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Nonpolar solvents with added charge control agents are widely used in various applications, such as E-paper displays. In spite of previous work, the mechanisms governing charge generation in nonpolar liquids, particularly those induced by electrochemical reactions at the liquid-solid interface, are not completely understood. We hypothesize that a physics-based model, according to the modified Butler–Volmer equation, can be used to quantitatively predict the injection of charges and the corresponding currents, in nonpolar solvents with surfactants. We propose a model to describe the migration and charge generation of inverse micelles. In addition to the mechanisms of electromigration, diffusion and charge generation via disproportionation that were introduced in earlier models, we include charge generation via electron injection at the electrodes using a microscopically justified expression as opposed to the previously used semi-empirical approaches. To validate our model, we compare its results to experimental current measurements in a simplified, effectively 1D, geometry. We find that the incorporation of both bulk and electrochemical reaction mechanisms in the model can effectively explain the experimental steady-state currents in a wide range of concentrations, voltages (0.5 V-5 V), and cell thicknesses. These numerical results of currents at longer time scales show a steady-state current only when both bulk and electrochemical reactions are taken into account. Moreover, we have observed in our simulation that at low applied voltages, the electric field in the bulk is fully shielded, and the steady-state current in this low-voltage regime is governed by the charge injection at the electrodes. Conversely, when the voltage is high enough and the electric field remains partially unscreened, the bulk disproportionation mechanism dominates the current generation. This also explains why we observe a non-Ohmic behavior where the steady-state currents at high voltages are independent of applied voltage. Hence, by elucidating the physical processes underlying the experimental observations, our model offers a more profound comprehension of charge transport in these systems, which could facilitate advancements in the design of enhanced E-ink displays and smart windows.   • Currents predicted by our numerical model agree well with experimental results. • Analyzing physical mechanisms clarifies the origins of observed electrical currents. • At high voltage, our model shows current saturation limited by bulk reaction. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) require ultra-precise electrical measurements due to their unique charge transport mechanisms and sensitivity to environmental factors, yet commercial semiconductor parameter analysers capable of such measurements are prohibitively expensive for many research laboratories. This study introduces a novel, cost-effective, and portable setup for high-precision OFET characterisation that addresses this critical need, providing a feasible substitute for conventional analysers costing tens of thousands of dollars. The suggested system incorporates measurement, data processing, and graphical visualisation capabilities, together with Bluetooth connectivity for local operation and Wi-Fi functionality for remote data monitoring. The device consists of a motherboard and specialised cards for low-current measurement, voltage measurement, and voltage generation, providing comprehensive OFET characterisation, including transfer and output characteristics, in accordance with IEEE-1620 standards. The system can measure current from picoamperes to milliamperes, with voltage measurements supported by high input resistance (>100 MΩ) and a voltage generation range of −30 V to +30 V. This versatile and accessible approach greatly improves the opportunities for future OFET research and development. [ABSTRACT FROM AUTHOR]

Fiber optic current sensors have made unprecedented contributions to the safety and security of power grids. The λ/4 retarder, as a key component for generating circular polarization, can significantly enhance the performance of fiber optic current sensors (FOCS) due to its superior characteristics. However, traditional methods of fabricating homemade λ/4 retarders have inherent flaws. This study replaced the traditional λ/4 retarder in the all‐fiber current sensor with an integrated λ/4 retarder, which is proposed to convert linearly polarized light into circularly polarized light by controlling different spin rates of the spun fiber. The current sensitivity was increased from 0.235 to 0.404 mV/mA, and the noise was suppressed. [ABSTRACT FROM AUTHOR]

Measurement of a qubit (quantum bit) is a key element of quantum computation and is necessary for extracting information from a quantum processor. The physical implementation of a measurement protocol involves monitoring a physical quantity of a sensor, such as a current or a voltage, that is correlated with the state of the qubit to be measured. The monitoring of these sensors used to measure qubits in modern quantum computer architectures is typically divided between RF reflectometry and current/voltage monitoring. There are tradeoffs involved with both approaches for the reliable and accurate readout of qubits when it comes to scalable quantum computing architectures. In this article, we will review the working principles of a selection of sensors that are used to measure the state of qubits in semiconductors. The goal is to introduce electronic engineers with little or no background in quantum computing to the working principles of charge sensors in semiconductor quantum computers, their identification in various physical systems, and an overview of their design tradeoffs when measuring a qubit. This will allow electronic engineers to begin working with physics literature in the field of charge sensing. [ABSTRACT FROM AUTHOR]

Non-toroidal-shaped primary pass-through protection current transformers (CTs) are used to measure high currents. Their design provides them with a big airgap that allow the passing of several cables per phase though them, which is the main advantage versus toroidal types, as the number of CTs required to measure the whole phase current is drastically reduced. The cables passed through the transformer window can be in several positions. As the isolines of the magnetic field generated by the primary currents are centered in the cables, if these cables are not centered in the transformer window, then the magnetic field will be non-uniform along the transformer core. Consequently, local saturations can appear if the cables are not properly disposed, causing the malfunction of the CT. In this paper, the performance of a non-toroidal-shaped protection CT is studied. This research is focused on the influence of the cable position on possible partial saturations of the CT when it is operating near to its accuracy limit. Depending on the cable position, the ratio of the primary and secondary currents can depart from the assigned ratio. The validation of this phenomenon was carried out via finite element analysis (FEA), showing that partial transformer core saturations appear in areas of the magnetic core close to the cable. By applying FEA, the admissible accuracy region for cable positioning inside the CT is also delimited. Finally, the simulation results are ratified with experimental tests performed in non-toroidal protection CTs, varying the primary cables' positions, which are subjected to currents up to 5 kA, achieving satisfactory results. From this analysis, installation recommendations are given. [ABSTRACT FROM AUTHOR]

