High Frequency Currents Research Articles

1.2: Speckle suppression method using high‐frequency driving current to semiconductor laser diode

Suppression of speckle noise is a key issue in the development and utilization of laser display and illumination. Many approaches to reduce the speckle contrast in laser display systems have been proposed and developed. A practical high frequency laser driver circuit is designed and developed to drive green semiconductor lasers. Speckle contrast under different driving frequencies from 100Hz to 15Mhz was tested by using a speckle contrast measurement system, the speckle contrast of green laser decreased from 13.35% to 5.23%. The results show that the modulation of high frequency current of the semiconductor laser diode will destroy the coherence of the laser light and reduce the speckle contrast. The effectiveness of this method to depress speckle noise was verified.

Sensorless Drive for Salient Synchronous Motors Based on Direct Fitting of Elliptical-Shape High-Frequency Currents

The article deals with a position sensorless control for synchronous motor drive with an ease tuning procedure and a reduced number of tunable parameters. The rotating high-frequency (HF) signals injection is implemented and the elliptical shape of the HF-induced current trace is fitted by means of the least square (LS) algorithm. The ellipse tilt is related to the rotor position and the latter is estimated by processing the fitted coefficients of the ellipse mathematical equation. The proposed LS algorithm processes the measured currents, without the need to filter them as occurs in conventional injection methods. Furthermore, no motor parameters are required to tune the proposed rotor position observer. The method was validated throughout several experimental tests performed on an interior permanent magnet synchronous motor.

Experimental Assessment of Ground Fault Protection in Frequency-Selective Grounded Systems Fed by a Single Transformer

This paper presents performance assessment of ground fault protection for systems supplied by a transformer, which has frequency-selective grounding. Frequency-selective grounding is a new grounding system that is designed to act as a solid-grounding for high frequency currents, and as a low resistance-grounding for low frequency currents. This grounding system is composed from a parallel <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R-C$</tex-math></inline-formula> circuit with an equivalent impedance able to affect system zero-sequence currents and ground potentials. Such effects on zero-sequence currents and ground potentials can directly impact the accuracy and response speed of ground fault protection. Effects of frequency-selective grounding on ground fault protection are experimentally assessed for different fault and non-fault events, when the transformer supplies linear and non-liner loads. Experimental results demonstrate responses of various implementations of ground fault protection to fault and non-fault events, when the protected system has frequency selective grounding. Moreover, presented results and discussions aim to demonstrate the ability of frequency-selective grounding to support the operation of ground fault protection during different loading conditions and fault events.

A Novel Control-Independent Online Fault Diagnosis of Interturn Short Circuits in SRMs Using Signal Injection Technique

Most of the existing diagnosis techniques for interturn short circuits (ITSCs) in switched reluctance motors (SRMs) suffer from three major issues. 1) The problem of lower sensitivity where the system cannot detect an ITSC if a lower number of turns are short-circuited; 2) Interference of load variation on the detection reliability in which the fault index might initiate false alarm without any fault; 3) The dependency of the diagnosis system on the control strategy on which the motor is operating. This article proposes a novel method to diagnose ITSCs in SRMs independent of control schemes with better sensitivity and reliability using the signal injection technique. In SRMs, not all the phases take part in the torque production at any instant. The idle or inactive phase is injected with a high-frequency (HF) voltage signal for a preselected injection ratio within an electrical cycle. Any change in the winding parameters owing to an ITSC fault is deciphered by monitoring the HF currents generated in the phase windings. The results are validated experimentally for a four-phase 8/6 SRM employing two control strategies: 1) chopped current control and 2) angle position control.

