Peak Value Of Voltage Research Articles

High Field and High Temperature Characteristics of Small Test Coil Using CVD-YBCO Tape for SMES

Magnetic field dependencies of the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of the IBAD/CVD-YBCO short tape sample and its small coil sample were measured in high fields, up to 18 T at 77 K. Compared with the Ic of the tape sample, the Ic of the coil sample at 0.1 muV/cm showed the same tendency in high fields. If YBCO tape is applied to a high-field coil application, the application should be operated at a temperature which is lower than 77 K. Using long CVD-YBCO tape, six stacked pancake coils were fabricated. Various current tests were conducted using one of these stacked coils. In AC current tests, thermal stability of the YBCO coil was estimated. When the peak values of AC current were 1.2 times higher than the maximum DC current in a thermal stable state, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dcmax</sub> , and the average electric field of the coil at the first triangular wave was about 10 times higher than 1 muV/cm criterion, the peak values of the built-up voltage did not tend to increase even after the 99th triangular wave current, and thermal run-away in the coil was not observed. In DC current with overlapped pulse current tests, the maximum peak current of the coil in a thermal stable state was obtained as a function of DC current and sweep time. It was 1.3 times higher than Ic and 1.4 times higher than I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dcmax</sub> in a test condition. These results indicate that the YBCO coil has high potential in short-time, over-current operations at high temperatures. In cases where built-up voltages did not disappear, they began to increase just after the coil currents reverted to the initial DC currents. It was found that DC current influenced the increasing speed of built-up voltages once the pulse current had decreased to zero.

An electronic meter for measuring the saving in electrical power

In electrical installation and building services engineering the power factor is a major consideration in efficient building or system operation. It is the measure of how effectively your equipment is converting electric current from power generation network to useful power output. Your industry can save money and gain other benefits when your power factor is high enough to avoid power factor surcharges on your electricity bills. For this purpose, this work presents an electronic circuit for the measurement of electrical energy. The design is based on a sample and hold method, which generates two DC signals. The first signal is proportional to the peak value of the line voltage, V m and the second signal is proportional to the instantaneous value of the line current at the instant of peak voltage, V m., i.e. I m cos Φ, where Φ is the phase angle between the line voltage and line current signals. Multiplication of the two signals over a predetermined period of time will provide an output proportional to the electrical energy consumed by the load. A voltage to frequency converter, VFC, is used to digitize the electrical energy signal. This signal is then digitally displayed through suitable circuitry. Results are presented to show the effect of a changing power factor on the power available at a constant current and the annual cost savings that can be made.

Progression of positive corona on cylindrical insulating surfaces. I. Influence of dielectric material

Experiments are described on the propagation of corona discharges over the surfaces of cylindrical PTFE and porcelain insulators under positive impulse voltages. A rod-plane electrode arrangement has been used to which a single value of peak voltage, with the same impulse profile, has been applied throughout. Quantities measured were inception times and voltages, corona current and light output at selected axial regions of the corona. Still photographs of the corona appearance have been taken. Comparison has been made between the surface corona and that in air alone. Interpretation is based on knowledge of the electric field profiles, as modified by the insulators and the possible effects of the surface on the discharge. These are discussed in terms of the presence or absence of charge attachment, the effects of the surface on electron production and the effect of the permittivity of the materials

Hysteresis of pulsed characteristics of field emission from nanocarbon materials

AbstractCharacteristics of pulsed‐field electron emission from nanocarbon films were investigated in experiments with a wide (1.5–5 mm) quasiplanar test gap. Parameters of the applied voltage (amplitude, shape and duration of pulsed component and d.c. bias) were varied; the maximum peak voltage value amounted to 40–45 kV. Dynamic I–V plots measured in 10–100 µs pulses combined inherent features of field emission (linearity in Fowler–Nordheim (FN) coordinates) with strong hysteresis. For the explanation of the latter, a model of emission via intermediate electron energy states is proposed. The simple quantitative model excellently agrees with the measured characteristics for different emitter samples and over a broad range of voltage parameters, but fails to simulate the phenomenon of emission efficiency boosting by fast voltage drops, also observed in the experiment. A possible mechanism of this dynamic effect may consist in the redistribution of electrons among the different field focuses at the nonuniform emitter surface under the effect of a strong nonstationary electric field. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Three Phase Three-Level PWM Switched Voltage Source Inverter With Zero Neutral Point Potential

