Current Components Research Articles

Effects of air gap eccentricity on different rotor structures for PMSM in electric vehicles

In addition to research related to static eccentricity and dynamic eccentricity examining fault and diagnostic methods in various types of motors, there are also studies conducted for motors with non-uniform air gaps similar to the condition. In these studies, improvements and changes in motor performance for such types of motors can be observed. In this study, the effects of the rotor structures determined in the study and the air gap shape, which is effective by changing the eccentricity ratio, on the motor performance of the interior permanent magnet synchronous motor designed for electric vehicle applications are examined. Besides the elliptical rotor structure, which is widely researched in dynamic eccentricity studies, these eccentric motor structures also include novel rectangular and polygonal eccentric rotor structures. Motor models with non-uniform air gap structures are designed in two dimensions and subjected to simulation and analysis studies using the finite element method. At the end of the study, along with the parameters identified for motor performance, the harmonic components of the stator current, radial air gap flux density and the output torque obtained through Fast Fourier Transform analysis have been provided.

Genuine anodic and cathodic current components in cyclic voltammetry

Implicit anodic and cathodic current components associated with the real net current at a given potential of a simple quasireversible electrode reaction can be accurately estimated using basic mathematical modeling within the framework of Butler-Volmer electrode kinetics. This methodology requires only prior knowledge of the formal potential of the dissolved redox couple, offering direct insight into the electrode kinetics. The proposed approach facilitates a unique transformation of a conventional cyclic voltammogram, allowing the replacement of the common, net current with authentic anodic and cathodic current components. This simple methodology introduces a novel perspective in analyzing voltammetric data, particularly enabling the kinetic characterization of fast, seemingly electrochemically reversible electrode processes on macroscopic electrodes at slow scan rates. Theoretical predictions are experimentally demonstrated using the electrode reaction for the reduction of the hexaammineruthenium(III) complex, serving as an example of one of the fastest electrode processes involving a dissolved redox species.

Cultivating Physical Literacy Through an Alternative Pedagogical Approach

Physical literacy (PL) was initially introduced during the first half of the 20th century in the United States. Since then, it has been gradually gaining in both usage and popularity in many physical education contexts worldwide. However, there has been limited discussion on the practical implication of facilitating PL. Thus, the purpose of this article is to (a) introduce a current definition and core components of PL, (b) provide a brief overview of the political application of PL and pedagogical approaches that have been utilized to facilitate PL, and (c) suggest the concept of humanities-oriented physical education (HOPE) as an alternative pedagogical approach to facilitate PL. The article concludes by sharing recommendations for and insight into ways of cultivating PL within physical education contexts.

Epilepsy-associated Kv1.1 channel subunits regulate intrinsic cardiac pacemaking in mice.

The heartbeat originates from spontaneous action potentials in specialized pacemaker cells within the sinoatrial node (SAN) of the right atrium. Voltage-gated potassium channels in SAN myocytes mediate outward K+ currents that regulate cardiac pacemaking by controlling action potential repolarization, influencing the time between heartbeats. Gene expression studies have identified transcripts for many types of voltage-gated potassium channels in the SAN, but most remain of unknown functional significance. One such gene is Kcna1, which encodes epilepsy-associated voltage-gated Kv1.1 K+ channel α-subunits that are important for regulating action potential firing in neurons and cardiomyocytes. Here, we investigated the functional contribution of Kv1.1 to cardiac pacemaking at the whole heart, SAN, and SAN myocyte levels by performing Langendorff-perfused isolated heart preparations, multielectrode array recordings, patch clamp electrophysiology, and immunocytochemistry using Kcna1 knockout (KO) and wild-type (WT) mice. Our results showed that either genetic or pharmacological ablation of Kv1.1 significantly decreased the SAN firing rate, primarily by impairing SAN myocyte action potential repolarization. Voltage-clamp electrophysiology and immunocytochemistry revealed that Kv1.1 exerts its effects despite contributing only a small outward K+ current component, which we term IKv1.1, and despite apparently being present in low abundance at the protein level in SAN myocytes. These findings establish Kv1.1 as the first identified member of the Kv1 channel family to play a role in sinoatrial function, thereby rendering it a potential candidate and therapeutic targeting of sinus node dysfunction. Furthermore, our results demonstrate that small currents generated via low-abundance channels can still have significant impacts on cardiac pacemaking.