Dynamic Model of Medium Voltage Vacuum Circuit Breaker and Induction Motor for Switching Transients Simulation Using Clark Transformation

A derivation of the dynamic model of a medium voltage vacuum circuit breaker and induction motor in space vectors in coordinates αβ0 allow us to model switching transients in various dynamic states of the motor. In the case of the Clark transformation, the corresponding numerical integration technique can be selected including variable time-step integration techniques to avoid numerical instabilities due to the stiffness of the system. Assymetrical operations such as switching cause the power system to become unbalanced and the transformed equations α, β, and 0 are not uncoupled. Therefore, it is necessary to derive a coupling matrix between circuit breaker voltages and currents in the coordinate system αβ0. The subject of our interest is switching overvoltages that arise when turning off small inductive currents by a vacuum circuit breaker. When deriving the model of a vacuum circuit breaker, all its properties encountered during this action are taken into account, i.e., current chop, virtual current chop, dielectric barrier in the circuit breaker and its recovery rate, and the ability of the vacuum circuit breaker to extinguish high frequency currents. Simulation results are compared with the measured results on a medium voltage motor as well as with the simulation results of the mathematical model of the test circuit according to IEC 62271-110 resolved using the nodal method (EMTP algorithm). Models are implemented in the MATLAB/Simulink programming environment.

MATHEMATICAL MODELING AND EXPERIMENTAL STUDY OF THE PROCESS OF ELECTROMAGNETIC-CONVECTIVE DRYING OF PLANT MATERIALS

The work on electromagnetic drying with heat supply to the dried material using high and ultrahigh frequency currents and in the infrared frequency range - with oscillating energy supply is analyzed. (Research purpose) The research purpose is in analytical mathematical describing the oscillating electromagnetic-convective drying of materials, as well as the method of drying seeds of vegetable crops, non-traditional and rare plants that improve their sowing qualities. (Materials and methods) Obtained solutions to the problems of heating the material using the analytical method of integral transformations. Experimental studies were carried out on oscillating infrared drying on seeds of vegetable crops, non-traditional and rare plants. (Results and discussion) The combined electromagnetic-convective drying of materials was considered, in which the energy for drying is supplied using an electromagnetic field and convectively using a preheated drying agent. Mathematical models describing the digitizing heating of bodies of different shapes (unlimited plate, infinite cylinder, ball) under conditions of convective drying were analyzed. The results of numerical modeling of the process of oscillating infrared drying of onion seeds in a fluidized bed are presented, which show that the necessary technological drying mode can be found by numerical modeling based on the obtained models. (Conclusions) Presented mathematical models that allow numerical modeling of electromagnetic-convective drying and finding the required hardware and technological design of the process. It was determined that oscillating infrared drying of seeds of vegetable crops, non-traditional and rare plants when the seed temperature fluctuates from tmin = 34 degrees Celsius to tmax = 40 degrees Celsius causes seed stimulation, which manifests itself in an increase in germination energy and germination. It was found that the germination of vegetable seeds increases by 11-24 percent (from control), and the germination energy - by 12-73 percent, seeds of non-traditional and rare plants, respectively, by 13-24 percent and 14-82 percent.

IMPROVEMENT OF PROTECTIVE EFFECTS ON DANGEROUS HIGH-FREQUENCY IMPRESSION SIGNALS

The interception of information that is discussed at the objects of information activity or processed by technical means can be carried out by means of special effects on the elements of technical means. One of the effective methods of such influence is high-frequency imposition, in which channels of information leakage are formed due to acoustoelectric transformations, which are formed during the simultaneous impact on the elements of technical means of confidential signals and a probing high-frequency signal, if radical measures were not taken to prevent the penetration of currents of high frequency into technical means. Processes of formation of technical channels of information leakage by methods of high-frequency imposition, method of technical protection of information from interception by these methods, the essence of which consists in the application of combined active interference, which changes the properties of dangerous signals of high-frequency imposition, are considered. The purpose of the work is to improve the protective effects on dangerous signals formed by high-frequency imposition to ensure the maximum possible destruction of their informative parameters and, as a result, reliable blocking of information leakage channels. The perspective of using quadrature generators of radio signals for the formation of protective signals not only relative to the fundamental frequency, but also relative to the harmonics of the dangerous signal is considered. The advantage of quadrature shapers is the possibility of performing modulation in them in a fairly wide range of changes in both modulating and carrier frequencies without rebuilding the circuit due to the absence of controlled reactive elements and frequency-sampling circuits. The stages of formation of output phase-modulated signals are considered, a structural diagram is given that implements the quadrature method of increasing the angular modulation index. As a result, it is believed that the considered method of forming radio-electronic interference simultaneously on several harmonics of the carrier frequency and ensuring the specified values of the modulation indices on each of them provide a basis for its use in the formation of protective effects on dangerous signals formed by high-frequency imposition, where an increase in the coefficient is required the quality of noise disturbances with angular modulation, as well as increasing the distance of influence.