In this letter, three battery-powered, custom Internet of Things (IoT) sensor nodes for the agribusiness, are presented: first, a Sigfox-based temperature-humidity index (THI) sensor to monitor the impact of heat stress in livestock, then a LoRaWAN version of an estrus detection collar for dairy farms, and finally a NB-IoT low-power A-GPS geolocation device for animals. Detailed power consumption measurements are presented and compared to highlight the benefits of each low-power wide-area network technology for the industry. The measured energy to transmit a single 10Byte payload packet was 90, 20, and 90 mJ for Sigfox, LoRa, and NB-IoT, respectively. With an adequate power management strategy, the nodes could operate up to 10 years in the case of the THI and estrus detector, and >1 yr in the case of the GPS tracker, powered by a single 1900 mA $\cdot \mathrm {h}~\mathrm {LiSOCl}_{2}$ battery. [ABSTRACT FROM AUTHOR]

Future wireless network technology will provide automobiles with a connectivity feature to consolidate the concept of vehicular networks that collaborate in conducting cooperative driving tasks. The full potential of connected vehicles, which promises road safety and a quality driving experience, can be leveraged if machine learning (ML) models guarantee robustness in performing core functions, including localization and controls. Location awareness, in particular, lends itself to the deployment of location-specific services and improvement of the operation performance. Localization entails direct communication to the network infrastructure, and the resulting centralized positioning solutions readily become intractable as the network scales up. As an alternative to the centralized solutions, this article addresses a decentralized principle of vehicular localization reinforced by ML techniques in dense urban environments with frequent inaccessibility to reliable measurement. As such, the collaboration of multiple vehicles enhances the positioning performance of ML approaches. A virtual testbed is developed to validate this ML model for real-map vehicular networks. Numerical results demonstrate the universal feasibility of cooperative localization, in particular, for dense urban area configurations. [ABSTRACT FROM AUTHOR]

Due to their compact structure and low laying cost, three-core power cables are widely used for power distribution networks. The three-phases of such cables are distributed symmetrically with a 120° shift to each other. Phase current is an important parameter to reflect the operation state of the power system and three-core cable. Three-core symmetrical power cables use a common shield, leading to magnetic field cancelation outside the cable during steady operation. Thus, traditional magnetic-based current transformers cannot measure the phase current on three-core cable non-invasively. In order to measure the phase current more conveniently, a phase current measurement method for three-core cables based on a magnetic sensor is proposed in this paper. Nonlinear equations of a phase current and the magnetic field of a measuring point are constructed. The calculated magnetic field distribution of the three-core cable is verified using a finite element simulation. The effectiveness of the measurement method is further validated through experiments. This proposed method is able to conveniently detect the phase current of three-core power cables, which can help cable maintenance. [ABSTRACT FROM AUTHOR]

Permanent-magnet synchronous motors (PMSMs) have played a key role in recent years in both industrial and commercial applications. Despite their many significant advantages, such as high efficiency, very good dynamics, and high power density, these types of motors are prone to various types of faults. This article proposes a low-cost microcontroller-based system for PMSM stator winding condition monitoring and fault diagnosis. It meets the demand created by the use of more and more low-budget solutions in industrial and commercial applications. A printed circuit board (PCB) has been developed to measure PMSM stator phase currents, which are used as diagnostic signals. The key components of this PCB are LEM's LESR 6-NP current transducers. The acquisition and processing of diagnostic signals using a low-cost embedded system (NUCLEO-H7A3ZI-Q) with an ARM Cortex-M core is described in detail. A machine learning-driven KNN-based fault diagnostic algorithm is implemented to detect and classify incipient PMSM stator winding faults (interturn short-circuits). The effects of the severity of the fault and the motor operating conditions on the symptom extraction process are also investigated. The results of experimental tests conducted on a 2.5 kW PMSM confirmed the effectiveness of the developed system. [ABSTRACT FROM AUTHOR]

If an R.M.U. (Ring Main Unit) cubicle is installed, operated and maintained in accordance with current standards and the manufacturer's instructions, the likelihood of internal arcing is reduced, but should not be completely ignored. This article outlines the experimental situations in which arcing can occur and the catastrophic effects seen if R.M.U. is not properly designed for this type of damage. This type of failure can be caused by a fault, abnormal operating conditions or a malfunction and represents a danger during its installation and to persons present. The situations in which this type of failure can occur are presented and experimentally analysed: bi-phase internal arcing in the connections compartment, three-phase internal arcing in the switching compartment, internal arcing in the fuse compartment and single-phase arcing between a phase and the switchgear enclosure. [ABSTRACT FROM AUTHOR]

