed through both simulations and experiments. The results show that the maximum step displacement of the motor is 16.3 μm, and the maximum speed is 9.78 mm/s, at a 600 Hz operation frequency with a combined alternating piezoelectric voltage of 135 V and 65 V. These findings validate the designed piezoelectric motor’s superior motion resolution, operational stability, and acceptable load capacity. Full article

Inter-turn short-circuit (ITSC) faults in permanent magnet synchronous machines (PMSMs) present a significant reliability challenge in electric vehicle (EV) drivetrains, particularly under non-stationary operating conditions characterized by inverter-driven transients, variable loads, and magnetic saturation. Existing diagnostic approaches, including motor current signature analysis (MCSA) and wavelet-based methods, are primarily designed for steady-state conditions and rely on manual feature selection, limiting their applicability in real-time embedded systems. Furthermore, the lack of publicly available, high-fidelity datasets capturing the transient dynamics and nonlinear flux-linkage behaviors of PMSMs under fault conditions poses an additional barrier to developing data-driven diagnostic solutions. To address these challenges, this study introduces a simulation framework that generates a comprehensive dataset using finite element method (FEM) models, incorporating magnetic saturation effects and inverter-driven transients across diverse EV operating scenarios. Time-frequency features extracted via Discrete Wavelet Transform (DWT) from stator current signals are used to train a Transformer model for automated ITSC fault detection. The Transformer model, leveraging self-attention mechanisms, captures both local transient patterns and long-range dependencies within the time-frequency feature space. This architecture operates without sequential processing, in contrast to recurrent models such as LSTM or RNN models, enabling efficient inference with a relatively low parameter count, which is advantageous for embedded applications. The proposed model achieves 97% validation accuracy on simulated data, demonstrating its potential for real-time PMSM fault detection. Additionally, the provided dataset and methodology contribute to the facilitation of reproducible research in ITSC diagnostics under realistic EV operating conditions. Full article

The construction of pumped storage power stations (PSPSs) is undergoing rapid expansion globally. Detecting operational faults and defects in pumped storage units is critical, as effective diagnostic methods can not only identify fault types quickly and accurately but also significantly reduce maintenance costs. This study leverages the symmetry characteristics in the vibration signals of pumped storage units to enhance fault diagnosis accuracy. To address the challenges of selecting the key parameters (e.g., decomposition level and penalty factor) of the variational mode decomposition (VMD) algorithm during vibration signal analysis, this paper proposes an algorithm for an improved subtraction-average-based optimizer (ISABO). By incorporating piecewise linear mapping, the ISABO enhances parameter initialization and, combined with a balanced pool method, mitigates the algorithm’s tendency to converge to local optima. This improvement enables more effective vibration signal denoising and feature extraction. Furthermore, to optimize hyperparameter selection in the bidirectional long short-term memory (BILSTM) network—such as the number of hidden layer units, maximum training epochs, and learning rate—we introduce an ISABO-BILSTM classification model. This approach ensures robust fault diagnosis by fine-tuning the neural network’s critical parameters. The proposed method is validated using vibration data from an operational PSPS. Experimental results demonstrate that the ISABO-BILSTM model achieves an overall fault recognition accuracy of 97.96%, with the following breakdown: normal operation: 96.29%, thrust block loosening: 98.60%, rotor-stator rubbing: 97.34%, and rotor misalignment: 99.59%. These results confirm that the proposed framework significantly improves fault identification accuracy, offering a novel and reliable approach for PSPS unit diagnostics. Full article

This paper investigates the performance of a five-phase silicon carbide (SiC)-based current-source converter (CSC) integrated with a Doubly Fed Induction Generator (DFIG) for wind energy applications. The study explores both healthy and faulty operation, focusing on system behavior under transient conditions and various load scenarios in stand-alone mode. A novel five-phase space vector PWM strategy in dual coordinate planes is introduced, which enables stable control during normal and open-phase fault conditions. Experimental results demonstrate improved stator voltage and current quality, particularly in terms of reduced Total Harmonic Distortion (THD), compared to traditional voltage-source converter-based systems. Furthermore, the system maintains operational stability under a single-phase open fault, despite increased oscillations in stator quantities. The results highlight the potential of five-phase CSC-DFIG systems as a robust and efficient alternative for wind power plants, particularly in configurations involving long cable connections and requiring low generator losses. Future work will focus on enhancing fault-tolerant capabilities and expanding control strategies for improved performance under different operating conditions. Full article

