Hz AC Voltage Research Articles

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.

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.

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%.

The Influence of a High-Voltage Discharge in a Helicoidal Twisted-Pair Structure on Enzyme Adsorption

The effect of a high-voltage discharge in a helicoidal structure on the adsorption properties of an enzyme on mica has been studied with the example of horseradish peroxidase (HRP). The discharge was generated at the expense of a sparkover in a 3 mm gap between two electrodes, to which a 10 kV, 50 Hz AC voltage was applied. The electrodes were connected to a twisted pair, which was wound onto a cone, forming the helicoidal structure. The incubation of the enzyme solution near the top of the helicoidal structure has been found to cause an increase in the degree of aggregation of HRP adsorbed on mica in comparison with the control HRP sample. The results obtained should be taken into account in studies of enzymes using biosensors with helicoidal structures as heating elements, as well as in refining models describing effects of low-frequency alternating current, flowing through helicoidal structures, on proteins and biological objects.

Switch Mode Power Supply (SMPS) Utilizing Flyback Converter Topology: Simulation and Experiment

This paper presents simulation and experimental works of a single, 5 volt DC output switch mode power supply (SMPS). The main objective of this work is to design, build and evaluate the SMPS using flyback converter topology. In this work, a 555 timer was chosen as the pulse width modulator. The 555 timer was chosen because it is easily available, cheap and has the capability to produce stable pulse width modulation. The complete circuit of the SMPS consist of full bridge rectifier, smoothing capacitor, pulse width modulator, high frequency transformer and flyback converter. The complete SMPS circuit was firstly designed and simulated using Proteus software. After obtaining acceptable results from the simulation process, the hardware part of the project, soon follows. Next, the SMPS circuit was constructed on a breadbroad. Testing and measurements of important parameters such as the input and output voltages and duty cycle were carried out using digital oscilloscope and multi meter. Both simulation and experimental results have shown that the designed circuit can convert single 24 Vrms 50 Hz AC voltage input into a stable single 5±0.15 V DC outputs. This work also has shown that pulsed DC voltage with peak value of 3.8 V and frequency lower than 4 kHz is adequate in controlling the switching frequency of a MOSFET transistor, thus regulating the output voltage within the desired range. Further analysis also shows close correlation between the simulation and experimental results.

Longitudinal Breakdown Strength of Wet-mate Solid-Solid Interfaces at VLF and 50 Hz AC voltages

The 50 Hz AC breakdown strength of dry interfaces is known to strongly depend upon the mechanical properties, contact pressure, roughness of the surfaces, and the type of lubricant used at the interface. This paper aims to experimentally examine how these factors affect the longitudinal AC breakdown strength of interfaces assembled in water, so-called wet interfaces. The main aim is to obtain data relevant to the design of power equipment operating at very low frequency (VLF) or DC voltages.Experiments were conducted using identical specimens made from 4mm thick plaques of PMMA and plane sections cut from XLPE cable insulation. The findings were discussed with respect to expected dimensions of interface voids and contact regions, considering tribology-based contact theory, including the impact of surface roughness, modulus of elasticity, and applied mechanical interface pressure. 
 The longitudinal 50 Hz AC breakdown strength values of wet samples were typically as low as 80 % of samples assembled in the air under dry conditions. In addition, the results verified previous findings that the AC breakdown strength strongly increases with reduced surface roughness, stiffness, and increased interface pressure. The breakdown values obtained during VLF breakdown testing were found to be 2 – 3 times higher than in the case of testing at 50 Hz AC voltages.

An Experimental Study of Co-Axial Dielectric Barrier Discharge for Ozone Generation

In this research work, co-axial cylindrical dielectric barrier discharge (CCDBD) system has been used as a ozone generator for ozone production with air as a working gas. The breakdown of air was generated inside the reactor by using low line frequency of 50 Hz and high AC voltage power supply system. The variation of air flow rate (Q) was taken from 10 to 16 l/min in this experiment. The O3 concentration denoted by C(O3) decreases with increasing the rate of flow of air at fixed discharge time and applied voltage. When discharge time (t) increases, C(O3) increases at fixed applied voltage. C(O3) also increases with increasing applied voltage (V) for constant discharge time. If the gap space between the electrodes increases then C(O3) increases. We have used glass tube reactor for this work having internal diameter of 18 mm and copper, brass and iron electrodes of diameter 8 mm. It was estimated that C(O3) found higher for copper electrode than both brass and iron electrode for certain discharge time, applied voltage and reactor diameter.