Transistor random threshold voltage variations due to process fluctuations seriously affects the stability of Static Random Access Memory (SRAM). In this paper, a SRAM bit transistors threshold voltage $({Vth})$ deviation monitoring scheme and system is proposed. This scheme ingeniously achieves on-chip measurement of all transistors threshold voltages without altering compact SRAM bit array layout. Control signal strategies and Transistor ${Vth}$ Determination Circuit (TVDC) for different types of Devices Under Test (DUTs) have been proposed. The system is implemented using a 65 nm CMOS process with a core area of 0.01875mm2. Through Monte Carlo analysis, the Weighted Average (WA) difference of the proposed scheme and the direct measurement method is not more than 10mV, and the Root Mean Square Error (RMSE) difference is not more than 3mV. This system can also effectively detect the cell position of the transistor threshold voltage mismatch simulated by modifying the substrate voltage. For SRAM arrays of different scales, the method proposed in this paper has area efficiency and flexible reconfigurability. [ABSTRACT FROM AUTHOR]

Energy efficiency is an important issue in industry, especially with the ever-increasing consumption of electrical energy. The power quality and the traceability of metering devices are essential when integrating energy metering systems for energy efficiency. This management requires an understanding of electrical current events such as pulse and transient currents. Current transducers are widely used to measure these electrical current events up to a few megahertz. Their use makes it possible to measure not only the main current flowing through the transducer, but also the bypass current that affects electrical equipment. Calibration of these sensors up to a few megahertz then becomes an essential step. Currently, most calibration methods are limited to 100 kHz frequency for a current of 10 A. This paper presents an improvement of a traceable calibration methodology for current transducers up to 10 A and 1 MHz, thus increasing, by 10 times, the current level for such high frequency applications. This calibration methodology is based on a metrological traceability chain (uninterrupted link to the International System of Units) with respect to a calculable current shunt and is currently the only traceable method for calibrating current transducers at 10 A and up to 1 MHz. The uncertainty obtained for the transimpedance ratio is less than 0.2%, which is considerably reduced with respect to the existing capabilities. [ABSTRACT FROM AUTHOR]

This paper suggests a technique to reduce noise in DC current measurements within an integrated power conversion system, which includes a three-phase inverter and a full-bridge converter both utilizing single shunt resistors as current sensors. Typically, current measurement is conducted after the stabilization of current ringing to minimize the impact of switching noise. However, in the integrated power conversion system with common DC-link, switching ripples of the inverter may cause errors in the current measurement of converter, and vice versa. Therefore, switching transitions are not allowed during the current sensing periods of both the inverter and the converter in the integrated power conversion system. This paper proposes a method to adjust the switching timing of a three-phase inverter by regulating the offset voltage. While the method is explained using space vector pulse width modulation, it reconfigures the pole voltage references through offset voltage and is not dependent on the modulation technique. The paper details the process for determining the offset voltage and verifies the noise reduction effect of the technique through experimental results.

This article presents a single current sensing method that achieves minimal current reconstruction errors, even at extremely low-speed region. In vector control applications, a drive system that combines single current sensor with position sensorless techniques is attractive as it minimizes the use of sensors. The current reconstruction method using the DC current measurement method introduces current reconstruction errors because of the sampling timing of single current sensor method. Moreover, current dc current measurement method has a dead zone where current reconstruction is not possible, leading to pronounced current ripple during the avoidance process. In the case of ultra-low inductance motors, the increase in current ripple exacerbates the drive performance, especially at low speeds. When the single current sensor method and sensorless drive are applied to an ultra-low inductance non-salient pole synchronous motor, it can lead to operational failures due to high current ripple and current reconstruction errors at low-speed region. This article proposes a technique to improve the performance in the low-speed region when current reconstruction method using dc current sensor and sensorless techniques are used together by eliminating dead zone in the low-speed region minimizing current reconstruction errors with a model-free method. The current reconstruction performance, sensorless startup, and operation performance have verified through experiments.

This article presents a noninvasive method of measuring three-phase currents using magnetic sensors that can be used for continuous monitoring, automation, and protection of power grids. The nonintrusive nature of these sensors gives operational and economic benefits in installing them at the existing distributed generation sites and power substations. These sensors are linear in operation, free of saturation, and need minimum duration or no outage for installation as compared to the conventional current transformers. This article describes magnetic field simulation, calibration, and experimental validation of magnetic sensors for accurate measurement of three-phase currents. Laboratory experiment results of three-phase low current measurements for two types of overhead structures: triangular and horizontal are rendered as a validation of the proposition. The performance verification of these sensors is further achieved by conducting field experiments for measuring currents up to 1500 A. The sensors yield promising results with a maximum error of 1.15% in the estimation of three-phase currents. The magnetic sensors showed satisfactory performance in accurately reproducing current waveforms consisting of fundamental frequency and harmonics that are typically present in modern power grids.

We report on the design and construction of a laser scanning optical beam-induced current (OBIC) microscope by assembling cost-effective commercial optical and electronic hardware components and developing data acquisition and control software in LabVIEW. A preliminary OBIC image of a Si photodetector acquired by the developed microscope is presented to demonstrate its operational capability. The versatility of the design will allow for the construction of other scanning microscope modalities on the same platform.

