Hz AC Research Articles

AC losses in macroscopic thin-walled superconducting cylinders

Measurements of the ac response represent a valuable method for probing the properties of superconductors. In the surface superconducting state (SSS), a current exceeding the surface critical current I c leads to breakdown of SSS and penetration of external magnetic field into the sample bulk. An interesting free-of-bulk system in SSS is offered by thin-walled cylinders. According to the full penetration of magnetic flux (FPMF) model, each time the instant value of an ac field is equal to a certain critical value, the ac susceptibility χ will exhibit jumps as a function of the ac field amplitude H ac because of the periodic destruction and restoration of SSS in the cylinder wall. Here we study the low-frequency (128–8192 Hz) ac response of thin-walled niobium cylinders under superimposed dc and ac magnetic fields applied parallel to the cylinder axis. In contrast to the FPMF model predictions, experiments reveal a smooth χ(H ac) dependence. To explain the experimental observations, we propose a phenomenological partial penetration magnetic flux (PPMF) model, which assumes that after restoration of the superconducting state, the magnetic fields inside and outside the cylinder are unequal and the magnitude of the penetrating flux is random for every penetration. This model fits very well the experimental data on the temperature dependence of the first harmonic χ 1 for any dc field and ac amplitude.

Quantifying Electric Charge on Cap-Pin Glass Insulator: Investigating the Impact of Pollution through Simulation and Experimental Approaches

The objective of this paper is to investigate the behavior of electric charges on cap-pin glass insulator under 50 Hz AC voltage. The study is conducted using COMSOL Multiphysics to understand the charge location, polarity, and parameters affecting their behavior. A 2D axisymmetric insulator design is used to visualize the overall charges on the insulating system (space charge) and along the insulating surface (surface charge density) under uniform and non-uniform pollution conditions. The research shows that the total charge accumulates over the surface area of the glass material. To quantify the amount of this charge, a simulation method based on using the surface integral of the electric displacement field over this area is introduced, which is supported by experimental tests. Comparing both simulation and experimental results provides insights into the simulation reliability and the parameters affinity used to those of the real model. Moreover, the simulation helps to identify the critical area where a high amount of charges is accumulated. The findings of this study are presented and examined.

Recent advances in single-phase rectification methods

With the increasing number of population, people are increasingly dependent on electricity. In recent years, more and more public transportations like bus, taxi take the mode of pure electric. The function of rectifier is to transform the AC current into DC current, which is a significant research direction in electrical industry, especially in power electronic technology. In our nation, the national grid supplies 220V 50Hz AC to residence, it is a voltage pattern that varies periodically. Due to the lower loss of power during long-distance transmission, it has become the basic mode of power transmission and supply in the world. In usual production and our daily life, we frequently need DC (such as: mobile phones, flashlights, computers, charging piles for electric vehicles, etc.), so rectifier has become a heated research part. At present, more and more researches are based on power electronic technology, design all kinds of rectifier circuit by using the between conductor and insulator property of semiconductors. This essay provides an overview of single-phase rectifier circuits (including half-wave rectifier, full-wave rectifier, and bridge rectifier) and passive power factor correction.

A Fault Diagnosis Method for Rectifier-Filter Circuit Integrating EEMD Algorithm and Transformer Network

Rectifier-filter circuit, as a critical component of the drive circuit in instrumentation and control systems of nuclear power plants, can convert the 50 Hz AC into the smooth DC. Thus, it plays a vital role in the power control of reactors. However, the weak waveform anomalies of soft faults in the rectifier-filter circuit make fault feature extraction difficult. Therefore, in this article, an ensemble empirical modal decomposition (EEMD) algorithm is employed to decompose the signal mode components in the monitor data of the rectifier-filter circuit. The weak waveform anomalies are indirectly enhanced by the IMF and residual components. Subsequently, the Transformer network is utilized to construct the feature extractor. With the advantage of multi-head attention (MHA) mechanism in the Transformer network, the multi-directional, multi-scale, and highly sensitive long-range time-dependent features in the EEMD feature data are extracted. Then, a deep Softmax classifier is adopted to reduce the dimensionality and diagnose the soft faults of the rectifier-filter circuit. Finally, a fault simulation model of the rectifier-filter circuit is constructed and the condition monitor data are collected. The effectiveness and diagnosis accuracy of the proposed method are verified by a real case experiment and some comparative methods.