Influence of electronic scavenger additives on AC breakdown voltage of synthetic ester

This study deals with the influence of two kinds of electronic scavenger additives/compounds, namely methyl iodide (iodomethane), CH3I, and carbon tetrachloride CCl4 on the breakdown voltage (U BDV) of MIDEL 7131 synthetic ester (SE). The tests are conducted under 60 Hz AC voltage according to the IEC 60156 standard, for various concentrations of additives ranging 0–600 ppm. Statistical analysis is performed to check whether the experimental data obey the most used probabilistic distributions for electrical BDVs, namely normal and Weibull laws. The estimation of the BDV with risk probabilities of 1 and 50% are also deduced. It is shown that the average BDV of SE increases with the concentration of both additives up to an optimum value beyond which it decreases; the optimum concentration for both cases is 400 ppm. The improvement of the average U BDV is about 27% with CH3I and 21% with CCl4. The values of U BDV conform to Weibull distribution with CH3I; it is also the case with CCl4, except for 200 ppm.

Об оценке коммутационной способности тяговых двигателей грузовых электровозов

An important direction in the development of JSC Railways is increasing the volume of freight traffic over the railway network. A number of measures are being taken to achieve the predicted strategic indicators in the locomotive complex. The most large-scale activities include research and experimental works aimed at improving the traction properties of electric locomotives in the Eastern polygon, which is one of the most heavily loaded sections of the Russian railway network. This is an important link connecting Southeast Asia and Europe. The conditions under which the railway transport operates require, among the priority tasks, efficient use of the locomotive fleet with high operational reliability to ensure safe train traffic. The Eastern polygon uses a system of electric traction powered by the 25 kV, 50 Hz AC voltage. Freight trains are driven by 2ES5K and 3ES5K electric locomotives equipped with pulsating current commutator traction machines. In implementing the required traction forces, the traction electric drive of such locomotives has a number of limitations. One of them is the quality of switching on the traction motor commutator. Achieving better reliability of traction motors, which are regarded as the weak link of electric locomotives, is a topical problem. The number of their failures due to faults of direct and pulsating current traction motors is at the level of 20--22%. The greatest difficulty is to increase the switching reliability. A switching quality criterion for traction electric motors of electric locomotives is proposed, which takes into account the degree to which the armature reaction magnetomotive force is compensated in the switching zone. The width of the sparkless operation region cannot fully characterize the traction electric motor switching capacity. Its calculation takes into account the spark voltage under the brush, the effect of electromagnetic factors on the switching, the design of additional poles, and the kind of load current. The accomplished calculations have shown that the proposed switching reliability quality criterion objectively characterizes the switching quality in the limiting mode and is consistent with the long-term experience of their operation in AC electric locomotives.

Plasma diagnostic of gliding arc discharge at atmospheric pressure

A gliding arc discharge (GAD) with a water spray system was constructed. A non-thermal plasma, generated between two V shaped electrodes in an ambient argon driven by 100 Hz AC voltage, was investigated using optical emission spectroscopy (OES) with different gas flow rates (0.5, 1, 1.5, 2 , 2.5 , 3 1/min). Boltzmann plot method was used to calculate electron temperature (Te) and electron density (ne). The electrodes design was spectrally recognized and its Te value was about 0.588-0.863 eV, while the ne value of 6.875×1017-10.938×1017 cm-3. The results of the plasma diagnostics generated by gliding arc showed that increasing gas flow rates was associated with decreased electron temperature (Te), Debye length, and Debye Number, along with decreased electron density (ne) and plasma frequency.

Design and Implementation of 150 W AC/DC LED Driver with Unity Power Factor, Low THD, and Dimming Capability

This paper presents the implementation of a two-stage light-emitting diode (LED) driver based on commercial integrated circuits (IC). The presented LED driver circuit topology, which is designed to drive a 150 W LED module, consists of two stages: AC-DC power factor correction (PFC) stage and DC/DC power converter stage. The implementation of the PFC stage uses IC NCP1608, which uses the critical conduction mode to guarantee a unity input power factor with a wide range of input voltages. The DC/DC power converter with soft-switching characteristics for the entire load range uses IC FLS2100XS. Furthermore, the design of an electromagnetic interference (EMI) filter for the LED driver and the dimming control circuit are discussed in detail. The hardware prototype, an LED lighting system, with a rated power of 150 W/32 V from a nominal 220 V/50 Hz AC voltage supply was tested to show the effectiveness of the design. The presented LED driver was tested for street lighting, and the experimental results show that the power factor (PF) was higher than 0.97, the total harmonics distortion (THD) was lower than 7%, and the efficiency was 91.7% at full load. The results prove that the performance of the presented LED driver complies with the standards: IEC61000-3-2 and CIRSP 15:2009.

