Search Results (220)

With the electrification of generator sets, electric locomotives, new energy vehicles, and other industries, AC motors subject bearings to an electric field environment, leading to galvanic corrosion due to the use of variable frequency power supply drives. The phenomenon of bearing discharge breakdown in subway traction motors is a critical issue in understanding the relationship between shaft current strength and the extent of bearing damage. This paper analyzes the mechanism of impulse discharge that leads to galvanic corrosion damage in bearings at a microscopic level and conducts electric thermal coupling simulations of the traction motor bearing discharge breakdown process. It examines the temperature rise associated with lubricant film discharge breakdown during the dynamic operation of the bearing and investigates how breakdown channel parameters and operational conditions affect the temperature rise in the micro-region of bearing lubrication. Ultimately, the results of the electric thermal coupling simulation are validated through experimental tests. This study revealed that in an electric field environment, the load-bearing area of the outer ring experiences significantly more severe corrosion damage than the inner ring, whereas non-bearing areas remain unaffected by electrolytic corrosion. When the inner ring reaches a speed of 4500_rpm, the maximum widths of electrolytic corrosion pits for the outer and inner rings are measured at 89 um and 51 um, respectively. Additionally, the highest recorded temperatures for the breakdown channels in the outer and inner rings are 932 °C and 802 °C, respectively. Furthermore, as the inner ring speed increases, both the width of the electrolytic corrosion pits and the temperature of the breakdown channels rise. Specifically, at inner ring speeds of 2500_rpm, 3500_rpm, and 4500_rpm, the widths of the electrolytic pits in the outer ring raceway load zone were measured at 34 um, 56 um, and 89 um, respectively. The highest temperatures of the lubrication film breakdown channels were recorded as 612 °C, 788 °C, and 932 °C, respectively. This study provides a theoretical basis and data support for the protective and maintenance practices of traction motor bearings. Full article

Sulfur hexafluoride (SF₆), an extraordinary gas insulation medium, must be replaced by environmentally friendly gas in electric equipment because of its high global warming potential (GWP). In this research work, the DC breakdown properties of R404a gas and its mixtures with N₂ and CO₂ are studied under a sphere–sphere electrode configuration and uniform field conditions. The GWP of R404a is 16% of SF₆ and its liquefaction temperature is also in the suitable range for practical applications. Nitrogen and carbon dioxide are mixed with R404a to reduce its boiling point and GWP. Other important parameters such as the self-recoverability, liquefaction temperature, GWP, and synergistic effect of R404a/CO₂ and R404a/N₂ were also studied to complement the insulation performance and the results are comparable to other gas mixtures. As a result, it was found that both the mixtures containing 80% R404a and 20% N₂ or 20% CO₂ possess a breakdown strength of 0.83 times that of SF₆. Mixtures containing an 80% concentration of R404a possess a GWP equal to only 15% of SF₆. These properties make gaseous mixtures containing 80% R404a and 20% N₂ or CO₂ a suitable alternative to SF₆ in medium-voltage gas-insulated equipment. Full article

To address the impact of insulation medium degradation in the arc quenching chambers of ultra-high-voltage SF₆ circuit breakers on phase-controlled switching accuracy caused by multiple operations throughout the service life, this paper proposes an adaptive switching algorithm. First, a modified formula for the breakdown voltage of mixed gases is derived based on the synergistic effect. Considering the influence of contact gap on electric field distortion, an adaptive switching strategy is designed to quantify the dynamic relationship among operation times, insulation strength degradation, and electric field distortion. Then, multi-round switching-on and switching-off tests are carried out under the condition of fixed single-arc ablation amount, and the laws of voltage–current, gas decomposition products, and pre-breakdown time are obtained. The test data are processed by the least squares method, adaptive switching algorithm, and machine learning method. The results show that the coincidence degree of the pre-breakdown time obtained by the adaptive switching algorithm and the test value reaches 90%. Compared with the least squares fitting, this algorithm achieves a reasonable balance between goodness of fit and complexity, with prediction deviations tending to be randomly distributed, no obvious systematic offset, and low dispersion degree. It can also explain the physical mechanism of the decay of insulation degradation rate with the number of operations. Compared with the machine learning method, this algorithm has stronger generalization ability, effectively overcoming the defects of difficult interpretation of physical causes and the poor engineering adaptability of the black box model. Full article

