High Current Measurement Research Articles

High Current Measurement of Commercial REBCO Tapes in Liquid Helium: Experimental Challenges and Solutions

Recent advances in high-temperature superconductors (HTS) have made them extremely attractive for low-temperature, high-magnetic-field-power applications such as in fusion technology, where the advantages over traditional low-temperature superconductors (LTS) allow for the design of fusion reactors operating in different and more convenient regimes. However, the performance enhancement exhibited by novel conductors poses several challenges for the measurement of their superconducting properties. The high critical currents coupled with the relatively low thermal stability of the conductors and their mechanical fragility render this task a challenge, as the angular anisotropies complicate the experimental setup. In this work, we describe the development of our novel high-current measurement facility, focusing on the solutions introduced regarding critical aspects such as the superconducting leads and the sample holder design. We show how simple but effectively designed solutions can be adopted to combat the complexity of the measurement. The results reported in this work guide the development of a measurement system able to withstand high critical currents (I > 1500 A) at high magnetic fields (µ0H > 12 T) by evaluating the angular response of 4 mm wide short samples (L ~ 7.5 cm) in a robust and reproducible manner.

Development and Evaluation of a Simple Shunt Module for High DC Current Measurement

This study aimed to develop and evaluate a shunt module for high direct currents (SMHC) to promote efficient use of DC power. Using offset and gain adjustments, the current-measurement error range improved from ±1.0% to ±0.04%, when measuring a 1000 A current. A real-time temperature correction (TC) function was used to improve the current measurement error from a maximum of 0.35% to less than ±0.04%, before and after the application of TC, respectively, for this current. The linearity evaluation showed the relative deviation to be less than ±0.06% for measured current in the range of 50 A to 1000 A. The measurement uncertainty of the SMHC was evaluated based on the guidelines to realize reliable current measurements. The relative uncertainty with confidence interval 95% (expanded relative uncertainty) for the measurement of 1000 A using the SMHC was estimated to be 0.20%.

TMR sensor current measurement technology for overhead lines

In order to meet the needs of TMR current sensors for overhead line high precision current measurement, a neighboring conductor interference magnetic field error elimination algorithm is proposed. Based on the Biot-Savard law, through the establishment of an interference magnetic field environment mathematical model, the accuracy of the error elimination algorithm is verified in maxwell simulation software. The simulation results show that under the working frequency current, the adjacent wire interference magnetic field elimination algorithm can reduce the error from 14% to less than 1%, and under the lightning wave environment, the error is reduced from 19% to less than 1%. This proves that the proposed algorithm is effective in reducing the measurement error caused by the interference magnetic field of the adjacent conductor.

Structural investigation of triangular defects in 4H-SiC epitaxial layers as nucleation source for bar shaped stacking faults (BSSFs)

The formation of recombination-induced bar shaped stacking faults (BSSFs) during forward voltage operation of SiC devices, can lead to increased voltage drop and enhanced device degradation. In this study, a triangular epitaxial defect is identified as a nucleation source for the growth of BSSF in forward-biased 4H-SiC p-n diode test structures. We performed low and high voltage current emission microscopy measurements in order to detect the position of BSSFs in the active area of the device and in-depth structural analysis to locate their nucleation source. It was found that basal plane dislocations that converted into threading screw dislocations, close to the surface of the epitaxial layer and included in the triangular defect, act as nucleation source for the BSSFs. Those BSSFs expand from the top towards the bottom of the epitaxial layer, which is a newly reported expansion mechanism compared to the already reported BSSFs growing from the substrate/epitaxial layer interface towards the epitaxial layer surface.

Current sensor based on diamond nitrogen-vacancy color center

High precision current measurement is very important for the calibration of various high-precision equipment and the measurement of other precision detection fields. A new current sensor based on diamond nitrogen-vacancy (NV) color center magnetic measurement method is proposed to realize the accurate measurement of current. This new current method can greatly improve the accuracy of current measurement. Experiments show that the linearity of the current sensor based on diamond NV color center can reach up to 33 ppm, which is superior to other current sensors and solves the problem of low linearity. When the range of input current is 5–40 A, the absolute error of the calculated current is less than 51 μA, and the relative error is 2.42 × 10−6 at 40 A. Combined with the research content and results of the experiment, the application of the current sensor in the field of current precision measurement is prospected.