A new three phase three-level pulsewidth modulation (PWM) switched voltage source inverter with zero neutral point potential is proposed. It consists of three single-phase inverter modules and each module is composed of a switched voltage source and inverter switches. The major advantage is that the peak value of the phase output voltage is twice as high as that of the conventional neutral-point-clamped PWM inverter. Thus, the proposed inverter is suitable for applications with low voltage sources such as batteries, fuel cells, or solar cells. Furthermore, three-level waveforms of the proposed inverter can be achieved without the switch voltage unbalance problem. Since the average neutral point potential of the proposed inverter is zero, a common ground between the input stage and the output stage is possible. Therefore, it can be applied to a transformerless power conditioning system. The proposed inverter is verified by a PSpice simulation and experimental results based on a laboratory prototype

Dynamic Performance of Surge Arrester Under Very Fast Transient Overvoltages

This paper studies the performance of Metal Oxide Surge Arrester (MOSA) for Gas Insulated Substation (GIS) applications. Few models proposed in the literature are used to describe the dynamic characteristic of the arrester and compared with experimental data to verify their accuracy. As percentage error is lesser in the case of a simplified IEEE model, for further analysis this model is chosen. MOSA of high-voltage rating have high stray capacitance, which cannot be neglected. The stray capacitance and zinc oxide block capacitance of the MOSA are calculated using Finite Element Method (FEM). In this study a 198 kV arrester is considered. By incorporating the effect of stray capacitance, we propose a new model. This model is analyzed for surges of different front times ranging from microseconds to nanoseconds. It is found that there is a delay to attain the initial peak value of residual voltage of the arrester due to the stray capacitance effect. The delay in the initial response time of the arrester may be one of the reasons for the failure of the arrester response in GIS when subjected to Very Fast Transient Overvoltage (VFTO). The use of guard rings allows delay due to the effect of stray capacitance to be minimized.

Response of thermoluminescent dosimeters to photons simulated with the Monte Carlo method

Personal monitors composed of thermoluminescent dosimeters (TLDs) made of natural fluorite (CaF 2:NaCl) and lithium fluoride (Harshaw TLD-100) were exposed to gamma and X rays of different qualities. The GEANT4 radiation transport Monte Carlo toolkit was employed to calculate the energy depth deposition profile in the TLDs. X-ray spectra of the ISO/4037-1 narrow-spectrum series, with peak voltage (kVp) values in the range 20–300 kV, were obtained by simulating a X-ray Philips MG-450 tube associated with the recommended filters. A realistic photon distribution of a 60Co radiotherapy source was taken from results of Monte Carlo simulations found in the literature. Comparison between simulated and experimental results revealed that the attenuation of emitted light in the readout process of the fluorite dosimeter must be taken into account, while this effect is negligible for lithium fluoride. Differences between results obtained by heating the dosimeter from the irradiated side and from the opposite side allowed the determination of the light attenuation coefficient for CaF 2:NaCl (mass proportion 60:40) as 2.2 mm −1.

Mechanism of voltage rise of high‐current arc at atmospheric pressure due to deion plates

AbstractA molded‐case circuit breaker has deion plates to raise an arc voltage. To understand the phenomenon of a rise in an arc voltage due to deion plates, an arc current, arc voltage, and voltages between the deion plates were measured for high‐current air arc. The peak value of the arc voltage rose with a decrease in distance between the deion plates and electrodes. This rise resulted from the voltages between the deion plates. The voltage between the deion plates was found to consist of two voltages: (1) an arc‐column voltage and (2) the voltage occurring between the arc column and the surface of the deion plates. These voltages (1) and (2) proved to be 2.3 V/mm and 25 V, respectively. On the basis of these results, the expression of the arc voltage affected by the arrangement of the deion plates was derived to be a function of current. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(3): 17–24, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10213