The remaining lifetime of the cable insulation is an important but hard topic for the industry and research groups as there are more and more cables nearing their designed life in China. However, it is hard to accurately and efficiently obtain the ageing characteristic parameters of cross-linked polyethylene (XLPE) cable insulation. This study systematically analyzes the evolution of the remaining insulation lifetime of XLPE cables under different ageing states using the step-stress method combined with the inverse power model (IPM) and a physical-driven model (Crine model). By comparing un-aged and accelerated-aged specimens, the step-stress breakdown tests were conducted to obtain the Weibull distribution characteristics of breakdown voltage and breakdown time. Experimental results demonstrate that the characteristic breakdown field strength and remaining lifetime of the specimens decrease significantly with prolonged ageing. The ageing parameter of the IPM was calculated. It is found that the ageing parameter of IPM increases with the ageing time. However, it can hardly link to the other properties or physic parameters of the material. The activation energy and electron acceleration distance of the Crine model were also calculated. It is found that ageing activation energy stays almost the same in samples with different ageing time, showing that it is a material intrinsic parameter that will not change with the ageing; the electron acceleration distance increases with the ageing time, it makes sense that the ageing process may break the molecule chain of XLPE and increase the size of the free volume. It shows that the Crine model can better fit the physic process of ageing in theory and mathematic, and the acceleration distance of the Crine model is a physical driven parameter that can greatly reflect the ageing degree of the cable insulation and be used as an indicator of the ageing states. Full article

In this research work, two distinct types of three-dimensional (3D) capacitors were successfully fabricated, each with its own unique features and advantages. The first type of capacitor is centered around a 3D nanoporous structure. This structure is formed on a nickel substrate through anodic oxidation. After undergoing high-temperature thermal oxidation, a monolithic Ni-NiO-Pt metal–insulator–metal (MIM) capacitor with a nanoporous dielectric architecture is achieved. Structurally, this innovative design brings about several remarkable benefits. Due to the nanoporous structure, it has a significantly increased surface area, which can effectively store more charges. As a result, it exhibits an equivalent capacitance density of 69.95 nF/cm², which is approximately 18 times higher than that of its planar, non-porous counterpart. This high capacitance density enables it to store more electrical energy in a given volume, making it highly suitable for applications where miniaturization and high energy storage in a small space is crucial. The second type of capacitor makes use of Through-Glass Via (TGV) technology. This technology is employed to create an interdigitated blind-via array within a glass substrate, attaining an impressively high aspect ratio of 22.5:1 (with a via diameter of 20 μm and a depth of 450 μm). By integrating atomic layer deposition (ALD), a conformal interdigital electrode structure is realized. Glass, as a key material in this capacitor, has outstanding insulating properties. This characteristic endows the capacitor with a high breakdown field strength exceeding 8.2 MV/cm, corresponding to a withstand voltage of 5000 V. High breakdown field strength and withstand voltage mean that the capacitor can handle high-voltage applications without breaking down easily, which is essential for power-intensive systems like high-voltage power supplies and some high-power pulse-generating equipment. Moreover, due to the low-loss property of glass, the capacitor can achieve an energy conversion efficiency of up to 95%. Such a high energy conversion efficiency ensures that less energy is wasted during the charge–discharge process, which is highly beneficial for energy-saving applications and systems that require high-efficiency energy utilization. Full article

Since epoxy resin has excellent mechanical and insulating qualities, it is frequently utilized in dry transformers. Low thermal conductivity, however, has prevented it from be developed further in high-frequency and large-capacity dry transformers. This study describes the preparation of sheet boron nitride (BN)/epoxy resin composites with superior electrical, thermal, and mechanical properties through the application of varying strengths of high-frequency alternating-current (AC) electric fields. Using an optical microscope, the orienting process of BN in epoxy resin under an electric field was studied. In parallel, tests were conducted on the BN/epoxy resin composites made with varying electric field strengths. The findings indicate that the preparation using a high-frequency AC electric field decreases BN agglomeration and improves the composite’s properties. The overall performance is comparatively ideal when the applied electric field strength is 30 V/mm, the tensile strength is 48.3 MPa, the breakdown field strength is 37.65 kV/mm, and the thermal conductivity of the BN/epoxy resin composite is 0.95 W/(m·K). The thermal conductivity greatly increased and BN was organized into chains when the electric field approached 60 V/mm. The tensile strength and breakdown field strength, on the other hand, declined. Full article

