Supply Frequency Research Articles

Use of Sphingomonas yunannensis to Improve Soil Drought Stress in Chili Plants

The availability of water plays an important role in plant growth. However, water availability depends on the climate and irrigation channels; therefore, there is little water available for plants during the dry season. Bacteria found in soil can produce exopolysaccharides to survive under extreme land conditions, namely, during drought conditions. The research objectives were to (1) isolate and select bacteria originating from dry land for use on chili plants and (2) determine the effect of water supply frequency and select soil bacteria on chili plants. The experiment consisted of two stages. (1) Bacterial selection and characteristics, which included exopolysaccharide bacteria selection on specific ATCC No. media. 14; pathogenicity test (hypersensitivity and hemolysis); characterization and biochemical testing including pH, temperature, salinity, oxidation, and catalase; bacterial functional tests (P and K solvents and nitrogen-fixing); and (2) tests of chili plants in the greenhouse. The treatment consisted of two factors: (a) application of selected bacteria, (b) frequency of water application (every 1, 2, 3, and 5 days), and (3) molecular identification of selected bacteria. The results showed that the best growth of chili plants was obtained by treating them with bacteria and watering them every other day. Molecular identification demonstrated that the selected bacteria was Sphingomonas yunannensis, which can grow under environmental conditions affected by drought. Keywords: exopolysaccharides, drought, Sphingomonas yunannensis, chili plants

Analysis of the Selected Design Changes in a Wheel Hub Motor Electromagnetic Circuit on Motor Operating Parameters While Car Driving

The drive system of an electric car must meet road requirements related to overcoming obstacles and driving dynamics depending on the class and purpose of the vehicle. The driving dynamics of modern cars as well as size and weight limitations mean that wheel hub motors operate with relatively high current density and high power supply frequency, which may generate significant power losses in the windings and permanent magnets and increase their operating temperature. Designers of this type of motor often face the need to minimize the motor’s weight, as it constitutes the unsprung mass of the vehicle. Another limitation for motor designers is the motor dimensions, which are limited by the dimensions of the rim, the arrangement of suspension elements and the braking system. The article presents two directions in the design of wheel hub motors. The first one involves minimizing the length of the stator magnetic core, which allows for shortening of the axial dimension and mass of the motor but involves increasing the thermal load and the need for deeper de-excitation. The second one involves increasing the number of pairs of magnetic poles, which reduces the mass, increases the internal diameter of the motor and shortens the construction of the fronts, but is associated with an increase in the motor operating frequency and increased power losses. Additionally, increasing the number of pairs of magnetic poles is often associated with reducing the number of slots per pole and the phase for technological reasons, which in turn leads to a greater share of spatial harmonics of the magnetomotive force in the air gap and may lead to the generation of higher power losses and higher operating temperatures of permanent magnets. The analysis is based on a simulation of the motor operation, modeled on the basis of laboratory tests of the prototype, while the car is driving in various driving cycles.

Improved Techniques for Analyzing Broken Rotor Bars at Different Supply Frequencies in Inverter-Fed Induction Machines

Improved Techniques for Analyzing Broken Rotor Bars at Different Supply Frequencies in Inverter-Fed Induction Machines

Effect of minimum quantity lubrication on energy consumption in multi-axis milling of LY12 aluminum alloy

Abstract The impact of milling parameters on energy consumption was investigated during blade machining by a four-axis milling machine under different conditions. LY12 aluminum alloy was used as a workpiece, and the single-factor experiments of different milling parameters (milling speed, feed rate, milling depth, and milling width) under minimum quantity lubrication (MQL) were carried out in the four-axis vertical machining center, as well as a comparison experiment with dry milling. The milling power was recorded by the three-phase electrical parameter tester, and the specific power was calculated. The overall milling power shows an upward trend with the increase of each milling parameter, while the specific power shows a downward trend under MQL and dry milling. MQL can effectively reduce milling energy consumption. The milling power and specific power decrease with the increase of oil-air flow rate and oil feeding frequency. When the oil supply frequency is 20 cy/min and the oil-air flow rate is 400 ml/min, the lubrication effect is relatively good.

