High-voltage pulsed generator for dynamic fragmentation of rocks

A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300?μF) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ～50?ns, current amplitude of ～6?kA with the 40?Ω active load, and ～20?kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations.     

Design and performance of a pulse transformer based on Fe-based nanocrystalline core

A dry-type pulse transformer based on Fe-based nanocrystalline core with a load of 0.88 nF, output voltage of more than 65 kV, and winding ratio of 46 is designed and constructed. The dynamic characteristics of Fe-based nanocrystalline core under the impulse with the pulse width of several microseconds were studied. The pulse width and incremental flux density have an important effect on the pulse permeability, so the pulse permeability is measured under a certain pulse width and incremental flux density. The minimal volume of the toroidal pulse transformer core is determined by the coupling coefficient, the capacitors of the resonant charging circuit, incremental flux density, and pulse permeability. The factors of the charging time, ratio, and energy transmission efficiency in the resonant charging circuit based on magnetic core-type pulse transformer are analyzed. Experimental results of the pulse transformer are in good agreement with the theoretical calculation. When the primary capacitor is 3.17 μF and charge voltage is 1.8 kV, a voltage across the secondary capacitor of 0.88 nF with peak value of 68.5 kV, rise time (10%-90%) of 1.80 μs is obtained.     

Mega-ampere submicrosecond generator GIT-32

The GIT-32 current generator was developed for experiments with current carrying pulsed plasma. The main parts of the generator are capacitor bank, multichannel multigap spark switches, low inductive current driving lines, and central load part. The generator consists of four identical sections, connected in parallel to one load. The capacitor bank is assembled from 32 IEK-100-0.17 (0.17 microF, 40 nH, 100 kV) capacitors, connected in parallel. It stores approximately 18 kJ at 80 kV charging voltage. Each two capacitors are commuted to a load by a multigap spark switch with eight parallel channels. Switches operate in ambient air at atmospheric pressure. The GIT-32 generator was tested with 10, 15, and 20 nH inductive loads. At 10 nH load and 80 kV of charging voltage it provides 1 MA of current amplitude and 490 ns rise time with 0.8 Omega damping resistors in discharge circuit of each capacitor and 1.34 MA530 ns without resistors. The net generator inductance without a load was optimized to be as low as 12 nH, which results in extremely low self-impedance of the generator ( approximately 0.05 Omega). It ensures effective energy coupling with low impedance loads like Z pinch. The generator operates reliably without any adjustments in 40-80 kV range of charging voltage. Maximum jitter (relative to a triggering pulse) at 40 kV charging voltage is about 7 ns and lower at higher charging voltages. Operation and handling are very simple, because no oil and no purified gases are required for the generator. The GIT-32 generator has dimensions of 3200 x 3200 x 400 mm(3) and total weight of about 2500 kg, thus manifesting itself as a simple, robust, and cost effective apparatus.     

A KPU-200 movable capacitor installation

A movable electrophysical capacitor installation with a 250-kJ maximum bank energy, which generates intense neutron pulses, is described. A current pulse generator with a capacitive energy storage forms the basis of the installation. When the initial voltage at the capacitor bank is up to 35 kV, the installation ensures a flow of current pulses with amplitudes of up to 2 MA in a gas-discharge plasma-focus chamber, which is filled with an equal-component deuterium-tritium (DT) mixture. Under these conditions, the chamber is capable of repeatedly generating single fast-neutron pulses with an energy of 14.1 MeV, a duration of ～70 ns, and an integral yield over 1013 neutrons/pulse.     

Compact inductive energy storage pulse power system

An inductive energy storage pulse power system is being developed in BARC, India. Simple, compact, and robust opening switches, capable of generating hundreds of kV, are key elements in the development of inductive energy storage pulsed power sources. It employs an inductive energy storage and opening switch power conditioning techniques with high energy density capacitors as the primary energy store. The energy stored in the capacitor bank is transferred to an air cored storage inductor in 5.5 μs through wire fuses. By optimizing the exploding wire parameters, a compact, robust, high voltage pulse power system, capable of generating reproducibly 240 kV, is developed. This paper presents the full details of the system along with the experimental data.     

