Contact Voltage Research Articles

Quantum Transport across Amorphous-Crystalline Interfaces in Tunnel Oxide Passivated Contact Solar Cells: Direct versus Defect-Assisted TunnelingSupported by the National Natural Science Foundation of China (Grant Nos. 61704083 and 61874060), the Natural Science Foundation of Jiangsu Province (Grant No. BK20181388), and NUPTSF (Grant No. NY219030).

Tunnel oxide passivated contact solar cells have evolved into one of the most promising silicon solar cell concepts of the past decade, achieving a record efficiency of 25%. We study the transport mechanisms of realistic tunnel oxide structures, as encountered in tunnel oxide passivating contact (TOPCon) solar cells. Tunneling transport is affected by various factors, including oxide layer thickness, hydrogen passivation, and oxygen vacancies. When the thickness of the tunnel oxide layer increases, a faster decline of conductivity is obtained computationally than that observed experimentally. Direct tunneling seems not to explain the transport characteristics of tunnel oxide contacts. Indeed, it can be shown that recombination of multiple oxygen defects in a-SiO x can generate atomic silicon nanowires in the tunnel layer. Accordingly, new and energetically favorable transmission channels are generated, which dramatically increase the total current, and could provide an explanation for our experimental results. Our work proves that hydrogenated silicon oxide (SiO x :H) facilitates high-quality passivation, and features good electrical conductivity, making it a promising hydrogenation material for TOPCon solar cells. By carefully selecting the experimental conditions for tuning the SiO x :H layer, we anticipate the simultaneous achievement of high open-circuit voltage and low contact resistance.

Verification Protocols for the Lightning Protection of a Large Scale Scientific Instrument in Harsh Environments: A Case Study

This paper is devoted to the study of the most suitable protocols needed to verify the lightning protection and ground resistance quality in a large-scale scientific facility located on a site with high risk of lightning strikes. We illustrate this work by reviewing a case study: the largest telescopes of the Northern Hemisphere Cherenkov Telescope Array, CTA-N. This array hosts sensitive and high-speed optoelectronics instrumentation and sits on a clear, free from obstacle terrain at around 2400 m above sea level. The site offers a top-quality sky but also features challenging conditions for a lightning protection system: the terrain is volcanic and has electrical resistivities well above 1 kOhm·m. In addition, the environment often exhibits humidities well below 5%, and strong winds pose challenging conditions. On the other hand, the high complexity of a Cherenkov telescope structure does not allow a straightforward application of lightning protection standards. We describe here how the risk assessment of direct strike impacts was made and how contact voltages and ground system were both tested. Finite Element Simulation (COMSOL Multiphysics) has been used to estimate the current flowing through the parts of the earthing system designed for the telescopes in the case of a direct strike impact. This work is intended to provide assistance to scientists and managers involved in the construction of scientific installations, particularly those in charge of defining verifiable reliability and safety requirements for lightning protection.

A Study on Contact Voltage Waveform and Its Relation with Deterioration Process of AgPd Brush and Au-Plated Slip-Ring System with Lubricant

A Study on Contact Voltage Waveform and Its Relation with Deterioration Process of AgPd Brush and Au-Plated Slip-Ring System with Lubricant

Simulation of contact voltages in two-roll modules

Mathematical models of the regularities of the distribution of contact stresses in the generalized two-roll module are obtained. These models take into account all the main parameters of two-roll modules and describe the distribution diagrams of contact stresses for all special cases of interaction of the processed material with pairs of rolls in two-roll modules. New data on the regularities of the distribution of contact stresses are revealed: normal contact stresses change from zero at the beginning and at the end of the contact zone of the rolls to a maximum at a point lying to the left of the center line (towards the beginning of the contact of the rolls); the tangential contact stresses change their signs at the neutral point, which in the driven roll is located towards the entrance of the material layer into the contact zone of the rolls, and in the free one - towards the exit.

