Hz AC Research Articles

Magnetic Field Measurement and Analysis of the CSNS/RCS Quadrupole Magnets

The China Spallation Neutron Source/rapid-cycling synchrotron (CSNS/RCS) quadrupole magnets excited by both dc current and 25 Hz ac biased dc current were tested and measured in the past two years. All the magnets had been installed in the tunnel by the end of December, 2015. The challenges of the field measurements included the measurement repeatability of the dc field and the time harmonic measurement of the dc+ac field. The paper will summarize the results of the dc field measurement and the dc+ac field measurement, the key techniques of the rotating coil fabrication and the measurement stability for the CSNS/RCS quadrupole magnets.

Space charge behavior in XLPE cable insulation under ac stress and its relation to thermo-electrical aging

The space charge features of cable insulation peelings are investigated under ac stress as a function of electrical aging imposed previously on cable sections. The investigated samples are 230-μm-thick peelings of crosslinked polyethylene cable insulation. The space charge profiles are resolved into 32 symmetric phase angles under 50 Hz ac stress. The space charge density in the phase angle of maximum applied field is the largest, as expected, but does not change visibly as a function of aging time. A method that involves averaging space charge in all phases is proposed. The all-phase averaged space charge, which appears in essence as stationary charge, exhibits an obvious increasing trend with stressing time. The aging characteristics of space charge formed under ac stress are investigated considering the all-phase averaged profiles, and the mechanical properties and degree of crosslinking are characterized as complementary methods. The change in the accumulation of space charge under ac stress follows opposite trends unlike the degree of crosslinking, which means that space charge under ac stress has a close relationship with defect concentration in cable insulation. This research contributes to the understanding of space charge features under ac conditions and the understanding of the ac aging principle of cable insulation.

Improved power quality based high brightness LED lamp driver

This paper deals with a power factor corrected (PFC) improved power quality based LED lamp driver. The proposed driver consists of a PFC Cuk DC-DC converter which operates in continuous conduction mode (CCM) to improve the power quality at input AC mains. The design, modeling and simulation of an 18W LED (six 3W LEDs in series) driver are carried out in MATLAB/SIMULINK environment for a 220V, 50 Hz AC mains with constant load voltage of 72V. Each LED has a forward voltage of 12V and a forward current of 0.25A. The power quality indices such as total harmonic distortion of AC mains current (THDi), power factor (PF), distortion factor (DF), displacement power factor (DPF) and crest factor (CF) are calculated to study the behavior of proposed LED lamp driver.Keywords: Continuous Conduction Mode (CCM), Cuk DC-DC Converter, Diode Bridge Rectifier (DBR), LED Lamp Driver, Power factor Correction (PFC)

Design and experimental evaluation of a single-stage AC/DC converter with PFC and hybrid full-bridge rectifier

This paper presents design and experimental evaluation of a single-stage AC/DC converter with PFC and hybrid full-bridge rectifier for supplying LED streetlight. The proposed converter consisted of one LLC resonant tank, two boost circuits and one shared inductor. By incorporating a relay switch at the secondary-side of the circuit, the output stage can be operated as two different types of rectifier: the first is as a full-bridge rectifier and the second type is as a full-bridge voltage doubler rectifier. The proposed converter was designed to receive a 240-V, 50-Hz single-phase AC supply as its input. MATLAB Simulink software was used to simulate the proposed converter, and later, a prototype was built for the experimental measurements at 100-W rated output power. The experimental results and the performance of the proposed converter were analyzed for PFC, efficiency, THD, and bus voltage. The proposed converter can achieve soft-switching characteristics since the power switches and output diodes were operated with ZVS and ZCS conditions, respectively. Furthermore, when the relay switch was closed, the output voltage was twice higher than that of when the relay switch was opened. The maximum efficiency of the proposed converter with hybrid full-bridge rectifier and full-bridge voltage doubler rectifier was about 92.6% and 93.3% respectively.

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.

Fuzzy peak current controlled integrated PFC convert-er with slope compensation

This propounded a novel method of design and implementation of a fuzzy peak current mode (PCM) controlled Buck Integrated Power Factor Correction (PFC) Converter with compensation ramp. It derives its advantages through low buck capacitor voltage and single control switch, which leads to reduced complex control and price. Sub-harmonic oscillations generates in peak current controller can be nullified by using ramp signal, there by improves the overall performance of the converter. The fuzzy controller (FLC) robust and effective than conventional linear controllers like P, PI, PID, hence in this work a (90 – 265V), 50Hz AC, 48V DC and 100 kHz frequency converter is implemented in MATLAB/Simulink software and results are presented. Results show that converter meets international regularity commission regulations.

