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Power conditioning system (PCS), which provides matched pulse energy for the amplifier, is the key subsystem of a giant solid-state laser facility. It consists of many power conditioning modules (PCMs). Some of the catastrophic faults such as capacitor short-circuit, high voltage cable head short-circuit, or high and low voltage busbar short-circuit, might occur when there is high voltage in the PCMs. To analyze these cases, first, the model of a PCM was proposed. Second, three main faults of a PCM were introduced and the models of them were built. Third, a PCM experimental device with ten xenon lamps in parallel was designed and built, and the experimental results verified the effectiveness of the proposed model. In this article, three fault simulation results were analyzed and the security design recommendations were presented, which can provide reference value for the design of such power system. [ABSTRACT FROM AUTHOR]

Erosion resistance of electrode materials is one of the key factors affecting the performance and working life of gap switches. In order to explore whether the electrode material with added nanoscale metalloid particles has better erosion resistance under the strong pulse current, a strong current discharge platform was built, and W80/Cu and W80/Cu–Al2O3 were selected as the research objects. The experimental study was carried out under a strong pulse current with a peak value of over 100 kA. By comparing the mass change, the microtopography, and surface roughness of the erosion area, it was found that the addition of nano-Al2O3 particles improved the erosion resistance of the W–Cu alloy. The anode loss was down about 14.7% slightly after adding Al2O3, and the cathode loss of W80/Cu–Al2O3 was down about half. The addition of Al2O3 will increase the working life by 25.3%. Besides, the microstructure of the erosion area became flatter and the roughness was reduced. [ABSTRACT FROM AUTHOR]

Optimal selection of features of Partial Discharge (PD) signals recorded from defects in High Voltage (HV) cables will contribute not only to the improvement of PD pattern recognition accuracy and efficiency but also to PD parameter visualization in HV cable condition monitoring and diagnostics. This paper presents a novel Random Forest (RF)-based feature-selection algorithm for PD pattern recognition of HV cables. The algorithm is applied to feature selection of both PD signals and interference signals with the aim of obtaining the optimal features for data processing. First, the experimental data acquisition and feature extraction processes are introduced. PD signals were captured from faults created in a cable to obtain the raw PD data, and then, a set of 3500 transient PD pulses and a set of 3500 typical interference pulses were extracted, based on which 34 PD features were extracted for further processing. Furthermore, 119 two-dimensional features and 1082 three-dimensional features were generated. The paper then discusses the basic principle of the RF algorithm. Finally, RF-based feature selection was implemented to determine the optimal features for PD pattern recognition. The results were obtained and evaluated with the Back Propagation Neural Network and Support Vector Machine. Results show that the proposed RF-based method is effective for PD feature selection of HV cables with the potential for application to additional HV power apparatus. [ABSTRACT FROM AUTHOR]

It is a great challenge to differentiate partial discharge (PD) induced by different types of insulation defects in high-voltage cables. Some types of PD signals have very similar characteristics and are specifically difficult to differentiate, even for the most experienced specialists. To overcome the challenge, a convolutional neural network (CNN)-based deep learning methodology for PD pattern recognition is presented in this paper. First, PD testing for five types of artificial defects in ethylene-propylene-rubber cables is carried out in high voltage laboratory to generate signals containing PD data. Second, 3500 sets of PD transient pulses are extracted, and then 33 kinds of PD features are established. The third stage applies a CNN to the data; typical CNN architecture and the key factors which affect the CNN-based pattern recognition accuracy are described. Factors discussed include the number of the network layers, convolutional kernel size, activation function, and pooling method. This paper presents a flowchart of the CNN-based PD pattern recognition method and an evaluation with 3500 sets of PD samples. Finally, the CNN-based pattern recognition results are shown and the proposed method is compared with two more traditional analysis methods, i.e., support vector machine (SVM) and back propagation neural network (BPNN). The results show that the proposed CNN method has higher pattern recognition accuracy than SVM and BPNN, and that the novel method is especially effective for PD type recognition in cases of signals of high similarity, which is applicable for industrial applications. [ABSTRACT FROM AUTHOR]

