K. Gregory

A novel flux compression/dynamic transformer technique for high-voltage pulse generation

This paper presents the basic concepts that underlie a fundamental research activity initiated recently at Loughborough University, U.K. A novel technique is described that enables the so-termed shock-wave-driven flux compression process to be performed inside a laboratory, without the need for any high-explosive charge, and results from preliminary proof-of-principle experiments are analyzed. Details of the necessary ancillary equipment, such as fast (TA/s) generators, electric guns, high-voltage helical transformers, and special transducers are presented, together with a study of the dielectric/metallic phase transition in aluminum powder. The paper concludes by showing how the different concepts can be combined, leading to a high-voltage pulse generator with a fast-rising output.

Experimental validation of a capacitor discharge induction launcher model

This paper describes the early stages of the experimental validation of a mathematical model of a capacitor discharge co-axial induction launching system. The model forms part of a family of computer programs produced to aid the design of launchers, so that either the maximum possible armature velocity on exit from the launcher or a specific performance requirement such as a controlled armature acceleration is achieved. The programs range in complexity from relatively simple models, used for initial capability studies, to detailed representations used in the design and development of launcher structures and their control systems. The model described is one of the more complex under development, being based on filamentary representations of both the stator and armature conducting regions. The single-stage experimental launcher described in the paper has been constructed purely for model validation purposes. To this end its geometry is constrained to a straightforward co-axial form, with the armature being a simple 80 gm aluminium ring of 100 mm diameter. The launcher operates vertically, accelerating the armature in free flight in order to avoid difficulties caused by barrel friction. Current and position data are obtained using digital sampling techniques, with post-processing allowing a direct comparison to be made with simulated results. >

Studies of a very high efficiency cryogenic launcher

Cryogenic experiments, in which ring-shaped projectiles are accelerated axially by a single-turn drive coil powered by a capacitor bank, have demonstrated that more than 50% of the initially stored electrostatic energy can be converted into kinetic energy in the projectile. Results provided by a detailed numerical modeling are shown to be in close agreement with experimental data.

Multiple-pulse, twin-output, high-voltage generator

This paper describes the development of a compact, proof-of-principle generator for the production of two synchronized series of high-voltage pulses from the single discharge of a capacitor. The pulses are produced by an array of parallel-connected exploding fuses, with compact transformers enabling the required level of output voltage to be obtained. Experimental results are presented and compared with theoretical predictions.

Pulsed-power research at Loughborough University

This is a companion paper to the other papers at the Conference that emanate from Loughborough University, UK. It introduces a few of the other interesting activities that are underway as part of the overall pulsed power research activity.

MATHEMATICAL MODELLING OF AN AUTOMATIC VOLTAGE REGULATOR

This letter describes the mathematical modelling of an automatic voltage regulator (avr) in a form which is compatible with models developed for many other items of electrical plant. The corresponding equations are suitable for numerical solution on a digital computer, and results are presented to illustrate the performance when the avr program is added to an existing generator program to produce an overall system model.

Modeling of brushless DC generating systems using diakoptics

The mathematical modeling of a brushless DC generator is described, as an illustration of the application of diakoptic techniques to the analysis of small-scale electrical power supply systems. Modeling of the generator and its output rectifier is accomplished using an established matrix technique that accounts for the continuously changing conduction pattern of the diode bridge network. The advantages of using diakoptics are discussed together with the main generator linked to its exciter and to the automatic voltage regulator and permanent magnet generator which are often included in a complete unit. A solution algorithm is presented for this overall arrangement and a comparison is made between theoretical and practical results for a typical 3-stage, 4000-rev/min, 10.3-kW, 28-V unit. >

High-power high-voltage generator with a multi-pulse twin output

This paper describes a technique for producing twin series of high-voltage pulses from the single discharge of a capacitor into multiple arrays of exploding metallic wires. Details are provided of the design and construction of a generator that is able to produce either three 150 kV pulses, two 250 kV pulses or a single 500 kV pulse on loads of between 50 /spl Omega/ and 100 /spl Omega/ at each output. In addition to describing how the exploding wire arrays are designed, the paper also details the other ancillary equipment that is needed for the generator. This includes the two compact air-cored transformers with coupling coefficients of 0.94 that provides the twin series of output pulses at the required voltage. The experimental performance of the generator is shown to be close to that that is predicted by theory.

A ring carbon plasma gun for the plasma opening switch

The carbon plasma gun is commonly used as a source of dense plasma for plasma opening switches. The plasma is produced by the surface flashover of an insulator, although an even distribution is difficult to achieve when overall space restrictions limit the number of guns that can be employed. This paper describes a novel ring gun that, in addition to overcoming this problem, also enhances the switch performance by producing a surface flashover of the insulation that travels along a circular path. A study is presented of an experimental gun, using measured data provided by electrical probes and optical techniques. Supporting theoretical explanations are given.

A recoilless electromagnetic launcher for model validation

Many previous papers have described well-developed simulation programmes for electromagnetic launchers, many of which use a coupled-circuit filamentary approach in describing the electrical circuits during the launch period. However, the accurate validation of these programmes presents several very significant problems, due to certain mainly mechanical effects that are extremely difficult to quantify in any relatively straightforward and accurate manner. The present paper explains these difficulties, and describes an experimental investigation in which their influence on the results is substantially absent, enabling close agreement with results predicted from a filamentary model to be achieved.