Influence of Connecting Cables on Stator Winding Overvoltage Distribution under High-Frequency Pulse Width Modulation

In the variable frequency motor drive system, because the cable impedance does not match the motor impedance, the reflection wave of the voltage wave will be generated. The superposition of reflected voltage waves can lead to overvoltage at the motor ends, which can damage the insulation structure. In this paper, the equivalent circuit models of cable and stator winding are established, respectively. The overvoltage distribution under different power supply frequencies and cable lengths is simulated and analyzed. The influence mechanism of power supply frequency and cable length on the overvoltage distribution of stator winding are studied. The simulation results show that the overvoltage of the first pulse falling edge will be superimposed on the overvoltage of the second pulse rising edge under high-frequency conditions, resulting in a further increase in the overvoltage. The voltage appears in all coils after the middle of the winding. The ground voltage is up to 1.32 times the input voltage, and the inter-turn voltage is up to 9.2 times the average voltage. The increase in cable length will lead to an increase in ground voltage, but the increase in speed will slow down after exceeding the critical length of 300 m. The maximum ground voltage can reach 1.93 times of the input voltage, which is 3.6% different from the calculation result under ideal conditions. The inter-turn voltage changes with the cable length in an N-shaped manner, up to 185 V. The results of this paper are of great significance to further study the insulation design of generator end input.

Simulation of pulse width modulation strategies: validation based on sound quality evaluations

Though the noise emitted by an electrical machine is less loud than the one from a combustion engine, the existing literature shows it is not always more pleasant. This is because of its strong tonal content, due to deterministic excitations (e.g. electromagnetic slotting and switching effects, mechanical gear mesh effects). The main source of magnetic noise is the radiation of the stator submitted to electromagnetic forces, which are harmonic by nature. Their highest frequency components are generated by the Pulse Width Modulation (PWM) technique designed to vary the supply frequency and operating speed of the electric machine. Several PWM strategies exist, leading to specific harmonic spectra. A temporal simulation model has been developed to auralize the corresponding electromagnetic noise emitted by the machine, considering its mechanical and electrical parameters. A testbench has been adapted to test the relevance of the model, both from an electrical and acoustic point of view. The simulation model and the testbench can be used to generate virtual and real sound stimuli to be assessed in a jury testing. The subjective evaluations allow to assess the relevance of the auralization model, but also to identify the least annoying strategies.

Highly energy-efficient degradation of simulated dye wastewater by array type underwater bubble discharge plasma: Key factors identification and degradation pathways

The extensive use of dyes presents a significant safety concern for the reuse of water resources, highlighting the critical need for a rapid and efficient degradation method for dye mixtures in wastewater. This study introduces a degradation system based on an array type underwater bubble discharge plasma specifically designed to treat a dye mixture wastewater containing methylene blue (MB) and methyl violet 2B (MV2B). Analysis of the optical and electrical characteristics reveals that the device experiences minimal temperature increase, with the highest intensity of the band associated with N2 in the emission spectra, and discharges occurring predominantly during the rising and falling edges of a pulse cycle. Experimental results demonstrate that the most effective degradation efficiencies (MB = 94.83%, MV2B = 93.48%) are achieved at an initial dye concentration of 50 mg/L, a power supply frequency of 6 kHz, an air flow rate of 2.5 SLM and an initial electrical conductivity of 50 μS/cm. The degradation of dyes is primarily attributed to the demethylation process of O3(aq) and other species. Toxicity analysis indicates that the plasma degradation process significantly reduces the toxicity of the intermediate products of dyes. This study not only presents a novel approach for treating high concentration mixed dye wastewater, but also provides valuable insights for future research in this area.

Research on Frequency Control Technology in Electrical Automation Control

With the continuous improvement of production efficiency, quality and flexibility, electrical automation control technology plays an increasingly important role in industrial production. As the core technology of electrical automation control, frequency conversion speed regulation is of great significance to improve production efficiency, reduce production costs, ensure stable operation of equipment and reduce energy consumption of electrical automation control system. Frequency conversion speed regulation refers to the frequency and voltage adjustment of motor power supply, so as to achieve accurate control of motor speed. The economy of this technology is mainly manifested in its ability to effectively reduce production costs, while its versatility is mainly manifested in its high degree of functional modularity and wide adaptability. Simply put, frequency conversion speed control technology is essential in the electrical automation control system. It reflects the scientific and technological progress of the enterprise, and also plays a decisive role in the enhancement of enterprise benefits. This paper provides a more comprehensive discussion on the application of frequency conversion speed control technology in electrical automation control for relevant personnel.