Fuzzy LPCM controlled buck integrated PFC convert-er for Class-C&D appliances

This propounded a novel method of design and implementation of a fuzzy linear peak current mode (LPCM) controlled Buck Integrated Power Factor Correction (PFC) Converter. It derives its advantages through low buck capacitor voltage and single control switch, which leads to reduced complex control and price. Sub-harmonic oscillations generates in peak current controller can be nullified by using ramp signal, there by improves the overall performance of the converter. The fuzzy controller (FLC) robust and effective than conventional linear controllers like P, PI, PID, hence in this work a (90 – 265V), 50Hz AC, 48V DC and 100 kHz frequency converter is implemented in MATLAB/Simulink software and results are verified experimentally. Results show that converter meets international regularity commission regulations.

FLAXSEED OIL ALONE AND AS AN ADJUVANT WITH PHENYTOIN IN MES-INDUCED SEIZURES IN ALBINO RATS

Objective: The objective of this study to evaluate the anticonvulsant activity of flaxseed oil alone and as an adjuvant to phenytoin sodium.Methods: A total of 24 albino rats were used for this study. Four groups - control, standard (phenytoin sodium), test (flaxseed oil), and flaxseed oil along with phenytoin were made with six rats in each group. Maximal electroshock seizures 60-Hz AC of 150 mA intensity for 0.2 s were induced using an electroconvulsiometer with ear electrodes 60 min after oral drug administration. Duration of tonic hind limb extension (THLE) in seconds was used as a measure of seizures induced.Results: The mean duration of THLE in 4 groups was 11.66 (Group I), 5.67 (Group II), 3.85 (Group III), and 2.69 (Group IV). Duration of THLE was reduced in flaxseed oil group (P < 0.000) compared to both control and standard. Other parameters such as regain of righting reflex and recovery time also showed improvement. The group where flaxseed oil was used as an adjuvant to phenytoin also showed significant anticonvulsant activity. It showed a greater reduction in the parameters compared to either drug alone.Conclusion: The study showed that flaxseed oil possesses marked anticonvulsant activity when used alone and as an adjuvant to phenytoin. This study shows the potential of flaxseed oil in generalized tonic-clonic seizure.

Comprehensive approach to risk assessment and evaluation regarding constructioning of the first 25 kV 50 Hz AC traction power supply sections in Poland

Railway lines in Poland are either equipped with 3 kV DC traction system or not electrified for traction purpose. Presently maximum line speed is 200 km/h while maximum train speed is 250 km/h. Speeding up limit for 3 kV DC traction is estimated to be around 220-230 km/h. Already present in Poland trains for 250 km/h are equipped with three electric power supply systems: 3 kV DC used in Poland, 15 kV 16,7 Hz AC used in Germany, and 25 kV 50 Hz AC foreseen to be used in Poland on high speed lines. Introducing 25 kV 50 Hz AC traction power supply will be associated with safety challenges, which have to be taken into account already during constructioning, starting even at the predesigned phase. Two key questions arise. First of all question regarding methodology, which should be used for safety level acceptance and secondly how to ensure that all safety aspects will be taken into account. Answering first question for railway safety experts seems to be easy – let’s apply risk assessment and evaluation methodology described by EU regulation under Railway Safety Directive. The challenge is however to define risk acceptance criteria which will be required, and that is analysed in the paper. The second challenge is even more challenging. Author proposes using 10-by-10 safety matrix which was defined by the author in previous publications [9, 10]. Its concept as well as principles for its application for new type of power supply is also presented in the paper.

A Modulation Compensation Scheme to Reduce Input Current Distortion in GaN-Based High Switching Frequency Three-Phase Three-Level Vienna-Type Rectifiers

Wide bandgap semiconductors are gradually being adopted in high power-density high efficiency applications, providing faster switching and lower loss, and at the same time imposing new challenges in control and hardware design. In this paper, a gallium nitride-based Vienna-type rectifier with SiC diodes is proposed to serve as the power factor correction stage in a high-density battery charger system targeting for aircraft applications with 800 Hz ac system and 600 V level dc link, where power quality is required according to DO160E standard. To meet the current harmonic requirement, PWM voltage distortion during the turn-off transient, is studied as the main harmonics contributor. The distortion mechanism caused by different junction capacitances of the switching devices is presented. A mitigation scheme considering the nonlinear voltage-dependent characteristics of these capacitances is proposed and then simplified from a pulse-based turn-off compensation method to a general modulation scheme. Simulation and experimental results with a 450 kHz Vienna-type rectifier demonstrate the performance of the proposed approach, showing a THD reduction from 10% to 3% with a relatively low-speed controller.

