Conference papers (RICE)
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Item Insulation for Rotating Machines Type II under Different Electrical Stress Conditions(IEEE, 2023) Zedan, Ousama Ahmed Abdalla; Haller, Rainer; Trnka, Pavel; Bärnklau, HansWith the increasing application of power electronic components in driving rotating machines, the electrical stress factors were significantly changed. This paper deals with the investigation of lifetime characteristics for insulation of type II rotating machines performed by breakdown measurement of pulse voltage at the different waveforms and rise time. The results were compared with those gathered at power frequency, using different time scaling parameters (number of pulses, effective time). It is found that the effective time of stress voltage provides a clearer perception to study the lifetime behaviour than the number of pulses, especially for comparing the effect of the different applied voltage waveforms on acceleration aging. The results indicate that the rise time of the pulse voltage is considered the main influence on the life of insulations, it leads to insulation failure in a lower time. Additionally, the effect of combined stress (electrical, thermal, mechanical) was studied by using a specially developed sample, which included the curved parts of windings. It was found that the most critical part of such "coil-windings"are those curved parts because they are stressed not only by higher mechanical but also by larger electrical field strength.
Item Textile-based Antennas(Trans Tech Publications Ltd, 2025) Blecha, Tomáš; Handrejch, Jan; Radouchová, Michaela; Fröhlich, Adéla; Soukup, RadekThis article explores the design, fabrication, and application of textile-based antennas within the rapidly growing field of electronic textiles (e-textiles). Textile antennas are lightweight, flexible, and capable of seamless integration into garments, making them ideal for wearable electronics, Internet of Things (IoT) devices, and wireless sensor networks. In addition to facilitating wireless data transmission, they can serve as strain or deformation sensors for health monitoring and structural applications. A critical focus of the study is the development of reliable electrical interconnections between textile antennas and conventional electronic components, a challenge due to the incompatibility between standard electronic processes and textile substrates.Item Fabrication of Conductive Contact on Graphene Monolayers via Direct Ink Writing(IEEE, 2025) Šorm, Martin; Štulík, Jiří; Janda, Martin; Hamáček, AlešThis study investigates the formation of conductive contacts directly on graphene monolayers using direct ink writing (DIW). A glass substrate coated with a graphene monolayer was patterned using femtosecond laser ablation to create test lines with 200μ m width. Silver paste was deposited on the patterned graphene using DIW and then sintered at 60∘C in ambient air. The electrical properties of the resulting heterostructure were characterized by resistance, impedance, and current-voltage (I-V) measurements. The results showed that the silver-graphene interface exhibits ohmic behavior, with linear I-V characteristics and negligible effect on the conductivity of the graphene pathways. The measured resistivity values were consistent with lower values than theoretical expectations. This study demonstrates that the combination of femtosecond laser patterning and DIW provides an efficient approach to forming reliable electrical contacts for graphene-based devices, potentially as a pathway for applications in flexible electronics and sensors.Item Overview of Open-Source PoS Blockchain Platforms Using Smart Contracts for Energy Data Management(IEEE, 2025) Vinš, Martin; Noháč, KarelConsidering the completely new principles of the required cooperation of energy and financial operations in energy systems of the near future, their frequency, and the necessity of their protocol irreversibility, it is a new challenge for the energy industry to implement advanced algorithms of chained cooperatively authorized platforms for most of the new processes. Platforms that exist are often based on the blockchain principle. There are a variety of these platforms with different characteristics, making it difficult to assess them for a specific application in energy data management. This paper outlines the basic characteristics and possible criteria for selecting a suitable platform, focusing on three representative examples with which the authors have become more familiar.Item Influence of Load Impedance on PD Monitoring Sensitivity for High-Voltage Cable Lines(IEEE, 2025) Musil, Ondřej; Kettner, Finn