Magnetic flux compression for high voltage pulse applications
Hernandez Llambes, Juan Carlos
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Helical Magnetic Flux Compression Generators (MFCG) are the most promising energy sources with respect to their current amplification and compactness. However, their intrinsic flux loss limits severely their performance and it is not yet well understood. All flux losses have a differing degree of impact, depending on the generator's volume, current and energy amplification, size of the driven load, and angular frequency of armature-helix contact point. Although several computer models have been developed, none of them truly quantify the ohmic and intrinsic flux losses. This dissertation describes a novel method that provides a separate calculation of intrinsic flux losses (flux that is left behind in the conductors and lost for compression) and ohmic losses. It also provides a second method that uses simple flux quantification, making a mathematical connection between the intrinsic flux losses, quantified by the first method, and the intrinsic flux losses observed in the generators. This second method can also be used with the first method to a priori estimate the MFCG performance. Simple MFCG with a single helix produce high output energy only into low inductance loads, thus producing several 100 kA of current at a voltage level of less than l0kV. Many pulsed power devices require less current but a considerably higher voltage level. For effectively driving a high inductance load of several µH, a multistage MFCG design has also been successfully tested with a total length of 250 mm, a helix inner diameter of 51 mm, achieving an energy gain of ~13 into a 3 µH load. Further power conditioning utilizing an exploding wire fuse enables driving an electron beam device. Typical load parameters of electron beam devices are several 100 kV operating voltage with an impedance of a few tens of Ohms. Utilizing a multi-stage FCG as primary source for inductive energy storage with opening switch enables the production of voltages in excess of 100's kV. We built an exploding wire fuse with a length of 140mm and 100mm in diameter (including the storage inductor), conditioned to the MFCG described above. We achieved a voltage of ~ 42kV directly across the 3µH inductor, and more than 130kV with the fuse opening switch operating into a ~12-15 Ù load.