Quantitative Evaluation of Electrical Life of AC Contactor Based on Initial Characteristic Parameters

In terms of estimating the ac contactor’s electrical life, a new method based on initial characteristic parameters is put forward in this article. First, the characteristic parameters of the contact voltage in the closing stage and the arcing energy in the breaking stage are selected to extract their statistical indexes due to different stages in the contactor’s action, and the correlation between the indexes and electrical life is calculated by means of the Spearman rank correlation coefficient. Next, the electrical life evaluation indexes corresponding to the stages of closing and breaking are computed according to the weighted Euclidean distance calculation; the electrical life comprehensive evaluation index is presented by secondary fusion of the abovementioned indexes. Finally, a life prediction model based on unitary regression is established to evaluate electrical life with the predicted input of the comprehensive evaluation index. The results have displayed that the proposed method succeeds in quantitatively evaluating the electrical life of an ac contactor.

Factors influencing the working temperature of quantum dot light-emitting diodes.

Quantum dot light-emitting diodes (QLEDs) possess huge potential in display due to their outstanding optoelectronic performance; however, serve degradation during operation blocks their practical applications. High temperature is regarded as one of major factors causing degradation. Therefore, a systematical study on the working temperature of QLEDs is very essential and urgent for the development of high stable QLEDs. In this work, different influence factors such as the electro-optic conversion efficiency (EOCE), voltage, current density, active area, substrate size, substrate type and sample contact are discussed in detail on the working temperature of QLEDs. The research results show that the working temperature of general QLEDs under normal operation conditions is usually smaller than 75 °C when the ambient temperature is 25 °C. However, temperature of QLEDs working under extreme conditions, such as high power or small substrate size, will exceed 100 °C, resulting in irreversible damage to the devices. Moreover, some effective measures to reduce the working temperature are also proposed. The analysis and discussion of various influencing factors in this work will provide guidance for the design of stable QLEDs and help them work at a safer temperature.

Friction Forces in a Linear-Guideway Type Recirculating Ball Bearing Under Grease Lubrication

Abstract This paper deals with friction forces in a linear-guideway type recirculating ball bearing (linear bearing) under grease lubrication. During the experiments, the friction force, temperature, and electric contact voltage of a grease lubricated linear bearing (test bearing) without seals were measured. Experimental results showed that the measured friction forces of the test bearing were fluctuated with the ball passage period. The measured time-average friction force FAVG (measured FAVG) was nearly constant when the grease filling rate x (=grease filling volume/internal space of the bearing) ≥0.13, while the measured FAVG decreased as x decreased when x < 0.13. In addition, the measured temperatures were almost constant, and the measured contact voltages indicated that the contacts of the balls and raceways were electrically insulated by the grease film. Next, the expressions of friction forces due to differential slip (FD), elastic hysteresis loss (FE), and rolling traction (FRT) were shown. The calculated FD + FE + FRT for the test bearing was almost equal to the measured FAVG around the grease filling rate of x = 0, while in cases where x > 0, the measured FAVG was greater than the calculated FD + FE + FRT. This means that when x > 0, an agitating resistance (FA) from the grease might cause the measured FAVG to be greater than the calculated FD + FE + FRT. Finally, an expression for the friction force of a linear bearing, FAVG = FD + FE + FRT + FA (which can estimate the measured ones) is proposed.

Quench detection using Hall sensors in high-temperature superconducting CORC®-based cable-in-conduit-conductors for fusion applications