An Integrated Control Strategy for a Fast Start-Up and Wide Range Input Frequency Operation of a Three-Phase Boost-Type PFC Converter for More Electric Aircraft

This paper presents an integrated control strategy to achieve fast start-up and enable wide input frequency operation in a three-phase six-switch power factor correction (PFC) converter. Limiting the inrush current with simultaneously minimizing the start-up time is achieved by implementing a nonlinear compensator in the voltage control loop. In addition, the concerning issues regarding unity PFC operation with an accurate reference tracking in a system with wide input frequency variation (typical for more-electric-aircraft) are resolved by a second-order compensator integrated with a state-feedback controller in the current loop. For a proof-of-concept verification, a hardware prototype of 6 kW, three-phase six-switch PFC is developed and tested with the proposed integrated control strategy in a wide source frequency range (360–800 Hz) ac input that shows perfect unity power factor operation throughout. Both the start-up time and inrush current are reduced to $ of their values in conventional PI compensation.

Phenomenology of Corona Discharge in Helium Admixtures Inside a Point-to-Point Electrode Geometry

Experimental investigations of the electrical discharge characteristics were performed primarily for helium admixtures in a point-to-point electrode geometry. The atmos- pheric pressure weakly ionized plasmas were generated using 60-Hz ac excitation voltage that generated a corona discharge without dielectric barriers on the electrodes. The admixtures used were helium/acetylene (He/C2H2), helium/oxygen (He/O2), and helium/dry-air (He/air) with comparisons made to corona discharges in an admixture argon/dry-air (Ar/air). Visual observations along with voltage–current characteristics have been presented. The discharge included streamers, glows, and return corona discharges inside the point-to-point high voltage gap. We developed from experimental data corona mode maps to delineate optimal regions for plasma operation in these admixtures. Helium carrier gas developed sufficient discharge power when mixed with acetylene, oxygen, or dry air. Peak discharge power was in the range 3–20 W and depended on the polarity of the voltage cycle being considered and depended also on chemical species in the admixture.

A Single-Stage Single-Switch Soft-Switching Power-Factor-Correction LED Driver

This paper proposes a new isolated single-stage single-switch soft-switching power-factor-correction (S6-PFC) driver without electrolytic capacitors for supplying light-emitting diodes (LEDs). In the proposed LED driver, all the semiconductor devices are soft-switched without employing any extra active switch. The leakage inductance of transformer acts as a resonant component so that the leakage energy is recycled. Soft-switching operation of the semiconductor devices together with absorption of the leakage energy improve the proposed driver efficiency. Furthermore, input current of the driver has very low harmonics resulting in high power-factor. Operating principles of the proposed S6-PFC LED driver as well as its design guidelines are presented. Also, experimental results of a laboratory prototype for supplying a 21 W/30 V LED module from 220 V/50 Hz ac mains are provided to verify the theoretical analysis. The presented results show that the implemented prototype has an efficiency of 92% under full-load condition and its input current total harmonic distortion is as low as 2.6%.

Effect of High Voltage Impulses on Surface Discharge Characteristics of Polyethylene

This paper investigates the influence of high voltage impulses on the surface discharge characteristics of polyethylene (PE) during subsequent application of 50 Hz AC voltage. The investigation is done on two types of PE to examine the generality of the phenomena. The effect of impulses on the surface discharge features of PE are studied for both cases of having either a streamer or flashover. For each case, the consecutive surface discharges behave differently when the insulation has been exposed to the transient voltages. The effect of impulses on surface discharge of PE is shown by the change of PD numbers and phase-resolved PD patterns. The results show a prompt change in the total number of discharges which decays with the time. After a surface flashover has occurred due to the impulse, the PD behaves quite differently compared to the similar case without flashover.

