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Experiments with and modelling of explosively driven mangetic flux compression generators
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents work performed on explosively driven magnetic flux compression generators. This kind of devices converts the chemically stored energy in a high explosive into electromagnetic energy in the form of a powerful current pulse. The high energy density of the high explosives makes flux compression generators attractive as compact power sources. In order to study these devices a generator was designed at FOI in the mid-90ies. Two generators remained unused and became available for this licentiate work.

The thesis reports experiments with, and simulations of, the operation of the two remaining generators. The aim was to fully understand the performance of the generator design and be able to accurately simulate its behaviour. The generators were improved and fitted with various types of diagnostics to monitor the generator operation.

Two experiments were performed of which the first generator was operated well below its current capability limits while the second was stressed far above its limits. Since the generator generates a rapidly increasing current, a current measurement is the most important diagnostic revealing the current amplification of the generator and its overall performance. Further it is important to measure the timing of various events in the generator. With a common time reference it is possible to combine data from different probes and extract interesting information which cannot be directly obtained with a single measurement.

Two types of numerical simulations have been performed: Hydrodynamic simulations of the high explosive interaction with the armature were used to verify the measured armature dynamics. A zero-dimensional code was used to perform circuit simulations of the generator. The model takes into account the inductance reduction due to the compression of the generator as well as the change in conductivity due to heating of the conductors in the generators.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , xii, 103 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:53
Keyword [en]
Magnetic Flux Compression, Explosives, Pulsed Power, Circuit Simulations, Hydrodynamic simulations
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9638ISBN: 978-91-7415-174-9 (print)OAI: oai:DiVA.org:kth-9638DiVA: diva2:126784
Presentation
2008-11-12, Seminarierummet, Alfvénlaboratoriet, KTH, Teknikringen 31, Stockholm, 10:00 (English)
Supervisors
Note
QC 20101103Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-11-03Bibliographically approved
List of papers
1. Small helical magnetic flux compression generators: experiments and analysis
Open this publication in new window or tab >>Small helical magnetic flux compression generators: experiments and analysis
2008 (English)In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 36, no 5, 2673-2683 p.Article in journal (Refereed) Published
Abstract [en]

 In order to gain experience in explosive pulsed power and to provide experimental data for modeling, a small high-explosive-driven helical magnetic flux-compression generator (FCG) was designed at the Swedish Defence Research Agency (FOI). 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 the design of, and tests with, this helical FCG. The generator had an initial inductance of 23 mu H and was operated into a load of 0.2 mu H. The generator is charged with 0.27 kg of high explosives (PBXN-5). Various types of diagnostics were used to monitor the operation of the generator, including current probes, optical fibers, and piezo gauges. With seed currents of 5.7 and 11.2 kA, final currents of 269 and 436 kA were obtained, corresponding to current amplification factors of 47 and 39. The peak of the current was reached about 30 mu s after the time of crowbar. The two generators showed only small losses in terms of 2 pi-clocking. Using signals from optical fibers, the deflection angle of the armature could be determined to be 10 degrees in good agreement with hydrodynamic simulations of the detonation process and the detonation velocity to be 8.7 km/s in agreement with tabulated value.

Keyword
Magnetic flux-compression generators (FCGs)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9634 (URN)10.1109/TPS.2008.2003966 (DOI)000261363400029 ()
Note
QC 20100929. Uppdaterad från Accepted till Published (20100929).Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2011-05-02Bibliographically approved
2. Modeling of a small helical magnetic flux compression generator
Open this publication in new window or tab >>Modeling of a small helical magnetic flux compression generator
Show others...
2008 (English)In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 36, no 5, 2662-2672 p.Article in journal (Refereed) Published
Abstract [en]

 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.

Keyword
Magnetic flux-compression generators (FCGs)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9635 (URN)10.1109/TPS.2008.2003077 (DOI)000261363400028 ()
Note
QC 20100922. Uppdaterad från Accepted till Published (20100922).Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2011-05-02Bibliographically approved
3. Numerical simulations of flux compression generator systems
Open this publication in new window or tab >>Numerical simulations of flux compression generator systems
2007 (English)In: Proceedings of the 20th IET Pulsed Power Symposium, 2007, 123-127 p.Conference paper, Published paper (Other academic)
Keyword
Flux-compression generators, high-voltage generation, system simulations
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9636 (URN)
Note
QC 20101103Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2011-05-02Bibliographically approved

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