Detecting and Locating Corona Discharges in Low-Pressure Aircraft Environments Using Optical Sensors

Today, there is a clear trend toward electrification of transportation systems, including aircraft. Due to the enormous power requirements, they must operate at high voltages. However, the combined effect of higher voltage levels and low pressure environments is conducive to the occurrence of electrical discharges in electrical systems. Therefore, there is an urgent need to develop cost-effective systems to detect the discharges in the early stages before major failures can occur. This paper compares two optical sensors for early discharge detection in a simulated aircraft environment. The experimental study is performed in a low pressure chamber using a needle plane electrode. The pressure is changed from that corresponding to ground level to that corresponding to flight altitude, i.e., from 100 kPa to 20 kPa. The effect of the supply frequency is also studied, since modern aircraft operate in a wide range of frequencies up to about 800 Hz. Both variables, especially pressure, have shown significant effects on the CIV value. The results have also shown a similar sensitivity of both sensors for all the experimental conditions analysed, allowing a fast and sensitive detection and localization of incipient electrical discharge activity.

High Frequency Breakdown Characteristics of Alumina Filler Content Epoxy Resin

Power electronic transformers have high insulation frequency and compact insulation structure, and insulation performance is one of the main factors restricting their further development. Epoxy resin is an important insulating material in the electrical industry, its thermal conductivity and mechanical properties can not meet the needs of high-frequency transformers, usually metal oxide (Al2O3, etc.) is added to form composite insulation material. It is of great reference value for the insulation design of power electronic transformer to study the insulation performance of composite insulation materials with different filler content ratio under high-frequency AC. The effects of power supply frequency and alumina filler content on the breakdown performance of the composite were investigated experimentally. The results show that the breakdown voltage of pure epoxy resin decreases exponentially with frequency. At any filler content, the breakdown voltage of epoxy resin decreases with the increase of frequency, and the decreasing trend gradually slows down when the frequency increases from 50Hz to 1000Hz, and the decreasing trend gradually increases when the frequency increases to 2000Hz. The breakdown voltage of epoxy resin showed a down-rise-down trend with the increase of filler content, and the effect of filler content on breakdown voltage gradually weakened with the increase of frequency.

ПІДВИЩЕННЯ ЕНЕРГЕТИЧНОЇ ЕФЕКТИВНОСТІ РЕГУЛЬОВАНОГО ЕЛЕКТРОПРИВОДУ ОДНОЦИЛІНДРОВОГО ПОРШНЕВОГО КОМПРЕСОРА

The peculiarities of the operation of closed systems of adjustable electric drives of single-cylinder reciprocating compressors due to the presence of a non-linear dependence between the motor load torque and the angular movement of its rotor are considered. The method of synthesis of the regulator of the amplitude of the supply voltage of an induction motor of such an electric drive at a fixed value of the supply frequency is proposed. According to the results of research, it was found that the effect of increasing energy efficiency (reducing the difference in efficiency for constant and periodic loads) due to the use of a voltage regulator increases with a decrease in the power supply frequency. It is shown that the optimization of the transmission coefficient of the voltage regulator of electric drives with a non-linear dependence between the motor load torque and the angular movement is expedient to be carried out according to the criterion of maximum efficiency. References 25, figures 10, table 1.

Analysis of Drinking Water Service in Shimla City, Himachal Pradesh

Water is an inevitable requirement for all. Existence of life without water cannot be imagined. Water scarcity is a burning issue and the need to tackle this problem is forefront issue. Shimla City, the capital of Himachal Pradesh is facing water scarcity consecutively from past many years. Though, administration is taking substantial steps to improve the situation, this problem is continuously witnessed by the residents every year. Being capital of the state, Shimla city is hub to various administrative units, educational and important health institutions also to name a few. Even the city is a famous tourist destination and internationally recognised one. All this drew the attention towards the growing need of water in the Shimla city. Since, residents are the first to face the problem of water scarcity, therefore, the present study tries to examine the situation of drinking water service at ground level using peoples’ perception. Hypotheses has been created with respect to certain parameters like relationship between hours of water supply and satisfaction, frequency of water supply with adequacy of quantity received using suitable testing methods. It has been found during the study that though the situation is improving but certain issues like frequency of water, awareness and responsible behaviour from residents is required.

Research on environmentally friendly regeneration of adsorbents for SF6 gas-insulated equipment based on dielectric barrier discharge

This study evaluates the effectiveness of Dielectric Barrier Discharge (DBD) technology in regenerating adsorbents from decommissioned SF6 equipment, aiming to provide an efficient method for such treatments. The experimental platform constructed for this purpose explores the impact of power supply frequency, input power, carrier gas flow rate, and treatment time on the regeneration performance. The adsorbent's optimal treatment outcomes were observed at the center frequency, showcasing rapid changes in regeneration rate and pH. Furthermore, increasing the carrier gas flow rate enhanced the regeneration rate, with the fastest recovery observed at 0.6 L/min, given constant power conditions. Characterization analyses using XPS, FTIR, XRD, and N2 adsorption-desorption tests indicated a reduction in F and S element compounds, confirming the efficacy of DBD. When compared to traditional thermal regeneration methods, DBD technology offers a more effective and structure-preserving solution for treating adsorbents from decommissioned SF6 equipment.