A.; Steiner, Christoph; Shevchenko, Iaroslav; Kaltenborn, Uwe; Pihera, Josef; Polanský, RadekThe aim of this paper is to discuss the influence of the load impedance on the sensitivity of partial discharge (PD) measurements. The investigated circuit is based on coupling capacitors to provide a current path for PD signals during resonance testing of cables. The choice of an appropriate value for this capacitance is crucial. However, the overall impedance at the point of measurement is also determined by the inductance of the test circuit. The presented PD measurement method is a nonconventional system using high-frequency current transformers (HFCTs) to measure and localize PD sources along the cable system. The sensitivity of the whole measurement is, among others, strongly dependent on the impedance at the point of measurement. The results of simulations and effective measurements are analyzed and compared. The impact of the different parameters like parasitic capacitances and inductances in the measurement circuit on the accuracy as well as the sensitivity will be discussed in detail.Item Overview of Technologies for Wearable Textile Antennas Realization Based on Hybrid Threads(IEEE, 2025) Radouchová, Michaela; Handrejch, Jan; Fröhlich, Adéla; Blecha, TomášThis paper provides a comprehensive overview of fabrication technologies for wearable textile antennas based on hybrid conductive threads used during research at the University of West Bohemia. Emphasis is placed on comparing knitting, embroidery, and weaving in terms of flexibility, durability, integration potential, and suitability for specific wearable applications. The study also explores various interconnection technologies – including hot-bar welding, ultrasonic and thermo-compression bonding, and adhesive methods – that are critical for ensuring mechanical and electrical reliability. The integration of hybrid threads allows for the development of antennas that are lightweight, washable, and adaptable to body movements, making them suitable for applications in telemedicine, health monitoring, sports, and emergency services. The findings highlight the importance of selecting appropriate materials and techniques to meet the functional and comfort requirements of modern e-textiles..Item Space Charge Accumulation and Measurement Method for Insulation Materials(IEEE, 2025) Sláma, Pavel; Steiner, František; Trnka, PavelThis study focuses on the space charge accumulation in insulations. The specimens used in this study consist of a metal base with an applied insulator. Such specimen consists of copper base with a conformal coating. The conformal coating used is a commercially available acrylic resin-based coating. The pulsed electroacoustic (PEA) method was used for these measurements. The measured data gives information about the amount of space charge, its distribution and its effect on the electric field. Information about the ability of material to accumulate space charge is important as space charge can affect lifetime of insulating material, in this case of conformal coating. This in turn can give us information about the possibility of electric breakdown and partial discharges in conformal coating. The secondary aim of this study is to determine the suitability of used measurement method for the measurement of such samples.Item Temperature Profile Optimization for Vacuum Soldering of Components on Heat Sink(IEEE, 2025) Steiner, František; Hirman, Martin; Rous, Pavel; Wirth, VáclavEfficient heat dissipation is critical to the reliability and performance of modern high power density electronic systems. Direct soldering of power components to heat sinks minimizes thermal resistance, but traditional reflow soldering methods often result in the formation of voids in the joints, degrading thermal conductivity. This paper focuses on optimizing the temperature profile and vacuum process when soldering electronic components to heat sinks to minimize the occurrence of these voids. Key parameters such as temperature rise rate, time above liquidus (TAL), peak temperature, and most importantly timing and level of vacuum application are described. Using an experiment with different settings of the TAL parameters and vacuum timing, analysis was performed by X-ray inspection and quantification of the percentage of voids. The results show that the correct timing of vacuum application is a critical factor - the most effective vacuum application is after the solder has completely melted. Premature vacuuming leads to an increase in the number of voids, despite the extended TAL time. By optimizing the temperature profile and timing the vacuum correctly, a significant reduction in the occurrence of voids in the joint has been achieved. The paper presents an experimental approach