The investigation of a compact auto-connected wire-wrapped pulsed transformer

For the power conditioning circuit used to deliver power efficiently from flux compression generator (FCG) to the load with high impedance, an air-cored and wire-wrapped transformer convenient in coaxial connection to the other parts is investigated. To reduce the size and enhance the performance, an auto-connection is adopted. A fast and simple model is used to calculate the electrical parameters of the transformer. To evaluate the high voltage capability, the voltages across turns and the electric field distribution in the transformer are investigated. The calculated and the measured electrical parameters of the transformer show good agreements. And the safe operating voltage is predicted to exceed 500 kV. In the preliminary experiments, the transformer is tested in a power conditioning circuit with a capacitive power supply. It is demonstrated that the output voltage of the transformer reaches -342 kV under the input voltage of -81 kV.     

Analysis of a modular generator for high-voltage, high-frequency pulsed applications, using low voltage semiconductors (< 1 kV) and series connected step-up (1:10) transformers

This article discusses the operation of a modular generator topology, which has been developed for high-frequency (kHz), high-voltage (kV) pulsed applications. The proposed generator uses individual modules, each one consisting of a pulse circuit based on a modified forward converter, which takes advantage of the required low duty cycle to operate with a low voltage clamp reset circuit for the step-up transformer. This reduces the maximum voltage on the semiconductor devices of both primary and secondary transformer sides. The secondary winding of each step-up transformer is series connected, delivering a fraction of the total voltage. Each individual pulsed module is supplied via an isolation transformer. The assembled modular laboratorial prototype, with three 5 kV modules, 800 V semiconductor switches, and 1:10 step-up transformers, has 80% efficiency, and is capable of delivering, into resistive loads, -15 kV1 A pulses with 5 micros width, 10 kHz repetition rate, with less than 1 micros pulse rise time. Experimental results for resistive loads are presented and discussed.     

新疆某水电站220kV出线间隔电流互感器之探究

新疆某水电站装有4台单机容量为80 MW的立轴混流式水轮发电机组。采用发电机与变压器组成带有发电机断路器的单元接线,装置2台容量为100 MVA的220 kV双卷主变压器和2台容量为100 MVA的220 kV三卷主变压器。电流互感器是利用变压器原理进行变换电流的一次电气设备,它的主要作用是将高压小电流和低压大电流变成低压小电流,因而在电力系统中得到了广泛的应用。重点阐述了电流互感器基本原理,电流互感器二次回路现场试验原则及使用注意事项。     

A compact high-voltage pulse generator with opening insulated-gate bipolar transistor switch and a high pulse repetition rate

A small-size high-voltage (～20 kV) microsecond pulse generator, which is based on a pulse transformer and loaded into a reactor with a pulse corona discharge, is described. Insulated-gate bipolar transistors (IGBTs) that form the switch are used in the low-voltage circuit of the generator. When the switch is open, voltage pulses with an amplitude of up to 1000 V are created across it and, hence, across the primary winding of the transformer. The pulse repetition rate of the generator is ～20000 pulses/s.     

A novel compact repetitive frequency voltage booster based on magnetic switches and Fitch generator

In this paper, a novel repetitive frequency voltage booster (named repetitive Fitch booster by the authors) based on magnetic switches and Fitch generators is proposed. The principle of operation is to charge capacitors in parallel when magnetic switches (MSs) are unsaturated and reverse voltage polarity of every other capacitor when MSs saturate. With the principle, circuit topology of a 4-stage repetitive Fitch booster (RFB) is presented. Simulation as well as experiment shows its feasibility in boosting voltage and compressing rise-time. In simulation, the input voltage of 100 V is boosted to 372 V, while test stand yields output voltage with frequency of 1 kHz, amplitude of 19 kV with each capacitor charged to about 5.6 kV, and rise-time compression from 7.3 μs to 700 ns. Meanwhile, calculations show that the 4-stage RFB effectively reduces core volume by about half, from 1093.5 cm(3) to 585.2 cm(3). Furthermore, design rules are proposed so that topologies of RFBs with stages other than four can be conveniently derived. As an example, an 8-stage RFB is proposed and verified with circuit simulation, which shows an output voltage of 759 V with the input voltage of 100 V.     