Morphology, properties and stress-strain state of carburized gear made of steel 12KhN3A after high-frequency currents quenching

The results of the study of the effect of cementation with subsequent induction quenching by high-frequency currents on the physical properties of a gear made of 12HN3A steel are presented, the influence of technological factors (temperature and time) on the cementation layer is studied. The study was carried out using a well-known pasty carbonatesoot carburetor and in a pasty carburetor with composition optimization through the synthesis of a di-ammonium salt of 2-monoethanolamine and citric acid, in terms of carbon saturation activity of steel not inferior to melts of cyanide salts. The structure and chemical composition of 12HN3A steel before and after cementation were studied. In the course of the work, the following mode of chemical-thermal treatment of 12HN3A steel was used: cementation due to exposure to highfrequency currents temperature T = 960 °C, medium — air; induction hardening due to exposure to high-frequency currents temperature T = 860 °C, medium — aqueous solution, tempering low temperature T = 190 °C, medium — aqueous a solution that provides an increase in the margin coefficient for fatigue strength to 86.1 MPa and yield strength to 820 MPa while maintaining a sufficient level of plastic properties. The stress-strain state of a gear wheel made of 12HN3A steel is estimated before and after cementation of its working surfaces with subsequent induction hardening by high-frequency currents.

دراسة نظرية حول طرق العلاج باستخدام التحفيز الكهربائي

This article deals with a theoretical study of methods of electrical stimulation therapy which is one of the physical therapy used to treat pain and increase the strength of the weak muscle where the treatment is done by connecting electrodes to the patient which in turn deliver electrical impulses through nerve paths at specific intervals. Also, the relationship between methods of electrical stimulation and types of electric current has been shown in this review, Stimulation methods were divided according to the type of current used where continuous current is used in the case of galvanic with high frequency and low current. Methods (Trabert, Leduc, Faradic, H-wave, Micro-current) use the pulse current with a frequency not exceeding 1000 Hz, while methods like Transcutaneous Electrical Nerve Stimulation (TENS), Four-pole interfering, Two-pole interfering, Isoplaner interfering, Neuromuscular, dipole interfering, diadynamic use alternating current with a frequency between (3600 Hz - 10000 Hz) and the value of the current is between (50 mA - 140 mA). The most important effect or use of electrical stimulation is to reduce pain (Analgesic effect), as well as, 2-pole and 4-pole interference effect on myorelaxation and spasmolytic. Finally, there are many studies that show that there are no long-term side effects of electrical stimulation, only some temporary effects resulting from the misuse of electrodes for the stimulation device or resulting from the use of high currents.

THE USE OF DIC TECHNOLOGY (INSTANT CONTROLLED PRESSURE DROP) IN FRUIT DESHYDRATATION

Over time, many methods of preserving fruit by drying/dehydration applied at the industrial level (convection, microwave, high frequency currents, infrared radiation, lyophilisation, etc.) have been discovered and perfected to improve the quality of dehydrated products as well as their resistance to storage. The application of many of them is quite expensive, the parameters of the drying process (processing time and energy consumption) having high values. Technological progress in this field involves the development of new dehydration techniques, optimizing existing ones or combining them, aiming to increase energy efficiency, obtain healthy products with high rehydration capacity, reduce costs and negative impact on the environment. The paper presents a brief summary of the basic principles of the DIC (Instant Controlled Pressure Drop) process, as well as the advantages of its uses in industrial fruit dehydration technologies or as pre-treatment.