Accurate Low Current Measurement Electronics With Self-Calibration Function for Ionization Chamber of Slow Extraction in HIAF

The new wide-range readout electronics with a self-calibration function are designed for ionization chambers (ICs) in the slow extraction of high-intensity heavy-ion accelerator facility (HIAF), booster ring (BRing). These electronics consist of a programmable trans-impedance amplifier (TIA), a self-calibration circuit, an 18-bit analog-to-digital converter (ADC), and a ZYNQ-7015 field-programmable gate array (FPGA). It is capable of monitoring weak current signals of 40 pA–4 mA with a sampling rate of 5 MHz. The ZYNQ-7015 FPGA manages the operation mode of the analog front-end (AFE) and the gain of the TIA. It also performs digital signal processing algorithms and data communication with the host computer. The self-calibration circuit uses a combination of a Schmitt trigger and voltage-to-current (V–I) converters to generate two square wave current signals with different peaks ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \mu \text{A}$ </tex-math></inline-formula> and 2 mA). During offline tests, the effective number of bits (ENOB) is 12.98 bits, and the nonlinearity is less than 0.075% for a full scale. Finally, the readout electronics are deployed for ICs’ slow extraction measurements at the extraction line of the cooling storage ring of the heavy-ion research facility in Lanzhou (HIRFL). With the help of a commercial dc-transformer in the cooling storage ring project of heavy ion research facility in Lanzhou (HIRFL-CSR), these electronics not only execute an accurate current measurement, but also can monitor the extraction efficiency reliably. In a word, these electronics play an important role in the fields of extremely weak and high dynamic current signal measurements.

PCB Rogowski Coils for Capacitors Current Measurement in System Stability Enhancement

In terms of high-current measurement of capacitors, PCB Rogowski coils have attracted much attention because of their small size and easy installation. However, they are vulnerable to electromagnetic interference. In order to improve the immunity of the coil, this paper studies the influence of the structure and parameter changes of the double-layer PCB coil on the measurement accuracy of mutual inductance. By testing the frequency response of four common coil structures, a differential winding coil structure is proposed. Based on the measurement of large capacitance current, the influence of non-electrical parameters of coils on the measurement accuracy of mutual inductance is experimentally verified.

Traceability Technology of DC Electric Energy Metering for On-Site Inspection of Chargers

The on-site inspection of high-power DC chargers results in new DC high-current measurement and DC energy traceability system requirements. This paper studies the traceability technology of electric energy value for automotive high-power DC chargers, including: (1) the traceability method of the built-in DC energy meter and shunt of the charger; (2) precision DC high current and small precision DC voltage output and measurement technology. This paper designs a 0.1 mA~600 A DC high current measurement system and proposes a 0.005 level DC power measurement traceability system. The uncertainty evaluation experiment of the DC power measurement calibration system and the high-power DC charger’s on-site calibration experiment results verify the method’s effectiveness and feasibility in this paper. The experimental results show that the combined standard uncertainty of the DC power metering verification system can be 0.0451%.

Contactless wide-range ferromagnetic high-current converters for monitoring and control systems in the electric power industry