Evaluation Method of Magnetic Field Stability for Robotic Arc Welding Based on Sample Entropy and Probability Distribution

In this study, we analyzed the arc magnetic field to assess the stability of the arc welding process, particularly in robotic welding where direct measurement of welding current is challenging, such as under water. The characteristics of the magnetic field were evaluated based on low-frequency fluctuations and the symmetry of the signals. We used double-wire pulsed MIG welding for our experiments, employing Q235 steel with an 8.0 mm thickness as the material. Key parameters included an average voltage of 19.8 V, current of 120 A, and a wire feeding speed of 3.3 m/min. Our spectral analysis revealed significant correlations between welding stability and factors such as the direct current (DC) component and the peak power spectral density (PSD) frequency. To quantify this relationship, we introduced a novel approach using sample entropy and mix sample entropy (MSE) as new evaluation metrics. This method achieved a notable accuracy of 88%, demonstrating its effectiveness in assessing the stability of the robotic welding process.

Genuine differential voltammetry

A novel form of differential voltammetry is proposed, developed through the implicit anodic and cathodic current components of the experimentally accessible conventional net current measured in a voltammetric experiment. By employing basic mathematical modelling of an electrode reaction of a dissolved redox couple at a conventional, macroscopic electrode within the framework of the Butler-Volmer electrode kinetic model, the implicit anodic and cathodic current components of the net conventional current are clearly defined and can be estimated. Consequently, a novel form of differential current, calculated as the difference between anodic and cathodic implicit current components associated with a single potential of the voltammetric experiment, can be established. This differential current demonstrates remarkable characteristics in terms of electrode kinetics and analytical performance, particularly in cases involving fast, seemingly electrochemically reversible electrode processes. It holds promise to be analytically superior to the best-known differential voltammetric techniques so far (e.g., square-wave voltammetry), as well as provides a means for estimating the rate constants of very fast, apparently reversible electrode processes at macroscopic electrodes under mild experimental conditions (i.e., studied at slow potential scan rates). The practical implication of the novel methodology is significant: a simple linear sweep voltammogram of a quasi-reversible electrode reaction with unknown electrode kinetic parameters can be readily transformed into the novel type of differential voltammogram through a convolution procedure of the conventional net current, paving a new way for studying electrode processes by voltammetry.

Model Parameter Calibration for Vibration Fatigue Analysis by Means of Bayesian Updating and Artificial Neural Network Based Surrogate Models

Abstract In this paper, a methodology for model parameter calibration for vibration fatigue analysis is proposed. It combines Bayesian updating of uncertain model parameters and artificial neural networks (ANNs). The calibrated parameters are used to increase the accuracy of fatigue lifetime calculations for components submitted to vibrational loads. The Bayesian updating uses eigenfrequencies, mode shapes, total mass, and the frequency response functions (FRFs). These quantities are predicted by ANN-based surrogate models to accelerate the Bayesian updating process. A novel strategy for the prediction of the magnitude and phase of FRFs with ANNs is proposed. The frequency is used as an additional input variable, and a schematic selection of significant points of the FRF curves is presented. A high prediction accuracy of the surrogate models could be achieved. The procedure includes the analysis of the relevant frequency range and a sensitivity analysis based on the Morris method to identify appropriate modes and the most-influential parameters. The proposed framework is applied to a current vehicle component subjected to vibrational loads. An experimental modal analysis is used for the calibration and consideration of real parameter uncertainty. First, the accuracy of the surrogate models and Bayesian updating is verified by a nominal reference simulation and then validated with experimental data. The measurable control parameter thickness and component mass are used to examine the calibration accuracy. Finally, a decrease in the dispersion of the vibration fatigue distribution is obtained with the calibrated parameters.

