Search Results (128)

Adopting mobile robots for high voltage (HV) live-line operations can mitigate personnel casualties and enhance operational efficiency. However, conventional mechanical arms cannot inspect concealed spaces in the power cable tunnel because their joint integrates metallic motors or hydraulic serial-drive mechanisms, which limit the arm’s length and insulation performance. Therefore, this study proposes a 7-degree-of-freedom (7-DOF) bionic mechanical arm with rigid-flexible coupling, mimicking human arm joints (shoulder, elbow, and wrist) designed for HV live-line operations in concealed cable tunnels. The arm employs a tendon-driven mechanism to remotely actuate joints, analogous to human musculoskeletal dynamics, thereby physically isolating conductive components (e.g., motors) from the mechanical arm. The arm’s structure utilizes dielectric materials and insulation-optimized geometries to reduce peak electric field intensity and increase creepage distance, achieving intrinsic self-insulation. Furthermore, the mechanical design addresses challenges posed by concealed spaces (e.g., shield tunnels and multi-circuit cable layouts) through the analysis of joint kinematics, drive mechanisms, and dielectric performance. The workspace of the proposed arm is an oblate ellipsoid with minor and major axes measuring 1.25 m and 1.65 m, respectively, covering the concealed space in the cable tunnel, while the arm’s quality is 4.7 kg. The maximum electric field intensity is 74.3 kV/m under 220 kV operating voltage. The field value is less than the air breakdown threshold. The proposed mechanical arm design significantly improves spatial adaptability, operational efficiency, and reliability in HV live-line inspection, offering theoretical and practical advancements for intelligent maintenance in cable tunnel environments. Full article

Accurate diagnosis of the insulation condition of stator windings in pumped storage generator-motor units is crucial for ensuring the safe and stable operation of power systems. Time domain dielectric response testing is an effective method for rapidly diagnosing the insulation condition of capacitive devices, such as those in pumped storage generator-motors. To precisely identify the conductivity and relaxation process parameters of the insulating medium and accurately diagnose the insulation condition of the stator windings, this paper proposes a method for identifying the insulation dielectric response parameters of stator windings based on sparsity-enhanced dynamic mode decomposition of the depolarization current. First, the measured depolarization current time series is processed through dynamic mode decomposition (DMD). An iterative reweighted L1 (IRL1)-based method is proposed to formulate a reconstruction error minimization problem, which is solved using the ADMM algorithm. Based on the computed modal amplitudes, the dominant modes—representing the main insulation relaxation characteristics—are separated from spurious modes caused by noise. The parameters of the extended Debye model (EDM) are then calculated from the dominant modes, enabling precise identification of the relaxation characteristic parameters. Finally, the accuracy and feasibility of the proposed method are verified through a combination of simulation experiments and laboratory tests. Full article

The detection of Partial Discharge Inception Voltage (PDIV) is vital for evaluating the insulation performance of random-wound inverter-fed motor stators. However, existing research on the impact of impulse parameters on PDIV patterns and their underlying mechanisms is limited, leading to inadequate guidelines for choosing suitable impulse parameters during PDIV tests of stator insulation under impulsive conditions. This lack of understanding significantly affects the precision of the accuracy of insulation test results for inverter-fed motors. To bridge this gap, this study systematically investigated the influence of key impulse parameters, such as pulse width, dead time, and impulse frequency, on the PDIV test outcomes in enameled wire samples (enameled twisted pairs and pig-tail wires) and random-wound inverter-fed motor stators. A differential bipolar repetitive impulse voltage and a sinusoidal voltage were applied to simulate the pulse-width modulation electrical stress typically experienced by these motors. Results reveal a negative correlation between PDIV test results and pulse width, a positive correlation with dead time, and a weak correlation with impulse frequency. Furthermore, the potential fundamental mechanisms are proposed for the influence of impulse voltage parameters on PDIV characteristics by analyzing the electric field distribution and discharge processes within insulating materials when subjected to impulsive voltages. Based on the experimental conclusion, this study proposes targeted recommendations for revising the current IEC testing standards. These improvements are anticipated to refine stator insulation testing methodologies for inverter-fed motors, ultimately contributing to enhanced insulation reliability in such electric motors. Full article