An approach to reduce common-mode voltage in matrix converter

In this paper, an approach to reduce common-mode voltage at the output of a matrix converter is discussed. A new modulation strategy which reduces the common-mode voltage at the output is presented. The proposed method maintains the active voltage vector and distributes zero vector equally within a sampling period and reduces square RMS of ripple components of input current. Advantages of the scheme include: 34% reduction in the common-mode voltage (peak value); improved harmonic spectrum; reduced switching losses and no more additional switching instants over one sampling period; and simplified implementation via software. Further, the voltage transfer ratio is unaffected by the proposed scheme. Simulation results are shown to demonstrate the advantages of the new pulsewidth modulation approach. Experimental results on a 230-V 3-kVA matrix converter-fed adjustable-speed drive based on a digital signal processor controller are presented.

Inter-ictal- and ictal-like epileptic discharges in the dendritic tree of neocortical pyramidal neurons.

Dendritic mechanisms have been implied to play a key role in the formation of epileptic discharges. However, presently only a handful of direct dendritic recordings have been reported during epileptic discharges. In this study, I performed simultaneous voltage recordings from the soma and apical dendrite of the same neuron combined with calcium-imaging measurements to investigate inter-ictal- and ictal-like epileptic discharges in dendrites of layer 5 pyramidal neurons. Neocortical brain slices treated with bicuculline (BCC) produced both isolated "inter-ictal" paroxysymal depolarization shift (PDS) responses and electrographic seizures. Concomitant voltage recordings from the soma and apical dendrite revealed that PDS responses developed in both the apical dendrites and soma. However, the two responses differed from one another. In apical dendrites, the PDS was significantly higher in amplitude and shorter in duration compared with the somatic PDS. The PDS response in dendrites had a peak amplitude of 68.9 +/- 2.2 (SD) mV, peak voltage value of 9.3 +/- 2.7 mV, and half-width of 203.8 +/- 38.4 ms. In contrast, the somatic PDS had a peak amplitude of 48.7 +/- 2.7 mV, peak voltage value of -11.9 +/- 3.1 mV, and half-width of 247.8 +/- 57.3 ms (P < 0.01, n = 18). In addition the apical dendritic PDS always preceded the somatic counterpart in all 18 neurons examined. Concomitant calcium-imaging measurements showed the PDS evoked large calcium influx into the entire dendritic tree including the apical tuft, basal, and oblique dendrites. The PDS evoked [Ca(2+)](i) were not uniform along the dendritic tree, being highest in the oblique dendrites (71.3 +/- 14.5 microM) and lowest at the distal tuft branches (9.3 +/- 0.7 microM). The PDS responses persisted after blockade of voltage-gated sodium channels by intracellular QX-314 but became narrower (by 69.6 +/- 9.7%) following intracellular administration of the voltage-gated calcium channel blocker D600. Electrographic seizures recorded in the soma and apical dendrites were composed of recurrent bursts. The initial bursts represented PDS responses. During the seizure the amplitude of bursts gradually attenuated and reached an average value of 26 +/- 13% of the initial ictal PDS burst. Double recordings during electrographic seizures revealed the initial one to four ictal bursts appeared first at the apical dendrite while later ictal bursts were always observed first at the soma. In conclusion, the results of this study show "inter-ictal" PDS responses originated in the apical dendritic tree, were partially mediated by voltage-gated calcium channels and spread throughout the dendritic tree including the fine tuft, basal, and oblique dendrites. During electrographic seizures the origin of epileptic bursts shifted from the apical dendritic tree to the soma-basal region.

Simultaneous switching noise in on-chip CMOS power distribution networks

Simultaneous switching noise (SSN) has become an important issue in the design of the internal on-chip power distribution networks in current very large scale integration/ultra large scale integration (VLSI/ULSI) circuits. An inductive model is used to characterize the power supply rails when a transient current is generated by simultaneously switching the on-chip registers and logic gates in a synchronous CMOS VLSI/ULSI circuit. An analytical expression characterizing the SSN voltage is presented here based on a lumped inductive-resistive-capacitive RLC model. The peak value of the SSN voltage based on this analytical expression is within 10% as compared to SPICE simulations. Design constraints at both the circuit and layout levels are also discussed based on minimizing the effects of the peak value of the SSN voltage.

