Capacitance plays a crucial role in high dv/dt situations, making the accurate estimation of parasitic capacitance essential. This paper introduces an improved method of moments (MoM) for calculating the capacitance of round conductors, with or without insulation layers. The proposed method combines MoM with an analytical solution based on Laplace's equation. Compared to the original MoM, the proposed method does not require consideration of polarization charges on the surface of the insulation layer, which reduces the matrix size. Additionally, the proposed method can provide asymptotic formulas for capacitance calculation. The proposed method is compared with the 2D finite-element method (FEM), MoM and measurements. The results demonstrate that the proposed method aligns well with both the FEM simulations and the actual measurements. The proposed method uses less than half the time to calculate the same cases compared to the original MoM.

Polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), and polyimide (PI) are widely used in aerospace due to their excellent properties. Understanding their aging behavior is essential for long-term performance in extreme environments. This study examines the effects of thermal oxidative aging (at 250°C over varying periods) under humid conditions on their chemical, structural, thermal, mechanical, and dielectric properties. In PEEK, aging led to solidification and crosslinking phenomenon which resulted in increased tensile strength and storage modulus, while elongation at break and tan δ decreased. Dielectric permittivity, polarization charge density, and leakage current also declined with aging, while AC breakdown strength increased by 1.6% in PEEK. PTFE exhibited surface oxidation, thermal degradation, and a decrease in storage modulus, with an increase in loss tangent. Breakdown strength slightly decreased, while dielectric loss and leakage current increased over aging time. PI underwent severe mechanical degradation, with tensile strength reduced by 54% and elongation by 16%, along with oxidation-induced discoloration. Low-mass polar molecules generated in PI during thermal degradation which contributed to the deterioration of its dielectric properties, lead to increased permittivity, polarization, leakage current, and a lower breakdown strength observed after aging. These findings provide insights into degradation mechanisms, aiding aerospace material selection for extreme environments.

In electron optics, calculation of the electric field plays a major role in all computations and simulations. Accurate field calculation methods such as the finite element method (FEM), boundary element method and finite difference method, have been used for years. However, such methods are computationally very expensive and make the computer simulation challenging or even infeasible when trying to apply automated design of electrostatic lens systems with many free parameters. Hence, for years, electron optics scientists have been searching for a fast and accurate method of field calculation to tackle the aforementioned problem in the design and optimization of electrostatic electron lens systems. This paper presents a novel method for fast electric field calculation in electrostatic electron lens systems with reasonably high accuracy to enable the electron-optical designers to design and optimize an electrostatic lens system with many free parameters in a reasonably short time. The essence of the method is to express the off-axis potential in an axially symmetrical coordinate system in terms of derivatives of the axial potential up to the fourth order, and equate this to the potential of the electrode at that axial position. Doing this for a limited number of axial positions, we get a set of equations that can be solved to obtain the axial potential, necessary for calculating the lens properties. We name this method the fourth-order electrode method because we take the axial derivatives up to the fourth order. To solve the equations, a quintic spline approximation of the axial potential is calculated by solving three sets of linear equations simultaneously. The sets of equations are extracted from the Laplace equation and the fundamental equations that describe a quintic spline. The accuracy and speed of this method is compared with other field calculation methods, such as the FEM and second order electrode method (SOEM). The new field calculation method is implemented in design/optimization of electrostatic lens systems by using a genetic algorithm based optimization program for electrostatic lens systems developed by the authors. The effectiveness of this new field calculation method in optimizing optical parameters of electrostatic lens systems is compared with FEM and SOEM and the results are presented. It should be noted that the formulation is derived for general axis symmetrical electrostatic electron lens systems, however the examples shown in this paper are with cylindrical electrodes due to the simplicity of the implementation in the software.

This paper investigates the high-frequency transformer losses attributed to eddy currents in both conductors and the core. A comprehensive model of a transformer winding is presented, meticulously incorporating skin and proximity effects. The winding resistance increase due to these effects is determined by applying analytical and finite element methods. The investigation highlights that eddy current losses in the magnetic core notably increase the resistance of each winding section in low frequencies. However, the impact of these losses diminishes as the winding length approaches the voltage wavelength at high frequencies. Consequently, the net magnetomotive force and flux in the core become negligible. As a result, the high-frequency impedance characteristics are remarkably similar for windings with and without a magnetic core. These findings are substantiated through rigorous simulations and empirical measurements.