Compressed air is used in spark gap switches as an insulating gas. Triggered by nanosecond pulsed voltage, the streamer bridges the electrode gap in the switch. During the streamer-arc transition, the spatial distribution of the arc changes drastically. The nitrogen and oxygen in the compressed air will react with each other under high temperatures. Damaging effects in the switch are caused by arc reaction. In this paper, by adjusting the parameters of the high-energy pulse discharge circuit, the arc is produced with different current waveform in the spark gap switch, while the gaseous product is analyzed. The results show that, when current pulse-width remains constant, the amount of transferred charge is approximately linear with the production of nitrogen oxides. The proportion of NO is higher when the current pulse-width is shorter. The concentration of nitrogen oxides is determined by the chemical reaction, which relies on the dynamic change of the impulse arc. During the arcing time, there is the collision dissociation reaction in the local thermodynamic equilibrium (LTE) plasma, leading to the production of gas atoms and excitation molecules. In the boundary of the arc channel, the nitrogen oxides formation reactions mainly occur in the arc quenching period. According to the characteristics of the high-current arc, a simplified analysis of chemical kinetics on the reactions of nitrogen and oxygen is implemented to expound the effect of pulsed arc on the gas composition. [ABSTRACT FROM AUTHOR]

This paper proposes an active resonance circuit based on multiple series gaps (MSG) with voltage-dividing network and self-charging trigger device. The working principle of active resonance circuit, MSG, and triggering device is described in detail. To determine the optimal parameter setting of MSG, the effects of the voltage frequency, equalizing resistance, and voltage-dividing capacitance on the voltage distribution of MSG are analyzed by simulation. To realize the interrupting process of short fault current and determine the operation requirements of the main devices of precharge direct current (dc) circuit breaker, a simulation model of interrupting short fault current is performed. Furthermore, an experiment of four-series gaps is presented to verify the turn-on characteristic of the MSG and an experiment of artificial current zero is set up to testify the feasibility of the active resonance circuit. The simulation and experimental results show that the active resonance circuit proposed in this paper can generate an artificial zero current and is suitable for precharge dc circuit breaker. [ABSTRACT FROM AUTHOR]

As a rule, the site pollution severity (SPS) is determined by the ESDD and NSDD of cap and pin standard disc insulator (reference insulator) under de-energized conditions. But now standard disc insulators are seldom used on transmission lines. In order to determine the SPS of certain districts, it is essential to figure out the coefficient of conversion from ESDD and NSDD of reference insulators to that of other profiles of insulators. Moreover, pollution condition prediction may require the quantification of insulator pollution characteristics. For the reasons above, a one-year-period natural pollution experiment of de-energized insulators was carried out in Henan, China. For the first time, the Dixon test is introduced to detect the outliers among the natural contamination data, which contributes to unveiling the data's law. The coefficient of conversion is defined as the relative contamination coefficient in the paper, which is based on the ratio of the contamination data of a certain type of insulator to that of the reference insulator. The Shapiro-Wilk test and normal quantile (Q-Q) plot testify the normality of the relative contamination values. Based on the normality of relative contamination values obtained in the experiment, the insulator pollution characteristic is quantified. Via the relative contamination coefficients, it is easy to judge the contamination accumulation difficulty between insulators and predict the pollution condition of most profiles of insulators. Moreover, a determination method of SPS is raised in the paper, which helps to reckon the pollution condition of one type of insulator on the basis of the known pollution condition of insulators of other types. Besides, the pollution discrepancy between the top and bottom surfaces of insulators is analyzed by the relative contamination values. [ABSTRACT FROM AUTHOR]

A 700-kA gas switch with graphite electrodes for pulsed power supply module has been developed. This paper describes the design, construction, and testing of the high-current gas switch and its trigger system. The two-electrode gas switch is selected, which suffers high peak and fast rise time currents. The trigger generator based on resonant charging of a pulse transformer is constructed to trigger the gas spark. An electrodynamic force model of switch electrodes is established. The electrodynamic force of connecting wires is also calculated. By comparison of the mechanical strengths of polyformaldehyde, epoxy, and fiber-reinforced plastic (FRP) rods, where FRP rods are selected as switch rods, the experimental results show that the mechanical strength of the switch increases by 200%. Extensive electric testing has proven the operating parameters of the switch and its trigger system. The experimental results show that the measured discharge current waveform is demonstrated to be over a 700-kA peak current and a 500- \mu \texts pulsewidth. The transfer charge per shot is more than 500 C. [ABSTRACT FROM PUBLISHER]