A Wind-Driven Rotating Micro-Hybrid Nanogenerator for Powering Environmental Monitoring Devices.

In recent years, environmental problems caused by natural disasters due to global warming have seriously affected human production and life. Fortunately, with the rapid rise of the Internet of Things (IoT) technology and the decreasing power consumption of microelectronic devices, it is possible to set up a multi-node environmental monitoring system. However, regular replacement of conventional chemical batteries for the huge number of microelectronic devices still faces great challenges, especially in remote areas. In this study, we developed a rotating hybrid nanogenerator for wind energy harvesting. Using the output characteristics of triboelectric nanogenerator (TENG) with low frequency and high voltage and electromagnetic generator (EMG) with high frequency and high current, we are able to effectively broaden the output voltage range while shortening the capacitor voltage rising time, thus obtaining energy harvesting at wide frequency wind speed. The TENG adopts the flexible contact method of arch-shaped film to solve the problem of insufficient flexible contact and the short service life of the rotating triboelectric generator. After 80,000 cycles of TENG operation, the maximum output voltage drops by 7.9%, which can maintain a good and stable output. Through experimental tests, the maximum output power of this triboelectric nanogenerator is 0.55 mW at 400 rpm (wind speed of about 8.3 m/s) and TENG part at an external load of 5 MΩ. The maximum output power of the EMG part is 15.5 mW at an external load of 360 Ω. The hybrid nanogenerator can continuously supply power to the anemometer after running for 9 s and 35 s under the simulated wind speed of 8.3 m/s and natural wind speed of 5.6 m/s, respectively. It provides a reference value for solving the power supply problem of low-power environmental monitoring equipment.

Studies on tensile and tear fracture of the S8210 tarpaulin

The tarpaulin of PVC-coated S8210 wagons is a composite textile membrane. This material is resistant to atmospheric factors (wind, rain, snow, etc.), durable for many practical applications and can be manufactured in various colors and prints. PVC membrane material is inexpensive, soft and easy to manufacture. These materials are widely used in large-opening spatial structures due to excellent mechanical behavior and beautiful textures. The tarpaulins are made by the method of welding with high frequency currents from the material S8210. In the present paper, the tensile and tearing mechanical properties of tarpaulins intended to protect goods carried by railway wagons are presented. The results of this study can be used in establishing the appropriate utilization of the fabric, in accordance to the warp and weft directions.

THE USE OF CUMNCO BRAZING ALLOY FOR THE FORMATION OF AN ADHESIVE LAYER, LAYERED COMPOSITE COATING (CUMNCO-TINIZR) BY HIGH-SPEED FLAME SPRAYING WITH FINISHING HIGH FREQUENCY CURRENTS (HFC) TREATMENT COATING (CUMNCO-TINIZR)-SUBSTRATE (ST45) TO INCREASE ADHE

The article takes into account the technological structure according to the structure of the formation of composite coating layers on the substrate surface, consisting of an adhesive layer, which is a CuMnCo solder, and an essentially functional layer based on alloys with thermoelastic alloys of TiNiZr compounds, using high-speed flame spraying technologies. Warehousing by processing the substrate with a composite coating with high-frequency currents (HFC), thin heating of the coating and the surface of parts to the melting temperature of the CuMnCo adhesive layer (T = 1030˚C). results of studying the structure and results of elemental analysis of a substrate with a layered composite coating in three zones: substrate; adhesive layer; functional layer after HFC processing. The structure of the interface between the layers and the adhesion line of the coating/substrate, as well as the line of destruction as a result of a combination of their residual traces after HFC treatment.&#x0D; Purpose is to justify the use of a high-temperature solder composition for adhesion between the substrate and the dense coating thickness.&#x0D; Methodology of the work contains according to the technology of soldering ceramic plates on the body of the cutter, there was a cosmetic solder composition as an adhesive layer on the experimental sample, after some thin sample was treated with HFC.&#x0D; Results. Recommendations on the selection of the composition of the solder and the technology of application and processing of HFC for the adhesive layer for various materials of the substrate and the functional layer and coating were present.&#x0D; Practical implications. Technology is an increased adhesive strength of surfaces with parts, which in turn expands the scope of the thermal spraying technology and can be applied to its type.