More electric aircraft (MEA) is an important direction for future aircraft development. The printed circuit boards (PCBs) of power electronics equipment in MEA operate in a complex environment of low air pressure, square wave voltage, compact layout, and strong electromagnetic interference, which makes the PCB more prone to partial discharge (PD). However, the effective detection method and related discharge characteristics for PCB PD under square wave voltage are still unclear. Therefore, this article proposes a PCB PD detection method based on fluorescent optical fiber, which has good anti-electromagnetic interference ability. The PD characteristics of the PCB with three typical structures under three air pressures are studied, including PD nonbreakdown characteristics, changes in optical pulse amplitude and pulse repetition rate during PD aging, PD breakdown path analysis, and PCB surface electric field simulation. The analysis shows that air pressure, space charge, and PCB surface flatness all have important influences on the PD of PCB under square wave voltage. It provides important theoretical support for the insulation protection design and fault diagnosis of PCB for MEA in the future.

Dealing with the fast-rising current of high voltage direct current (HVdc) systems during fault conditions, is one of the most challenging aspects of HVdc system protection. Fast dc circuit breakers (DCCB) have recently been employed as a promising technology and are the subject of many research studies. HVdc circuit breakers (CBs) must meet various requirements to satisfy practical and functional needs, among which fast operation, low voltage stress, and economic issues are the key factors. This article presents the procedure for designing a superconductive reactor-based DCCB (SSR-DCCB) for HVdc applications. In the proposed structure, a full-bridge power electronic configuration controls the superconducting reactor to limit the dc fault current and create a dc zero-crossing; it is connected to the HVdc line by a series transformer. After successfully suppressing the line fault current (current zero current), an ultrafast disconnector isolates the faulty line. The main advantage of the proposed HVdc CB is its ability to interrupt the dc fault current without using the solid-state main breaker and limit the magnitude of the fault current and voltage stress. The proposed SSR-DCCB is investigated in MATLAB/Simulink, and an experimental prototype setup validates the results.

The energy transition involves integrating numerous pieces of equipment that undergo frequent switching operations and face the risk of lightning strikes. Consequently, power systems are exposed to fast transient switching and lightning surges, necessitating enhanced protection solutions for power equipment. Over the past decade, viable solutions have emerged to mitigate fast transients and safeguard transformers in the form of a ring-core parallel inductor and resistor circuit (R-PIR). Although this device effectively protects medium-voltage transformers from fast transients, a precise and comprehensive model for this component is still lacking, especially considering the importance of refining the R-PIR for broader applications. This paper introduces a detailed model of the R-PIR as a protective device, validated by electromagnetic transient simulations and finite element methods, which are also confirmed by experiments. The main goals of the research work are to investigate the performance and design features of the R-PIR comprehensively and demonstrate how the designed R-PIR protects transformers against fast transients. The research work is validated by experiments conducted in a lab environment. It is concluded that designing the R-PIR within an appropriate frequency range can considerably suppress transient overvoltages to which the transformer is exposed.

Innovative test methods are required to keep up with the increased demand for insulation materials which can withstand the high-frequency square-wave voltages generated by power-electronic equipment. Test systems using high-voltage, high-frequency transformers have proven versatile and easy to realise. The authors investigate the application of amorphous cut cores in such transformers. Analytical and numerical models for the transformer and its frequency response are developed, aiding the design process. An amorphous core-based transformer is designed for 8 kV_pk output at 100 kHz and compared to two previous designs based on ferrite cores. The frequency and pulse response, as well as the high-voltage and thermal performance, are evaluated. The comparison shows that while the low parasitics of the amorphous-based transformer allow for superior frequency response, they are unsuitable for long-duration tests with high pulse repetition frequencies (25–100 kHz) due to increased core losses. The partial discharge inception and flashover voltage are comparable to the ferrite-based transformers.

The aviation industry, responsible for over 2% of energy-related CO₂ emissions in 2022, aims for Net Zero Emissions by 2050. Despite electric aircraft's environmental benefits and improved operational efficiency, the current battery technology limits their range and size. Based on the optimal system voltage and power profile of the reference all-electric aircraft, this paper presents the design of a hybrid reconfigurable battery pack. The design incorporates a combination of high-specific-energy (263 W h kg^-1 at cell level) and high-specific-power (1800 W kg^-1 at cell level) battery types and its performance is compared with that of a fixed configuration battery pack comprising a single battery type. Simulation results suggest a potential 900 kg (18% lighter than fixed configuration) weight savings with reconfigurable pack, translating into enhanced payload, energy savings, or range extension for 9 PAX Eviation Alice electric aircraft at just 0.4% more energy capacity loss in 500 cycles.

This paper studies the power density limits of propulsion motor for electric aircraft considering thermal aspects and breakdown voltage reduction of insulation. The study em-ploys multi-objective optimization (MOO) to explore various mo-tor cooling options and filter configurations. The results show that motors with direct winding heat exchanger (DWHE) can reach higher specific power, while those equipped with water jacket cooling (WJC) offer a moderate design with simpler structure. Furthermore, the impact of sine wave and dv/dt filters on electric motors design is studied. The findings demonstrate that dv/dt filters enable designs with higher overall specific power compared to sine wave filters. Through simulations, this study identify the challenge faced by aviation motor design in significantly increased insulation thickness, necessitating advanced insulation materials with a minimum thermal conductivity of 5 W/(m.K) to facilitate a high specific power design. Based on this assumption, a preliminary design of 9.6 kW/kg with an efficiency of 98% is presented.