Fault diagnosis of power transformers is crucial to the healthy operation of transformers. In order to enhance its accuracy and reliability, a new fault diagnosis method based on Set Pair Analysis (SPA) and association rules was proposed in this paper. Via analyzing the relationship of fault symptoms and fault types, the corresponding association rules could be established. Via computing the support degrees and confidence degrees of the association rules, the constant weight coefficient of each symptom and the variable weight coefficient of each type could be obtained. The diagnosis method could avoid the subjective defects effectively. Via introducing the concept of subordinate degree, the connection degrees of each fault type and the whole running state of transformer could be obtained. This method could also improve the accuracy of uncertainty factors of transformer fault diagnosis. Experimental results of the test substation proved this method had a higher accuracy by comparing with both association rules and SPA. [ABSTRACT FROM PUBLISHER]

Air-core Tesla transformer combined with semiconductor devices can generate repetitive high-voltage pulses effectively. Air-core Tesla transformer of spiral type is suitable for repetitive operation since its primary voltage is relatively low. Based on the double resonance circuit of air-core Tesla transformer, the expressions of secondary voltage, primary current, and the maximum rise-rate of primary current are deduced. The effects of tuning characteristic on the output voltage and energy efficiency are simulated, and further verified by experiments. An air-core Tesla transformer prototype of spiral type is developed. To achieve repetitive operation, a resonant charging and discharging circuit based on air-core Tesla transformer is designed. The repetitive system based on this prototype can generate microsecond pulses with an average peak voltage of -140 kV at 300 Hz repetition rate. In repetitive mode, the tuning ratio is recommended to range in 1.0-2.0 to achieve high energy efficiency. The output voltage could be higher by increasing the charging voltage or tuning ratio. [ABSTRACT FROM PUBLISHER]

Two-electrode graphite spark gap switch (TGSGS) is used as the main discharge switch and triggered by a reliable trigger generator in pulsed power conditioning system (PPCS). There would be 108 energy modules in PPCS working at the same time. The reliable operating and jitters of the trigger generators will have impact on the PPCSs performance. In this paper, the working modes of the TGSGS are discussed and the performance of trigger generators in PPCS is tested and presented. A protection strategy of the trigger generator in PPCS is introduced, and effect of the blocking capacitor on the trigger pulse transmission is analyzed and tested. The protection strategy of the trigger generator based on blocking capacitor and fuse can effectively prevent the energy anti-irrigation failure when the pulse transformer core saturated. The blocking capacitor has some effect on the trigger pulse transmission, and has the larger capacitance, getting the higher peak amplitude on the cathode of the TGSGS. It is tried to discuss the working characteristics of the thyristors, and proposes a selection reference of the thyristors in this and other similar applications. The combination of analysis and measurement would be useful for the selection of thyristors and other components. [ABSTRACT FROM PUBLISHER]

Fe-based nanocrystalline (FE-N) cores are widely used in pulsed-power and power electronic systems. In this paper, FE-N cores with high and low residual flux were tested and compared under single impulses. The loss density and permeability of the two FE-N types are evaluated in the usable flux swing range of \(\sim 0.0\) –1.4 T, and a range of magnetization rates of \(\sim 1.0~\mu \) s–6.0 T/ \(\mu \) s. When the loss density and average relative permeability are evaluated for magnetization from initial point to positive saturation based on the initial magnetization curves, the FE-N with low residual flux has lower loss density and larger average relative permeability than the one with high residual flux under low magnetization rates. The loss density and average relative permeability of the two FE-N types are almost the same values under high magnetization rates. The application of the measured results in magnetic switch design and performance analysis is presented. The presented results of the two FE-N cores can be aided in the practical magnetic designs of magnetic switches, pulse transformers, and inductors, but not restricted to those. [ABSTRACT FROM PUBLISHER]