The paper shows that the impossibility of breaking the current circuit for the production necessity of temporarily switching on electrical measuring instruments, large power losses on shunts, and the need to obtain quick information about the quality of the functioning of technological processes have led to the widespread use of non-contact conversion and measurement of high direct currents in circuits without breaking them. Light detachable wide-range stationary and portable non-contact transducers and meters of high direct currents are not yet mass-produced. In this regard, it is expedient to develop and study non-contact converters and meters of high direct currents, which are distinguished by a wide range of converted currents, small dimensions and weight, increased accuracy, and sensitivity of electric power facilities. The questions of sensitivity of magneto-modulation non-contact transducers are considered. The expression for the optimal static characteristic of the developed magneto-modulation non-contact transducer is determined and analyzed. Its maximum deviation from the calculated value does not exceed 6%. The expressions for the current, average sensitivity, and sensitivity regarding the magnitude of the excitation of a magneto-modulation non-contact transducer are obtained and investigated. In this case, the maximum sensitivity of the transducer reaches a value of 0.425 with an optimal excitation value of 1.65. It is recommended to take the allowable limit of the input value of the converter to be less than one. Its input value must be taken equal to 0.7. The developed magneto-modulation non-contact transducer has an increased sensitivity due to longitudinal modulation. It can be widely applied in control and management systems in melioration and irrigation, water supply, industry, metallurgy, railway transport, science, technology, GIS technology, and, in particular, digital coverage and database visualization, and as well as for checking electric meters at the place of their installation for non-contact control of direct, as well as alternating currents.

Bridging the gap between basic research and application: a half-cell setup for high current density measurements of Ir-based oxygen evolution reaction catalysts on porous transport electrodes

Innovative PTE setup enhances laboratory benchmarking of next-generation catalysts for the oxygen evolution reaction under technologically relevant conditions.

Sensorless Control and Inductances Estimation of IPMSMs Using FPGA and High Bandwidth Current Measurement

This paper presents a sensorless control method and a very fast on-line inductances identification of an IPMSM. The current slopes (derivatives) at one active-voltage vector and one zero-voltage vector are measured every PWM cycle to estimate the rotor speed and position with the aim of increasing the estimation accuracy and reducing total harmonic distortion. In addition to these current slopes, the DC bus voltage of the inverter is measured to estimate the machine inductances on-line. The proposed on-line parameter identification method can overcome the drawback of the existing off-line methods, such as: the requirement of a robust mechanical clamping system and test signal generators. The proposed on-line method also addresses the limit of the existing on-line methods, such as slow update and the possibility of incorrect convergence of the estimated parameters. Extensive experimental studies were conducted to verify the effectiveness and robustness of the proposed sensorless control and parameters identification of the IPMSM.

Benchmarking proton exchange membrane fuel cell cathode catalyst at high current density: A comparison between the rotating disk electrode, the gas diffusion electrode and differential cell

The intrinsic activity of oxygen reduction reaction (ORR) electrocatalysts for proton exchange membrane fuel cell (PEMFC) is usually evaluated with the rotating disk electrode (RDE), an easy-to-use technique requiring little amount of electrocatalyst. However, the liquid environment of the RDE implies strong limitation of O2 mass-transport and the intrinsic activity is only accessible on a narrow potential range (from 0.95 to 0.85 V vs. RHE) that is not relevant for the PEMFC operating conditions. This work compares results obtained with the RDE (0.2 cm2), the gas diffusion electrode (GDE, 0.07 cm2) and a small unit PEMFC (DC, 1.8 cm2). Three widely used ORR electrocatalysts are compared: Pt/Vulcan carbon, PtCo/Vulcan carbon and Pt/graphitized carbon, catalytic layers being prepared with a loading of 20 μgPt cm−2 and characterized at 25–30 °C and full hydration. The results show that all setups have their own advantages and drawbacks. Regardless the electrocatalyst nature, the GDE allows to assess the intrinsic activities on a large potential range (from 0.9 to 0.6 V), in agreement with the results obtained in RDE for high potential and with the DC for lower potential. The GDE is therefore promising, enabling easy high current density measurements with little amount of electrocatalyst.

Optical Inline-Sagnac Current Sensor, Part II: Performance and Applications

The performance and applications of the optical inline-Sagnac current sensor/transducer in utility high voltage alternating current measurements (metering and protection) and high voltage direct current measurements (control, metering, and protection) are presented. New measurements of commercially available sensors are presented for a 216 kA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">peak</sub> transient current, scale factor linearity for alternating currents from 5 mA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> to 32 kA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> and for direct currents from 100 mA to 27 kA, and temperature performance of ±0.11% over the temperature range of −60 °C to +65 °C. New properties of polarizer temperature-wavelength effects on the scale factor of the sensor are presented. Power quality measurements are discussed over the frequency range of 16.66 Hz to 5 kHz. A discussion of the limitations of optical noise on low current measurements is given. The experimental and calculated sensor response functions are compared. The limitations for low current measurements due to the IEC 61869 standard digital output are presented.