Experimental and numerical analysis of 3D end effects in Naval Magnetohydrodynamic propulsion motors

This study explores the impact of end electric current on the performance of a marine magnetohydrodynamic (MHD) propulsion motor or thruster using a comprehensive 3D numerical simulation. The investigation focuses on various operating parameters, such as electromagnetic and drag forces, efficiency, losses, current, and different pressure components. To validate the numerical findings, a scaled-down experimental setup is utilised. The results demonstrate that certain operating parameters of MHD motors are not affected by the three-dimensional characteristics of their channels. These parameters, including fluid velocity, can be accurately calculated using the analytical model based on the effective electric current of the motor. Conversely, other operating parameters of MHD motors are significantly influenced by the end effects in their channels. For example, the overall efficiency, which depends on the total electric current of the motor, should be calculated using a more precise simulation method.

An Improved Control Method of DC Voltage for Series Hybrid Active Power Filter

DC voltage is one of the important parameters of active power filters. Since the series hybrid active power filter does not withstand the fundamental voltage, it cannot absorb energy from the power grid, making it too difficult to control its DC voltage. In order to solve the DC voltage control problem, an improved control method for the series hybrid active power filter with magnetic flux compensation is proposed in this paper. In this improved method, the fundamental magnetic flux compensation coefficient is equal to 1, meeting the condition of fundamental magnetic flux compensation. This improved method does not rely on the precise detection and phase-locking of the fundamental voltage at the port of the series transformer. A phase-fixed active current component is generated directly by the inverter, enabling the active power filter (APF) to absorb active power from the power grid. Consequently, the active power absorbed by the APF from the power grid has a linear relationship with the active current component. Both simulation and experimentation verified the correctness and effectiveness of this proposed method.

Passive imaging through inhomogeneous scattering media

According to the atmospheric scattering model (ASM), the object signal’s attenuation diminishes exponentially as the imaging distance increases. This imposes limitations on ASM-based methods in situations where the scattering medium one wish to look through is inhomogeneous. Here, we extend ASM by taking into account the spatial variation of the medium density, and propose a two-step method for imaging through inhomogeneous scattering media. In the first step, the proposed method eliminates the direct current component of the scattered pattern by subscribing to the estimated global distribution (background). In the second step, it eliminates the randomized components of the scattered light by using threshold truncation, followed by the histogram equalization to further enhance the contrast. Outdoor experiments were carried out to demonstrate the proposed method.

A flexible loss reduction formulation for simultaneous capacitor placement and network reconfiguration in distribution grids

Efficiently reducing power losses involves various strategies such as opening normally closed switches and closing normally open tie-lines in distribution feeders, and optimally placing shunt capacitors in distribution networks. In this process, the accurate modeling of the demand side is crucial in understanding the behavior of electricity consumers appropriately. It is important to note that loads are not constant; they vary with changes in voltage magnitude, which in turn depend on the type of consumer. Each load can be represented by its constant power, current, and impedance components. In this regard, establishing a clear relationship between these components and consumer types can significantly enhance the flexibility of the network switching or capacitor placement strategy. Therefore, this study aims to mathematically formulate the correlation between load components and consumer types, aiming at establishing an efficient reconfiguration and capacitor allocation formulations. This is achieved by transforming polynomial load formulations into quadratic ones, while establishing mathematical relationships between the quadratic and polynomial models for various load types. The accuracy and convergence time of the proposed model was tested through its application to 16- and 33-bus distribution networks, and the results have been compared with the nonlinear metaheuristic approach. The results demonstrated that the proposed framework can efficiently provide optimal solutions within a shorter computational time as compared to the nonlinear and metaheuristic approaches.