Methyl 5-Imino-2-methyl-1,10a-dihydro-5H-chromeno[2,3-b]pyridine-3-carboxylate

Multicomponent reactions are valuable synthetic tools to deliver highly functionalized motifs starting from simple building blocks in only one step and in an atom-economical way. Herein we disclose the structure of a new and unexpected compound, the methyl 5-imino-2-methyl-1,10a-dihydro-5H-chromeno[2,3-b]pyridine-3-carboxylate, which was formed in the ohmic-heating-assisted multicomponent Hantzsch reaction of 3-formylchromone with methyl acetoacetate and ammonium acetate, in aqueous medium, in the presence of tetrabutylammonium bromide as phase transfer catalyst. The title compound was isolated with no need of chromatographic separation and was analyzed by nuclear magnetic resonance (1H and 13C-NMR, HSQC and HMBC) spectroscopy, mass spectrometry (MS) and high-resolution mass spectrometry (HRMS). Its formation as the main reaction product was observed when the reaction was performed using ohmic heating, which may lead to some speculations about the possible existence of specific effects of ohmic heating in the reactivity pathway because of the passage of an alternating electric current of high frequency within the reaction media, opening new opportunities for further investigations of the potential of this thermal processing method in organic synthesis and reactivity optimization.

Wireless networks of injectable microelectronic stimulators based on rectification of volume conducted high frequency currents

Objective. To develop and in vivo demonstrate threadlike wireless implantable neuromuscular microstimulators that are digitally addressable. Approach. These devices perform, through its two electrodes, electronic rectification of innocuous high frequency current bursts delivered by volume conduction via epidermal textile electrodes. By avoiding the need of large components to obtain electrical energy, this approach allows the development of thin devices that can be intramuscularly implanted by minimally invasive procedures such as injection. For compliance with electrical safety standards, this approach requires a minimum distance, in the order of millimeters or a very few centimeters, between the implant electrodes. Additionally, the devices must cause minimal mechanical damage to tissues, avoid dislocation and be adequate for long-term implantation. Considering these requirements, the implants were conceived as tubular and flexible devices with two electrodes at opposite ends and, at the middle section, a hermetic metallic capsule housing the electronics. Main results. The developed implants have a submillimetric diameter (0.97 mm diameter, 35 mm length) and consist of a microcircuit, which contains a single custom-developed integrated circuit, housed within a titanium capsule (0.7 mm diameter, 6.5 mm length), and two platinum–iridium coils that form two electrodes (3 mm length) located at opposite ends of a silicone body. These neuromuscular stimulators are addressable, allowing to establish a network of microstimulators that can be controlled independently. Their operation was demonstrated in an acute study by injecting a few of them in the hind limb of anesthetized rabbits and inducing controlled and independent contractions. Significance. These results show the feasibility of manufacturing threadlike wireless addressable neuromuscular stimulators by using fabrication techniques and materials well established for chronic electronic implants. Although long-term operation still must be demonstrated, the obtained results pave the way to the clinical development of advanced motor neuroprostheses formed by dense networks of such wireless devices.

Multiple detections of insulation defects partial discharge in gas-insulated equipment

Gas-insulated equipment is an important part of the power system owing to its advantages of small footprint, large transmission capacity, and high reliability. Detection of insulation defects partial discharge (PD) is important for its operation and maintenance, and the combination of multiple detection methods can greatly improve the accuracy of PD detection. In this study, the three kinds of insulation defects, namely, floating defect, void defect, and surface defect, are set up on the PD simulation platform and detected using the ultra-high frequency (UHF) method, high-frequency current (HFCT) method, and acoustic emission (AE) method. The partial discharge inception voltage (PDIV) and phase-resolved partial discharge (PRPD) spectrum of defects measured by these three methods are recorded in the experiments. The experimental results show that the UHF method is effective for the detection of the three defects. The HFCT method is sensitive to floating defects but not to void and surface defects. Discharge signals of these two defects can be detected by HFCT when the discharge amplitude is large. The AE method can detect floating defects effectively but cannot detect void defects and surface defects.