Non-toroidal-shaped primary pass-through protection current transformers (CTs) are used to measure high currents. Their design provides them with a big airgap that allow the passing of several cables per phase though them, which is the main advantage versus toroidal types, as the number of CTs required to measure the whole phase current is drastically reduced. The cables passed through the transformer window can be in several positions. As the isolines of the magnetic field generated by the primary currents are centered in the cables, if these cables are not centered in the transformer window, then the magnetic field will be non-uniform along the transformer core. Consequently, local saturations can appear if the cables are not properly disposed, causing the malfunction of the CT. In this paper, the performance of a non-toroidal-shaped protection CT is studied. This research is focused on the influence of the cable position on possible partial saturations of the CT when it is operating near to its accuracy limit. Depending on the cable position, the ratio of the primary and secondary currents can depart from the assigned ratio. The validation of this phenomenon was carried out via finite element analysis (FEA), showing that partial transformer core saturations appear in areas of the magnetic core close to the cable. By applying FEA, the admissible accuracy region for cable positioning inside the CT is also delimited. Finally, the simulation results are ratified with experimental tests performed in non-toroidal protection CTs, varying the primary cables’ positions, which are subjected to currents up to 5 kA, achieving satisfactory results. From this analysis, installation recommendations are given.

Due to their compact structure and low laying cost, three-core power cables are widely used for power distribution networks. The three-phases of such cables are distributed symmetrically with a 120° shift to each other. Phase current is an important parameter to reflect the operation state of the power system and three-core cable. Three-core symmetrical power cables use a common shield, leading to magnetic field cancelation outside the cable during steady operation. Thus, traditional magnetic-based current transformers cannot measure the phase current on three-core cable non-invasively. In order to measure the phase current more conveniently, a phase current measurement method for three-core cables based on a magnetic sensor is proposed in this paper. Nonlinear equations of a phase current and the magnetic field of a measuring point are constructed. The calculated magnetic field distribution of the three-core cable is verified using a finite element simulation. The effectiveness of the measurement method is further validated through experiments. This proposed method is able to conveniently detect the phase current of three-core power cables, which can help cable maintenance.

LQXFA/B production series cryogenic assemblies are being built for the LHC upgrade by the HL-LHC Accelerator Upgrade Project (AUP). These contain a pair of MQXFA quadrupole magnets combined as a cold mass within a vacuum vessel, and are to be installed in the IR regions of the LHC. The LQXFA/B are being tested at 1.9 K to assess alignment and magnetic performance at Fermilab's horizontal test facility. The ∼10 m long assembly must meet stringent specifications for quadrupole strength and harmonic field integrals determination, magnetic axis location, and for variations in axis position and local field profiles. A multi-probe, PCB-based rotating coil and a Single Stretched Wire system are employed for these measurements. To accurately determine rotating coil location and angles within the cold mass, a laser tracker is utilized to record multiple targets at one end of the probe. This paper describes the measurements, probes/equipment, and techniques used to perform the necessary characterization of the cold mass.

To increase the acceptance of electric vehicles (EVs), inductive charging technology can be an important tool because of the simplified charging process for the user. This paper presents the fundamentals of wireless power transfer (WPT) for EVs, while focusing on electromagnetic compatibility (EMC). This work deals with the investigation of the conducted and field-bound interference emissions using a WPT system with a max. input power of 3.6 kW. During the research, a new frequency-tracking algorithm is developed, to find the optimal operating frequency at any coil misalignment. The impedance behavior as well as the possible interference paths are investigated, showing the great geometric influence of the test bench setup. The conducted interference currents are analyzed and subsequently filtered. The filter shows good performance in attenuating common mode currents. The measured radiated magnetic field is directly rated against the proposed limits of various standards. Finally, the EMC influence of the direct current (DC) power supply line to the inverter is examined, which is not defined precisely in the standard. This underlines the significance of a standardized test setup, since the limit values can be met under different geometric circumstances of the DC cable.

The Japan Aerospace Exploration Agency has developed a power processing unit for a 6 kW Hall thruster, a candidate for propulsion systems for geostationary satellites. Hall thrusters have a discharge instability of tens of kHz, which may damage thrusters, power processing units, and satellite systems. This paper proposes our system for detecting discharge current amplitudes that exceed the specified limit of the thruster. The discharge current is converted into a voltage by the current sensor and is output to a digital controller through an AD converter. The system's innovation includes a frequency prediction model and a damping correction algorithm, which allow the system to accurately detect the peak amplitude of the discharge current without testing to measure the frequency characters of the Hall thruster. The design of the amplitude detection system considers the frequencies of the ionization oscillation and the switching frequency of the power processing unit. The frequency prediction model estimates the frequency of discharge current oscillations from simple parameters: the output voltage of the discharge power supply and the thruster dimensions. The amplitude of the discharge current is damped slightly by the frequency characteristics of the system, but the algorithm corrects this. The results of the frequency prediction model agreed well with the actual measurements. The predicted value was 13.2 kHz, while the actual measurement was 8–15 kHz. The integration test showed that the amplitude detection system identified 36 peaks exceeding the specified limit of 80% peak-to-peak during a 100 ms segment, although the actual number was 34. This difference is acceptable. The proposed amplitude detection system can accurately count the peaks in the discharge current that exceed specifications. • An amplitude detection system detects discharge current oscillations that exceed the specifications for protecting satellites. • The algorithm and frequency response of the system are designed considering the frequency of ionization oscillations. • The frequency is estimated by a simple model with only the output voltage of the discharge power supply and thruster dimensions. • The system detected the amplitude of the discharge current oscillations with an error of 5.8%. [ABSTRACT FROM AUTHOR]