Electrical Treeing Behavior in Polyethylene Filled with Aluminum Oxide Nanoparticles

Electrical treeing behavior in low density polyethyleneand its nanocomposite filled with 1.0 wt% and 3.0 wt%aluminum oxide nanoparticles was investigated bymeans of a real-time microscope recording system and asynchronized partial discharge measurement. Forpreparing the nanocomposite, uncoated aluminum oxidenanoparticles with 99.5% purity (Nanodur, CAS 1344-28-1) were used. These were of almost spherical shapewith an average diameter of 45 nm. The test objectswere prepared in form of the wire-plane electrodegeometry [1]. The electrical treeing tests were carriedout by applying 50 Hz AC voltage at a ramping speed of22 V/s. The obtained experimental results indicate thatthe addition of the nanoparticles has a positive impacton the resistance to electrical treeing. Both the scale andthe shape of the distribution of the treeing initiationvoltage improved. The magnitude of partial dischargeactivity associated with the treeing in polyethylenenanocomposites was also lower than in the referencematerial.

Experimental study on breakdown voltage of high pressure and high temperature helium gas between parallel electrodes

The DC and 50Hz AC breakdown voltage of helium between two parallel copper electrodes were measured to obtain the base data for insulation design of the electrical equipment working in the high pressure and high temperature helium gas in High Temperature Reactor (HTR). The measurements were performed in the distance of 0.25–0.53mm, the temperature of 15–180°C, and the pressure of 0.05–7MPa. It has been proved that, for both DC and 50Hz AC, the breakdown voltage increases with the increasing of the pressure, with the increasing of the distance, and with the decreasing of the temperature. The DC breakdown voltage is about 1.4 times of the value of 50Hz AC or, in other words, is similar to the peak value of 50Hz AC. The Paschen law, describing the relationship between the breakdown voltage of helium (Ub) and the product of gas density and electrode distance (ρd), was presented for DC and 50Hz AC respectively, based on the experimental data at high pressure and high temperature. Good linearity is shown in the data. Furthermore, the linear fitting equation was also presented. The slope of Paschen curve about Ub-ρd at the range of large ρd is influenced by the collision cross section and the ionization energy of helium atom, and not influenced by the temperature, for DC. Both for DC and 50Hz AC, the slope of Paschen curve about Ub-ρd is about 6×105 times of the slope of Paschen curve about Ub-Pd, where Pd is the product of gas pressure and electrode distance. Both for DC and 50Hz AC, the breakdown voltage of helium is less than one fifth of the value of air, at 0.1MPa and room temperature. However, the breakdown voltage of helium at 180°C and 7MPa is larger than the value of air at 0.1MPa and room temperature.

Impact of alternative electrical stunning parameters on the ability of broilers to recover consciousness and meat quality

Broilers in the United States are typically electrically stunned using low voltage-high frequency (12–38 V, ≥400 Hz) DC or AC water bath stunners. In the European Union, however, broilers are required to be electrocuted using high voltage-low frequency (50–150 V, 50–350 Hz) AC. Low voltage stunned broilers regain consciousness in the absence of bleeding. In contrast, high voltage stunned broilers die due to induction of cardiac fibrillation. For birds stunned with low voltage systems, concerns have been raised regarding animal welfare during bleeding. This work evaluated the impact of extended DC stunning duration and alternative stunning methods (DC+AC combination) on the recovery of bird consciousness and meat quality. In the absence of bleeding, broilers that were DC stunned for extended times (60, 90, or 120 s), 63, 10, or 0% of broilers, respectively, were able to recover consciousness. Alternative stunning protocols included water bath stunning broilers at 15 or 25 V DC for 10 s followed by plate stunning at 100, 110, or 120 V AC for 5 s. Prior to shackling, live body weight and shank width were measured and during stunning, maximum mA for both DC and AC stuns were recorded. All of the alternative stunning protocols (DC+AC) resulted in non-recoverable stunning. The maximum mA recorded during both DC and AC stunning were moderately/strongly (r = 0.54–0.81) correlated to body weight and poorly/moderately (r = 0.27–0.74) correlated to shank width. No significant differences for carcass or meat quality characteristics (hemorrhages, red wing tips, broken clavicles, pH, cook loss, a* and b* color values, and MORS shear energy) were detected between control (15 or 25 V DC only) and treatment groups (DC+AC combination stunning). The only significant different meat quality parameter was L* values where the lowest voltage group (15 V DC) had the darkest fillets (53.27) and the 15 V DC+100 V AC group had the lightest fillets (55.61) with all other groups intermediate. These data indicate that stunning parameters combining DC and AC stunning may be viable protocols when a stun-to-death is desired.