Current observations on and around a deep-ocean island/reef: northern Palau and Velasco Reef

Current and hydrographic measurements were made in the equatorial Pacific Ocean between the westward-flowing North Equatorial Current and the eastward-flowing North Equatorial Counter Current. Nine moorings containing current profilers and hydrographic sensors were deployed on and around Velasco Reef, just north of Palau Island, from May 2016 to March 2017, when the Pacific Ocean was relaxing after the 2015/16 El Niño. Currents and their interactions with this abrupt bathymetric feature are characterized on spatial scales of 10–30 km, and frequencies from semidiurnal to intraseasonal. Currents near the reef displayed a two-layer structure and were not stationary due to the shifting of the major currents and eddy passages. Energy was significant at tidal and inertial periods, and at periods longer than ten days. Tides and higher frequency currents were responsible for about half the energy on the reef but for only about 20% of the energy in the deep water. Cyclonic (anticyclonic) vorticity occurred on the western (eastern) side of the reef during westward (eastward) flows, indicating recirculation on the leeward side of the reef. Vorticity west of the reef was much stronger than vorticity on the east side. When the cyclonic vorticity was large, the divergence flow patterns supported strong upwelling in the upper layer. Differences in both vertical and horizontal velocity coherences and correlations between moorings indicated that the reef affected the currents. The reef seemed to significantly impact water exchange. Currents near the reef are difficult to be described, particularly at depth by satellite products, making their prediction problematic.

Modeling the process of hardening of rods with high-frequency currents

The results of a study on increasing the wear resistance of plunger pump rods are presented. To increase the life of rods, it is proposed to use hardening with high-frequency currents. Keywords: hardening, surface, wear resistance, inductor, rod, high frequency current. elmancam@gmail.com, h.ibo@mail.ru

Three Winding Coupled Inductor-Based Dual Active Bridge DC-DC Converter With Full Load Range ZVS Under Wide Voltage Range

In this article, a three winding coupled inductor-based dual active bridge (TWCI DAB) dc-dc converter is proposed. Similar to the current-fed DAB converter, the proposed TWCI DAB has small input current ripple and wide input voltage range. In addition, the zero-voltage switching (ZVS) of all switches in the full load range under wide input voltage variation can be realized. With the magnetic integration structure, the size of the total magnetics can be reduced, and the efficiency is also increased compared with the discrete magnetic case. To better analyze the working principle of the three winding coupled inductor, a general analysis method based on magnetic reluctance model is first introduced to obtain the expressions of high frequency current. Furthermore, ZVS analysis and inductor design to obtain low inductor root mean square (rms) current and full load range ZVS based on the ZVS conditions, maximum power transfer and rms current are presented. Finally, the validity of the proposed topology and design are verified by experimental results from a 1-kW laboratory prototype.

ВЫБОР МАТЕРИАЛА ЗУБЬЕВ ШЕСТЕРЕН НА ОСНОВЕ ИЗНОСОСТОЙКОСТИ

This article reviews a method for selecting a gear material based on the wear resistance properties of teeth. The approach takes such properties as hardness, number of loading cycles leading the destruction a deformed layer of friction surface material and correlation of hardness of gear material and strength of abrasive particles in wedgeshaped gap of teeth, into account. The research has maintained principles of alteration of the wear rates and service life of open and closed gears, with and without abrasive particles in the process of gear teeth wear, depending on the meshing module and the type of hardening surface treatment, at volume hardening, hardening by current of high frequency and cementation.