To increase the acceptance of electric vehicles (EVs), inductive charging technology can be an important tool because of the simplified charging process for the user. This paper presents the fundamentals of wireless power transfer (WPT) for EVs, while focusing on electromagnetic compatibility (EMC). This work deals with the investigation of the conducted and field-bound interference emissions using a WPT system with a max. input power of 3.6   k W . During the research, a new frequency-tracking algorithm is developed, to find the optimal operating frequency at any coil misalignment. The impedance behavior as well as the possible interference paths are investigated, showing the great geometric influence of the test bench setup. The conducted interference currents are analyzed and subsequently filtered. The filter shows good performance in attenuating common mode currents. The measured radiated magnetic field is directly rated against the proposed limits of various standards. Finally, the EMC influence of the direct current (DC) power supply line to the inverter is examined, which is not defined precisely in the standard. This underlines the significance of a standardized test setup, since the limit values can be met under different geometric circumstances of the DC cable. [ABSTRACT FROM AUTHOR]

The measuring current of the traditional electromagnetic transformer is vulnerable to electromagnetic interference and the insulation cost is high, to solve the problem, the all fiber technology has been applied in the power system with its advantages of insulation, high precision, large dynamic current measurement and digital output. With optical fiber sensing technology at home and abroad, the progress and existing problems of all optical fiber current measurement technology applied in power system were reviewed, and the development trend of all fiber optical current sensor (AFOCS) was forecasted. The advantages and disadvantages of polarization, reflection and double modulation all-fiber current sensors were evaluated, and the application prospect of each type of sensor in power system was analyzed. The effects of different factors such as temperature, linear birefringence and data processing algorithm on the measurement accuracy of the all-fiber sensor were compared. The results show that with the improvement of sensor structure and the application of various algorithms, the application of all fiber optical current sensor in the power system has become a new trend, the accuracy and stability of current measurement has been significantly improved, and that efforts need to be taken to improve the stability of sensor in outdoor environment to measure current and reduce the failure rate. [ABSTRACT FROM AUTHOR]

If an R.M.U. (Ring Main Unit) cubicle is installed, operated and maintained in accordance with current standards and the manufacturer’s instructions, the likelihood of internal arcing is reduced, but should not be completely ignored. This article outlines the experimental situations in which arcing can occur and the catastrophic effects seen if R.M.U. is not properly designed for this type of damage. This type of failure can be caused by a fault, abnormal operating conditions or a malfunction and represents a danger during its installation and to persons present. The situations in which this type of failure can occur are presented and experimentally analysed: bi-phase internal arcing in the connections compartment, three-phase internal arcing in the switching compartment, internal arcing in the fuse compartment and single-phase arcing between a phase and the switchgear enclosure.

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Supercapacitors are becoming increasingly important storage system components. To effectively control their terminal voltage, even in real time, numerous circuit models capable of faithfully simulating their behavior in energy systems and various applications have been explored. The three-branch supercapacitor model appears to be a good compromise between simplicity and accuracy. Typically, this model lacks accuracy in dynamic cycling and long stand-by periods. In this study, a new model identification method based on the state equations of the circuit is described and tested on a 400 F supercapacitor, and the obtained results are validated by measurements. Such an approach, suitably optimized, provides good agreement with the measurements, with discrepancies below 50 mV even in repeated cycles. In static identification, after 90 minutes of self-discharge, the discrepancy was approximately 5 mV. The study also discusses the sensitivity of the model output to the circuit parameters, which is useful for choosing the appropriate timespan for parameter optimization, and introduces variable leakage resistance and a method for its determination. Using this parameter, good agreement with the measurements is observed during the long self-discharging phases. A discrepancy of less than 50 mV between the measured and computed results is observed after one week. The union of the circuit state equations based model and the nonlinear leakage resistance determination allows the three-branch circuit model to achieve a high accuracy both in real-time simulation and in the presence of long stand-by phases.

The sudden short-circuit test is the gold standard for determining the equivalent diagram of wound-field synchronous machines (WFSMs). Only a single measurement is needed while the machine is in saturated mode. However, this destructive test can significantly reduce the lifetime of the stator winding. Moreover, determining the equivalent diagram in the q-axis is more complicated and is often not performed. DC-decay tests are low-power alternatives that allow for the determination of the equivalent diagram in both axes without damaging the machinery. Until recently, they required the rotor to be aligned with the axes, which is not feasible in large power plants. A recent breakthrough eliminated the need for rotor alignment by proposing a DC-decay test that can be performed with the rotor in any position. However, numerous independent measurements are needed to obtain the equivalent diagram in both axes. This paper addresses the question of the minimum number of independent measurements needed for the DC-decay test to be practical for industrial use. Around 10 measurements are sufficient for reasonable precision, while 5 of high quality are sufficient using the symmetry of the root locus. Finally, a comparison against the short-circuit test shows that the DC-decay test is a valid alternative.

