Effect of Die Pattern on Explosively Formed Fuse Performance

IEEE Transactions on Plasma Science, 2000

The environment surrounding an exploding wire is known be a controlling factor in electro-explosive fuse performance. Recent experiments have shown that the application of an insulating surface coating to the fuse wire can significantly increase the rate of impedance transition and impedance magnitude of the exploding wire. This paper discusses the performance of surface coated fuses tested in commonly used solid and gaseous media. For comparison, these experiments are compared to bare wire fuse experiments in identical environments. Previously developed exploding wire models are utilized to aid in the interpretation of the experimental fuse behavior. Differential wire voltage, voltage pulse length, and degree of post vaporization conduction (i.e., restrike) are discussed for each experiment.

IEEE Transactions on Plasma Science, 2000

Compact electroexplosive fuses (EEFs) as part of an explosively driven system are of interest for the one-time single-shot generation of high-power pulses. For instance, the transition from a very large driving current produced by an explosively driven flux compression generator (FCG), i.e., low impedance, to a large voltage spike delivered to the load, i.e., high impedance, can be done using an inductive storage system and an EEF. Typically, the EEF can be as large as, if not larger than, the current driver attached to it, thus making it one of the largest components in the system. Reduction in the size of the fuse will allow for size reductions of the entire high-power microwave (HPM) system. The goal of optimizing an EEF as an opening switch is to produce the greatest voltage multiplication possible to drive a load under physical size constraints. To optimize the fuse, several parameters are taken into account, including, but not limited to, fuse material, fuse length, fuse shape, and quenching medium. Individual optimization of these parameters will lead to complete optimization of an EEF, therefore resulting in a compact fuse capable of consistently producing maximum voltage multiplication for HPM systems.

1993

The need to reduce solid armature and launch package start-up acceleration for an inductively driven railgun necessitates an increase in the storage inductor to gun commutation time. For this purpose, a "fused," high current, explosively actuated opening switch has been designed and tested at the Electric Armaments Division, ARDEC, Picatinny Arsenal, New Jersey. The switch has been operated in the 600 kA to 1300 kA current range and has repeatedly demonstrated opening times from 720 ~s at 600 kA to 840 ps at 1000 kA. Armature jerk for an 615 gram solid armature has been reduced from 350 Megagees (MG)/sec to 38 MG/sec at the 600 kA operating point. The design premise for the thermal fusing section, operating experience and test results are presented.

The development of explosive generators that do not require an outside electrical power source, such as ferroelectric generators, requires novel switching components to allow for maximum transfer of the produced electrical energy. One critical component to achieve efficient operation is an effective closing switch. Typically a spark gap is used, although these systems tend to be relatively large compared to the explosive generator, require high pressure containers for reliable voltage breakdown operation, and are costly to manufacture. It may be possible to greatly simplify a closing switch by using a material which uses the explosive shockwave to switch. This can allow for a compact closing switch to be integrated into an explosive generator system. Significant research has been conducted on the change of conductivity of different solid bulk materials -insulators, semiconductors, and metals -under shock loading. A limited amount of research has also been conducted on powders. Aluminum powder has the unique characteristic of being very resistive in powder form due to the thin layer of aluminum oxide which forms on the grain surfaces. However, under shock loading it may be possible to fracture this layer allowing a highly conductive wavefront to propagate through the material. HEM Technologies and Texas Tech University researched different aluminum powder grain sizes as potential candidates for an explosive switch. Comparative results under shock loading and pulsed voltage holdoff are presented for the different aluminum grains researched.

