ABSTRACT High‐frequency transformers provide galvanic isolation and voltage transformation in power electronic systems, and their performance—especially loss and power density—is strongly influenced by the core material. In this study, PC40 ferrite and 1K107B nanocrystalline toroidal cores are selected for investigation. An experimental platform is built to characterise their magnetic and loss properties at 10 kHz. Using the measured magnetization curves and actual core dimensions, 3D finite element models of transformers with the two toroidal cores are developed. The magnetic flux density and loss density distributions are simulated and analysed, and the calculated core losses are compared with experimental results. The relative mean errors for both cores are within 15%, verifying the model's accuracy. The results show that the model can reliably predict core loss and provides guidance for the design and analysis of high‐frequency transformers.
ABSTRACT Since its discovery, surface hydrophobicity has been extensively studied and applied, and it has been preliminarily implemented in the prevention of ice accretion on power equipment within electrical systems. However, current research on anti‐icing and the freezing process of hydrophobic surfaces primarily focuses on observational and experimental studies, whereas there is a relative scarcity of research on the microscopic mechanism analysis and numerical simulation of the water droplet freezing process on hydrophobic surfaces. From a thermodynamic perspective, this paper combines the finite element numerical method with theoretical knowledge of fluid heat transfer. Selecting actual experimental parameters from artificial climate conditions as simulation parameters, it conducts computational simulations and experimental measurements on the freezing time and temperature of individual water droplets during the freezing process on various hydrophobic surfaces. The study finds that the latent heat of the water–ice phase transition determines the temperature variation pattern of water droplets, and the release of latent heat slows the rate of temperature decrease in the droplets, thereby prolonging the freezing time. As the static contact angle of the material surface increases, the freezing time of water droplets also increases with the two exhibiting an approximately linear relationship. This indicates that enhancing the hydrophobicity of a material surface can delay droplet freezing, and the findings of this study can provide a reference for the research and development of passive anti‐icing coatings.
ABSTRACT Lithium‐ion pouch batteries are widely used in electric vehicles and energy storage systems due to their high energy density. However, irreversible expansion and nonuniform stress distribution during the cycling process severely limit battery lifespan and safety performance. In this study, a distributed stress monitoring system for battery surfaces was developed to investigate the influence of various factors on surface mechanical stress under actual operating conditions of battery modules and to reveal the expansion mechanism of batteries. The results indicated that the evolution of mechanical stress exhibited a three‐stage characteristic: charging increase, stable standby and discharge recovery. Spatial distribution shows significant gradients, with maximum stress values at the centre, intermediate stress near the tabs and minimal stress at the edge constraint zone. Regarding influencing factors, within the studied range, both charging/discharging rates and pre‐tensioning force generally correlate positively with mechanical stress. Moderate pre‐tensioning enhances discharge capacity. Temperature effects exhibited differentiated characteristics: Mechanical stress significantly increased under high‐temperature conditions, whereas high stress levels persisted at low temperatures due to lithium ion surface accumulation. This research provides a theoretical foundation for selecting buffer materials for battery casings, optimising module structures and implementing pressure‐adaptive control in battery management systems.
ABSTRACT A ZB/CNTs/E606 conductive anti‐corrosion composite coating was prepared on Q235 steel via a physical blending process. The coating consists of E606 epoxy resin as the matrix, carbon nanotubes (CNTs) as the conductive filler, and a metal‐organic framework ZIF‐8 encapsulating the corrosion inhibitor benzotriazole (BTA) as a functional modifier (denoted as ZB). The coating with 0.5 wt.% ZB retains low resistivity (∼10 −2 Ω·m) after 30‐day saline immersion/salt‐spray exposure, exhibits high low‐frequency (|Z| 0.01Hz ) impedance (3.3 × 10 5 Ω·cm 2 ), and shows no corrosion after 40‐day salt‐spray testing. Adhesion remains above 10 MPa in all tested conditions. The coating combines sustained conductivity, strong adhesion and active corrosion inhibition, offering a durable solution for grounding systems in aggressive environments.