Condition assessment for power transformer requires not only integrating the known artificial intelligence (AI) technology, but also exploiting the interrelation of the measured data. According to the association rule of information data and the variable weight synthesizing theory of factor spaces, an assessment method of transformer condition was proposed in this paper. Via analyzing the interrelation of the independent status parameters (ISP) and transformer fault types, the set of synthetic status parameters (SSP) can be built up. For avoiding interference from subjective experience, association rule theory was used to calculate the constant weight coefficients (CWC) of the ISPs. Since the true transformer condition may not always be accurately reflected under the condition of CWCs of a few SSPs, the method of variable weight synthesizing was used for computing the variable weight coefficients (VWC) of the SSPs. Then, combining with the existing maintenance procedures, a preferable condition assessing system of power transformer was proposed. Operational example proved the condition assessing system may reflect the real operation condition of power transformer. [ABSTRACT FROM PUBLISHER]

Starting from the updated requirements of an advanced laser system, a switch–trigger system for a 2.0-MJ pulsed power supply (PPS) module is developed. This paper discusses the design, construction, and testing of this switch–trigger system. The two-electrode construction for the spark gap switch is selected because of its superiority in terms of long working life, high peak currents, and fast rise time of currents. The trigger generator based on resonant charging of a pulse transformer is constructed. A magnetic isolator and a pressure controller are the auxiliary equipment of this system. In the section based on mathematical principles, the equations of the lifetime and stability of this spark gap switch with graphite electrodes are given. These expressions can be regarded as the design basis of the same type of switch. As for the trigger generator, the analysis states that an appropriate ratio can be obtained when using the resonant charging based on a core-type pulse transformer. The charging time is dependent on the leakage inductance and the capacitance of the primary and secondary capacitors. Extensive testing proves the operating parameters of the switches and the trigger generator. The measured discharge current waveform of the 2.0-MJ capacitive PPS module is demonstrated to be over 500 kA peak current and 500 \mus pulse width. The life test proves that the switch–trigger system can support more than 200 kC transfer charge. By replacing the electrodes, the lifetime of this switch can be extended furthrer. [ABSTRACT FROM PUBLISHER]

The development of a three-electrode trigatron gap with the trigger electrode inside the main electrode is discussed in this paper. Two models of the operation mechanism are proposed to explain the breakdown in the trigatron gap. In addition, a mathematical model was proposed to calculate the breakdown time based on the theoretical analysis. The influence of different parameters on the breakdown time is discussed. Some characteristics in dry air have been experimentally determined such as the influence of the air pressure and the influence of the undervoltage ratio on the spark gap operation. The experimental results show that the operating voltage range between 0.5 and 0.7 might be reasonable. Then, the experimental results and analysis demonstrate that there are three regions divided by two inflection points, and the corresponding values of the undervoltage ratio are threshold values presenting different breakdown processes. [ABSTRACT FROM PUBLISHER]

The limited lifetime in a high current is the main drawback of spark-gap switches. Electrode replacement is an easily suggested method to extend the lifetime. In order to perform electrode replacement, thermal damage caused by heating effect should be prevented at the static electrical contact interfaces between the electrodes and the holders. Based on the Holm model, the Hertz formula, and the heat conduction theory, a mathematical model of the contact temperature rise is proposed in this paper. This mathematical model can prove quantitatively that the pulse-current integral (action integral), material physical properties, and mechanical characteristics of spark-gap switches are key parameters affecting the temperature rise. The action integral is determined by the electrical parameters. Material physical properties include the thermal conductivity, the specific heat, the density, the electrical resistivity, the elasticity modulus, and the Poisson ratio. Mechanical characteristics of spark-gap switches include the contact radius/area, the contact force, and the contact surface roughness. The implementation of electrode replacement depends on the reasonable configuration of these key parameters. The experiments in a 1.2-MJ power supply module give that the phenomenona correspond with our analysis. Based on the analysis in this paper, an electrode holder structure is proposed as a practical solution for extending the useful lifetime of spark-gap switches with graphite electrodes. [ABSTRACT FROM PUBLISHER]