Cryogenic propulsion with hydrogen fuel cells replacing fossil fuels is a promising solution to cut carbon emissions in the aviation sector. Hydrogen will also be used for cooling the superconducting machines and power converter circuits. This article aims to test devices suitable for power electronic converters supplying a 1.6 MW superconducting machine. SiC MOSFET and Si IGBT modules with ratings of 1200 V and more than 450 A are selected to assess their performance at different temperatures. Four tests are conducted to determine: 1) the forward voltage drop, 2) the breakdown voltage, 3) the switching behavior, and 4) their operation with two modules in parallel. A bespoke current sensing rig has been developed that avoids the need to extend conductors outside the cryogenic zone in the switching losses measurement test. This configuration introduces minimal stray inductance into the circuit, which minimizes errors in the measurement. One of the aims of this article is to assess the suitability of different module technologies for SiC MOSFET and Si IGBTs in cryogenic applications. Six power modules (SiC MOSFETs and Si IGBTs) were evaluated at both room and cryogenic temperatures. Three of the modules employed conventional bond wire technology, while the other three utilized solid cover (SLC) technology that has no internal bond wires. It was found that the modules which employed SLC technology were the only ones able to survive the extreme temperatures. Following this, a comparison was made between the energy losses of the three SLC modules (two Si IGBTs and one SiC MOSFET) that were able to withstand low temperatures. The results indicated that the performance of the SiC MOSFET module worsens at cryogenic temperatures, whereas the performance of the Si IGBT modules improves with decreasing temperatures. Finally, an inverter simulation was conducted with each of the IGBT modules to estimate the efficiency.

Sheath currents in high voltage cable circuits have proven to be one of the most convenient indicators for assessing cable health. The sheath currents are regularly distributed with fluctuation in a certain range under normal conditions, while the principle of distribution characteristics is still unclear when the cross-bonded grounding system of the cable circuit is abnormal. This paper classifies the common defects of grounding system into three types of circuit topologies and analyzes the correspondence between grounding system conditions and sheath currents. A fault diagnosis method is proposed to detect irregular distribution of sheath currents by quantifying the difference of sheath currents in each of the minor sections and the average currents of each sheath loop. Sensitive analyses are provided to evaluate the criteria, clarifying the influence of fault resistance in each defect. The results show that the method can be very effective when the ratio of the fault resistance to the earth resistance is less than 7.6 for a short-circuit defect in metallic sheath, or less than 1.2 for a short-circuit defect between metallic sheath and ground. The performance of the method is also shown to be very efficient by evaluation with the data collected on site.

The medium-voltage direct-current (MVDC) electrical energy system has attracted increasing attention because of its high energy density and low carbon potential. Accurately characterizing, measuring, and monitoring the DC voltage and current are crucial for the control, protection, and energy metering of the MVDC system. Nonetheless, so far, neither industry nor academia has reached no consensus on the technical specifications of voltage and current measurement apparatuses for the MVDC systems. This paper analyzes the technical specifications of voltage and current measurement apparatuses for typical ±10kV MVDC systems considering the systems requirements and compares the adaption of the voltage and current sensors. Typical two-terminal and four-terminal MVDC system simulation models are constructed. The events that would generate the worst transient waveforms are modeled respectively to figure out the technical specifications for the control, protection, and metering systems. The closed-loop tunnel magnetoresistance (TMR) based current sensor and the resistors-based voltage divider are proposed as the most suitable apparatuses for MVDC system measurements. The research results can guide the research of sensors for MVDC systems and provide references for engineering applications.

A three-phase GaN-based motor inverter IC with three integrated phase current mirror sensors (sense-FETs or sense-HEMTs, 1200:1 ratio), a temperature sensor, and an amplifier is presented and experimentally operated. The three low-side currents are read out by virtual grounding transimpedance amplifiers. A modified summed DC current readout circuit using only one amplifier is also discussed. During continuous 24 V motor operation with space-vector pulse width modulation (SVPWM), the sensor signal is measured and a bidirectional measurement capability is verified. The measured risetime of the sensor signal is 51 ns, indicating around 7 MHz bandwidth (without intentional optimization for high bandwidth). The IC is operated up to 32 V on DC-biased semi-floating substrate to limit negative static back-gating of the high-side transistors to around −7% of the DC-link voltage. Analysis of the capacitive coupling from the three switch-nodes to the substrate is calculated for SVPWM based on capacitance measurement, resulting in four discrete semi-floating substrate voltage levels, which is experimentally verified. Integrated advanced power converter topologies with sensors improve the power density of power electronics applications, such as for low-voltage motor drive. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) has all-weather, all-day, large-area observation capability and can measure ocean total surface currents with Doppler frequency shift. However, conventional SAR can only obtain the radial velocity of the ocean’s total surface current. In this letter, we propose a method for inverting ocean total surface current vectors using a 2-D Kalman filter and a priori information about ocean current fields from ocean surface current analyses real-time (OSCAR). We establish a complete filtering process including filter creation, filtering path selection, and fusion of filtering results. We construct the Kalman filter according to the motion characteristics of ocean currents and transform the ocean surface current vector inversion problem into a filtering problem. The introduction of 2-D filtering can better adapt to the directionality of ocean currents. Furthermore, we design the filtering path to obtain smoother filtering results. To synthesize the filtering results of different filtering paths, we use the covariance intersection (CI) fusion method in distributed fusion to obtain the final ocean current vector inversion results. The accuracy of the inversion is verified by the measured data. The root mean square error (RMSE) of the proposed method with the mean Doppler error of 5.43 Hz is 0.182 m/s at eastward speed and 0.141 m/s at northward speed. The reduction is 0.009 and 0.029 m/s against OSCAR. [ABSTRACT FROM AUTHOR]