750 kV电容式电压互感器现场检验系统的研究

针对目前750 kV电容式电压互感器(CVT)测试中传统比较测差法和"低校高"法存在的问题,研究并开发出750 kV CVT测试和检验系统。通过对750 kV CVT的工作原理、等效电路和误差组成的分析,提出了750 kV CVT空载误差、负荷误差的测试方法和测试线路,研制了30.6 kV带升压器标准电压互感器、变频电子电源和低频互感器检验仪,组成了一套完整的检验系统。通过现场试验,测试数据准确可靠,可以满足0.2级750 kV CVT量值溯源的要求,具有较高的实用和推广价值。     

A high-voltage pulse transformer with a modular ferrite core

A high ratio (winding ratio of 1:80) pulse transformer with a modular ferrite core was developed for a repetitive resonant charging system. The magnetic core is constructed from 68 small blocks of ferrites, glued together by epoxy resin. This allows a high degree of freedom in choosing core shape and size. Critical issues related to this modular design are the size tolerance of the individual ferrite blocks, the unavoidable air gap between the blocks, and the saturation of the core. To evaluate the swing of the flux density inside the core during the charging process, an equivalent circuit model was introduced. It was found that when a transformer is used in a resonant charging circuit, the minimal required volume of the magnetic material to keep the core unsaturated depends on the coupling coefficient of the transformer and is independent of the number of turns of the primary winding. Along the flux path, 17 small air gaps are present due to the inevitable joints between the ferrite blocks. The total air gap distance is about 0.67 mm. The primary and secondary windings have 16 turns and 1280 turns, respectively, and the actually obtained ratio is about 1:75.4. A coupling coefficient of 99.6% was obtained. Experimental results are in good agreement with the model, and the modular ferrite core works well. Using this transformer, the high-voltage capacitors can be charged up to more than 70 kV from a low-voltage capacitor with an initial charging voltage of about 965 V. With 26.9 J energy transfer, the increased flux density inside the core was about 0.23 T, and the core remains unsaturated. The energy transfer efficiency from the primary to the secondary was around 92%.     

Development of a press-forming technology of the pressboard for a 154 kV transformer

A pressboard consisting of an angle ring and a cap is installed at the primary and secondary coil windings of a transformer. This pressboard is related to transformer durability. Since transformer capacities are increasing, it is necessary to develop a pressboard of high voltage grade (above 150 kV). In this study, a press-forming technology was developed for the pressboard of a 154 kV transformer. To determine the optimum shape of the pressboard, the press-forming factors were experimentally evaluated through the mechanical tensile strength and AC withstand voltage tests under wet conditions. From the results, the optimum size and shape of the pressboard was found to be R15??R20 mm under a forming pressure of 10 MPa. When the relative humidity (RH) was less than 50%, the moisture absorption rate in oil decreased by 25??40% compared to that in air. However, when RH exceeded 50%, the difference in the moisture absorption rate between the cases of oil and air was just 8??10%. The AC withstand voltage of the pressboard was weak against moisture. The average AC withstand voltage at 40°C and RH of less than 50% decreased by about 15% compared to the dried condition, and the maximum value decreased by 30% at 40°C and RH of more than 50%.     