Power transformer energization involves a significant electromagnetic energy exchange among system components, which periodically oscillates with the natural frequencies of the system. As a result, weakly damped resonating overvoltages (OVs) may prevail, overstressing the system and thus leading to potential insulation failure. This phenomenon is particularly notable in cable-transformer systems, where the coinciding of natural frequencies is more likely to occur. The prestriking phenomenon during circuit breaker (CB) closing plays an important role in the excitation of the resonance frequencies. Specifically, repeated prestrikes can create high-frequency resonances during switching-on operations. This paper deals primarily with the mutual interactions between cable and transformer during transformer energization. Furthermore, by using a suitable model, the impact of CB prestrikes on the resultant resonance excitation is analyzed. Results demonstrate that cable-transformer interactions can lead to high-frequency oscillatory OVs with extreme magnitudes.

This paper discusses the prototype development and testing of a load invariant, high voltage gain DC power supply using inductive power transfer. The developed supply is intended to power the submodules of the CHB based arbitrary waveshape generator for testing high voltage components and materials. Using the Series Parallel topology, a load invariant voltage gain of 15 is obtained from a 350 V input DC Bus, with an efficiency of 88% and a load regulation of 18%. The obtained 5 kV output can conduct DC breakdown of dielectrics with a damping resistor and can test insulation aging, breakdown under high frequency AC.

Litz wires, which are utilized to suppress eddy current, often have complex structures. This paper presents a partial element equivalent circuit (PEEC)-based 3D model for Litz wires with round conductor. The model accounts for both transverse and longitudinal magnetic fields. The discretization of the Litz wire is based on cylindrical elements resulting in a reduced number of elements. Cylindrical element analysis is based on a 2D analytical method. The proposed model is compared with 3D FEM, which shows the model has good accuracy and fast computational speed. It is promising to facilitate Litz wires optimization.

Optimized power system architectures and lighter weight are enabling considerations for the successful development of all-electric aircraft (AEA). In this article, a cross-redundant connection architecture and weight reduction solutions are investigated for a 90-seater full battery-electric aircraft from the perspective of high-power aviation cable. Design criteria of the power system architecture are introduced. Material selection, sizing, and weight estimation methods of cable for AEA are discussed by combining ground cable standards with aviation requirements. The influence of the conductor materials, voltage level, current, battery pack quantity, and operating temperature on cable evaluation is thoroughly discussed and analyzed. Weight comparison under two controversial voltage level options (800V and 3kV) is conducted. Comparison results show that the utilization of an aluminum conductor, PTFE insulator, and a voltage level of 3kV proves to be a preferable selection for current AEA medium and high voltage cables. Increasing the rating operation temperature to 120°C is a conservative and secure option. The layout of battery packs consistent with the quantity of distributed electric motors is preferable to achieve the lightest cabling system. This study provides a guideline for the cable sizing methods of high-power aviation cables and an optimized design solution for the power system architecture of AEA from the perspective of cable layout and weight assessment.

SF6 is being phased out of the electrical grid as it is a strong greenhouse gas. A 'green' alternative to SF6 is fluoronitrile (C4-FN). The dutch transmission system operator (TSO) TenneT wanted to investigate the electrical behavior of this 'green' alternative as a pilot-gas insulated line (GIL) filled with C4-FN/CO2 (5%/95%) experienced multiple electrical breakdowns during the site acceptance tests (SATs). TenneT hypothesized that the breakdown was caused by the effect of (too much) humidity in the gas. Therefore, the ac breakdown behavior of the gas mixture has been researched under different amounts of humidity and operating pressures. This article also makes a small introduction on how humidity affects partial discharge (PD) behavior of corona, which is often a breakdown indicator. The results of this research conclude that humidity affects the ac breakdown strength. An increase in humidity in the gas results in a decrease in the ac breakdown strength. Moreover, the field configuration determines the amplitude of the impact. The impact of humidity on the ac breakdown strength in a homogenous field is substantially more compared to an inhomogeneous field, where the impact can almost be ignored. Yet, the effect of humidity decreases as the operating pressure increases. The phase-resolved PD pattern and PD characteristics of corona in a C4-FN gas mixture also differ with humidity. On the other hand, the PD inception voltage did not change with the humidity content. As a result of the findings in this research, further research is proposed toward the affected breakdown mechanism and more various PD behavior.