High-power closing switches with graphite electrodes have been used in power-supply system for a large laser pump. The useful lifetime of this kind of switch is an interesting and important issue. Previous researchers have observed that the graphite erosion loss is proportional to the amount of transfer charge in a high-power pulsed discharge. Therefore, the erosion rate of graphite may be used for predicting and estimating the electrodes' useful lifetime. According to the mathematical model proposed in this paper, the lifetime of a closing switch with graphite electrodes is dependent upon several key parameters, including the dimensions of electrode, density, the erosion rate of graphite electrodes, undervoltage ratio, working temperature, and the amount of energy transfer. A mathematical formula describing the relationship between lifetime and those parameters has been deduced. Based on a newly developed spark-gap switch which can support over 100-C single transfer charge, this proposed lifetime model has been verified. This paper may quantitatively perform the function of guidance in engineering applications of graphite electrode switches in large pulsed-power facilities. [ABSTRACT FROM AUTHOR]

In this paper, starting from the project requirements, a 1.2-MJ pulsed power supply (PPS) module for a high-power laser system has been developed. The main circuit of this module consists of a high energy density capacitor bank, a spark gap switch, a magnetic switch, a trigger generator, and a load subsystem. Due to the superiority in the stability and service life, the two-electrode construction for the spark gap switch, high peak currents, and rise time of the currents is selected. Since a two-electrode spark gap switch has no separate trigger electrode and must be directly overvolted by the trigger generator, a small Marx generator has been designed and constructed for the advantage of the proven compactness and electrical performance. The effect of the magnetic switch represents a couple of functions. One is to block the triggering pulse produced by the Marx generator. Another is to permit the discharging current coming from the main capacitor bank. Finally, the measured discharge current waveform of the 1.2-MJ capacitive PPS module is demonstrated to be over a 300-kA peak current and a 500- \mu\s pulsewidth. Moreover, the life test has proved that the switch–trigger system can support more than 1500 discharging processes. [ABSTRACT FROM AUTHOR]

A miniature amplitude-shift-keying (ASK) demodulator without any passive elements, i.e., R or C, for low-frequency applications is presented in the paper. The noise margin of the envelope detector in the proposed ASK demodulator is enlarged such that any Schmitt trigger or current limiting resistor is no longer needed. It results in the number of transistors required for the ASK demodulator circuit is reduced to 12, while the area is merely 0.003025 mm² using 0.35-µm 2P4M CMOS process. The power consumption is found to be 1.01 mW by physical measurement on silicon. The data rate is measured to be 250 kbps for 2-MHz carrier frequency and 27% modulation index. [ABSTRACT FROM AUTHOR]

This brief presents the design and implementation of a clock-and-data recovery (CDR) design for low-voltage differential signals (LVDS) transceiver operations. Instead of using an oversampling scheme which requires a high-speed clock generator, we adopt an interpolation scheme which relaxes the demand of a high-speed phase-locked loop with very high precision. A dual-tracking design is proposed to precisely align both edges of a data eye. Hence, the center of a data eye can be optimally sampled. A standard foundry 0.25-μm 1P5M CMOS technology is used to realize the proposed dual-tracking CDR for 7 x 100 (bit-MHz) LVDS signaling. The post-layout-extracted simulation reveals that the worst-case jitter of the sampling clocks is less than 450 ps (peak-to-peak) and 250 ps (rms) at all process corners. [ABSTRACT FROM AUTHOR]

This work addresses the problem of finding boundary points in multidimensional data sets. Boundary points are data points that are located at the margin of densely distributed data such as a cluster. We describe a novel approach called BORDER (a BOundaRy points DEtectoR) to detect such points. BORDER employs the state-of-the-art database technique-the Gorder kNN join and makes use of the special property of the reverse k nearest neighbor (RkNN). Experimental studies on data sets with varying characteristics indicate that BORDER is able to detect the boundary points effectively and efficiently. [ABSTRACT FROM AUTHOR]