Iyer-Wald ambiguities and gauge covariance of Entropy current in Higher derivative theories of gravity

In [1, 2] [arXiv:2105.06455, arXiv:2206.04538], the authors have been able to argue for an ultra-local version of the second law of black hole mechanics, for arbitrary diffeomorphism invariant theories of gravity non-minimally coupled to matter fields, by constructing an entropy current on the dynamical horizon with manifestly positive divergence. This has been achieved by working in the horizon-adapted coordinate system. In this work, we show that the local entropy production through the divergence of the entropy current is covariant under affine reparametrizations that leave the gauge of horizon-adapted coordinates invariant. We explicitly derive a formula for how the entropy current transforms under such coordinate transformations. This extends the analysis of [3] [arXiv:2204.08447] for arbitrary diffeomorphism invariant theories of gravity non-minimally coupled to matter fields. We also study the Iyer-Wald ambiguities of the covariant phase formalism that generically plague the components of the entropy current.

TRACK CIRCUITS INTERFERENCE RESISTANCE INCREASE UNDER THE TRACTION CURRENT INFLUENCE

Purpose. The aim of the work is to increase the electromagnetic compatibility of track circuits with the traction power supply system of railways under the influence of reverse traction current disturbances. Conducting research and analysis of the causes of malfunctions of rail circuits on electrified sections of the railway, existing means and methods of increasing the interference resistance of track circuits and ensuring the electromagnetic compatibility of signaling, centralization and blocking devices with the traction power supply system, and the development of effective technical solutions for normalizing the operation and rail circuits in the conditions influence of traction current interference. Conducting a study of the electromagnetic characteristics of the DT-1-150 track choke-transformer in normal mode and under the influence of external factors on the magnetic system. Methods. During the research, methods of comparative analysis, theories of electric and magnetic circuits, methods of spectral analysis of signals, as well as mathematical, schematic and physical modeling were used. Findings. Situations in which the traction current significantly affects the operation of the rail wheel equipment have been analyzed in the work. The effect of the traction current constant component on the normal operation mode of the track circuits is considered. The coefficients value of the choke-transformer DT-1-150 with traction current asymmetry was determined. A comparative analysis of resistance to reverse traction current disturbances of track receivers of station rail wheels used at the docking station was conducted. The principle-structural scheme of the protective unit for blocking the leakage of direct traction current interference on the section of alternating current traction was developed. The scientific novelty. The scientific novelty of the work consists in identifying and justifying the causes of some specific failures of track circuit; in confirming the integral effect of choke-transformer steel core saturation, created by the constant component of the traction current in the railway power supply system. Practical significance. Based on the conducted research, the interference resistance of the 25 Hz track circuit with the DSSH-16 track relay and DT-06-500S was confirmed. A protective valve block was developed, which prevents the flow of the first periods of the largest amplitude transient current in the track circuit its protects and ensures, thereby, normal operation of track circuit.

Generalised component method for bolted bearing type connections

AbstractThis paper develops a new generalised component method (GCM) model for bolted bearing type connections that predicts their full‐range response and all relevant strength limit states, including the bolt shear, bearing, shear‐out, net section fracture and block shear limit states. The proposed model divides a bolted bearing type connection into components that significantly contribute to its deformation and/or strength limit states. For each component, the force‐deformation curve is derived, including the post‐ultimate response, and expressed as a trilinear relationship. By assembling all components (springs) into the connection model, the multi‐linear force‐displacement response of the connection can be predicted, including the ultimate strength and ultimate deformation capacities. The proposed GCM can consider the interaction of adjacent bolts in modelling multi‐bolt connections. The new GCM is shown to accurately predict force‐displacement responses obtained from experimental tests and non‐linear finite element analyses. It is also shown to predict experimental responses significantly more accurately than the current component method implemented in Eurocode 3‐1.8.