and provides a instructions for achieving a high quality solder joint with minimal thermal resistance.Item Relative Resistance of PEEK and XLPE Insulated LV Cables in Nuclear Power Plants(IEEE, 2025) Kupilík, Tomáš; Prosr, Pavel; Pihera, JosefThis work focuses on high-temperature insulation materials for cables intended for use in nuclear power plants, emphasizing their stability and durability under harsh operating conditions. The introduction provides an overview of cable structures and insulation materials used in cable technology and describes diagnostic methods for analyzing their structural and phenomenological properties. In the experimental part, PEEK (polyetheretherketone) and XLPE (cross-linked polyethylene) insulated cables were selected for testing. The cables were subjected to accelerated thermal aging to simulate 60 years of operation in a nuclear power plant environment, with PEEK additionally undergoing radiation aging. The results show that XLPE exhibited significant degradation during thermal aging, while PEEK maintained stable structural and electrical properties throughout the tests.Item Mechanical Strength of Aged Solder Joints: Impact of Plasma Treatment(IEEE, 2025) Rous, Pavel; Krammer, Olivér; Medgyes, Bálint; Steiner, FrantišekThe reliability of solder joints, crucial for electronic assemblies, is influenced by factors including intermetallic compound (IMC) growth during aging and surface properties. This study investigated the impact of atmospheric plasma pre-treatment on the shear strength and IMC formation of aged (thermal aging and thermal shock) SAC305 solder joints on various PCB finishes (Cu, ImT, HASL, ENIG). Shear testing revealed that plasma treatment had a limited effect on mechanical strength under the applied test conditions. Fracture mode analysis indicated that failures predominantly occurred at the component’s lead metallization, suggesting that component quality was the limiting factor, masking potential effects of the plasma treatment applied to the PCB pads. Thermal shock aging was observed to be more detrimental to joint strength than thermal aging, particularly affecting the component-level integrity. IMC analysis showed expected growth with thermal aging. Plasma treatment had negligible impact on IMC thickness for ENIG finish, while an unexpected trend of reduced IMC thickness was observed for HASL finish, warranting further investigation. The study highlights the critical role of component robustness in reliability testing and suggests its potential to overshadow the influence of PCB surface treatments.Item Additional losses calculation in dry-type transformer(IEEE, 2025) Vurm, Vojtěch; Kroták, Stanislav; Svoboda, Michal; Knedlík, Michal; Rot, David; Cihla, TomášThis paper addresses additional losses in dry-type transformers, specifically focusing on stray electromagnetic, dielectric, thermal conduction, and mechanical vibration losses occurring in structural and non-active components. The study highlights the necessity of identifying, quantifying, and minimizing these losses through advanced computational methods, such as Finite Element Analysis (FEA), and experimental techniques including thermography and acoustic emission testing. Results underline the significant impact of material selection and structural optimization on reducing additional losses, thereby enhancing transformer efficiency,reliability, and compliance with regulatory standards.Item Augmented Reality in Industrial applications(IEEE, 2025) Kropík, Petr; Matoušek, Jan; Racek, Jakub; Šroubová, LenkaThe objective of this paper is to demonstrate the design and implementation of methods for interactive visualization of dynamic spatial data in augmented and mixed reality (AR/XR) using Microsoft HoloLens 2. The visualized data encompasses not only robot work zones and sensor data, but also a plethora of additional information pertaining to the devices and the environment. Data can be measured or generated dynamically. The development of software modules facilitates the real-time viewing and interaction with data by users. The emphasis is placed on efficient data transfer between physical devices and augmented reality (AR) headsets, integration of gesture control, and development of ergonomic user interfaces customized for industrial applications.Item Textile-Based Flexible Coaxial Cable with Improved EMC(IEEE, 2025) Handrejch, Jan; Blecha, TomášThis paper examines the performance of a modified textile-based coaxial cable with enhanced electromagnetic shielding. The improved design integrates hybrid threads, specialized coating, and advanced textile materials to optimize RF transmission in a flexible, textile coaxial structure. The core consists of a polyurethane-coated