A novel low-power and small-area digital I/O cell is proposed in this work. The new input/output (I/O) cell drastically reduces the I/O power consumption, which has been considered as the major power dissipation of the whole chip. The maximum operating clock is 500 MHz given a 10-pF offchip load. On top of the power saving feature, the proposed cell occupies merely 10535.2 = 4167.45 (transmitter) + 6367.8 (receiver) μm² which is far less than any prior commercially available I/O and low-voltage differential signaling I/O cells. Physical measurements of the proposed I/O cells show that the delays of the transmitter and the receiver are 1.1 and 1.8 ns, respectively. The largest power/bandwidth of the proposed design is 38.9 μW/MHz when transmitting. [ABSTRACT FROM AUTHOR]

New clinical studies suggest that narrowing of the retinal blood vessels may be an early indicator of cardiovascular diseases. One measure to quantify the severity of retinal arteriolar narrowing is the arteriolar-to-venular diameter ratio (AVR). The manual computation of AWL is a tedious process involving repeated measurements of the diameters of all arterioles and venules in the retinal images by human graders. Consistency and reproducibility are concerns. To facilitate large-scale clinical use in the general population, it is essential to have a precise, efficient and automatic system to compute this AVR. This paper describes a new approach to obtain AVR. The starting points of vessels are detected using a matched Gaussian filter. The detected vessels are traced with the help of a combined Kalman filter and Gaussian filter. A modified Gaussian model that takes into account the central light reflection of arterioles is proposed to describe the vessel profile. The width of a vessel is obtained by data fitting. Experimental results indicate a 97.1 % success rate in the identification of vessel starting points, and a 99.2% success rate in the tracking of retinal vessels. The accuracy of the AVR computation is well within the acceptable range of deviation among the human graders, with a mean relative AVR error of 4.4%. The system has interested clinical research groups worldwide and will be tested in clinical studies. [ABSTRACT FROM AUTHOR]

A low-cost video decoder for NTSC signals is described in this paper. The proposed NTSC video decoder design employs a 2D2L comb filter, and a DDFS (Direct Digital Frequency Synthesizer) -based DCO (digital control oscillator) based on a trigonometric quadruple angle formula in a digital PLL to track and lock the demodulation clocks. The complexity of the digital video decoder is consequently drastically reduced. The overall cost of the proposed design is 7.22 mm² (26 K gates). The maximum power dissipation is 109.2mW at the highest clock rate which is 21.48 MHz. [ABSTRACT FROM AUTHOR]

Addresses a linear-matrix inequality based strictly-positive-real (SPR) characterization and its application to absolute stability problem for discrete-time descriptor systems. Use of the Cayley transformation to establish formulas bridging the admissible descriptor form realizations for SPR and strictly-bounded-real transfer matrices; Application of the obtained result to the absolute stability problem.

This paper describes the feasibility of selecting fractal feature vector based on M-band wavelet transform to classify ultrasonic liver images-normal liver, cirrhosis, and hepatoma. The proposed feature extraction algorithm is based on the spatial-frequency decomposition and fractal geometry. Various classification algorithms based on respective texture measurements and filter banks are presented and tested. Classifications for the three sets of ultrasonic liver images reveal that the fractal feature vector based on M-band wavelet transform is trustworthy. A hierarchical classifier, which is based on the proposed feature extraction algorithm is at least 96.7% accurate in the distinction between normal and abnormal liver images and is at least 93.6% accurate in the distinction between cirrhosis and hepatoma liver images. Additionally, the criterion for feature selection is specified and employed for performance comparisons herein. [ABSTRACT FROM AUTHOR]

A spindle-shaped diffuse plasma cage is represented by photoreportage in the room-temperature atmospheric-pressure air. It is found that a closed plasma cage covered with diffuse plasma can be obtained only in an appropriate ring-ring electrode distance. By adjusting the ring-ring distance, we can destroy the closure property characterized by the appearance of corona or arc discharge on the surface of the cage. In addition, much larger plasma cage can be acquired using larger rings or adding more rings. [ABSTRACT FROM PUBLISHER]

The impact of the wire length on the large-scale diffuse discharge is investigated. The images and electrical measurements show that for a nanosecond pulse with a long tail, the decrease of the wire length can result in the transition from a diffuse mode to a spark discharge. [ABSTRACT FROM PUBLISHER]