Inter-turn short circuits (ITSCs) in permanent magnet synchronous motors (PMSMs) pose significant risks due to their subtle early symptoms and rapid degradation. To address this, we propose an online real-time diagnostic method for assessing the degradation state. This method employs the Sparrow Search Algorithm (SSA) for the online real-time identification of fault characteristic parameters. Following an analysis of the fault mechanisms of inter-turn short circuits, a mathematical model has been developed to include the short-circuit turns ratio and insulation resistance. An evaluation index has also been developed to assess the degree of fault-related degradation. To address the strong nonlinearity of parameters in the fault model, the SSA is employed for the real-time joint identification of parameters that characterize the relationship between fault location and degradation degree. Simulation experiments demonstrate that the SSA achieves convergence within 40 iterations, with a relative error below 5% and absolute error less than 0.007, outperforming traditional algorithms like the PSO, a significant improvement in the early detection of degradation caused by inter-turn short circuits and a step forward in technical support ensuring greater reliability and safety for the traction systems used in rail transit. Full article

In light of the large and fast-growing use of power electronics in electrical generation, distribution and utilization systems, and with the focus on electrified transportation, evaluating the significance of testing insulation systems for design and quality control under AC sinusoidal or power electronics waveforms is a due knowledge step. This paper has a twofold aim. One is presenting a procedure for the comparison between two insulation system solutions for partial discharge, PD, free design, referring to motorettes of a MV speed-controlled motor. The other is to carry out an evaluation of the most effective testing waveform, from AC sinusoidal to AC modulated (PWM), varying the number of inverter levels and switching the slew rate. It is shown that AC sinusoidal is effective for a qualitative evaluation of insulation system design as regards partial discharge risk, but PD inception voltage can be significantly dependent on supply voltage waveforms. Hence, if quantitative estimation of partial discharge inception voltage is requested, for design and quality control purposes, PWM waveforms as close as possible to those planned under operation should be used. Full article

The performance of enameled wires has an important impact on new energy vehicle motors. The mainstream practice of existing technology is to improve partial discharge inception voltage (PDIV) by doping powder to inhibit corona and increase varnish thickness, the limitations of which are also obvious. Powder doping has the problem of dispersion stability, and increasing the varnish thickness affects the size and power density of the motor. In this paper, a novel insulation structure design was given. The electronic field stress was controlled by using different dielectric constant materials, and the dielectric constants can be controlled by adjusting the free volume of the polymer. Finally, we specifically create a preparation scheme to increase the corona voltage and the PDIV, without a loss of the breakdown margin of the enameled wire, and the simulation results show that the outermost electric field strength of the enameled wire model decreases by 22.11% and the enameled wire breakdown margin increases by 26.85%. Full article

Accurate prediction and efficient suppression of conducted electromagnetic interference(EMI) in electric drive systems(EDS) are achieved through an innovative technique proposed in this paper, leveraging a key path impedance characteristic model. The influence of critical components—namely; three-phase alternating current modules; motors; and insulated gate bipolar transistor drive parameters—on EMI is meticulously analyzed by establishing a current spectrum characteristic analysis model of the critical path impedance. This study calculates current characteristic curves under varying filter parameters for interference suppression, while voltage characteristic curves are computed based on a comprehensive electric drive system model. The mapping relationship between current and voltage spectrum characteristics is scrutinized, revealing a high consistency between the model’s current spectrum curves and the conducted interference voltage spectrum. This alignment enables precise prediction of risk frequency points. Moreover, the critical path impedance model remarkably enhances computational efficiency by 87.5%, thereby facilitating an efficient evaluation and design of EMI suppression in electric drive systems. The proposed technique effectively reconciles the incompatibility between accurate EMI prediction and efficient filter circuit design. Experimental results corroborate the technique’s accuracy and reliability. This method, validated through stringent testing, holds significant practical value and broad applicability, marking a substantial advancement in the field of electromagnetic compatibility for electric drive systems. Full article