Trust between group members has many implications for how well a group performs. In this study, we predict perceived trustworthiness of group members when there are subversive group members. We collected multimodal verbal and nonverbal data from a group interaction experiment. During the interaction, we periodically surveyed the group members about their perceptions of trustworthiness of other group members. We used this data to model the relationship between observable behavior and perceptions of trustworthiness. We report the most predictive features and describe them in the context of existing literature on verbal and nonverbal correlates of trust. This research advances the study of behavioral measurement in groups and the role of behavior on perceived trustworthiness. [ABSTRACT FROM AUTHOR]

After eons of evolution, biological systems have developed excellent actuating methodology in micro-nano scale, which inspired the design and development of advanced microrobots. Cardiomyocytes have received extensive attention following the development of bio-syncretic robots in terms of its spontaneous contraction and high energy efficiency. However, the multipoint, high-precision synchronized, and comprehensive acquisition of the axial motion parameters of cardiomyocytes still constitutes the major factor hindering the development of quantitative control methods for bio-syncretic robots. Herein, off-focus imaging method was proposed to quantify the axial beating of cardiomyocyte. The spontaneously beating of cardiomyocytes were quantitative analyzed based on the combination of cross-correlation and off-focusing imaging. We also validated the use of the proposed SiO2 microspheres in cardiotoxicity test. Following the administration of isoproterenol, cardiomyocytes exhibited positive inotropic and chronotropic effects. Finally, we analyzed the beating responses of individual cardiomyocytes at different locations, and we validated the feasibility of multipoint, synchronized measurements. In the future, this study can also be extended to the analysis of the motion coupling relationship between individual cardiomyocytes and cardiomyocyte clusters, thus providing a data acquisition platform for the dynamic analysis and modeling of bio-syncretic robot actuators. [ABSTRACT FROM AUTHOR]

This paper reports the complementary resistive switching (CRS) characteristics exhibited by Au/ZnO/Al2O3/ Fluorine doped tin oxide (FTO) bilayer device for the first time, where both ZnO and Al2O3 are active switching layers exhibiting resistive switching properties. The I-V characteristics of the device initially show bipolar resistive switching (BRS) for a few cycles (∼12) before permanently switching to CRS with the extension of SET voltage. The stable CRS state of the device exhibits a high current of ∼500 μA during the ON-state and low current of 3 × 10−7 A during OFF-state at low input voltages (−0.5 V to 0.5 V) enables the proposed device suitable to use in crossbar array to mitigate the sneak path current. The device performance to write and read processes is evaluated with pulses of magnitudes ∼|2.5| V and 1.3 V, respectively, and showed a ∼60 μA difference in read-out current between data bits 0 and 1. Similarly, the device's power consumption is also measured to elucidate that the device is suitable to use as a memory unit with power consumption in the order of microwatts (μW). Further, the possible switching mechanism is demonstrated based on oxygen vacancies migration. [ABSTRACT FROM AUTHOR]

In this article, the integration into a single measurement system of device level and nanoscale measurement equipment is presented and applied to the electrical characterization of emerging electron devices. This system is a smart solution to simplify the test procedure, since it allows a fast switching between measurement modes (device or nanoscale level), also featuring an enlarged testing capability. Key in the system is a custom-made inkjet-printed circuit board (I-PCB) that connects the device terminals to the proper instrumentation. The flexibility offered by inkjet-printing technologies is a clear advantage, since many kinds of devices can be tested, without the need of expensive hardware modifications. As a particular case of study, the proposed strategy is demonstrated by implementing a system that alternates between standard electrical measurements with a Semiconductor Parameter Analyzer (SPA) and Conductive Atomic Force Microscopy (CAFM) nanoscale measurements on back-gate graphene field-effect transistors. [ABSTRACT FROM AUTHOR]

Energy efficiency is an important issue in industry, especially with the ever-increasing consumption of electrical energy. The power quality and the traceability of metering devices are essential when integrating energy metering systems for energy efficiency. This management requires an understanding of electrical current events such as pulse and transient currents. Current transducers are widely used to measure these electrical current events up to a few megahertz. Their use makes it possible to measure not only the main current flowing through the transducer, but also the bypass current that affects electrical equipment. Calibration of these sensors up to a few megahertz then becomes an essential step. Currently, most calibration methods are limited to 100 kHz frequency for a current of 10 A. This paper presents an improvement of a traceable calibration methodology for current transducers up to 10 A and 1 MHz, thus increasing, by 10 times, the current level for such high frequency applications. This calibration methodology is based on a metrological traceability chain (uninterrupted link to the International System of Units) with respect to a calculable current shunt and is currently the only traceable method for calibrating current transducers at 10 A and up to 1 MHz. The uncertainty obtained for the transimpedance ratio is less than 0.2%, which is considerably reduced with respect to the existing capabilities.