To address wear failure in screw pump stator and rotor friction pairs, this study constructed a numerical model of a rhombus-like micro-dimple texture on friction pair surfaces based on the scale structure of rhombus rattlesnakes. The model was based on the fluid dynamic pressure lubrication mechanism. The CFD method was used to calculate the bearing capacity, friction coefficient, flow field pressure distribution, and flow trace distribution of an oil film carrying surface. The effects of the area rate, depth, shape, and angle of the rhombus-like dimple texture and the actual well fluid viscosity of shale oil on the surface lubrication performance of screw pump stator and rotor friction pairs were analyzed. The results demonstrated that increasing the texture area rate and the angle of the long sides and decreasing the texture angle resulted in a decrease in the oil film surface friction coefficient and an increase in the average pressure and net bearing capacity as well as the hydrodynamic lubrication performance. The average pressure increased and then decreased as the texture depth increased, while the friction coefficient of the oil film surface initially decreased and then increased. At a texture depth of 20 μm, the friction coefficient reached its lowest value while the average pressure and net bearing capacity of the oil film reached their highest value, which resulted in optimal hydrodynamic lubrication performance. When the texture depth became greater than 20 μm, vortices were gradually formed within the texture, which decreased the hydrodynamic lubrication performance. When the area rate of the rhombus-like dimple texture, depth, angle between long sides, and angle were, respectively, equal to 27%, 20 μm, 74°, and 0°, the net bearing capacity of the oil film was maximized, the friction coefficient was minimized, and the hydrodynamic lubrication performance and anti-wear effect reached their highest values. The increase in the viscosity of the actual well fluid could enhance the dynamic pressure lubrication performance and improve the bearing capacity. Full article

Aiming at the defects of long axial size and low torque density of the existing radial flux permanent magnet motor, this paper proposes an axial flux permanent magnet synchronous motor (AFPMM) with a double-stator and single-rotor structure based on the design requirements of the motor for mechanical dogs’ electric drive joints. The finite element method is employed to evaluate the static magnetic field, load characteristics, and associated losses. The analysis indicates that the average magnetic flux density in the air gap reaches approximately 0.95 T, with a rated torque of around 2.72 N.m, a peak torque of 7.6 N.m, and an efficiency of approximately 87.73%. The electromagnetic torque model is developed using the Maxwell tensor method, allowing for the effects of critical structural parameters on torque to be investigated. By optimizing the design for torque density, an improvement of nearly 20% is achieved. A prototype was fabricated and tested, demonstrating good agreement between simulation and experimental results. This research introduces a novel approach for designing axial flux motors with high torque and power densities. Full article

This paper develops a composite weaving structure, combining hexagonal micro-bumps and hexagonal grooves, in the design of the rubber surface of the screw pump. This allows us to solve the problem of high torque and fast wear of the rubber stator during the operation of screw pump lifting oil recovery, based on the bionic hexagonal surface structure, traditional surface damping principle, and fluid dynamic pressure lubrication theory. Finite element analysis is first conducted to quantitatively analyze the impacts of the parallel side distance, groove width, and groove depth on the surface flow field and wall pressure field of the composite hexagonal structure. Based on the simulation law, the rubber surface laser structure is then designed and prepared by nanosecond laser processing. Afterward, tribological experiments are conducted under the condition of long-term immersion in the actual extraction fluid of shale oil wells. This aims at simulating the actual downhole oil production conditions and quantitatively studying the impact of the size of the composite hexagonal structure on the lubrication characteristics of the friction part of the stationary rotor, as well as the effect of abrasion reduction. The results show that, within the simulation range, the smaller the parallel side distance, the higher the load-carrying capacity. In addition, the hexagonal weave with a parallel side distance of 3 mm has a higher wall load carrying capacity than that with distances of 4 mm and 5 mm. When the groove width is equal to 0.4 mm, the oil film load carrying capacity is higher than that in the case of 0.2 mm. When the groove depth increases, the oil film pressure first increases and then stabilizes or decreases after reaching 0.3 mm. In the hexagonal weave, the friction ratio of the rotor is equal to 0.4 mm. In the tribological experiment of hexagonal weave, the smaller the parallel side distance, the smaller the friction coefficient, and the 0.5 mm weave has the highest performance. Full article

In order to improve the operation control performance of high-speed maglev trains, an improved finite-time rotor magnetic Field-Oriented Control method was proposed in this paper. Aiming at the stator current control problem of long-stator linear synchronous motors under parametric perturbation, this paper investigates the double-feeding mode, combines the predefined-time stability theory and designs an improved sliding mode controller to optimise the dynamic characteristics of the inner-loop system. In the outer-loop cruise control, the predefined-time sliding mode control is combined with a finite-time disturbance observer, which effectively solves the problems of inaccurate modelling and parameter ingestion. It was verified through simulation and analysis that the control strategy has significant advantages in improving the dynamic tracking performance and anti-interference ability, with the stator current stabilisation time within 0.1 s, the absolute value of the fluctuation error within 20 A, the outer-loop response time within 0.5 s, the maximum speed error within 0.0005 m/s and the maximum displacement error within 0.0005 m. The control strategy has the advantages of improving the dynamic tracking performance and anti-interference ability. Full article