This paper illustrates an observation of large-scale cold plasma generated by repetitive nanosecond pulses and barrier-free wire electrodes in atmospheric air. The length of plasma tape achieved 110.0 cm and can be further lengthened. The applied repetitive nanosecond pulses are with \(\sim 30\) -ns rise time, negative \(\sim 70\) -kV peak, and \(\sim 750\) -ns width at the 500-Hz repetition frequency. The discharge images indicate that the large-scale homogeneous nonthermal plasma in open air can be stably formed with appropriate conditions. [ABSTRACT FROM PUBLISHER]

Analysis of breakdown mechanism in gas-insulated trigatron switches is important for the engineering design and function prediction. Based on the gas discharge theory, a physical model was proposed to estimate the breakdown time for gas-insulated trigatron switches. And the model can explain the breakdown in the trigatron switches with two modes of the breakdown mechanism, i.e., fast breakdown mode (FBM) and slow-breakdown mode (SBM). Based on Raether breakdown criterion, this paper discussed the factors affecting on the E-field enhancement. The E-field is composed of the static E-field and the dynamic E-field, which leads to transformation of breakdown mechanism. Some coefficients could be determined by experiment and simulation, which are helpful to get the quantitative solution of breakdown time. [ABSTRACT FROM AUTHOR]

Working characteristics of a three-electrode trigatron spark gap is discussed in this paper. Breakdown probability is proven to fit a Weibull distribution. For an engineering application, the lower limit of undervoltage ratio depends on breakdown probability, and the upper limit of undervoltage ratio depends on self-breakdown probability. Some characteristics have been determined experimentally, such as the influence of the air pressure and the influence of the undervoltage ratio on spark gap operation. Curve fitting and quasi-data mining are good methods for research on triggering characteristic in the paper. Therefore, a maximum operation range curve and a boundary line of expected delay time could be determined by application requirements, theory calculation, experimental data and curve fitting. On this basis, optimization operation range could be obtained, which represents a preferable performance of breakdown with expected delay time. It may provide guidance for engineering application. [ABSTRACT FROM AUTHOR]

In a high-power laser facility with multiplex power modules, the dispersion of self-breakdown voltages of spark gap switches might result in a so-called pre-fire problem. Pre-fire probability of spark gap switches with graphite electrodes must be constrained at extremely low level. In this paper, Pedersen model was used to explain the causes of pre-fire. The microscopic surface roughness of worn graphite electrodes had a major impact on pre-fire. And this paper had deduced the cumulative probability distribution of pre-fire, and given a relevant Weibull distribution equation. Several typical graphite materials were tested too. The experimental results revealed that electrodes should use graphite with higher hardness, smaller particle size and greater flexural strength. This was consistent with the analysis of Pedersen model. More significantly, based on the experiments of typical graphite materials, two Weibull constants of the cumulative probability distribution of pre-fire were obtained by a graphing method. Therefore, it is possible to calculate, reduce or control the occurrence of pre-fire in a facility with many gas switches. Via optimizing the operating under-voltage ratio of multiplex switches, the expectable pre-fire probability can be achieved. [ABSTRACT FROM PUBLISHER]

Electrode replacement is an effective method to extend the useful lifetime of the spark gap switch with graphite electrodes. In order to perform electrode replacement, suppressing temperature rise and preventing static welding/erosion should be considered for the static electrical contact interface between the electrode and the holder. In this paper, a mathematical model of contact temperature rise is proposed based on the Holm model and heat-conduction equations. This mathematical model can quantitatively prove that some material properties of the metal holder and some mechanical characteristics of the spark gap switch are key parameters affecting temperature rise. Material properties of the metal holder include thermal conductivity, specific heat, density, electrical resistivity, elasticity modulus, and the Poisson ratio. Mechanical characteristics of the spark gap switch include contact radius/area, contact pressure, and contact surface roughness. Optimum configuration of these key parameters reduces temperature rise and prevents static welding/erosion. [ABSTRACT FROM AUTHOR]