Advanced magnet systems for fusion applications would greatly benefit from the use of high-temperature superconductors (HTS). These materials allow fusion magnets to operate at higher magnetic fields, allowing for more compact fusion machines, and allow for operation at elevated temperatures, enabling demountable coils that provide access for maintenance of the fusion reactor. Quench detection remains a major challenge in the protection of HTS magnets that are vulnerable to localized conductor burnout due to their low quench propagation velocities. One of the methods explored is the use of Hall sensors that are incorporated in or near the magnet terminations that can detect local field variations that occur as a result of current redistribution within the conductor to bypass a hotspot within the magnet winding. This method is potentially well suited for Cable in Conduit Conductors, such as those made from Conductor on Round Core (CORC) cables, in which sub-cables containing HTS tapes are connected to the terminations at a low resistance. To demonstrate the technique, a CORC® triplet consisting of three sub-cables, rated for 4 kA operation at 77 K, was manufactured and Hall sensors were used to measure local field variations next to the terminations due to current redistribution between the cables. The Hall response was compared to voltages that developed over the cables and terminations as a local hotspot was applied to different cables in the triplet. It was found that the Hall sensors were faster and more sensitive than voltage contact measurements and were able to reliably detect current redistribution of only a few amperes caused by a hotspot, well before the triplet exceeded its critical current. The method also allowed the detection of heater-induced hotspots during high ramp rates of 2 kA s−1 relevant for fusion applications. Hall sensors have a distinct benefit of being less sensitive to inductive pickup of AC interference compared to voltage contact measurements that make quench detection through voltage measurements in magnets especially challenging. The method can also be used for diagnostic measurements of current redistribution caused by other sources such as inhomogeneous current injection from faulty joints, or localized conductor damage. The Hall sensors are likely capable of detecting the onset of a quench that may occur a far distance away from the sensor location, presenting a breakthrough in HTS quench detection that potentially removes one of the remaining barriers to reliable operation of large HTS magnet systems.

Micromechanical Switch-Based Zero-Power Chemical Detectors for Plant Health Monitoring

In this paper, for the first time we demonstrate zero-power volatile-organic-chemical (VOC) detectors based on micromechanical switches suitable for plant health monitoring. Differently from state-of-the-art active chemical sensors, the device presented here exploits a completely passive, chemically-sensitive switch based on a bimaterial micro-cantilever and a passive switch-based readout mechanism to detect VOCs exceeding a pre-determined concentration released by unhealthy plants. When exposed to target VOCs, the polymer/metal bimaterial beam bends downward and trigger the switch due to the stress induced from the absorption of chemicals in the polymer layer. Here we show experimental demonstrations of detecting toluene, hexenol (cis-3-Hexen-1-ol, a chemical released from plants under attack by pests) and ethanol, respectively, with our fabricated prototypes. The demonstrated high sensitivity to ethanol (~8 nm/ppm ) and hexenol (~3.3 nm/ppm ) was achieved by the optimization of device geometries showing a great promise of the proposed technology to ultimately achieve 10s ppm detection limit (with a sub-micron contact gap and voltage bias) which is required for the device operation in close proximity to a plant in an open environment. [2020-0190]

CORC® wires containing integrated optical fibers for temperature and strain monitoring and voltage wires for reliable quench detection

Safe operation of large superconducting magnets wound from high-temperature superconductors (HTS) requires reliable detection of the onset of a quench. A novel method to integrate optical fibers and voltage wires within the core of multi-tape HTS CORC® wires has been developed that allows real time monitoring of local changes in strain, temperature and of the superconducting state of the magnet windings. The ability to detect highly localized changes in temperature with Rayleigh scattering in the embedded optical fibers provides invaluable information about local heating at hot spots from which a quench may originate. Integrated voltage contacts allow accurate voltage measurements in long CORC® wires without being affected by high current ramp rates or electromagnetic interference. They also allow detection of inductively driven redistribution of current between tapes in CORC® wires that may occur at high current ramp rates. Continuous monitoring of temperature and voltage was used to detect the formation of local hot spots induced by a heater or by operating the CORC® wire above its critical current. The results show that, within the boundary conditions of the experiment and the method by which the optical fibers were integrated into the CORC® wire in this study, the speed and resolution with which hot spots can be detected with optical fibers lagged that of the integrated voltage wires. This study also shows that integrated voltage wires reliably detected the formation of a local hot spot in a 5.1 meter long coiled CORC® wire, down to a hot spot size covering 0.1% of the conductor length and at current ramp rates as high as 2000 A s−1. Voltage measurements thus remain an effective option for quench detection in magnets wound with HTS conductors for which current sharing between tapes allows for operation within the flux flow regime.