A High-Current Pulse Generator SIGNAL with an Inductive Energy Storage and a Microsecond Plasma Opening Switch

The primary energy storage in the SIGNAL installation is a 4.7-F capacitor bank with a stored energy of up to 24 kJ switched by a gas-discharge gap switch of the trigatron type. The plasma source and the design of the microsecond plasma opening switch ensure current flow through this switch and inductive storage for a time of up to 1.7 s. The current amplitude reaches 330 kA. The current switched to the load is 20–300 kA in various modes with a rise time of 10–200 ns. The voltage across the feedthrough insulator reaches 400 kV. The installation is used in experimental studies of linear pinches, capillary discharge, and microsecond plasma opening switches.     

A compact, low jitter, nanosecond rise time, high voltage pulse generator with variable amplitude

In this paper, a compact, low jitter, nanosecond rise time, command triggered, high peak power, gas-switch pulse generator system is developed for high energy physics experiment. The main components of the system are a high voltage capacitor, the spark gap switch and R = 50 Ω load resistance built into a structure to obtain a fast high power pulse. The pulse drive unit, comprised of a vacuum planar triode and a stack of avalanche transistors, is command triggered by a single or multiple TTL (transistor-transistor logic) level pulses generated by a trigger pulse control unit implemented using the 555 timer circuit. The control unit also accepts user input TTL trigger signal. The vacuum planar triode in the pulse driving unit that close the first stage switches is applied to drive the spark gap reducing jitter. By adjusting the charge voltage of a high voltage capacitor charging power supply, the pulse amplitude varies from 5 kV to 10 kV, with a rise time of <3 ns and the maximum peak current up to 200 A (into 50 Ω). The jitter of the pulse generator system is less than 1 ns. The maximum pulse repetition rate is set at 10 Hz that limited only by the gas-switch and available capacitor recovery time.     

Design of an ultrahigh-energy hydrogen thyratron/SCR research defibrillator.

The design features of an ultrahigh-energy research defibrillator are described. Three voltage sources are used. The first is a 60-Hz supply of adjustable amplitude and duration for inducing fibrillation. The second source uses an 18.000-joule capacitor bank which can be charged to 800, 1600, or 2400 volts. SCRs in series with the chest are used to initiate the discharge, and SCRs shunting the capacitor bank terminate the discharge. The third source employs another 18,000-joule capacitor bank which can be charged to 5000, 10,000 or 15,000 volts. In this source, large ceramic-enveloped hydrogen thyratrons are used for both initiating and terminating the discharge. In the second and third sources, which can deliver rectangular, trapezoidal, truncated exponential, or untruncated exponential waveforms, capacitor charge time is 10 sec and the duration of the delivered shock is continuously adjustable from 100 musec through 1 sec.     

Application of a fast electrical pulse in gated multichannel plate camera

An eight-frame gated microchannel plate (MCP) camera and a gating electrical pulse are described in this article. The gating electrical pulse is obtained by first generating a high voltage fast step pulse using avalanche transistors in Marx bank configuration, and then shaping it using avalanche diodes. The high voltage fast step pulse is about 200 ps in fall time and 4 kV in amplitude. The gating pulse wave form with width of 160 ps and amplitude of 2.5 kV is achieved. Each frame photocathode coated with gold on the MCP is part of a 12 Omega transmission line with open circuit end driven by the gating electrical pulse. The camera is tested by illuminating its photocathode with ultraviolet laser pulses, 266 nm in wavelength, which shows exposure time as short as 120 ps.     

一种新型低功耗小型高压电源

介绍一种新型低功耗小型高压电源，该电源采用全集成化电路设计。由振荡电路产生脉冲方波推动开关电路，采用自举升压电路，提高高压变压器的初级电压。脉冲高压经高压变压器升压整流后，可得到需要的稳定直流高压，对于正高压，在高压升压电路后采用倍压整流，用直接取样反馈方式来凋整输出高压，使高压更趋稳定。该电源具有功耗低、体积小、重量轻、绝缘性能好等特点，而且输出高压连续可凋。电源的正负高压输出值分别为：正高压0～＋50kV、负高压0～-25kV。可用于小功率X光管供电和其他相关科学研究及野外作业。