Flexible thin-film capacitors have gained a lot of attention in energy storage applications because of their high energy storage densities and efficient charge–discharge performances. Among these materials, antiferroelectric compounds with low residual polarization and strong saturation polarization have shown great promise. However, their comparatively low breakdown strength continues to be a major issue restricting further developments in their energy storage performance. While La³⁺ doping has been explored as a means to enhance the energy storage capabilities of antiferroelectric thin films, the specific influence of La³⁺ on breakdown strength and the underlying mechanism of phase transitions have not been thoroughly investigated in existing research. In this study, Pb_1−3x/2La_xZrO₃ thin films were successfully synthesized and deposited on mica substrates via the sol–gel process. By varying the concentration of La³⁺ ions, a detailed examination of the films’ microstructures, electrical properties, and energy storage performances was carried out to better understand how La³⁺ doping influences both breakdown strength and energy storage characteristics. The results show that doping with La³⁺ significantly improves the breakdown strength of the films, reduces the critical phase transition electric field (E_F-E_A), and enhances their energy storage capabilities. Notably, the Pb_0.91La_0.06ZrO₃ thin film achieved an impressive energy storage density of 34.9 J/cm³ with an efficiency of 58.3%, and at the maximum electric field strength of 1541 kV/cm, the recoverable energy density (W_rec) was 385% greater than that of the PbZrO₃ film. Additionally, the film still maintains good energy storage performance after 10⁷ cycles and 10⁴ bending cycles. These findings highlight the potential of flexible antiferroelectric Pb_0.91La_0.06ZrO₃ thin films for future energy storage applications. Full article

Polymer-based nanocomposites have demonstrated significant strategic value in dielectric energy storage systems due to their tunable high energy density and rapid charge–discharge efficiency. Poly(arylene ether nitrile) (PEN), owing to its superior thermal stability, high mechanical strength, chemical corrosion resistance, and outstanding dielectric properties, exhibits distinct advantages in the field of high-performance dielectric energy storage devices. This review focuses on key strategies for enhancing the dielectric energy storage performance of PEN-based composites, emphasizing molecular engineering approaches, microstructural design, the multiscale interface regulation mechanisms within composite systems, and the optimization of the dielectric constant (ε_r) and breakdown strength (E_b) through thermal stretching. Furthermore, the potential of PEN-based polymer composites in energy storage devices is highlighted, and future research directions are proposed, including the establishment of a dynamic balance mechanism between dielectric/insulating properties and the development of novel composite systems that offer both high energy storage density and stability. These advancements will provide the material foundation for the miniaturization and intellectualization of advanced pulse power equipment. Full article

Although polyethylene is widely used in electrical insulation, it does not possess dielectric properties. It is therefore desirable to develop insulation materials with excellent dielectric properties. In this study, low-density polyethylene (LDPE) was used as a matrix resin, while MgO, wollastonite, and montmorillonite (MMT) were employed as inorganic nano-additives. Three composites were prepared using the boiling–melt blending approach. Power frequency breakdown tests were performed on the original LDPE and on the prepared nanoparticle/LDPE composites. Upon combination with the Weibull distribution, the breakdown test results revealed that the addition of these nano-additive particles to the LDPE matrix increased the breakdown field strength of the material. The highest breakdown field strength for the nano-MgO/LDPE composite was obtained using a MgO loading of 0.5%. Notably, the obtained value was 1.8% higher than that of the pure LDPE. In addition, the highest breakdown field strength for the nano-wollastonite/LDPE composite was obtained using a wollastonite loading of 1% (7.48% higher than that of pure LDPE). Similarly, the highest breakdown field strength of the nano-MMT/LDPE composite was obtained using an MMT loading of 3%, giving a value that was 6.67% higher than that of the pure LDPE. Full article

Relaxor ferroelectrics based on sodium bismuth titanate (Bi_0.5Na_0.5TiO₃, BNT) have attracted more interest recently as potential ecologically acceptable materials for pulse power technology because of their excellent full-energy storage capabilities. This paper formed (1 − x){0.97[0.98(BNT-ST)-0.02CN]-0.03AlN}-xNN ceramics through a traditional solid-state reaction process. It was noted that the incorporation of NaNbO₃ enhances the property of energy storage by elevating the breakdown strength and causing the creation of an ergodic relaxation state. The effective energy storage density (W_rec) and the energy storage efficiency (η) are 1.09 J/cm³ and 85%, respectively. The breakdown field strength E_b reached 155 kV/cm at x = 40%. These ceramics have excellent temperatures and frequency stabilities from 0.5 to 50 Hz and 20 to 60 °C. Full article