Limitations Regarding Use of the ABC-Model for Interpretation of Partial Discharge Measurements

The main purpose of the work presented here is to facilitate use of partial discharge (PD) measurements as a diagnostic tool for condition assessment of hydropower generator bars. The main aim of the work is to clarify how measured inception and extinction voltage, detected number and magnitude of PDs relate to the void size and the physical discharge mechanisms in the voids. The laboratory tests were performed on 3 mm thick samples, consisting of three 1 mm thick layers containing a cylindrical disc shaped void in the center of the middle layer. The void diameters varied from 3 to 20 mm. Insulation discs of polycarbonate and generator insulation based on mica and glass fiber reinforced epoxy tape were examined. In case of the polycarbonate samples comparable tests were performed on objects with either conductive or insulting void surfaces. During application of a stepwise increasing/decreasing 50 Hz AC voltage, the partial discharge activity was detected using a conventional PRPDA detection system.The inception voltage was found to decrease with increasing void diameter, in accordance with results from electric field calculations showing increased field enhancement in the larger voids. In all cases the apparent discharge magnitude increased with increasing diameter. In case of conducting void surfaces this discharge magnitude and number of PDs per period were, in accordance with the theory, found to be proportional to the total surface area of the void. In case of voids with insulating surfaces, this proportionality was valid up to a void diameter of 10 mm. Larger voids resulted in higher number of PD each at lower apparent charge magnitude than expected, indicating several parallel discharges, during which a section of the void surface is discharged only. In contradiction to the assumptions of the abc-model nearly no difference was observed between the PD inception and extinction voltage, indicating a high and rapidly decaying remanent charge.Thus, the abc-model assumption of each PD causing a complete void discharging is only fulfilled if the surfaces are conducting, or the voids are small. The results indicate that changes of internal conditions of the void during the period of PD measurements

Understanding the influence of nano micro filler on electrical and mechanical behaviour of epoxy nanocomposites

The study of epoxy nano micro composites clearly indicates that the material has better dielectric properties with a good discharge resistance and less surface charge accumulation on its surface. The impact of high-frequency AC voltage and the percentage of ripple content in DC voltage on corona inception caused by water droplets was analyzed. Under a high frequency, the variation in the shape of the water droplet is the same as that under 50 Hz AC voltage. The UHF signal radiated due to water droplet initiated discharges have signal bandwidth in the range of 300 MHz-3 GHz. The influence of corona discharge on surface properties of the material, its variation to contact angle and water droplet initiated corona activity under AC voltage was analyzed. The surface potential characteristics were altered with corona-aged specimen. The impact of an ion-trapping particle on nanocomposites clearly exhibits its characteristics through surface potential studies. Water diffusion into the insulating materials varies with the type of filler material. The temperatures measured during arcing, analyzed through laser-induced breakdown spectroscopy (LIBS), were correlated with the hardness of the material. In addition, the mechanical properties, especially storage modulus and tan δ, were analyzed through dynamic mechanical analysis (DMA) studies.

A Study of Carteria sp. Cell Electrical Lysis in Straight and Tapered Microfluidic Systems

Electrical cell lysis is one of the most efficient techniques in cell analysis in extracting intracellular components for further use or examination. Cells are exposed to high electric field strength that can rupture cell membrane due to nano-size pores creation. Thanks to microfabrication technology, electrodes can be materialized in close proximity to each other leading to high electric field strength with low applied voltage. In this study, two microfluidic systems were designed: straight and tapered systems. The straight channel was chosen due to the ease of fabrication, while the tapered channel was picked since it intensifies electric field strength in the tapered area. Finite element method was used to simulate electric field distribution inside the microfluidic systems and transmembrane potential (TMP) across cell membrane. In the experiment, green algae Carteria sp. which contains large amount of lipid was used in performing microfluidic electrical cell lysis. For 30 nm thick gold planar electrodes with 110 μm spacing fabrication, the simulated TMPs produced in both microfluidic systems exceed 0.2 V which is a threshold potential for pore generation in cell membranes when applying 34 Vp–p, 1000 Hz AC voltage. Only Carteria sp. cells were successfully lysed in straight microfluidic system after being exposed to high electric field strength for several minutes. Although electric field in the tapered region was higher than that of the straight microfluidic system, the cells were rushed out of the tapered region due to electrohydrodynamic effects.