Power generation characteristics of 0.50(Ba0.7Ca0.3)TiO3–0.50Ba(Zr0.2Ti0.8)O3/PVDF nanocomposites under impact loading

Power generation characteristics of 0–3-type 0.50(Ba0.7Ca0.3)TiO3–0.50Ba(Zr0.2Ti0.8)O3/PVDF nanocomposites, prepared using a melt-mixing process, under impact loading have been presented in this paper. A solid-state reaction process was utilized to prepare lead-free nanoceramic powder of 0.50(Ba0.7Ca0.3)TiO3–0.50Ba(Zr0.2Ti0.8)O3 (BCZT50) which was then milled by high-energy ball milling technique. The BCZT50 as filler distribution in the PVDF matrix was checked from scanning electron microscope and the formation of BCZT50 and BCZT50/PVDF nanocomposites were ascertained by X-ray diffraction method. The free dielectric constant ( $$\varepsilon_{33}^{T}$$ ), loss tangent (tanδ), piezoelectric coefficient (d33), piezoelectric voltage constant (g33), shore hardness (D), and figure of merit (FoM) were observed to increase while that of applied mechanical force (F3) decreases with the increase in filler concentration. Studies of voltage responses of all the BCZT50/PVDF nanocomposites due to impact loading using drop weight method have been carried out. A marked increment in the contact voltage due to different heights (applied mechanical energy) of impact was noticed as the concentration of filler particles was increased from 0 to 25% in the BCZT50/PVDF nanocomposites. The contact voltage and generated energy increase, respectively, from 5.37 to 11.62 V and 0.53 nJ to 6.8 nJ with the increase in BCZT50 content from 0 to 25% at a height of impact = 21 cm. In addition, the low value of tanδ (~ 10–2), high values of d33, g33, D and FoM along with better voltage responses (proportional to the applied mechanical energy) foreshadowing the prospect of BCZT50/PVDF nanocomposites a better non-lead option for structural health monitoring, piezo-sensing/detection, and/or energy harvesting applications.

Self-heating effects and hot carrier degradation in In0.53Ga0.47As gate-all-around MOSFETs

In0.53Ga0.47As based gate-all-around (GAA) metal-oxide-semiconductor field-effect transistors (MOSFETs) are being pursued as a promising solution to high speed ultra-large-scale integration chip design because of improved gate-channel electrostatic, excellent immunity to short channel effects, high carrier mobility and increased drain current. However, the GAA devices are highly prone to self-heating, and hot carrier injection (HCI) induced effects because of the absence of a proper heat take out mechanism. In this paper, 3-D electrothermal simulations are performed on In0.53Ga0.47As GAA MOSFETs using the hydrodynamic model to access the impact of self-heating on the electrical characteristics of the device. The Fiegna hot-carrier injection model is used in simulations to estimate the HCI into the oxide region. A thorough understanding of dependencies of lattice temperature and carrier temperature on spacer length, drain voltage, gate voltage, and thermal contact resistance is acquired. HCI degradation dependence on thermal contact resistance is also extensively studied using the Sentauras based TCAD simulator.

Maximum deformation of charged dielectric droplets

In this study, the maximum deformation of micrometer sized droplet of dielectric water-based paint impact onto a flat steel surface and exposed to a constant and uniform electric field was investigated by simulation based on the level-set method within the framework of Navier-Stokes. Upon a series experiments for droplet impacting and spreading of water-based paint on dielectric solid substrate with different initial impacting velocities in external electric field, results demonstrated that the maximum deformation ratio increases with the increase of initial impacting velocity, and can scale as We1/4 where We is the Weber number. The effect of electric field intensity to the final shape of droplet of water-based paint on a hydrophobic surface was investigated. It was found that the eccentricity of droplet can scale as E where E is the electric field intensity, and a prediction model of droplet between the deformation ratio (ξF) of droplet at final equilibrium contact angle and E was presented. Finally, the effect of applied voltage and equilibrium contact angle was studied.