Frequency optimisation and performance analysis of photovoltaic-battery water pumping system

Photovoltaic-battery water pumping systems (PVBWPSs) can provide fresh water and irrigation in off-grid areas. Previous research has focused on direct current (DC) voltage versus frequency to control the speed of a pump. However, the use of photovoltaic (PV) modules with batteries to create a high-performance hybrid system with fixed and variable frequencies of supply power remains challenging, particularly in an off-grid water pumping system with limited power and water supplies. Based on a conventional frequency conversion mode and power balance, this work addresses fixed and variable frequencies under changing solar irradiance conditions for a PV system and a PV system combined with a battery (PVB) mode to improve energy utilisation. According to DC power balance and centrifugal pump theories, a mathematical model of the power supply frequency in the PVBWPS is presented, as well as the loss of load probability (LLP) and pumping coefficient (Cp), through which the performance metrics are obtained. The formulated models are validated through the experimental PVBWPS, which includes 2.19 kWp PV modules, a 9.6 kWh battery bank, and a 0.75 kW centrifugal pump. The experimental results show that the root mean square error (RMSE) and maximum relevant error (RE) of the frequency are 0.14 Hz and 0.74 %, respectively. Consequently, the output performances are revealed via software simulation. The calculated results indicate that the maximum pumping volume for fixed-power-frequency operation is 48 Hz, which is 27.56 m3 on a sunny day and 17.63 m3 on a cloudy day. On a rainy day, the maximum pumping volume is 3.27 m3 at 41 Hz. Similarly, the Cp values reach maxima of 2.51 m3/kWh and 2.11 m3/kWh at 48 Hz in both sunny weather and cloudy weather, respectively, while on rainy days, the Cp peaks at 0.77 m3/kWh at 41 Hz. Moreover, every 1 Hz increase in the fixed frequency mode leads to a rise in the LLP, while the minimum change is at 46–48 Hz for cloudy and rainy days. Furthermore, the simulations revealed that for variable frequency control, the volume of water pumped in the PVB mode reached 40.19 m3, 29.36 m3, and 15.11 m3, which are increased by 4.91 %, 21.83 % and 103.09 % compared with the variable frequency PV mode, and 45.83 %, 66.53 % and 362.08 % higher than in PV fixed frequency mode, respectively. Compared with the PV mode, the system weighted efficiency of the variable-frequency PVB mode is increased by 2.06 %, 4.98 %, and 8.36 % under three weather conditions. This work provides critical theoretical guidelines for the design and operation of high-performance PVBWPs.

Improved ADRC Current Low‐Frequency Ripple Suppression Strategy Based on VFNF

AbstractIn the two‐stage inverter system, due to the space vector modulation (SVM), the midpoint potential of active neutral point clamped three‐level inverter system (ANPC‐TLIS) will have triple frequency fluctuation, under the influence of the closed‐loop control strategy, the fluctuation amplitude of the lithium battery energy storage system (LBESS) output current will increase. To reduce the low‐frequency output current fluctuation, a voltage loop strategy based on active disturbance rejection control (ADRC) with notch filter (NF)is proposed in this paper. In this scheme, the voltage outer‐loop control strategy not only maintains voltage stability, but also reduces the fluctuation amplitude of reference current. In addition, during the electromagnetic transient process, the LBESS output current fluctuation frequency is constantly changing because the power supply frequency required by linear motor is constantly changing. To solve this problem, the inverter output current frequency is feedforward to the LBESS controller, forming a variable frequency notch filter (VFNF). Finally, the effectiveness of the proposed strategy is verified by fixed‐frequency and variable frequency conditions experiments on RT‐LAB experimental platform. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

An intelligent fault diagnosis method for rolling bearing using motor stator current signals