Measurement and Evaluation of Voltage Unbalance in 2 × 25 kV 50 Hz High-Speed Trains Using Variable Integration Period

This article addresses the need for a standardized method to measure power quality in railroad systems, which differ from distribution and transmission networks. It evaluates the applicability of existing standards in detecting variations and short-term disturbances in railroad networks powered by the 50/60 Hz AC grid or the 2 × 25 kV AC network used for high-speed trains. The objective is to propose a standardized algorithm capable of accurately identifying disturbances to assess power quality on railway traction substations. A new method is proposed to characterize voltage imbalances more precisely. Practical demonstrations confirm that a short integration period, as used in existing standards, provides a more accurate estimation of disturbance amplitude and duration. Field experiments validate the proposed solution, embedded in equipment installed on the 225 kV line supplying the 2 × 25 kV AC substation for high-speed rail. Comparative analysis of results obtained during high-speed train journeys confirms the algorithm’s potential to aid standards committees in reviewing and updating existing standards, as well as expediting the creation, approval, and implementation of new standards for railway installations. Experimental comparisons of other power quality parameters, such as frequency and voltage harmonics, also underscore the algorithm’s utility in railway power quality assessment.

Automatic Star Delta Starter with an Arduino and Relays for Three Phase Induction Motor

Abstract: The most popular low voltage starters for 50 Hz industrial motors are either star or delta starters. Their purpose is to minimize the starting current that is supplied to the motor at the beginning of operation. Three contactors, a timer, and a thermal overload are typically used in the manufacturing of Star/Delta starters, which are used to run three-phase motors at 440 volts and 50 Hz AC mains supply. But in our project, we've used the same to run a\ 3-phase motor at 440-volt AC mains supply 50 Hz with a series of 12-volt DC relays, an Arduino-provided electronically adjustable timer, and a series of tiny circuit breakers. While maintaining its application for a 3-phase motor starting with a single phasing prevention, the interlocking arrangement of the relay coils and the electronic Arduino is all wired in low voltage DC of 12 Volt fed from an inbuilt DC power supply for safe handling of the starter during the study. The timer consists of an Arduino, whose output is sent to a relay to switch the mains supply from a three-phase star to a delta. Since the 3-phase motors could burn if one of the phases disappears while they are operating, the project additionally includes single-phase protection. In the case of a phase failure, the lamps' output will be switched off. In addition, the project can be improved by utilizing thyristors in a firing angle control principle to soft start the induction motor, which would eliminate all of the star delta starter's shortcomings.

Airport Microgrid and Its Incorporated Operations

This paper presents the development of an airport bipolar DC microgrid and its interconnected operations with the utility grid, electric vehicle (EV), and more electric aircraft (MEA). The microgrid DC-bus voltage is established by the main sources, photovoltaic (PV) and fuel cell (FC), via unidirectional three-level (3L) boost converters. The proposed one-cycle control (OCC)-based current control scheme and quantitative and robust voltage control scheme are proposed to yield satisfactory responses. Moreover, the PV maximum power point tracking (MPPT) with FC energy-supporting approach is developed to have improved renewable energy extraction characteristics. The equipped hybrid energy storage system (HESS) consists of an energy-type battery and a power-type flywheel; each device is interfaced to the common DC bus via its own 3L bidirectional interface converter. The energy-coordinated operation is achieved by the proposed droop control. A dump load leg is added to avoid overvoltage due to an energy surplus. The grid-connected energy complementary operation is conducted using a neutral point clamped (NPC) 3L three-phase inverter. In addition to the energy support from grid-to-microgrid (G2M), the reverse mcrogrid-to-grid (M2G) operation is also conductible. Moreover, microgrid-to-vehicle (M2V) and vehicle-to-microgrid (V2M) bidirectional operations can also be applicable. The droop control is also applied to perform these interconnected operations. For the grounded aircraft, bidirectional microgrid-to-aircraft (M2A)/aircraft-to-microgrid (A2M) operations can be performed. The aircraft ground power unit (GPU) function can be preserved by the developed microgrid. The MEA on-board facilities can be powered by the microgrid, including the 115 V/400 Hz AC bus, the 270 V DC bus, the switched-reluctance motor (SRM) drive, etc.