hybrid thread, ensuring durability and mechanical flexibility, while a double-layered PESh insulator improves dielectric performance. The outer shielding, which is the primary focus of the enhancement, has been densified and reinforced with a double braid, resulting in a significant reduction of surface transfer impedance ZT and improved signal transmission characteristics. To evaluate robustness under real-world conditions, the textile coaxial cable was subjected to mechanical stress tests, including bending cycles, to assess signal stability under deformation. Furthermore, environmental testing was conducted to examine performance under varying climatic conditions, such as humidity and temperature fluctuations. These tests confirmed that the enhanced structure maintains consistent RF transmission and shielding effectiveness even under mechanical strain and environmental exposure. Electrical performance was validated using a Vector Network Analyzer (VNA), with scattering parameter analysis confirming the effectiveness of the modified shielding design. These findings demonstrate the potential of textile-based coaxial cables for use in wearable electronics, conformal antennas, and textile-integrated IoT systems, offering a promising pathway for further material and structural optimization in flexible RF interconnects.Item Investigating Partial Discharge Mitigation at the Triple Point Interface in Power Modules(IEEE, 2025) Kvasnička, Petr; Rous, Pavel; Pihera, JosefAdvancements in power electronics, particularly new semiconductor technologies like Wide Bandgap (WBG) and Ultra-Wide Bandgap (UWBG) materials, enable higher power levels. This drives the need for improved insulation materials to handle increased electrical stress. With higher power levels, issues arise at the triple junction interface (dielectric – conductor - substrate), where strong electric fields are concentrated. This phenomenon increases the probability of partial discharges, which can degrade insulation. The challenge is to investigate and statistically compare different materials at this critical interface. This study aimed to develop a controlled experimental setup that accurately simulates the triple junction, enabling a systematic evaluation of electrical strength and partial discharge inception voltage across various potting compounds. Based on the research, field-dependent conductivity composite and field-dependent permittivity composite were prepared, and their effect on the inception voltage was investigated.Item Interactive Visualization of Data from a Ceramic Printer(IEEE, 2025) Šroubová, Lenka; Kropík, Petr; Slobodník, Karel; Racek, Jakub; Prokeš, Michal; Rejzek, JanThis project aims to develop a system for interactive visualization of data from the KEPrint ceramic 3D printer using augmented reality and extended reality (AR/XR) technologies. The printer will be equipped with sensors monitoring key operational parameters such as pressure, temperature, axis movement, and printing status. These sensor data will be transmitted to an MQTT broker, and then delivered to subscribers represented by end-user devices, including smartphones, tablets, augmented reality/extended reality (AR/XR) headsets, and servers (web servers, database servers). Users will be able to remotely view the current status of the printer, even if it is located in a restricted laboratory environment. This approach enables safe and informed access to laboratory equipment that may be inaccessible due to safety regulations, GDPR constraints, or health-related limitations.Item Study of Dielectric Strength of Ceramic Substrates for Power Electronics(IEEE, 2025) Kupilík, Tomáš; Kvasnička, Petr; Hlína, Jiří; Pihera, Josef; Prosr, Pavel; Řeboun, JanThis paper is focused on a detailed study of dielectric strength and surface and inner morphology of ceramic substrates for power electronics applications. Dielectric strength is a key parameter in this field. It depends on the type of ceramic material and substrate thickness. The presented study includes five types of ceramic substrate material and five different thicknesses of substrate. The results of dielectric strength measurement depend on ceramic material and substrate thickness and related to morphology are described in this paper.Item Comparative Analysis of Dielectric Properties of Polyethylene and Polypropylene with Flame Retardants for Cables(IEEE, 2025) Kadlec, Petr; Šipla, Jan; Polanský, RadekModern sustainable cable insulation development increasingly emphasises recyclable materials, and widely used cross-linked polyethylene-based materials are often identified as problematic regarding low recyclability. Alternatives with better recyclability, such as polyethylene (PE) without cross-linking and polypropylene (PP), are being explored, particularly regarding their flame retardancy. This study evaluates the dielectricproperties of PE and PP filled with 5 wt% of aluminium hydroxide (ATH), magnesium hydroxide (MDH), or halloysite nanotubes (HNT). The characterisation and comparison of all tested materials were performed based on measurement of volume resistivity, dielectric strength, dielectric constant and dissipation factor. The volume resistivity of polymers decreased minimally with the addition of flame retardants, while the dissipation factorincreased, especially for HNT-filled polymers, but remained at an acceptable level. PE exhibited higher dielectric strength than PP, with MDH further enhancing this property in both materials, while ATH improved it only in PE. The tested filling level of ATH or MDH does not deteriorate the dielectric properties of PP and may even improve them, especially the dielectric strength; therefore, the tested PP-based composite becomes a viablealternative to conventional cable insulation materials.Item Evaluation IoT Platform for Textile-Based Elements(IEEE, 2025) Handrejch, Jan; Blecha, TomášThis paper presents the design of an IoT test platform developed for the testing and visualization of textile-based electronic components. The system integrates various textile peripherals, including flexible LED ribbons, textile antennas for sub-GHz band (ISM), and fabric-embedded sensors, enabling real-time monitoring, data acquisition, and performance assessment in dynamic environments. The platform is built around an ESP32 microcontroller, featuring a LoRa module based on the SX1278 chip (862-931 MHz) for long-range wireless connectivity. Additionally, it supports Wi-Fi and Bluetooth, offering flexible communication options depending on application needs. It includes I2C, SPI, and UART interfaces, ensuring seamless integration with textile-based sensors and other peripherals. A rechargeable battery with monitoring enables autonomous operation, making the system suitable for portable and wearable applications. To enhance communication reliability, the platform incorporates specialized error-correction algorithms, reducing the impact of signal degradation in textile-based interconnects. The platform facilitates the evaluation of textile antennas, sensor performance, and RF behavior in sub-GHz ISM bands, such as 868 MHz, commonly used in IoT and wireless sensor networks. The acquired data is processed and can be visualized in real time, providing valuable insights into the feasibility of textile-integrated electronics for smart fabric applications, wearable technology, and scalable textile IoT solutions.Item Estimation of Damping Effects in a Salient Pole Synchronous Machine without a Damper Using SSFR Testing with a VSI(IEEE, 2025) Rozhon, Ondřej; Janouš, Štěpán; Cibulka, JiříAccurate estimation of damping effects in salient pole synchronous machines is essential for improved modeling and stability analysis. Although the application of the Standstill Frequency Response (SSFR) method to machines without damper windings has been discussed in previous studies, this work focuses on demonstrating its practical applicability using a Voltage Source Inverter (VSI) with a sine filter to ensure highquality excitation signals. The objective is to evaluate whether SSFR can effectively capture damping phenomena arising from eddy currents and magnetic saturation in the pole structure, even in the absence of explicit damper bars. Experimental tests are carried out under controlled standstill conditions, and the resulting frequency responses are analyzed to identify dampingrelated characteristics. The results confirm that, with proper excitation and measurement setup, the SSFR method remains valid for such machines. This study contributes by validating a practical, inverter-based approach for SSFR testing, offering enhanced precision and applicability in modern synchronous machine analysis.Item Knitted Bow-Tie Frequency Resonators with Hybrid Conductive Threads for Wearable Strain Monitoring(IEEE, 2025) Radouchová, Michaela; Kalaš, David; Blecha, Tomáš; Marterer, Verena; Fröhlich, AdélaThis paper presents the development of knitted frequency resonators designed for strain monitoring in wearable e-textile applications. These textile frequency resonators, knitted from basic 100 % cotton and conductive hybrid yarns, are suitable for e-textiles. Frequency resonators were designed as bow-tie antennas and are stretchable thanks to the knitted structure. Electrical parameters change due to the elongation of the conductive structure; this causes a shift in the resonant frequency. The resonant frequency decreases as a function of elongation.