Design and software implementation of solid state transformer

The work presented in this paper concerned with the analysis, design and software implementation of the Solid State Transformer as an alternative to the conventional power transformer. The proposed transformer aims to perform the same task as the conventional one with additional facilities and advantages. Three stages are considered to configure the Solid State Transformer. The first stage which is known as input stage and implemented using Vienna rectifier which converts the AC voltage of the main supply to a DC voltage. The second stage (isolation stage) step down the DC voltage to a lower level DC voltage. This stage consists of a single – phase five-level diode clamped inverter, 1 KHz step – down transformer and fully controlled bridge rectifier. The output stage (third stage) is a three-phase three-level diode clamped inverter which converts the low level DC voltage to a three-phase, 50 Hz AC voltage. Model Predictive Current Control has been employed for driving transformer’s stages. The gating signal is produced directly when the given cost function is minimized, therefore there is no need of any modulator. Behavior of the proposed structure is achieved by simulation which shows high quality power conversion with low Total Harmonic Distortion.

Comparative study on various dielectric barriers and their effect on breakdown voltage

Non-pressurised air is extensively used as basic insulation medium in high-voltage equipment. Unfortunately, an inherent property of air-insulated design is that the system tends to become physically large. On the other hand, the application of dielectric barriers can increase the breakdown voltage and therefore decrease the size of the equipment. In this study, the impact of dielectric barriers on breakdown voltage enhancement is investigated under both direct current (dc) and alternating current (ac) applied voltages. For this purpose, three kinds of dielectric barriers in two different high-voltage electrode structures are investigated. In the first structure, several experiments are carried out with four different electrode arrangements, keeping the inter-electrode gap constant while varying the position of the dielectric barrier between the electrodes. In the second structure, the inter-electrode gap is varied while the high-voltage electrode is covered with dielectric materials. The influences of different parameters such as inter-electrode spacing, electric field non-uniformity factor, and dielectric materials on the breakdown voltage are investigated for applied 50 Hz ac and dc voltages. In addition, a simulation model to approximately calculate the breakdown voltage is proposed and validated with the experimental results.

Micro converter with a high step-up ratio to drive a piezoelectric bimorph actuator applied in mobile robots

In this study, a micro converter for driving a piezoelectric actuator is designed and implemented. The converter can produce 100 V, 80 Hz AC voltage from 3.7 V DC voltage. With regard to the requir...

The Effect of DC Electro-thermal Ageing on Electrical Treeing in Polyethylene

Electrical treeing is among the main mechanisms responsible for electric breakdown in polymeric high voltage cables. In this paper, electrical treeing in electro-thermally aged low density polyethylene (LDPE) was evaluated by means of a real-time microscopic detection system. A wire – plane electrode test object with semiconducting tab was used in the study. The ageing was performed at a constant temperature of 80°C and an applied DC voltage of 10 kV of both polarities and lasted from 100 up to 800 hours. For testing the resistances to electrical treeing, tests were performed by applying 50 Hz AC voltage at a ramping speed of 0.5 kV/s. The obtained experimental results showed that mainly the thermal component of the ageing had an influence on electrical treeing parameters, namely on the initiation voltage as well as the shape and occurrence frequency of the trees. With an increase of the ageing time, the tree inception voltage gradually decreased.

Enhancement of Water Tree initiation due to residual and applied Mechanical Strain on XLPE Cables

This paper present results from laboratory water tree experiments performed on samples of commercial available 6/10 kV XLPE insulated cables. The main purpose of the investigation was to examine possible water tree enhancement, due to mechanical tension of the insulationDuring water tree ageing at 50 Hz AC voltage of 14 kV (E_max = 5.2 kV/mm) the cable samples were mechanically stretched at 1%, using both static and dynamic mechanical load varying at 0.1 Hz. In addition, thermal treatment indicated a total residual longitudinal mechanical strains of 6%, frozen in during th emanufacturing process.Both the density and growth rate of vented and bow-tie water trees was found to increase with increasing applied mechanical tension. During non-strained thermal treatment the axial length of cables was reduced by about 6%. The low density of vented trees originating from te outer insulation screen supports the assumption that frozen in compressive stresses at the outer insulation surface may balance the effect of applied strain.