Calibration of a precision current measurement system for high AC voltages using an AC quantum voltmeter

This paper describes the calibration of a high precision AC current measurement device which is required in a system to measure AC voltages up to 800 kV in the frequency range of 10 Hz to 400 Hz. The AC current measurement unit of such a system requires the calibration of the input current in the milliampere range at a frequency of approximately 50 Hz, and all measurements have been made at a suitable frequency of 62.5 Hz. An AC quantum voltmeter (AC-QVM) is used to achieve a traceability chain from DC resistance calibration, when it works as DC quantum standard, and as AC quantum standard for the AC current measurement. All DC and AC measurements needed for one calibration point (one current level) can be done in a rapid sequence within 30 min using the same AC-QVM, such that the combined uncertainty is at a level of 1 μA A−1 (k = 1).

A non-contact broad bandwidth current sensor

Power metering, relay protection, lightning current measurement, fault current measurement, and traveling current measurement in the field of power systems, as well as high-current measurement in the field of pulse power, require safe, high-accuracy, large-range, and wide-frequency-band current sensors. Current transformers and Rogowski coils can basically meet the requirements of measurement accuracy and range, but they are not good enough to meet the two requirements of safety and broad frequency bands. In this study, a non-contact broad-band current sensor is designed, which is based on the improvement of the traditional Rogowski coil to realize non-contact measurement of current. The equivalent circuit of the sensor was established, and the output characteristics of the sensor were calculated from the theoretical level as well as the design parameters were optimized. The sensor samples were made, and the usability of the sensor and the correctness of the theoretical calculation model were verified by 50 Hz AC current and 1.6 μs/3.4 μs impulse current tests. The non-contact current sensor designed in this paper has the advantages of simple structure, low cost, safety and reliability, large range, and wide operating band, and can be widely used for AC current or impulse current measurement in power systems and pulsed power fields.

Research on the performance of a fiber optical current transformer for high voltage filtering capacitor unbalanced current measurement

Subject of study. A fiber-optic measurement scheme for the unbalanced current of a high-voltage filtering capacitor is proposed, where an all-fiber temperature sensor based on temperature birefringence is presented to realize the real-time correction of temperature errors. Method. Prototypes of an all-fiber filter unbalanced fiber optical current transformer type and a magneto-optical crystal type with a rated current of 1 A and a rated voltage of 258 kV have been developed and performance tested. Main results. After temperature correction, the accuracy of the all-fiber filter unbalanced fiber optical current transformer type in the range of −40∘C to 70°C meets the error limit requirements of class 0.2 specified in the Chinese Standard GB/T 20840.8-2007 (Instrument transformers—Part 8: Electronic current transformers standard), whose accuracy, integration, reliability, and anti-interference ability are better than the magneto-optical crystal type. The proposed scheme has the ability of small current (less than 20 mA) measurement in high voltage (more than 110 kV) scenarios.

Algorithm Research on the Conductor Eccentricity of a Circular Dot Matrix Hall High Current Sensor for ITER

To meet the high current measurement requirements of the international thermonuclear experimental reactor polar field (ITER PF) power supply, a noncontact dot matrix Hall high current sensor without a magnetic core is designed. Due to the existence of installation error, the measurement accuracy will be reduced due to conductor eccentricity in practical use. To solve this problem, this article will take the circular dot matrix Hall current sensor composed of eight Hall elements as an example and note the shortcomings of the two algorithms by analyzing the numerical integration algorithm and conductor positioning algorithm. Based on the two algorithms, a digital signal processing (DSP) conditioning algorithm is proposed. The DSP conditioning algorithm detects the output voltage of each Hall element after conductor offset and adjusts the output voltage of each Hall element by self-feedback, which simplifies the complexity of algorithm operation and eliminates conductor eccentricity error at the same time. Through simulation and field measurement verification, DSP self-feedback conditioning of the Hall element output voltage can eliminate the influence of conductor eccentricity error and improve the measurement accuracy of the sensor.