Fuel Cells Bulletin, 2001

High explosive pulsed power (HEPP) techniques can address a wide range of pulsed power needs. The basis for HEPP techniques is the use of high explosives to reduce the inductance of a current-carrying circuit, thus multiplying the current due to magnetic flux conservation. For the past twenty years at Los Alamos, the authors' high energy density physics (HEDP) program has followed a path leading to more sophisticated and higher current (and often power) systems. Twenty years ago, they had the capability of conducting tests at 10, or even 30 MA, with no power conditioning and low inductance loads. The time scale of the experiment was the time it took to compress the flux explosively, and their fastest generator with high current capability was a plate generator. The operating time of the generator is less than 15 /spl mu/s, and flux loading requires either an additional /spl sim/60 /spl mu/s or a reduced-efficiency inductive coupling scheme. They could also deliver shortened pulses to select loads by completing their generator circuit, initially, with a relatively high inductance circuit element, then switching in a lower inductance with 2-3 /spl mu/s left of the generator pulse.

AIP Conference Proceedings, 2017

Simulations of high voltage detonators, such as Exploding Bridgewire (EBW) and Exploding Foil Initiators (EFI), have historically been simple, often empirical, one-dimensional models capable of predicting parameters such as current, voltage and in the case of EFIs, flyer velocity. Correspondingly, experimental methods have in general been limited to the same parameters. With the advent of complex, first principles magnetohydrodynamic codes such as ALEGRA and ALE-MHD, it is now possible to simulate these components in three dimensions, predicting a much greater range of parameters than before. A significant improvement in experimental capability was therefore required to ensure these simulations could be adequately validated. In this first paper of a three part study, the experimental method for determining the current, voltage, flyer velocity and multi-dimensional profile of detonator components is presented. This improved capability, along with high fidelity simulations, offer an opportunity to gain a greater understanding of the processes behind the functioning of EBW and EFI detonators.

The International Journal of Multiphysics, 2017

The explosive forming is a characteristic method. An underwater shock wave is generated by underwater explosion of an explosive. A metal plate is affected high strain rate by the shock loading and is formed along a metal die. Although this method has the advantage of mirroring the shape of the die, a free forming was used in this paper. An expensive metal die is not necessary for this free forming. It is possible that a metal plate is formed with simple supporting parts. However, the forming shape depends on the shock pressure distribution act on the metal plate. This pressure distribution is able to change by the shape of explosive, a mass of explosive and a shape of pressure vessel.

Pre-arcing stage is the first working step in high breaking capacity (HBC) fuse operation and affects the following step, namely, the arcing step. We have performed realistic HBC fuse tests for short (<10 ms) and medium (>10 ms) pre-arcing times by varying the phase angle of the electrical fault (defined as the phase angle of the fault current once the supplied voltage is applied to the fuse) in the range from 0 • to 160 • , for two values of the power factor (cos ϕ ∼ 0.9 and cos ϕ ∼ 0.1). Experimental values of the pre-arcing time and the arcing time (t arc) are given for t prearc /t arc 1 to ∼4.2, and discussed from the energetic point of view by taking into account the inductive source term. The adiabatic assumption classically used in the modelling is also examined. The influence of the pre-arcing step on the arcing step is analysed by means of the Joule integral, the energy dissipated in the fuse and the mass and length of the fulgurite.

Digest of Technical Papers. 11th IEEE International Pulsed Power Conference (Cat. No.97CH36127), 2000

Fcr the experimental investigation of high cument high voltage tises (HVF), a two-stage opening switch was designed and tested. It cmnprises of a vacuum circuit breaker serving as a fmt stage and an HVF in series with an SCR as a second stage. 'fhe switch offers a low resistance of 201.K2during charge intervals of several hundred mitliseconda, controlled time to opening and a relatively fast opening of 0.2S-O.7ma. fn a series of experiments, the current of 30-40kA was commutated routinely from a 130pH inductor into the resistive load at a voltage of 3kV. Liquid quenching media were examined and found to yield a high transfer efficiency, witl fuse losses as low as 5-8% of the stored energy. A strong correlation existing between these parameters and the pressure generated in the fuse is discussed. A semi-analytical engineering time model based on an electron-ion recombination mechanism of the fuse resistance change is develeped. This model is integrated into a PSpiee circuit simulation. The cakadations are in fairly gmd qualitative and quantitative agreement with experimental results.