A comparative analysis of power pulsating buffer architectures for mitigating high‐frequency and low‐frequency ripple in PV microinverter applications

AbstractThis study provides a comparative analysis of feasible architectures of Power Pulsating Buffer (PPB) as an actively controlled energy storage solution alternative to the electrolytic capacitors in a single‐stage isolated, single‐phase 120 V AC 60Hz grid‐connected photovoltaic (PV) microinverter for a 400 W rated system with 20–40 V input range. The comparison encompasses key factors including energy density, volume reduction, efficiency, frequency operation, and system stability. The findings shed light on the primary advantages and disadvantages of the buck‐ and boost‐derived PPB under study. The results indicate that the boost PPB exhibits enhanced stability, a more compact design, and higher power efficiency compared to the buck PPB. However, for low switching frequency operations, the buck PPB proves to be more effective in mitigating DC port voltage ripple and ensuring controller over microinverter load variation.

The discharge characteristics and benzene degradation performance of a three-electrode DBD reactor powered by dual AC power generators

A three-electrode hybrid volume/surface dielectric barrier discharge (V-SDBD) configuration with two plane electrodes and six grounded strips electrode was designed for enhancing the generation of discharge plasma to degrade gaseous benzene. Two plane electrodes were separately powered by a 5 kHz AC generator and a 50 Hz AC generator, respectively. Compared with the typical two-electrode volume DBD (VDBD) reactor excited by 50 Hz AC generator, the hybrid V-SDBD reactor has lower onset discharge voltage and better discharge homogeneity, and the benzene degradation efficiency of V-SDBD was 1.12 times higher than that of VDBD at a similar energy efficiency. Moreover, an increase in the voltage on HVE-II promoted benzene degradation, but decreased the energy efficiency of benzene degradation.

MOSFET-based HTS flux pump

We have developed a high-temperature superconducting (HTS) flux pump using high-power metal-oxide-semiconductor field-effect transistors (MOSFETs) for switching. For its primary coil, two commercial transformers are utilized, each consisting of two copper coils wound on a single iron core, which enables changing the load current over primary current ratio (101 or 194) between the primary and secondary coils. Full-wave rectification is achieved with two half-wave secondary circuits, each of them having six HTS one-turn coils to lower the resistance. Each secondary coil is composed out of nickel-reinforced BSCCO tapes, where 12 MOSFETs have been soldered in parallel straight to the tapes and controlled with analog electronics. Secondary coils are clamped to custom-made copper-stabilized HTS current leads. A support structure for keeping the HTS coils in place was 3D-printed using cryogenic-compatible composite material PETG-CF20. Resistances of the two secondary circuits were measured to be 4 and 7 at 77 K with a total critical current of 980 A. We successfully ramped up a 50 µH Conductor on Round Core solenoid at 77 K using our HTS flux pump with 50 Hz AC voltage source. We achieved a maximal load current of 900 A and exceeded the 715 A critical current of the solenoid. During the thermal runaway of the magnet, the increased load voltage limits the maximum load current supplied by the flux pump.

Effect of Working Gas and Applied Voltage on the Estimation of Power and Electron Density in Gliding Arc Discharge (GAD) System

Abstract: Atmospheric pressure gliding arc plasma is generated by a 50 Hz (0-13 kV) AC power supply. The electrical properties of the produced plasma are investigated with the help of an oscilloscope. In this work, the relationship between applied voltage, breakdown voltage, and discharge current is studied for air, argon, oxygen, and nitrogen gases. Similarly, the effect of the nature of gases on breakdown voltage and discharge current is studied. The power consumed by the discharge for different gases is obtained by current-voltage characteristics. It is found that among air, nitrogen, argon, and oxygen, argon consumes minimum and nitrogen consumes maximum power. Specifically, at the maximum applied voltage of 10.2 kV, oxygen and nitrogen consume approximately 56-57% more power than argon. Electron density, one of the most essential plasma parameters, is evaluated and compared using an electrical approach for several fading gases. The electron density is found to be increasing with the increase in applied voltage, and the value of electron density is found to be larger in argon discharge. Keywords: Gliding arc discharge, I–V characteristics, Power consumption, Discharge voltage, Electron density.