Binary solvent systems for durable self-adhesive conductive hydrogels

Abstract Conductive hydrogels without adhesiveness and durability characteristics face great challenges in practical applications, such as inconvenient use, unstable contact voltage, and difficult to store. Herein, we present sodium polyacrylate (PAANa) hydrogels with binary solvent systems composed of water and an alcohol [ethylene glycol (EG), glycerol (GLY), or poly(ethylene glycol) (PEG)] as solvent instead of traditional water to research their self-adhesiveness, durability, conductivity, and mechanical properties. PAANa hydrogels exhibited higher self-adhesive properties and durability after alcohol content increased, and GLY/water hydrogels showed the best self-adhesive and stable properties. With more alcohols added, the weaker conductivity became, and EG/water hydrogels showed the highest conductivity. It was observed the long carbon chain length of alcohol could help improve the rheological properties of hydrogels. Thus, PEG/water hydrogels had the highest storage modulus, loss modulus, and consistency. The results demonstrated that the GLY/water binary solvent could provide good self-adhesiveness and durability, but EG/water and PEG/water showed better conductivity and mechanical properties, respectively. Therefore, our work may provide novel physical insights into the long-term usage of self-adhesive conductive hydrogels to practical requirements.

Optimal design and control of a new permanent magnet AC contactor with forced breaking mechanism

This study addresses the design of a new type of permanent magnet contactor, which uses forced breaking to overcome failure conditions. A multi-objective optimisation method based on the genetic algorithm is used to design the contactor considering the effects of average closing time, average breaking time, impact energy, Joule heat and contactor volume. Four prototypes have been fabricated according to the optimised parameters. A control circuit is developed to increase breaking reliability. The circuit is designed as two separate modules: a normal working module and a protection module. The former is used during the normal contactor operation and the latter is used for forced breaking protection. Breaking failures are detected by comparing the time delay between the breaking control voltage and the auxiliary contact voltage. A durability experiment has been conducted to verify the protection function of the proposed PM contactor. Experimental results show that the normal working module fails to break the contactor in the last testing cycle. However, under the actuation of the protection mechanism, the contactor is forced to break and the power circuit can be successfully switched off.

Дистанційне виконання лабораторних занять з модуля 2 «Основи охорони праці» дисципліни «Безпека життєдіяльності та основи охорони праці»

The relevance of the study is due to the fact that the pandemic of the infectious disease COVID-19 is spreading in the world and in Ukraine. This requires the introduction of radical changes in the educational process of higher education institutions, in particular the conduct of laboratory work in the disciplines of the cycle of labor protection. The purpose of the article is to study the problem of development and implementation of remote laboratory classes in the study of the module 2 "Fundamentals of labor protection" based on the functioning of the electronic system JetIq VNTU. The object of the study is the educational distance training of bachelor students in the institutions of the cycle of disciplines in labor protection. The subject of research is the theory and methods of development and implementation of remote laboratory classes in the module 2 "Fundamentals of labor protection" on the topic «Research of touch and step voltage». The Regulations on distance and blended learning of Vinnytsia National Technical University are considered and the emphasis is placed on the need to introduce virtual experiments in conducting laboratory classes in the disciplines of the cycle of labor protection. The main elements of the scheme of realization of the educational platform − JetIq VNTU learning management system are generalized and examples of the corresponding interaction «Teacher – Student» are given. A virtual laboratory lesson with a detailed description of it, which is given in the guidelines for its remote implementation on the topic «Investigation of contact voltage and step" in the discipline discipline "Life safety and basics of labor protection" (module 2 "Fundamentals of labor protection") for students of educational degree Bachelor in the field of knowledge 07 − Management and administration in the electronic system JetIq VNTU. The structure of methodical instructions for the laboratory lesson «Investigation of contact and step voltage» in the discipline discipline "Life safety and basics of labor protection" (module 2 "Fundamentals of labor protection"). Conducting the experimental part, summarizing and forming a student report and communication in the system «Teacher – student». These guidelines allowed in the quarantine conditions to approach in the mode of a virtual experiment to investigate the physical processes that occur when a person is exposed to the voltage of touch and step; take readings from the voltmeter and ammeter; to construct the corresponding schedules, in particular concerning action on the person of force of current; draw conclusions, etc. Developed and implemented guidelines for conducting a virtual experiment «Study of the voltage of touch and step» allow in practice to consolidate the knowledge that was learned as a result of the lecture «Fundamentals of Electrical Safety», in video conferencing, based on the platform «Google Meet». This should raise the professional level of future graduates and form a holistic system of occupational safety competencies, which will ultimately save their lives and health in the process of professional activity.