Characteristics of a new non-invasive x-ray output analyzer

The X-ray systems study group used the Victoreen NERO mAx model 8000, a new non-invasive X-ray output analyzer, to measure the tube voltage, tube voltage waveform, tube current, and irradiation time for conditions corresponding to general radiography and mammography. The measurement results were then compared with those obtained using a conventional invasive measuring instrument. The peak values of the tube voltage measured by the NERO mAx and the invasive measuring instrument were compared. The NERO mAx had a good measurement error range of -1.2 to +0.9 kV. For tube current measurement by the NERO mAx, the maximum error for general radiography conditions was +11 mA and that for mammography conditions was +6 mA. For irradiation time measurement, the value for general radiography conditions was slightly greater and the value for mammography conditions was slightly less than the corresponding values obtained by the invasive measuring instrument. If radiation quality is changed during measurement of the characteristics, measurement values change. Since the NERO mAx incorporates two types of X-ray detectors, it shows good measurement reproducibility. The NERO mAx has been shown to have suitable characteristics for use as a measuring instrument for constancy tests. In the future, constancy tests should be used to quantitatively control the factors determining clinical image quality.

A fast and accurate distance relaying scheme using an efficient radial basis function neural network

The paper presents a new approach for classification and location of faults on a transmission line using a newer version of radial basis function neural network (RBFNN) which provides a more efficient approach for training and computation. The input data to the RBFNN comprise the normalised peak values of the fundamental power system voltage and current waveforms at the relaying location obtained during fault conditions. The extraction of the peak components is carried out using an extended Kalman filter (EKF) suitably modelled to include decaying d.c., third and fifth harmonics along with the fundamental. The fault training patterns required using the efficient version of RBF neural network are much less in comparison to the conventional RBF network and the choice of neurons and the parameters of the network are systematically arrived without resorting to trial and error calculations. The new approach provides a robust classification of different fault types for a variety of power system operating conditions with resistance in the fault path. Further a new fault location strategy is formulated using four neural networks, one each for the major category of faults like LG, LL, LLG and LLL faults. The proper feature selection for the networks results in an accurate and fast distance relaying scheme. © 2001 Published by Elsevier Science B.V.

The electrochromic properties of tungsten oxide thin films deposited by solution thermolysis

Tungsten oxide thin films were prepared by solution thermolysis (ST-WO 3). Films were deposited onto fluorine-doped tin oxide (FTO)-coated glass substrates maintained at 300°C, which were then used as working electrodes in a three-electrode electrochromic (EC) cell. The EC cell configuration was FTO/WO 3/0.1 N H 2SO 4/C, SCE. Cyclic voltammetry (C-V) was carried out in the potential range −0.7 to +0.7 V (SCE), at different scan rates. The values of anodic peak potential and threshold voltage are extracted from C-V. The diffusion coefficient of H + ions during intercalation and deintercalation are calculated. They are of the order of 10 −12 cm 2/s. Chronoamperometric (C-A) studies were carried out at different double potential steps and response times are calculated. The films before and after colouration were further characterized by optical absorption technique. The colouration efficiency at 633 nm is 25 cm 2/C. The ST-WO 3 films were found to be stable in 0.1 N H 2SO 4 up to 2×10 3 cycles.

Development of a high precision quadrupole mass filter using the zero-method control circuit

A high precision quadrupole mass filter has been developed using the zero-method control circuit. With this method, peak values of a control voltage are compared with a high-precision reference voltage and detected by a diode and signal-producing resistance connected in series. The dc component of the signal is selectively amplified and fed back to a module in the amplifying system of the rf voltage so as to minimize the voltage in excess of the reference voltage. An instrument has been constructed and the doublet of He+4–D2+ has been successfully separated.