Use of partial discharges measurements and video recordings to investigate the influence of relative humidity on zinc oxide subjected to high electric fields

This study investigates the influence of humidity on the high voltage behaviour of zinc oxide porous pellets at room temperature, using the phase resolved partial discharge (PRPD) method. The experimental configuration corresponds to the one that would be used for flash sintering cylindrical ZnO pellets at low temperatures in possibly scalable conditions: planar Pt electrodes without Pt paste. The study explores the incubation period by increasing the 50 Hz AC electric field up to 8 kV cm−1 (applied by steps or with a continuous ramp) in an air atmosphere with varying relative humidity (RH). Experiments were repeated on several samples and showed that the maximum amplitude of PDs decreased while their number increased as the RH increased. With the support of video recording of the experiments, different characteristics in the PD pattern evolution with increasing AC voltage could be attributed to various locations between the electrodes, at the sample surface, or at the interface with the electrodes. By examining the PRPDs, it was possible to identify two distinct types of PDs having different thresholds of inception: one type corresponds to PDs occurring mostly at the triple junction ‘ZnO-platinum-air’ or in the ZnO-electrodes gap and depends strongly on the RH level and; the other type corresponds to electric arcs between the electrodes, with an inception threshold much less affected by the RH level.

Epoxy-based high-k composite vitrimer: With low dielectric loss, high breakdown strength and surface electrical damage repairability

High dielectric constant/permittivity (high-k) polymer-matrix composites (PMCs) are widely used in the electronics and electrical industries since their high energy density, ease of processing and light weight. However, the high dielectric permittivity (εr) usually leads to a significant increase in dielectric loss (tanδ) and an obvious decrease in breakdown strength (Eb), which is still a major problem that restricts the development of high-k PMCs. In addition, to extend the service life, the next generation electrical/electronic components also demand materials have electrical damage repairability. In this study, a new epoxy-based high-k composite vitrimer was constructed. The dynamic disulfide bonds were introduced into the cross-linked network to provide the high-k composite vitrimer with excellent repairability, while the nanoparticle (NPs) fillers surfaces were modified by grafting disulfides to improve the dynamic rearrangement ability of the composite network and enhance the electrical properties of the high-k composite vitrimer. The results show that this high-k composite vitrimer has low tanδ and high Eb, which is about 0.025 (at 0.1 Hz and room temperature) and 26.0 kV/mm (under 50 Hz AC voltage of 1 mm samples), respectively. Moreover, it has excellent mechanical damages and electrical damages repairability. For mechanical damages, it can repair mechanical scratches by heating at 180 °C for 10 min. For surface electrical damages, it can also eliminate the residual carbons, regain the surface organic structure, and restore more than 94% insulation strength by thoil treatment under 80 °C for 60 min. This study provides a new reference method for the preparation of low tanδ, high Eb and repairable high-k PMCs.

Dual Outputs Switch Mode Power Supply (DOSMPS) Utilizing Forward Converter Topology