ABSTRACT To address the challenges of noise control in urban substations, a detailed noise characteristic analysis was conducted, identifying 100, 200 and 300 Hz as the primary low‐frequency noise components. To effectively absorb these frequencies, a neck‐embedded honeycomb‐shaped Helmholtz resonator was proposed, with its structural parameters optimised via genetic algorithms for selective sound absorption. An ultrastructured acoustic plate was then designed using array coupling between cavities and numerical analysis methods. Simulation results demonstrated that the proposed model achieved absorption coefficients exceeding 0.9 at the target frequencies. Experimental validation, conducted using impedance tube testing on a 3D‐printed version of the acoustic plate, showed strong agreement with the simulation results, confirming the potential and practicality of the proposed ultrastructured material for low‐frequency noise reduction in urban substations. Finally the application effect of acoustic metamaterial was testified using acoustic field simulation in a 110 kV substation.
ABSTRACT Ferroelectric (Ba, Zr)TiO 3 (BZT) glass‐ceramics doped with varying BaO–B 2 O 3 –SiO 2 glass contents (0–0.15 wt.%) were synthesised via solid‐state reaction. It was found that the introduction of the glass additive significantly reduced the sintering temperature of the pure perovskite BZT phase (1180°C) compared to conventional BZT ceramics, while simultaneously increasing the relative density to over 96%. This phenomenon is primarily attributed to the liquid phase formed by the glass additive at lower temperatures, which enhances particle wetting and inhibits grain boundary migration. Although dielectric constant decreased progressively with increasing glass content, the sample doped with 0.1 wt.% glass retained favourable dielectric characteristics at the paraelectric state. This study demonstrates a viable strategy for optimising key performance parameters low‐temperature sintering, low loss, high breakdown strength and high‐frequency stability exhibiting competitive performance relative to lead‐free ferroelectric ceramics in low‐temperature co‐fired multilayer ceramic capacitors (MLCCs).
Subsea cable connectors are critical components in offshore power delivery systems. They consist of a plug and receptacle, where current‐carrying parts are enclosed in solid insulation and placed within a liquid‐filled diaphragm. With the growing demand for power transfer and renewable energy integration in subsea environments, there is a need for alternative insulation materials that ensure system integrity while minimising environmental impact. This paper proposes integrating polyether ether ketone (PEEK) with a synthetic ester liquid as the composite insulation system for subsea cable connectors. The study commences with a comparative analysis of the electrical performance of PEEK when immersed in synthetic ester versus mineral oil. The AC breakdown strength (BDS) of PEEK in synthetic ester liquid under varying temperatures and thicknesses is also investigated. Results show that the breakdown strength of PEEK immersed in synthetic ester liquid surpasses that in mineral oil, largely due to the closer permittivity match between PEEK and the ester liquid. Likewise, the BDS decreases with increasing thickness, following a power‐law relationship but remains stable within the tested temperature range of 20°C–80°C. Breakdown locations, estimated using an in‐house MATLAB programme, occurred predominantly near the triple point junction.
The substation framework exhibits a relatively large thermal expansion coefficient and undergoes considerable deformation under elevated temperatures; this deformation may result in localised structural failures, potentially triggering the collapse of the entire system. In this study, ABAQUS software was employed to simulate three distinct fire conditions based on the standard heating curve; the displacement characteristics, deformation curves and deflection changes of the steel pipe herringbone column substation frameworks were analysed and the performance characteristics of the substation framework with and without fire-resistant coating were compared. The research results indicate that: Under the static force, the location of the maximum displacement occurs at the connection points between the two central web elements and the chord, measuring 0.01033 m. The bare steel truss components subjected to high temperatures experience significant deformation, with displacement surpassing 100 mm, potentially leading to brittle failure of the steel. In contrast, when fire-resistant coating is applied, structural deformation is considerably mitigated, limiting displacement to within 20 mm. The maximum deflection observed in bare steel structures exceeds the regulatory threshold of 70 mm. However, with the application of fire-resistant coating, the entire steel structure remains in an upward expansion stage and the resulting deflection remains under 20 mm.