This paper develops a novel graph convolutional network (GCN) framework for fault location in power distribution networks. The proposed approach integrates multiple measurements at different buses while taking system topology into account. The effectiveness of the GCN model is corroborated by the IEEE 123 bus benchmark system. Simulation results show that the GCN model significantly outperforms other widely-used machine learning schemes with very high fault location accuracy. In addition, the proposed approach is robust to measurement noise and data loss errors. Data visualization results of two competing neural networks are presented to explore the mechanism of GCNs superior performance. A data augmentation procedure is proposed to increase the robustness of the model under various levels of noise and data loss errors. Further experiments show that the model can adapt to topology changes of distribution networks and perform well with a limited number of measured buses.

In this paper, the performance limits of faults localization are investigated using synchrophasor data. The focus is on a non-trivial operating regime where the number of Phasor Measurement Unit (PMU) sensors available is insufficient to have full observability of the grid state. Proposed analysis uses the Kullback Leibler (KL) divergence between the distributions corresponding to different fault location hypotheses associated with the observation model. This analysis shows that the most likely locations are concentrated in clusters of buses more tightly connected to the actual fault site akin to graph communities. Consequently, a PMU placement strategy is derived that achieves a near-optimal resolution for localizing faults for a given number of sensors. The problem is also analyzed from the perspective of sampling a graph signal, and how the placement of the PMUs i.e. the spatial sampling pattern and the topological characteristic of the grid affect the ability to successfully localize faults. To highlight the superior performance of presented fault localization and placement algorithms, the proposed strategy is applied to a modified IEEE 34, IEEE-123 bus test cases and to data from a real distribution grid. Additionally, the detection of cyber-physical attacks is also examined where PMU data and relevant Supervisory Control and Data Acquisition (SCADA) network traffic information are compared to determine if a network breach has affected the integrity of the system information and/or operations.

Power-electronic-converter-induced motor bearing currents are a widespread problem in the field of electrical drives. Parasitic capacitances between the electrical machine's parts provide a path for leakage currents, which finally harm metallic ball bearings. Remembering that end-windings have a significant contribution in building up stray capacitances, a countermeasure affecting both the lamination stack and end-winding areas is needed. This article focuses on a countermeasure against the noncirculating bearing currents in the cluster of solutions at the motor side. The electrostatic shielding approach, which is a known principle to reduce capacitive couplings, is applied in electrical machines every now and then. In this article, the principle of slot-embedded grounded electrodes is extended to cover also the end-windings. Thus, the electrodes provide a better shaft-to-ground voltage mitigating effect compared to the case where electrodes are applied only in the lamination stack area. The feasibility and effectiveness of such a countermeasure are investigated. Different options in terms of scaling of both the machine size and diameter of the electrodes were analyzed and corresponding conclusions were pointed out. [ABSTRACT FROM AUTHOR]

Fast and reliable dc line protection is one of the key techniques for flexible dc grid with the development of flexible dc transmission technology. However, the serious overcurrent caused by dc faults has a prominent contradiction with the weak overcurrent capability of power electronics. In this article, the high-fidelity dynamic model of the transmission line is first established based on the frequency-dependent characteristic of line parameters. Then, a new dynamic state estimation based protection (DSEBP) scheme is proposed, which uses the redundancy feature of state estimation to improve the dependability of protection. Finally, the actual measurements and the estimated states are compared with the similarity to identify the fault by the chi-square distribution. The proposed method's effectiveness is verified through simulations power systems computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) and experiments, and the factors affecting the performance of DSEBP are analyzed. Compared with the existing protection methods, the proposed method is more dependable, more sensitive, and available for actual projects. [ABSTRACT FROM AUTHOR]

Integrated gate-commutated thyristors (IGCTs) have successfully demonstrated to be well-suited devices for an application in medium-voltage dc transformers based on LLC resonant converter topology. This appli- cation enables unusually high switching frequencies in kilohertz range thanks to the zero-voltage switching while maintaining the high conversion efficiency. Moreover, the clamp circuit that is an inseparable part of every hard-switched IGCT-based converter can be completely omitted—further lowering the converter complexity and cost. Nevertheless, without the clamp circuit, the effect of shoot through becomes fatal, considering that the IGCTs have a defined mode of failure in short circuit and the desaturation effect is practically nonexistent. To prevent the shoot through, this letter proposes a simple, yet effective, protection method based on anode-voltage measurement that can be implemented locally on the IGCT gate unit. The validity of the solution is demonstrated using a custom IGCT gate unit in a medium-voltage resonant test setup. [ABSTRACT FROM AUTHOR]