A high-frequency model of an oil-immersed transformer, and its use in lightning surge analysis

A circuit model of an oil-immersed transformer for use in surge analyses in the high-frequency region is proposed, and its effectiveness is evaluated by comparison with measurements on a model winding. The circuit model is used for lightning surge analyses of a 500-kV substation, and the effect of transformer modeling on the lightning surge voltage at the transformer terminals is investigated. When the new circuit model is used for transformer modeling, the peak value of the surge voltage is lower but the rate of voltage rise is higher than in conventional transformer modeling by a lumped capacitance. This difference can be explained in terms of the charging of capacitances in the transformer model. © 2000 Scripta Technica, Electr Eng Jpn, 134(1): 28–35, 2001

Impulse breakdown of short rod–plane gaps and the influence of humidity

An attempt is made to assess the extent of influence of various parameters on the breakdown mechanism in short rod–plane gaps under positive impulses. Such parameters include front duration and peak value of the impulse voltage, gap length, profile of the rod and, in particular, absolute humidity. Depending on the above parameters, breakdown occurs either through a streamer-dominated breakdown mechanism or through one involving the development of a small leader. The second corona was found to predesignate which mechanism will take place, thus influencing the statistical behaviour of breakdown. Calculated humidity correction factors were found to be different from those proposed by IEC.

A field analysis of an overcurrent state and an incidental break in the secondary circuit of a current transformer

Considers the concerns of engineers designing overcurrent protection and measuring systems. Looks at the use of software to determine the instrument security fader with higher accuracy than with traditional calculation methods. An application of a space‐and‐time analysis makes it possible to calculate the peak value of the secondary voltage.

Optical study of active species produced by a pulsed streamer corona discharge in water

Various active species (· OH, · H, · O, 1O 2, · HO 2, O 2 −, etc.) can be formed by a pulsed streamer corona discharge in water and these active species may play an important role in the killing of bacteria and degrading of organic compounds. Therefore, it is necessary to identify the active species produced by the pulsed discharge and to investigate the effects of the discharge parameters on species production. In the present investigation, analysis of optical emission spectra was used for the detection of O, H and OH radicals, and the effects of the physicochemical parameters and discharge conditions on radical formation were studied. The influence of gas bubbling was also studied and compared with the case without bubbling. It was found that radical formation due to the streamer corona discharge was very dependent on the discharge conditions (applied voltage polarity and peak value, discharge electrode tip curvature radius) and on the physicochemical parameters (pH, conductivity of the water and additives). The radical density increased greatly when gas was bubbled in the discharge region. However, some O radicals were detected using both voltage polarities even when oxygen or inert gas was not bubbled in the discharge region.

負グローの周波数依存性についての研究

The performance of a Ne-Hg negative glow lamp (having no positive column) was measured at different frequencies. The results showed that the efficiency decreased as frequency increased. The plasma characteristics were measured by a Langmuir probe and spectroscope to analyze this phenomenon. The following results were observed:1. There were two groups of electrons, first electrons and second electrons, in this plasma, and there was a period without first electrons at high frequency.2. The energy of the second electrons at high frequency operation is lower than at low frequency.3. Peak energy of the first electrons at high frequency operation is higher than at low frequency.From these results we attribute the reason the efficiency of this lamp becomes lower at high frequency to the following.(1) The energy of the second electrons at high frequency operation is lower than at low frequency because the second electrons, which can get the energy only from electron-electron collision, but cannot get energy in the period without first electrons.(2) Ionization loss at high frequency operation is higher than at low frequency because the peak energy of the first electrons at high frequency operation is higher than at low frequency.Lastly the performance of negative glow, in a Ne-Hg lamp and Ar-Hg lamp with a positive column, was checked by observing the spectrum. The measurement results shows that there was no discrepancy to the conclusion that the peak value of cathode fall voltage at high frequency operation is higher than at low frequency.It has been reported that the cathode fall voltage at high frequency operation is lower than at low frequency. In this paper we found out that the m.r.s. of cathode fall voltage at high frequency operation was lower than at low frequency, but that the peak value of cathode fall voltage at high frequency was higher than at low frequency.