(K, Na)NbO 3 ‐based lead‐free piezoelectric materials are considered a promising candidate to replace a lead‐containing counterpart in actuator applications, with electrical fatigue being a major concern during this transition. This study elaborates on a promising material with a nominal composition of 0.92(K 0.5 Na 0.5 )NbO 3 ‐0.02(Bi 0.8 Li 0.2 )TiO 3 ‐0.06BaZrO 3 (BZ6) and evaluates its unipolar fatigue resistance. After 10 7 cycles of unipolar fatigue, the strain variation of the BZ6 ceramic is within 8% of its initial value, and both its S ( E ) and ε 33 ( E ) curves exhibit less pronounced asymmetry than that of PIC151. Strain asymmetry and the development of internal bias fields are observed in the composition, which originates from the agglomeration of space charge during unipolar cycling. The post‐annealing treatment allows the full restoration of electrical properties for the fatigued BZ6 ceramic, making it highly suitable for actuator applications.
In this work, stereo lithography apparatus (SLA) additive manufacturing (AM) was employed to fabricate the Al 2 O 3 ceramic substrate for circuit board. The influence of sintering temperature on microstructure and mechanical properties was investigated. The XRD and SEM were carried on to detect the phase transformation and morphology. With an increment of sintering temperature, the grain size of bulks displays an increasing tendency, while the flexural strength exhibits a trend of first increasing, reaches a peak, and subsequently decreasing. This work provides a method to prepare a high‐performance Al 2 O 3 ceramic, which can be applied in electronics and semiconductors.
Dual‐phase composite magnetic materials represent a novel class of magnetic systems formed through exchange coupling between soft and hard magnetic phases. These materials combine the high remanence of hard magnetic phases with the low coercivity of soft magnetic phases, enabling rapid functional switching with minimal energy loss. This makes them promising candidates for power equipment. In this work, Nd 2 Fe 14 B/α‐Fe dual‐phase magnets were prepared using a hot‐pressing and hot‐deforming process on mixed powders. The effect of α‐Fe content (10–60 wt.%) on the phase structure and magnetic properties was investigated. Increasing α‐Fe content enhances the saturation magnetic polarization ( J s ) from 1.48 to 1.77 T, but reduces remanence ( J r ) from 1.28 to 0.73 T and coercivity ( H c ) from 133.35 to 13.51 kA/m, attributing to the breakdown of exchange coupling mechanisms under excessive soft‐phase fractions. Magnets with 40–50 wt.% α‐Fe exhibit excellent high‐temperature (400 K) properties, maintaining J r ≥ 0.80 T and H c ≤ 26.82 kA/m. Furthermore, these magnets demonstrate a low remanence temperature coefficient (−0.19%/K to −0.25%/K) and retain hardness above 50 HRC. This work achieves synergistic optimization of magnetic properties, thermal stability and mechanical performance, providing valuable supports for developing the dual‐phase composite magnetic materials with high J r and low H c for power equipment.
Urban low-frequency noise is an increasingly urgent environmental issue. This study explores the development of low-carbon, sound-absorbing materials using fly-ash cenospheres as lightweight aggregates and solid waste cementitious materials as binders. Fly-ash cenospheres plates were fabricated using varying cementitious material/bead mass ratios and bead sources. The results demonstrated that both parameters significantly influenced the mechanical and acoustic properties of the composites. Notably, plates prepared with 20–40 mesh fly-ash cenospheres at a cementitious material/bead ratio of 1.5:1 exhibited superior sound-absorbing performance. Without a backing cavity, the maximum and average sound absorption coefficients within 50–1600 Hz were 0.65 and 0.39, respectively. With a 40-mm cavity, the peak sound absorption reached 0.98, and the average coefficient within 100–500 Hz was 0.56. These findings support the feasibility of using recycled industrial waste to produce efficient low-frequency sound-absorbing materials, offering both environmental and functional benefits.