Characterizing Non‐Phase‐Locked Tidal Currents in the California Current System Using High‐Frequency Radar

AbstractOver 9 years of hourly surface current data from high‐frequency radar (HFR) off the US West Coast are analyzed using a Bayesian least‐squares fit for tidal components. The spatial resolution and geographic extent of HFR data allow us to assess the spatial structure of the non‐phase‐locked component of the tide. In the frequency domain, the record length and sampling rate allow resolution of discrete tidal lines corresponding to well‐known constituents and the near‐tidal broadband elevated continuum resulting from amplitude and phase modulation of the tides, known as cusps. The FES2014 tide model is used to remove the barotropic component of tidal surface currents in order to evaluate its contribution to the phase‐locked variance and spatial structure. The mean time scale of modulation is 243 days for the M2 constituent and 181 days for S2, with overlap in their range of values. These constituents' modulated amplitudes are significantly correlated in several regions, suggesting shared forcing mechanisms. Within the frequency band M2 ± 5 cycles per year, an average of 48% of energy is not at the phase‐locked frequency. When we remove the barotropic model, this increases to 64%. In both cases there is substantial regional variability. This indicates that a large fraction of tidal energy is not easily predicted (e.g., for satellite altimeter applications). The spatial autocorrelation of the non‐phase‐locked variance fraction drops to zero over a distance of 150 km, a scale that is comparable to the swath width of the Surface Water and Ocean Topography altimeter.

MANAGEMENT CONSULTING OF THE AGRICULTURAL KNOWLEDGE AND INNOVATION SYSTEM (AKIS) IN UKRAINE

European Integration of Ukraine in the Ukrainian aspiration to join the European Union (EU) entails rapprochement with the Common Agricultural Policy (CAP) of the EU. One important element for the attainment of CAP objectives is a strong Agricultural Knowledge and Innovation System (AKIS). This article analyses the describable potential of the AKIS framework in the pre-accession phase of Ukraine. We review current AKIS components, their key issues identified, and strategies to reinforce them. Using a literature review, policy document analysis and expert interviews with key stakeholders that shape the current landscape of Ukrainian agriculture, the analysis was constructed. The results revealed that while UE is well placed as far as AKIS functionality is concerned, there are considerable areas that require improvements. Enhancing synergies between research, extension and farmers, encouraging co-creation of knowledge and harnessing digital technologies are some key steps. An effective AKIS standing behind the Ukrainian agriculture can make the country more productive, sustainable, and competitive improving its compatibility with the EU's CAP mechanisms.

Анализ частотных характеристик токовых датчиков цифрового трансформатора тока и напряжения

Digital measuring current and voltage transformers (DCVT), which incorporate various current and voltage sensors are the key sources of information about processes at modern digital substations. Classic small-sized current transformers, Rogowski coils, magnetotransistor sensors, Hall effect sensors, fiber-optic Faraday effect sensors, as well as shunts can be used as current sensors in DCVTs. For redundancy purposes, current channels are performed in several copies and on different sensors. Sensors that are different in nature have their own set of advantages, which together makes it possible to obtain the effect of eliminating the shortcomings of specific sensors. For example, they may not have a saturation effect or transmit the direct current component quite accurately, which is a significant advantage over classic current transformers. At the mains frequency, the behavior of these sensors is predictable, but their behavior is not well studied at higher and lower frequencies. Thus, it is decided to study the frequency response and phase response of these sensors in a wide frequency range. To solve the problems within the framework of this study, physical experiment, analytical and empirical solution methods have been used. As a result of the study, the frequency response and phase response of current sensors of DCVT in a wide frequency range have been obtained. Analog filter has been designed to correct the signal of the magnetotransistor sensor. The results obtained coincide with theoretical data and can be considered when developing digital relay protection and automation algorithms.