A New Technique for High Current Calibrations Using Low Voltage Reference Standards

In the electrical power industry, high current measurements have a fundamental importance. This necessitates the use of highly accurate, precise, and traceable techniques to calibrate measuring instruments in order to preserve the output quality. High current measuring techniques are being developed continuously to improve measurement accuracy and reduce uncertainty [1]. [2]. It is crucial to develop traceable strategies for calibrating high current sourcing instruments such that high current measurements can be traced to SI units, hence ensuring that the specifications and calibration procedures are in agreement with quality standards [3]. Calibrators combined with current coils are commonly used in high current measurements in industrial applications and laboratory measurements. Measuring high currents involves current clamps in both laboratory and industrial measurements as they provide safety due to their high insulation level [4], [5]. Clamp meters and clamp transducers that are based on Hall-effect current sensor are capable of measuring dc and ac currents [6]. Hall-effect sensors sense the magnetic field due to the flow of current, in terms of low voltage corresponding to the high current induced in the current coil [7]. Thus, the low voltage detected will facilitate the traceability of high current measurements to the SI units.

Design &amp; Implementation of High Dynamic Range Current Measurement System for IoT Applications

Internet-of-Things (IoT) devices have a strict necessity for power consumption to achieve the expected battery life. Therefore, measuring and optimizing the energy consumption of IoT nodes are essential. IoT nodes feature extreme current consumption range over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {100}}~\text {dB}$ </tex-math></inline-formula> between their operating modes. The main focus of this article is to design and implement a low-power and low-cost current measurement circuit, which can be integrated into IoT nodes. A new pass element is introduced for measuring the current consumption. This element is placed in the current path to measure current over a high dynamic range with a constant voltage drop. The introduced pass element consists of a capacitor and analog switches. The current consumption is measured based on the charge and discharge times of the capacitor in the specified period of time. The voltage across the pass element is buffered and fed to a low-power microcontroller. The proper operation of the proposed circuit is verified numerically with simulations and experimental measurements. The implemented current measurement circuit offers a load regulation of 0.23%, a dynamic range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {173.98}}~\text {dB}$ </tex-math></inline-formula> , and a linearity error of 0.522%. It is expected that the proposed system provides clear information on the power behavior of IoT devices, which can be used for power optimization of IoT networks and self-power test equipment.

Rapid determination of lithium-ion battery degradation: High C-rate LAM and calculated limiting LLI

Herein, incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries, which inevitably exhibit capacity fading caused by multiple mechanisms during charge/discharge cycling. Because battery degradation modes are complex, the simple output of capacity fading does not yield any useful data in that respect. Although IC and DV curves obtained under restricted conditions (<0.1C, 25 °C) were applied in non-invasive analysis for accurate observation of degradation symptoms, a facile, rapid diagnostic approach without intricate, complex calculations is critical in on-board applications. Herein, LiNi0.5Mn0.3Co0.2O2 (NMC532)/graphite pouch cells were cycled at 4 and 6C and the degradation characteristics, i.e., loss of active materials (LAM) and loss of lithium inventory (LLI), were parameterized using the IC-DV curves. During the incremental current cycling, the initial steep LAM and LLI slopes underwent gradual transitions to gentle states and revealed the gap between low- and high-current measurements. A quantitative comparison of LAM at high and low C-rate showed that a ICHC revealed the relative amount of available reaction region limited by cell polarization. However, this did not provide a direct relationship for estimating the LAM at a low C-rate. Conversely, the limiting LLI, which is calculated at a C-rate approaching 0, was obtained by extrapolating the LLI through more than two points measured at high C-rate, and therefore, the LLI at 0.1C was accurately determined using rapid cycling.