The excellent temperature stability and high saturation polarization of Bi_0.5Na_0.5TiO₃ (BNT) make it a promising candidate for energy storage capacitors. However, its disadvantages, such as low breakdown strength, high remnant polarization, and a complex sintering process, limit its further development. To address this, (1 − x) Bi_0.5Na_0.5TiO₃−x Sr(Mg_1/3Nb_2/3)O₃ ceramics were fabricated, where ion doping was employed to modify the domain structure, reduce the grain size, and improve the energy storage performance. With the increase in dopant concentration, the evolution from long-range-ordered ferroelectric micro-domains into short-range-ordered randomly oriented polar nanoregions (PNRs) was revealed, as demonstrated by XRD and Raman spectroscopy. This resulted in a diffuse phase transition peak and a significant reduction in remnant polarization. However, the saturation polarization also decreased. Finally, the optimal energy storage performance was achieved at a medium dopant concentration (x = 0.10), accompanied by reduced grain size and a dense microstructure. This composition exhibited a discharged energy density of 1.64 J/cm³ at a low electric field of 150 kV/cm, representing a notable improvement over pure BNT, which showed a highly lossy P-E loop and a discharged energy density of only 0.14 J/cm³ at the same electric field. 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

Magnetron sputtering allows for the accurate estimation of film thickness. Strontium titanate (STO) thin films were deposited on Nb-doped STO substrates using radiofrequency magnetron sputtering technology. The microstructures and dielectric properties of STO thin films were investigated. X-ray diffraction (XRD) analysis indicates that uniform polycrystalline STO films were obtained after thermal annealing at 650 °C. The films exhibit a significant correlation between thickness, annealing temperature, and breakdown field strength. The optimal film with a thickness of 1150 nm achieves a capacitance density of 1688 pF/mm² and a breakdown field strength of 270 kV/mm. Additionally, STO films annealed at 650 °C maintained their capacitance value within ±15% across a temperature range of −55 °C to 125 °C. These results highlight the potential of STO thin films for high-performance capacitor applications. Full article

GaN High-Electron-Mobility Transistors have gained some foothold in the power-electronics industry. This is due to wide frequency bandwidth and power handling. Gallium Nitride offers a wide bandgap and higher critical field strength compared to most wide-bandgap semiconductors, resulting in better radiation resistance. Theoretically, it supports higher speeds as the device dimensions could be reduced without suffering voltage breakdown. The simulation and experimental results illustrate the superior performance of the Gallium Nitride High-Electron-Mobility Transistors in an amplifying circuit. Using a spice model for commercially available Gallium Nitride High-Electron-Mobility Transistors, non-distorted output to an input signal of 200 ps was displayed. Real-world measurements underscore the fast response of the Gallium Nitride High-Electron-Mobility Transistors with its measured slew rate at approximately 3000 V/μs, a result only 17% lower than the result obtained from the simulation. This fast response, coupled with the amplifier radiation resistance, shows promise for designing improved detection and imaging circuits with long Mean Time Between Failure required, for example, by next-generation industrial-process gamma transmission-computed tomography. Full article

Propylene carbonate (PC) has several advantages, including a high dielectric constant, high resistivity, and excellent environmental adaptability, making it a promising candidate as a novel energy storage medium for pulse forming lines (PFL). In this study, an experimental platform for liquid insulation that is capable of delivering a maximum output voltage of 700 kV and a pulse rise time of approximately 100 ns is employed to examine the breakdown characteristics of PC under different electrode gaps. For comparison, the breakdown characteristics of deionized (DI) water are also investigated. The experiment utilizes a sphere-to-plate electrode configuration with a hemispherical electrode diameter of 5 cm, plate electrode diameter of 9 cm, and an adjustable electrode gap ranging from 0 to 1.5 cm. The results indicate that the breakdown voltages of both PC and DI water increase almost linearly with the electrode gap, whereas the average breakdown field strength decreases exponentially as the electrode gap widens. Unlike DI water, PC does not exhibit polarity effects under the test conditions. However, the insulation performance exhibits a measurable decline after the first breakdown. These findings highlight the advantages and limitations of PC as an energy storage medium and offer valuable insights into its potential applications in related fields. Full article