This paper compares the electromagnetic performances of radial-flux, dual-rotor, permanent magnet (DRPM) machines with series (S) and parallel (P) magnetic circuits for two rotors, i.e., SDRPM and PDRPM, accounting for different slot/pole number combinations, stator winding configurations, and machine sizes. The machines are optimized using the finite element analysis (FEA) based on the genetic algorithm. It shows that the PDRPM machine with the tooth coil (TC) configuration has the highest permanent magnet (PM) utilisation compared to the PDRPM with toroidal winding (TW) configuration and the SDRPM machine with the TC configuration under different slot/pole number combinations. The scaling effects of the machine size on the torque have been investigated. The TW-PDRPM machine is suitable for large-radius and short-axial length applications due to the short end-winding length of the TW configuration, while the TC-PDRPM is better for small-radius and long-axial length applications. The TC-SDRPM performs well when both the machine outer radius and axial length increase. Finally, the TC-SDRPM and TW-PDRPM machines are prototyped and validated experimentally. Full article

Permanent magnet synchronous motors (PMSMs) play a crucial role in industrial production, and in response to the problem of PMSM turn-to-turn short-circuit and demagnetization faults affecting production safety, this paper proposes a PMSM turn-to-turn short-circuit and demagnetization fault diagnostic method based on a convolutional neural network and bidirectional long and short-term memory neural network (CNN-BiLSTM). Firstly, analyzing the PMSM turn-to-turn short-circuit and demagnetization faults, one takes the PMSM stator current as the fault signal and optimizes the variational modal decomposition (VMD) by using the Gray Wolf Optimization (GWO) algorithm in order to achieve efficient noise reduction processing of the stator current signal and improve the fault feature content in the stator current signal. Finally, the fault diagnostics are classified by using the CNN-BiLSTM, which collects advanced optimization algorithms and deep learning networks. The effectiveness of the method is verified by simulation experiment results. This scheme has high practical value and broad application prospects in the field of PMSM turn-to-turn short circuit and demagnetization fault diagnosis. Full article

The double-stator superconducting brushless machine (DS-SCBM) combines high torque density and excellent static sealing characteristics, as well as advantages in reliability and cost-effectiveness. To ensure the long-term stability of the superconducting magnet and Dewar (SCMD) system, this study evaluates the pressure-bearing capacity and heat leakage from the support frame, selecting appropriate materials and dimensions. Furthermore, a model of the thermal and mechanical fields for the SCMD system is developed using finite element analysis which assesses the impact of various reinforcement structures on the mechanical and thermal properties of the superconducting (SC) magnet. Based on this analysis, the dimensions of the reinforcement structures, Dewars, and vacuum interlayer are optimized. Subsequently, efforts are made to manufacture the designed system and its performance is tested. Full article

A pump-turbine may generate high-amplitude hydraulic excitations during operation, wherein the flow-induced response of the spiral case and concrete is a key factor affecting the stable and safe operation of the unit. The preloading spiral case can enhance the combined bearing capacity of the entire structure, yet there is still limited research on the impact of the preloading pressure on the hydrodynamic response. In this study, the pressure fluctuation characteristics and dynamic behaviors of preloading a steel spiral case and concrete under different preloading pressures at rated operating conditions are analyzed based on fluid–structure interaction theory and contact model. The results show that the dominant frequency of pressure fluctuations in the spiral case is 15 $f_n$, which is influenced by the rotor–stator interaction with a runner rotation of short and long blades. Under preloading pressures of 0.5, 0.7, and 1 times the maximum static head, higher preloading pressures reduce the contact regions, leading to uneven deformation and stress distributions with a near-positive linear correlation. The maximum deformation of the PSSC can reach 2.6 mm, and the stress is within the allowable range. The preloading pressure has little effect on the dominant frequency of the dynamic behaviors in the spiral case (15 $f_n$), but both the maximum and amplitudes of deformation and stress increase with higher preloading pressure. The high-amplitude regions of deformation and stress along the axial direction are located near the nose vane, with maximum values of 0.003 mm and 0.082 MPa, respectively. The contact of concrete is at risk of stress concentrations and cracking under high preloading pressure. The results can provide references for optimizing the structural design and the selection of preloading pressure, which improves operation reliability. Full article

Accurately sizing vehicle components is an impactful step in the aircraft design process. However, existing methods of sizing brushless DC (BLDC) motors for small unmanned aerial systems (SUAS) ignore how cooling affects motor size. Moreover, the literature methods do not predict a notional motor’s electrical constants, namely winding resistance, torque constant, and figure of merit. We developed a sizing algorithm that predicts the optimal mass and electrical constants using a combination of sizing, efficiency, and thermal models. The algorithm works for radial-flux BLDC motors with masses up to 800 g. An experimental teardown of seven motors informed the algorithm’s sizing models. The teardown motors varied in mass (24–600 g) and geometry (stator aspect ratio of 1.4–9.0). Validated against an independent catalog of 30 motors, the sizing models predicted mass and resistance within 10% and 20% of catalog specifications, respectively. Validated against experimental data, the full algorithm predicted mass, efficiency, and temperature within 20%, 5%, and 10% accuracy, respectively. The algorithm also captured how lowering mass would increase losses and temperature, which the literature models ignore. The algorithm can help users develop more viable concepts that save costs in the long run. Full article