To enhance the voltage-handling capability of a switch, the series connection of switching devices is a cost-effective method that preserves many advantages of mature low-voltage devices. Dynamic voltage imbalance and electrical isolation for the devices at the high voltage (HV) side are two important challenges associated with series connection topology. Transformer-coupled gate drivers are excellent for providing both dynamic voltage balance and high galvanic isolation. However, they can only provide the switching function at the transformer pulse frequency. To generate complex waveforms of future power-electronics-dominated grids, a switch with user-defined turn-on/off timing is required for testing grid assets under high-voltage conditions. This article presents a simple, cost-effective open-loop gate driver that overcomes this limitation by introducing two sets of complementary pulse transformers to initialize programmable frequency and duty cycle. Successful experimental verification of the series-connected SiC mosfets prototype is performed at 3.2 kV at various frequencies and duty cycles. The article also demonstrates that the measurement probes placed across series-connected mosfets significantly affect the voltage distribution and validate a compensation mechanism.

More and more printed circuit boards (PCBs) will be used in electric aircraft to achieve higher power density of the on-board electric system, while PCBs in aircraft are more likely to generate partial discharges (PDs) due to external factors such as compact structure and low air pressure. Therefore, this article proposes a fluorescent fiber-based method for detecting and evaluating PDs on PCBs. The detection method is effectively immune against the presence of the electromagnetic, acoustic, and vibration interference. Based on the optical detection, the evolution regularities of PCB surface appearance changes, optical PRPD patterns, and optical pulses during the aging process of PCB under different air pressure are analyzed in this article. Then, 12 assessment features are extracted for the PD aging process, and the contribution of these 12 features to the severity assessment at different air pressures is obtained using the minimal-redundancy-maximal-relevance (mRMR) algorithm. Finally, different numbers of PD features are tested for PD severity assessment by the support vector machine (SVM) algorithm. The evaluation results show that the severity assessment method proposed in this article can achieve an assessment accuracy of at least 91.1% and up to 94.4% under all three air pressures, which has good application and guidance value.

This paper comprehensively reviews several techniques that address the static and dynamic voltage balancing of series-connected MOSFETs. The effectiveness of these techniques was validated through simulations and experiments. Dynamic voltage-balancing techniques include gate signal delay adjustment methods, passive snubbers, passive clamping circuits, and hybrid solutions. Based on the experimental results, the advantages and disadvantages of each technique are investigated. Combining the gate-balancing core method with an RC snubber, which has proven both technically and commercially attractive, provides a robust solution. If the components are sorted and binned, voltage-balancing techniques may not be necessary, further enhancing the commercial viability of series-connected MOSFETs. An investigation of gate driver topologies yields one crucial conclusion: magnetically isolated gate drivers offer a simple and cost-effective solution for high-frequency (HF) applications (2.5–50 kHz) above 8 kV with an increased number of series devices. Below 8 kV, it is advantageous to move the isolation barrier from the gate drive IC to an optocoupler and isolated supply, allowing for a simple design with commercially available components.

This article proposes a new configuration of a modular multilevel converter (MMC) and a Marx generator to generate fast-rising impulse waveforms. This new configuration improves the capabilities of the MMC-based high voltage arbitrary wave shape generator to generate fast-rising impulse since the MMC topology faces many inherent limitations. Similar to the conventional superimposed circuit of the ac transformer or dc rectifier circuit with the Marx generator, three hybrid circuits of MMC and the Marx generator are introduced, where the most optimal choice is made considering the practical aspects of testing, such as the size, cost, and preparation time. Then, a detailed analytical study is performed on the Marx generator circuit and the MMC circuit, and both circuits are coupled together to deliver a complete guideline on choosing various system parameters when the impulse wave shape and the load capacitor are given. The concept of this new hybrid configuration is demonstrated with a scaled-down prototype where the impulse with a rise time of 1 μs is superimposed on different arbitrary wave shapes. Similarly, the MATLAB-Simulink simulation model validates the proposed configuration for a 200, k V dc link voltage and 67 submodules with the desired impulse performance.

In the production of green hydrogen, electrolyzers draw power from renewable energy sources. In this paper, the design of Solid State Transformer (SST) for large-scale H ₂ electrolyzers is benchmarked. The three most promising topologies are chosen for design and comparison, including Modular Multi-level Converter (MMC) based SST, Modular Multi-level Resonant (MMR) based SST, and Input-Series-Output-Parallel (ISOP) based SST. The distance between converter towers for insulation and maintenance, the insulation system of the transformer, and the cooling system are designed with practical considerations in order to have an accurate estimation of the volume and weight of the SST. Losses in the switches are calculated based on equations, and losses in passive components are calculated based on FEM simulation. The operating frequency for each topology is optimized to minimize loss, weight, and volume. The best of each topology is then compared with each other to identify the most suitable one for large-scale H ₂ electrolyzers.