Experimental works of dual, 5 volt DC outputs switch mode power supply (DOSMPS) is presented in this paper. To design, construct and evaluate the DOSMPS using forward converter topology are the objectives of this article. In this work, a 556 timer was picked as the pulse width modulator. The 556 timer was picked because it is widely used, cheap and capable of producing stable dual pulse width modulations. Since, this work targeted dual DC outputs, two forward converter circuits were built. However, switching frequencies at two transistors were controlled by only one 556 timer. The complete circuit of the DOSMPS consist of full bridge rectifier, smoothing capacitor, two high frequency transformers and two forward converter circuits. At the first stage of this work, the DOSMPS circuit was designed using Proteus software. Later, the complete DOSMPS circuit was constructed on two breadbroads after all of the electronic components and devices were available. Important parameters such as the input and output voltages and duty cycles were measured using digital oscilloscope and multimeter. Results from these measurements have shown that the designed circuit can convert single-phase 24 Vrms 50 Hz AC voltage input into dual and stable 5±0.1 V DC outputs. Also from this work, it was observed that, pulsed DC voltages with peak value of 2 V and frequency less than 20 kHz are sufficient in controlling the switching frequencies of both BJT transistors. This allows the regulation of the output voltage within the desired range. Analysis carried out after the measurements has shown close correlation between the theoretical and experimental results, where the calculated and measured switching frequencies had only deviated by 1.1%.

Five-level cascaded H-bridge inverter for renewable energy applications

This paper presents a five-level inverter based on the phase-disposition pulse width modulation (PD-PWM) technique for renewable energy applications. The conventional cascaded H-bridge (CHB) five-level inverter structure is reproduced, and an LC filter is designed to get optimum results from the inverter output. Two batteries are used as renewable energy sources to investigate the performance of the designed inverter. The system can provide 220 volts and 50 Hz AC supply with a 6.9 kW power supply to the load/grid. The designed output is compared with filter and without filter circuit. It provides sinusoidal voltage and current output with a very low total harmonic distortion (THD) of 2.75% which is compliant with IEEE 519 standards. MATLAB/Simulink software tool is used for the entire design. The inverter’s output is graphically represented, and discussed various parameters like switching frequency, THD, modulation index, and rated voltage.

СРАВНИТЕЛЬНАЯ ОЦЕНКА МЕТОДОВ УСРЕДНЕНИЙ ДЛЯ ФИЛЬТРАЦИИ ИЗМЕРИТЕЛЬНЫХ СИГНАЛОВ

To improve the quality of manufactured products, it is necessary to improve all technologicalprocesses, which requires increasing the accuracy of the entire measuring path as a whole.For this it is necessary to carefully analyze systematic, random and fluctuating errors in the measurementchannel and take all measures to reduce them. Digital filtering or averaging of intermediatemeasurements (observations) according to certain rules is a radical means of improving theaccuracy of measurements performed. The aim of this work is to compare the quality of suppressionof near-real noise interference using the eight most well-known averaging methods. A model of the measurement path and a general block diagram for modeling the measurement process on acomputer under the influence of random interference are proposed for eight averaging algorithms.As a criterion for evaluating the quality of averaging methods, the ratios of absolute error variancesand mean square deviations before the computing device and after applying the specified averagingalgorithm are taken. Based on the simulation results, the following conclusions are made. 1. All averagingalgorithms provide suppression of random error components of complex interference to thelevel of 40–60 dB. Three algorithms are the best: arithmetic mean AR, a-truncated mean AU5 and atenderizedmean AB5, which provide for the suppression of 5 % of anomalous results. With an increasein the number of observations, the suppression coefficients increase proportionally. 2. Thesampling time must be a multiple of the duration of the 50 Hz AC mains period (20 ms). The optimalnumber of observations (measurements) is 100–128; with 128 measurements, the division operationis reduced to a simple shift, and the averaging result can be obtained in 1–2 μs. 3. When experimentallyapplying the AR averaging method for filtering a highly noisy measurement signal in a communicationline with a length of 800 m, a decrease in the spread of ADC output codes was observedfrom ± 3.5 % to ± 0.1 % after filtering (AR, 64 measurements in 40 ms).