There is a strong demand for polymers with high thermal conductivity; however, traditional composite fabrication methods frequently fall short of achieving the desired performance, primarily due to limitations at the polymer–filler interface. In this work, we experimentally demonstrate that molecular chain rearrangement in the interfacial region originates from chemical bonding between nanoparticles and the surrounding polymer matrix, which plays a crucial role in thermal transport. To examine this effect, we prepared boron nitride (BN)/polyimide (PI) composites in situ using fillers of unmodified BN as well as BN grafted with amino, carboxyl and hydroxyl groups. The thermal diffusivity of these composites was systematically evaluated, and the results show that chemical bonding promotes both improved phonon transport and optimised polymer chain distribution, leading to a peak in thermal diffusivity at moderate filler contents. This study highlights the essential role of interfacial chemical bonding and chain rearrangement in determining the thermal properties of polymer composites and provides useful guidance for designing materials with enhanced thermal conductivity.
The accelerating shift towards electric vehicles (EVs) has intensified the demand for efficient, reliable and scalable power electronic converters (PECs), which are critical in managing energy flow between batteries, traction motors, regenerative braking systems and auxiliary loads. This paper presents a comprehensive review of DC–DC converter topologies across four major EV architectures: battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PEVs) and fuel cell electric vehicles (FCEVs). Converters are categorised into unidirectional, bidirectional and multi-input types and evaluated by voltage gain, ripple mitigation, efficiency, switching strategies and control complexity. Typical efficiency ranges are highlighted: nonisolated bidirectional converters at 83%–88%, interleaved topologies commonly 90%–96% and resonant converters using wide-bandgap (WBG) devices at 95%–98.9%. Advanced designs, such as zero-voltage switching (ZVS)/zero-current switching (ZCS), isolated full-bridge and multiport converters, are explored. Special emphasis is placed on silicon carbide (SiC) and gallium nitride (GaN) devices for high-frequency operation in the hundreds of kHz (with lab demonstrations approaching ∼1 MHz) and high-power density. Persistent challenges include electromagnetic interference (EMI), thermal management during ultrafast charging (ΔTj > 70°C) and WBG reliability. Emerging directions include AI-based diagnostics achieving > 99% capacitor ageing prediction, vehicle-to-grid (V2G) with ISO 15118 and the integration of silicon photonics and quantum control for next-generation EVs.
To improve the mechanical properties and heat resistance of iron powder cores for inductors, the carbonyl iron powder was insulation-treated via phosphating and epoxy-modified bismaleimide resin coating. The addition of epoxy into bismaleimide resin significantly enhanced the magnetic performance, mechanical strength and thermal stability of powder cores. The optimised core exhibited an effective permeability μ e of 25.8 and a quality factor Q of 54.9 at 1 MHz, with a power loss P cv of 510.2 kW·m −3 at 100 kHz/50 mT. The radial crushing strength increased by 102% compared to the core coated with only bismaleimide. After thermal exposure at 155°C for 336 h, the cores coated with epoxy-modified bismaleimide showed lower reductions in saturation magnetisation and minimal changes in μ e (4.41%), Q (4.96%) and P cv (3.82%), indicating improved heat resistance. Epoxy modification enhanced bismaleimide performance by forming hydroxyl groups through their interaction, creating strong polar bonds with iron powder. The interaction results in a three-dimensional network structure consisting of rigid and flexible molecular chains. This structure reinforced the mechanical properties and heat resistance of the iron powder core.
Insulators and conductors as the electric and the electronic materials are discussed. These insulators and conductors are supporting materials; however, they are mandatory to enhance device performances and provide the functions and roles to the devices that the mainstream semiconductors cannot cover. The review aims to introduce the fundamental roles and the examples of the implementations on state-of-the-art electric and electronic fields. Referring to Part I: semiconductors will also provide a deeper understandings.
Epoxy resin (EP) has become the larger amount of insulation material for dry-type electrical equipment due to its excellent electrical insulation, chemical stability, and process adaptability. However, the mechanical properties deterioration and structure cracking of insulation caused by internal heat accumulation and mechanical stress in electrical equipment runtime restricted the development of high-voltage equipment. In this work, epoxy-terminated butadiene nitrile rubber (ETBN) was employed as a mechanically enhanced filler, and hexagonal boron nitride (h-BN) was used as thermally conductive functional filler. The stress dissipation channels and heat conduction paths in EP composites were constructed, respectively, via utilising sheet-like h-BN content to regulate the morphology of ETBN distribution holes. The toughness was 1198 and 2304 kJ/m 3 at 25°C and 80°C in the EP-ET 20 /h-BN 5 composite, respectively, and the thermal conductivity had increased by 67.0% compared to the EP-ET 20 composite. This work provides a new microstructure design in EP composite with excellent comprehensive performance for dry-type electrical equipment.