Disturbance-Observer-Based Sliding-Mode Speed Control for Synchronous Reluctance Motor Drives via Generalized Super-Twisting Algorithm

In this study, a novel composite speed controller combining a sliding-mode speed controller with a disturbance observer is proposed for the vector-controlled synchronous reluctance motor (SynRM) drive system. The proposed composite speed controller employs the generalized super-twisting sliding-mode (GSTSM) algorithm to construct both the speed controller and the disturbance observer. The GSTSM speed controller is utilized to stabilize the speed tracking error dynamics in finite time, while the GSTSM disturbance observer compensates for the total disturbance in the speed tracking error dynamics, which includes external disturbances and parametric uncertainties. Under the framework of the constant direct-axis current component vector control strategy for the SynRM drive system, comparative simulation studies are conducted among the standard STSM speed controller, the GSTSM speed controller, the composite speed controller using a GSTSM speed controller and a standard STSM disturbance observer, and the proposed composite speed controller. The effectiveness and superiority of the proposed composite speed controller are verified through simulation results.

Investigation of the forward gate leakage current in pGaN/AlGaN/GaN HEMTs through TCAD simulations

In this study, we examined the gate leakage characteristics of normally off pGaN/AlGaN/GaN HEMTs through a simulation study. The Fowler Nordheim Tunneling (FNT) mechanism mainly contributes to the gate leakage process as indicated by the Technology Computer-Aided Design (TCAD) simulation. However, at low bias, the FNT undercalculates the leakage current since the electric field is low in this region. This extra leakage current component at this low bias region can be attributed to the presence of surface traps. Trap-assisted tunneling current along with the FNT current can explain forward leakage characteristics of the pGaN HEMTs. Our TCAD simulations were matched with the experimental data for five devices from four different research groups to support this claim. Using TCAD simulations, we have been able to analyze several device parameters including the various potential drops inside the gate stack structure. We were able to identify some of the trap levels and compare them to the dominant defects expected to be present in the pGaN cap layer. Furthermore, we studied the effects of different device parameters on the gate leakage process in the pGaN HEMT.

An experimental study on the combustion characteristics of the cavity-stabilized supersonic premixed flame

With the overwhelming trend of fast and economic aviation, it is becoming increasingly difficult for fuel to burn stably and efficiently in a constrained space and time period in the combustor of a hypersonic air-breathing vehicle. Conventional supersonic diffusion flame runs the risk of blowing out in the incoming flow at such high velocity. Upstream fuel injection of the flame holder is gaining popularity due to its prominent advantage in improving mixing efficiency, and this fuel injection method contributes to the organization of supersonic premixed combustion. In order to study the combustion characteristics of the supersonic premixed flame, corresponding experiments are carried out on a direct-connected scramjet platform with the inflow total temperature of 1700 K and the inflow Mach Number of 2.0. Gaseous ethylene with an equivalence ratio of 0.15 was injected transversely 670 mm upstream of a cavity. Optical measurements including laser-induced fluorescence on the hydroxyl radical (OH-LIF), CH*chemiluminescence photography, and high-speed photography were performed to investigate the steady-state and transient combustion characteristics of the cavity-stabilized supersonic premixed flame. From steady-state OH-LIF and CH* results, the flame could be divided into reactant zone, preheating zone, intense reacting zone, and product zone. It could be inferred that the preheating zone induced by the hot product in the cavity acts as a radical source and heat source for combustion stabilization in the cavity. In addition, the transient flame morphology analysis was carried out from the high-speed photography results. The flame base position and flame spreading angle were abstracted from the binarized image. The results showed that there existed a subtle flame flashback phenomenon for the flame base, whereas the flame spreading angle maintained a relatively constant value with a small deviation. The frequency-domain analysis revealed that both the flame base position and flame spreading angle reached the peak amplitude in the direct current component (0 Hz), exhibiting no explicit high-amplitude resonance component within 1500 Hz compared to those in the diffusion combustion mode. In all, the supersonic premixed flame presented a stabilized flame morphology.