Electrical Properties of Silicone Gel for WBG-Based Power Module Packaging at High Temperatures

Trends toward high power density designs and emerging wide bandgap (WBG)-based semiconductors will lead to a severe temperature rise in power electronic modules. In this regard, the insulation performance of silicone gel used for power module packaging deteriorates at high temperatures and frequencies is a concern and has not been well studied. This study focuses on the electrical properties of silicone gel at high temperatures, including its dielectric properties, volume resistivity, and breakdown strength. A Cole-Cole model was used to describe the dielectric response process. In particular, the dielectric loss density under PWM voltage was calculated, and the temperature rise of the encapsulation structure caused by the dielectric loss was observed. It was found that the high-frequency dielectric constant at 200°C decreases by 24% compared to room temperature; when the temperature is raised to 180°C, the volume resistivity drops by three orders of magnitude, and the 50 Hz AC and 10 kHz unipolar square wave breakdown strength of silicone gel is reduced by 50% and 42% compared with those at room temperature. The dielectric loss under PWM voltage increases by four orders of magnitude as the temperature increases up to 200°C but does not lead to a significant temperature rise in the encapsulation structure.

Ultrafast flexible PEDOT:PSS supercapacitor with outstanding volumetric capacitance for AC line filtering

Flexible supercapacitors are among the most important power supply devices for fulfilling the energy/power demands of future flexible and wearable electronics. While significant achievements have been made in improving the energy density of the flexible supercapacitors, ultrafast flexible supercapacitors remain in their infancy. Herein, an ultrafast flexible supercapacitor with outstanding capacitance is demonstrated based on the facile, one-step electropolymerization of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). In comparison to the state-of-the-art all-solid-state ultrafast flexible supercapacitors, the as-fabricated flexible PEDOT:PSS-based supercapacitor provides the highest volumetric capacitance of 38 F cm−3 in the high-frequency regime (e.g., 120 Hz) while maintaining a sufficient ultrafast response speed for 60-Hz AC line filtering applications. In addition, the electropolymerized PEDOT:PSS flexible supercapacitor provides excellent mechanical flexibility, with bending radii of 4.0–0.6 mm, and durability, with an ∼ 94% capacitance retention after 1,000 bending cycles. The high processability and outstanding electrochemical/mechanical performance are expected to contribute greatly towards the further development of high-performance ultrafast flexible supercapacitors.

A Crystal-Less Embedded Cardiorespiratory Radar System With Duty-Cycled and Pulse-Based Detection for Vital Signs

A duty-cycled and pulse-based embedded radar system without a quartz crystal unit is presented for cardiorespiratory monitoring. A reference clock source with features of high accuracy and temperature independence is directly gained from ac electric power grids. The 50/60 Hz power-line interference is further utilized and converted to a reliable clock source as a substitute for the conventional crystal that can be fed into the radar system. The theoretical analysis of the clock source conversion circuit and the experimental instantaneous frequency deviation from the wall outlet will be described to investigate frequency stability and uncertainty based on statistical evidence and significance. In addition, a pulse control unit (PCU) with a duty-cycle mechanism is implemented to convert the initial clock into a duplet-pulse sequence with a tunable phase delay for simultaneously performing the probing and demodulated pulses. A fully customized embedded radar system driven from a 60 Hz ac source is proposed for real-time physiological detection.

Ultrafast PEDOT:PSS/H2 SO4 Electrical Double Layer Capacitors: Comparison with Polyaniline Pseudocapacitors.

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is one of the most widely studied conductive polymers, owing to its excellent electrical, optical, and mechanical properties, with various applications such as organic electrochemical transistors, electrochromics, and flexible/stretchable supercapacitors. The charging mechanism of PEDOT:PSS supercapacitors has been traditionally believed to be faradaic, which involves the transfer of charge across the electrode/electrolyte interface. In the present work, however, robust experimental evidence suggests that the PEDOT:PSS supercapacitors mainly store and deliver charge nonfaradaically. The various electrochemical properties of PEDOT:PSS electrical double layer capacitors (EDLCs) are clearly distinguishable from those of polyaniline (PANI) pseudocapacitors, which store charge faradaically. Owing to the nonfaradaic mechanism, the frequency response of PEDOT:PSS supercapacitors is comparable to that of state-of-the-art ultrafast EDLCs with carbon-based electrodes, making them suitable for high-frequency applications such as 60 Hz AC line filtering. This result is of great importance for the fundamental understanding of the charging mechanism of mixed ionic-electronic conducting polymers, such as PEDOT:PSS, and is expected to contribute to the development of various electrochemical devices based on this type of material.