Abstract In the diagnosis of rolling bearing faults, the Motor Current Signature Analysis (MCSA) method offers advantages such as low cost, simplicity, and convenience compared to using vibration signals, temperature information, and other diagnostic objects. However, owing to the interference of high-frequency noise, power frequency, and its harmonics in current signals, which can severely affect the accuracy of bearing fault diagnosis, it is extremely challenging to use the original current signals during bearing faults directly for diagnostic purposes. Therefore, this paper proposes an intelligent fault diagnosis method based on the feature reconstruction (FR) method and convolutional neural networks (CNN). This method can achieve high-precision fault diagnosis using single-phase stator current signals from motors as the diagnostic objects. First, the FR method effectively removes the impact of high-frequency noise, supply frequency, and its harmonics from the current signals, while also highlighting subtle fault feature signals to a certain extent. Second, a CNN suitable for learning the characteristics of the current signals was constructed. Through feature extraction, learning, and classification of the current signal samples processed by the FR method, a diagnostic method with a high classification accuracy was obtained. Visualization techniques were used to present the final diagnosis results intuitively. The experimental results demonstrated the highest diagnostic accuracy and average diagnostic accuracy of the proposed method in diagnosing rolling bearing fault types, with an average diagnostic accuracy of approximately 99% for actual faulty bearing samples.

Frequency and power shaving controller for grid-connected vanadium redox flow batteries for improved energy storage systems

In this research, the performance of vanadium redox flow batteries (VRFBs) in grid-connected energy storage systems centering on frequency and power sharing using voltage source inverters was evaluated. VRFBs are increasingly promising due to their scalability and long lifespan. We explore the impact of voltage source inverters on the frequency of the power supply when there is a change in load and power sharing between the grid and VRFB through MATLAB simulations. The test system demonstrates a storage system at an 11-kV substation and considers a load profile commencing from residential and commercial consumers. The outcome of this study reveals that VRFBs provide the required power to maintain load demand. Due to fast response time, VRFBs also regulate the frequency efficiently during the change in load demand and maintaining current total harmonic distortions (THDs). This research confirms the design and operation of VRFB-based energy storage systems, contributing to resilient grid infrastructure and reliable power distribution systems.

交叉导流式振动种箱设计与机理研究

Aiming at the existing rice mechanized seeding technology it is difficult to meet the hybrid rice low seeding volume precision seeding requirements. In this paper, based on the friction characteristics of rice seed and the theory of silo arching, the structure and parameters of seed filling room with staggered oriented plates and vibration in the quantitative seed supply device were designed. EDEM software was used to simulate the working process of the quantitative seed supply device, and it was determined that staggered oriented plates structure in the seed filling room combined with vibration could effectively prevent seed arching, thus improving the uniformity of seed supply. Finally, the results of the simulation analysis were verified by rice quantitative seed supply test. The results showed that the vibration could increase the seed supply frequency by 3.64% for large sowing weight of conventional rice and 5.52% for small sowing weight of hybrid rice. In addition, the analysis of the coefficient of variation of the seed supply frequency by quantitative seed supply devices showed that the vibration effect could increase the stability of seed supply device by 2.47 % for the conventional rice seed and 1.33 % for the hybrid rice seed, which increased the seed supply stability.

Near-Field Probing of Microwave Oscillators with Josephson Microscopy.

Voltage-controlled oscillators, serving as fundamental components in semiconductor chips, find extensive applications in diverse modules such as phase-locked loops, clock generators, and frequency synthesizers within high-frequency integrated circuits. This study marks the first implementation of superconducting Josephson probe microscopy for near-field microwave detection on multiple voltage-controlled oscillators. Focusing on spectrum tracking, various phenomena, such as stray spectra and frequency drifts, were found under nonsteady operating states. Parasitic electromagnetic fields, originating from power supply lines and frequency divider circuits, were identified as sources of interference between units. The investigation further determined optimal working states by analyzing features of the microwave distributions. Our research not only provides insights into the optimization of circuit design and performance enhancement in oscillators but also emphasizes the significance of nondestructive near-field microwave microscopy as a pivotal tool in characterizing integrated millimeter-wave chips.

An ultra energy-efficient hardware platform for neuromorphic computing enabled by 2D-TMD tunnel-FETs

Brain-like energy-efficient computing has remained elusive for neuromorphic (NM) circuits and hardware platform implementations despite decades of research. In this work we reveal the opportunity to significantly improve the energy efficiency of digital neuromorphic hardware by introducing NM circuits employing two-dimensional (2D) transition metal dichalcogenide (TMD) layered channel material-based tunnel-field-effect transistors (TFETs). Our novel leaky-integrate-fire (LIF) based digital NM circuit along with its Hebbian learning circuitry operates at a wide range of supply voltages, frequencies, and activity factors, enabling two orders of magnitude higher energy-efficient computing that is difficult to achieve with conventional material and/or device platforms, specifically the silicon-based 7 nm low-standby-power FinFET technology. Our innovative 2D-TFET based NM circuit paves the way toward brain-like energy-efficient computing that can unleash major transformations in future AI and data analytics platforms.