This study investigates the critical issue of arc-induced partial discharge in high-voltage motor stator windings and proposes a cost-effective, targeted maintenance approach to mitigate these effects. Diagnostic techniques, including insulation resistance tests, tan δ measurements, partial discharge analyses, and UV camera inspections, were employed to identify and assess fault points. A novel partial maintenance method involving felt-pad insulation reinforcement was implemented to address the arc discharge issues. Post-maintenance diagnostics confirmed a significant reduction in partial discharge levels, with an average decrease of over 80%, demonstrating the effectiveness of the proposed approach. Compared to traditional rewinding methods, this technique offers substantial savings in time and cost while enhancing motor reliability. The findings underscore the importance of precise diagnostics and tailored interventions in extending the lifespan and operational stability of high-voltage motors, providing practical insights for industrial maintenance strategies. Full article

This study addressed the challenges of excessive eddy current losses and elevated thermal risks to permanent magnets in titanium alloy rotor sleeves for high-speed permanent magnet synchronous motors (HSPMSMs). Focusing on a 10 kW, 30,000 rpm high-speed motor, we innovatively propose incorporating insulating layers between axially laminated sleeve structures. Current research primarily mitigates eddy currents through the limited axial segmentation of sleeves/permanent magnets or radial shielding layers, while the technical approach of applying insulating coatings between laminated sleeves remains unexplored. This investigation demonstrated that compared with conventional solid sleeves, segmented sleeves, and carbon fibre sleeves, the laminated structure with a coordinated design of aluminium oxide and epoxy resin insulating layers effectively blocked the eddy current paths to achieve a substantial reduction in the sleeve eddy current density. This research concurrently highlights that the dynamic stress response and long-term operational reliability require further experimental validation. Subsequent investigations could explore optimised lamination patterns, parameter matching of insulating layers, and integration with emerging cooling technologies, thereby advancing synergistic breakthroughs in lightweight design and thermal management for high-speed motor rotors. Full article

Previous reviews by authors indicate the continuing development and improvement of thermal protective systems through the introduction of polymer nanocomposites into polymer matrix composites. These materials perform as thermal protective systems for a variety of aerospace applications, such as thermal protection systems (TPSs), solid rocket motor (SRM) nozzles, internal insulation of SRMs, leading edges of hypersonic vehicles, and missile launch structures. A summary of the most recent global technical research is presented. Polymeric resin systems continue to emphasize phenolic resins and other materials. New high-temperature organic resins based on phthalonitrile and polysiloxane are described and extend the increased temperature range of resin matrix systems. An important technical development relates to the transformation of the resin matrix, primarily phenolic resin, into an aerogel or a nanoporous material that penetrates uniformly within the reinforcing fiber configuration with a corresponding particle size of <100 nm. Furthermore, many of the current papers consider the use of low-density carbon fiber or quartz fiber in the use of low-density felts with high porosity to mimic NASA’s successful use of rigid low-density carbon/phenolic known as phenolic impregnated carbon ablator (PICA). The resulting aerogel composition with low-density non-wovens or felts possesses durability and low density and is extremely effective in providing insulation and preventing heat transfer with low thermal conductivity within the aerogel-modified thermal protective system, resulting in multiple features, such as low-density TPSs, increased thermal stability, improved mechanical properties, especially compressive strength, lower thermal conductivity, improved thermal insulation, reduced ablation recession rate and mass loss, and lower backside temperature. The utility of these TPS materials is being expanded by considering them for infrastructures and ballistics besides aerospace applications. Full article

Titanium (Ti) thin films deposited on insulated substrates were progressively anodized and formed titanium dioxide (TiO₂) nanotube arrays on the surface through a customized anodization tool designed to improve the uniformity and diameters of the nanotubes. With a motorized vertical moving arm attached to the anode, the sample was gradually submerged into the electrolyte at a controlled speed alongside the continuous anodization from the edge to the center to prevent the discontinuation of the conductive Ti layer and its nanotube surface. The effects of Ti deposition rate, anodization voltage, NH₄F concentration, and post-etching conditions on nanotube morphology were also explored. Scanning electron microscopy (SEM) analysis revealed that smaller Ti grain sizes, higher anodization voltages, higher electrolyte concentrations, and optimized post-etching times produce uniform, mature nanotubes with larger diameters, which are crucial for practical applications. This work enhances the applicability of nanotube surfaces with non-conductive substrates, such as Zirconia dental implants, and establishes a foundation for future process optimizations. Full article