This study investigates the influence of rolling passes and annealing methods on the microstructure and texture of ultrathin grain-oriented silicon steel, aiming to improve its magnetic properties by optimising processing parameters. The results show that under identical total rolling reductions and annealing conditions, more rolling passes weaken η-fibre recrystallisation texture, thus reducing magnetic induction (B 8 ). Meanwhile, more rolling passes lead to coarser microstructure after short annealing, whereas non-η-fibre oriented grains exhibit more pronounced growth advantage with prolonged annealing. Consequently, the sheets rolled by 4–5 passes show an initially decreasing and then increasing trend in iron loss. When the rolling method is same, higher annealing temperatures accelerate non-η-fibre oriented grain growth. This not only drives grain sizes into a critical range that raises iron loss but also exacerbates the weakening of η-fibre texture, collectively deteriorating magnetic properties. To sum up, the magnetic properties of ultrathin grain-oriented silicon steel are predominantly determined by the extent to which η-fibre oriented grains are consumed by other growing grains during annealing. In this study, optimal magnetic properties, specifically B 8 > 1.8 T and P 1.5/400 < 12 W/kg, can be achieved through four-pass rolling combined with annealing at 820°C or 850°C by adjusting the annealing time.
Dual-phase composite magnetic materials represent a novel class of magnetic systems formed through exchange coupling between soft and hard magnetic phases. These materials combine the high remanence of hard magnetic phases with the low coercivity of soft magnetic phases, enabling rapid functional switching with minimal energy loss. This makes them promising candidates for power equipment. In this work, Nd 2 Fe 14 B/α-Fe dual-phase magnets were prepared using a hot-pressing and hot-deforming process on mixed powders. The effect of α-Fe content (10–60 wt.%) on the phase structure and magnetic properties was investigated. Increasing α-Fe content enhances the saturation magnetic polarization ( J s ) from 1.48 to 1.77 T, but reduces remanence ( J r ) from 1.28 to 0.73 T and coercivity ( H c ) from 133.35 to 13.51 kA/m, attributing to the breakdown of exchange coupling mechanisms under excessive soft-phase fractions. Magnets with 40–50 wt.% α-Fe exhibit excellent high-temperature (400 K) properties, maintaining J r ≥ 0.80 T and H c ≤ 26.82 kA/m. Furthermore, these magnets demonstrate a low remanence temperature coefficient (−0.19%/K to −0.25%/K) and retain hardness above 50 HRC. This work achieves synergistic optimization of magnetic properties, thermal stability and mechanical performance, providing valuable supports for developing the dual-phase composite magnetic materials with high J r and low H c for power equipment.
This paper investigates the effect of β-crystal on the electrical tree growth and breakdown characteristics of polypropylene (PP) cable insulation under mechanical stress. Mechanical stress promotes the growth of electrical trees and reduces the breakdown strength of PP insulation. When mechanical stress is applied, electrical trees exhibit a more dispersed distribution, with a notable expansion of the damaged area, evolving into a bush–branch configuration. β-crystals enhance the mechanical properties of PP insulation, effectively suppressing electrical tree degradation and partial discharge (PD) under mechanical stress. Compared to stressed PP/0 (PP insulation containing 0 wt% β-nucleating agent), the cumulative damage area of stressed PP/0.2 (PP insulation containing 0.2 wt% β-nucleating agent) decreases by 0.137 mm 2 and the maximum PD amplitude is reduced by 493.2 pC. Moreover, β-crystals mitigate the reduction in breakdown strength of PP insulation under mechanical stress. Among all samples, PP/0.2 exhibits the smallest reduction in breakdown strength, showing a 30.90% improvement over stressed PP/0 at 30°C. The inclusion of 0.2 wt% β-nucleating agents effectively suppresses the growth of electrical trees and mitigates the reduction in breakdown strength of PP cable insulation under mechanical stress, thereby improving the stability of PP insulation in stress environments.
