Helical explosive magnetic generators (HEMG) represent the inductive generators of electromagnetic energy. Operation of HEMG is based on compression of magnetic field, preliminary delivered to the helical coil, by the metal armature, placed coaxially in the coil center and expanding during an explosion. Circuit compression results in a decrease of its inductance, while the magnetic energy and the current increase. Current in HEMG reaches a magnitude of several dozen million amperes. When using HEMG, the designers, as a rule, try to get the maximum energy the generator is designed for. It means that usually explosive magnetic generators operate under limiting conditions. The objective of this work is to reduce the risk during explosive experiments by obtaining the possibility to develop new, and to use the available, HEMGs with guaranteed margins for the critical parameters.
[Show abstract][Hide abstract] ABSTRACT: The authors present a conceptual approach to improve the yield, efficiency, and pulse shape characteristics from an explosively-driven magneto-cumulative generator (MCG). We propose that a Bitter coil with tailored and configurable electromagnet windings and insulation be used for the MCG stator. Several features of Bitter coil construction lend themselves as design solutions for a number of inherent MCG problems. Standard Bitter coils have been used for decades to conduct high currents and produce correspondingly high magnetic fields. The Bitter coil is a series of conducting annular disks of considerable conducting cross-section. An azimuthal sector of conductor is removed from each annulus, which permits a break point for an axial "jumper" to connect each turn to its neighbor. The disks are stacked with interleaved insulation. For MCG application, the windings of the Bitter coil can in principle be modified, turn-by-turn, to change each winding's inner and outer radius and thickness, as well as the material, size, shape, and spacing of the interleaving insulation. This design variability seems to solve a number of performance problems of conventional MCGs. The authors have searched the open available technical literature and have not found any MCG research using this approach. Fabricating a Bitter coil-type stator may have been previously impractical, but with the advent of computer-numerical-controlled shop machines the lack of ease to fabricate such a stator may no longer be a hurdle for its use.
[Show abstract][Hide abstract] ABSTRACT: High-efficiency simple, compact and robust opening switches capable of generating hundreds of kV are key elements in the development of autonomous explosivelydriven pulsed power sources. The paper presents results of the first phase of development of such an opening switch, based on exploding wire technology. By implementing a matched inductor in the circuit and optimising the wire parameters, a very compact and robust device is capable of generating reproducibly 240 kV. Full details of the system are given together with experimental data and theoretical predictions.
Pulsed Power Conference, 2007 16th IEEE International; 07/2007
[Show abstract][Hide abstract] ABSTRACT: In order to gain experience in explosive pulsed power and to provide experimental data as the basis for computer modeling, a small high-explosive-driven helical magnetic flux-compression generator (FCG) was designed at the Swedish Defence Research Agency. The generator, of which three have been built, has an overall length of 300 mm and a diameter of 70 mm. It could serve as the energy source in a pulse-forming network to generate high-power pulses for various loads. This paper presents a simulation model of this helical FCG. The model, which was implemented in Matlab-Simulink, uses analytical expressions for the generator inductance. The model of resistive losses takes into account the heating of the conductors and the diffusion of the magnetic field into the conductors. The simulation results are compared with experimental data from two experiments with identical generators but with different seed currents, influencing the resistive losses. The model is used to analyze the performance of the generator.
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