Safety analysis of live working operators under zero potential

With the application of the live working method of the zero phase potential of the working phase more and more widely, the safety of the live working operators is urgently needed for research. Considering the influence of electric shock time and frequency on the allowable current of the human body, the safe current is analyzed during live operation, and it is concluded that in the frequency range of 50~60Hz, the current below 50mA can basically guarantee that it will not die after electric shock. In the three scenarios where the insulator maintenance personnel accidentally touch the ground, the grounding wire shocks the electric shock and the charged electric shock of the tower, the human body electric shock is further analyzed. Finally, based on the CDEGS, the model of the human body contacting the grounding conductor is established. The simulation verifies the influence of the allowable current on the time and frequency of the human body withstand current under the zero potential state through the contact voltage diagram and the danger degree diagram.

Effect of electrical current density, apparent contact pressure, and sliding velocity on the electrical sliding wear behavior of Cu–Ti3AlC2 composites

The purpose of this research was to investigate the potential use of Cu–Ti3AlC2 composites sliding against a Cu–5%Ag alloy as a viable electrical contact couple. Sliding friction and wear tests were conducted in the presence of an electric current using a custom-designed block-on-ring wear testing apparatus. The electrical current density was 0–15 A/cm2 along with an apparent contact pressure of 1.25–7.5 N/cm2 and sliding velocities ranging from 2.5 to 15 m/s. The results indicate that friction coefficient, wear rate, and contact voltage drop measured for the sliding couple increases with an increase in the electrical current density. As the apparent contact pressure increases, the contact voltage drop of Cu–Ti3AlC2 composites increases gradually, while friction coefficient and wear rate first decrease and then increase. With an increase in the sliding velocity, the friction coefficient of the sliding pair decreases and the contact voltage drop increases gradually, while wear rate decreases first, then increases. Adhesive wear and arc erosion wear proposed as the main wear modes. A lubricating film was observed to form on the wear surfaces under each test condition, and that film apparently improves the tribological properties of the sliding couples.

Optimal management strength of cutting parts of tools from STM when there is turning heatresistant alloys on CNC machines

The article considers the developed and implemented in the cutting process methodology for managing the dynamic strength of the cutting parts with the tops of tools from STM simultaneously on the front and back surfaces of these tools at thin turning of heatresistant alloys on CNC machines. The specified methodology is based on optimizing (physical, thermal) models of process of thin turning of heatresistant alloys tools from STM developed by us and the offered concept of passing of process of interaction of the processed and tool materials in the conditions of optimization of contact voltage and temperatures at the same time on the front and back surfaces of the tool from STM when cutting.

Rolling resistance of mechanism with point and linear contact scheme

Problem statement.In most problems, mechanics rolling coefficient of friction either neglect or set its value without taking into account the contact patterns of the rolling bodies, their materials and sizes. Based on the theory of contact stresses by Hertz, analytical dependences are obtained that allow calculating the rolling friction parameters with the greatest reliability in comparison with the analogues of other authors. But in the Hertz formulas, the parameter hysteresis loss coefficient is introduced, the determination of which requires time and money no less than obtaining the value of the rolling friction coefficient itself. This makes it impossible to use them in engineering practice to determine the magnitude of the friction force, and, accordingly, the coefficient of performance (COP) of a number of mechanisms with rolling. This leads to the fact that the drive power of the mechanisms has to be overestimated due to the uncertainty of its efficiency. The purpose of the article. To determine the efficiency of widely used mechanical devices in which rolling friction is present. In accordance with the stated goal, in the process of studying the operation of devices it is necessary to use only generally accepted mechanical constants and sizes. Conclusions.The efficiency of crab traverse mechanism does not depend on the direction of load application of movement relative to the direction of motion. The efficiency of conical friction gear depends on the coefficient of rolling friction, assumed contact voltage and elastic modulus. The proposed analytical dependences for determination of the coefficient of rolling friction in the ball guide allow us to resolve the total resistance into the rolling and sliding and conduct measures to reduce the more significant component. The main component of the motion resistance in the ball guide is a component of slide friction and it is a minimum at the angle of opening guide 2α = 90°.