This paper comprehensively presents an approach for modeling form wound coils of a motor driven by an inverter, with focus on the electric stresses on the coil insulation. A 10 kV SiC testbed for medium voltage form wound coils was developed to support and validate the modeling techniques discussed. A finite element analysis (FEA) model of the motor coil is presented using COMSOL 6.1. The FEA model was used to determine parameters for an electrical model based on the multi-conductor transmission line theory. The linking of these models allows for a rapid analysis of the electrical stresses the insulation can be exposed to. An experimental method for model validation using the empirical transfer function estimation (ETFE) approach to find the impedance response of the testbed for comparison to the proposed electrical model is presented and employed. The paper also uses the model to analyze the impact of insulation delamination and voids and to demonstrate the implementation of a metric called insulation state of health monitoring for both healthy and damaged coils. Full article

Electric vehicles (EVs) rely on robust inverter-to-motor connections to ensure high-efficiency operation under the challenging conditions imposed by wide-bandgap (WBG) semiconductors. High switching frequencies and steep voltage rise times in WBG inverters lead to repetitive transient overvoltages, causing insulation degradation and premature motor winding failure. This study proposes a wideband (WB) model of EV cables, developed in EMTP-RV, to improve transient voltage prediction accuracy compared to the traditional constant parameter (CP) model. Using a commercially available EV-dedicated cable, the WB model incorporates frequency-dependent parasitic effects calculated through the vector fitting technique. The motor design is supported by COMSOL Multiphysics and MATLAB 2023 simulations, leveraging the multi-conductor transmission line (MCTL) model for validation. Using practical data from the Toyota Prius 2010 model, including cable length, motor specifications, and power ratings, transient overvoltages generated by high-frequency inverters are studied. The proposed model demonstrates improved alignment with real-world scenarios, providing valuable insights into optimizing insulation systems for EV applications. Full article

This study presents a flywheel energy storage system utilizing a new multi-axial flux permanent magnet (MAFPM) motor–generator for coil launchers. The traditional winding structure of the flywheel is effective for energy recovery over several minutes. However, because the projectile is launched from coil launchers in less than one second, the traditional winding structure experiences insulation deterioration and winding damage due to the high current. This study proposes a winding structure made of an 8 × 0.5 mm conductor with eight turns to meet the energy requirements of coil launchers. Furthermore, the motor winding was divided into two sections, which were compared using both series and parallel connection methods as described in the literature. The proposed system produces energy that is 29.96%, 85.63%, and 81.11% lower than the A winding (where A and B are identical), the A + B winding (series connected), and A//B winding (parallel connected) at the same speed. However, as the speed increases by 258.26%, the energy output rises by 215.88%. The flywheel motor–generator’s series-parallel winding structure reaches its current carrying capacity at 1188 rpm. By utilizing a separate winding instead of the traditional motor–generator winding, a current of 38.4 A is achieved, ensuring that the winding’s current carrying capacity remains within the design parameters. Experimental data have proven that the proposed multi-wire winding structure is an innovative solution for coil launchers, surpassing various combinations of motor–generator windings found in the literature. Furthermore, the placement of the proposed winding in a single slot in the design ensures a compact structure. Full article

Inspired by earthworm peristalsis, a novel modular robot suitable for narrow spaces is proposed, capable of elongation, contraction, deflection and crawling. Unlike motor-driven robots, the earthworm-inspired robot achieves extension and deflection in each module through “on–off” control of the SMA springs, utilizing the cooperation of mechanical skeletons and gears to avoid posture redundancy. The return to the initial posture and the maintenance of the posture are achieved through tension and torsion springs. To study the extension and deflection characteristics, we established a model through kinematic and force analysis to estimate the relationship between the length change and tensile characteristics of the SMA on both sides and the robot’s extension length and deflection angle. Through model verification and experiments, the robot’s extension, deflection and movement characteristics in narrow spaces and varying curvature narrow spaces were comprehensively studied. The results show that the earthworm-inspired robot, as predicted by the model, possesses accurate extension and deflection performance, and can perform inspection tasks in complex and narrow space environments. Additionally, compared to motor-driven robots, the robot designed in this study does not require insulation in low-temperature environments, and the cold conditions can improve its movement efficiency. This new configuration design and the extension and deflection characteristics provide valuable insights for the development of new modular robots and robot drive designs for extremely cold environments. Full article