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==Construction==
Discrete component VIGs (pictured) consist of a stack of well-coupled common mode chokes interconnected with a stack of capacitors,. theyThe areinductors conceptuallypresent equivalenta high inductance to currents that are in-phase in the distributedtwo componentwindings, spiraland VIGa far lower inductance when the winding currents are flowing in opposite directions. The capacitors are charged with alternating polarity and when the switch (usually a triggered or free running spark gap in practice) is closed the voltage across every second capacitor rapidly inverts inas polaritya duehalf tocycle theof lowoscillation reactanceat seena byfrequency aset differentialby currentthe flowingcapacitance throughresonating with the commondifferential mode inductance of the chokes. At the same whereastime the other capacitors discharge very slowly due to not having a differential current flowing to cancel the reactance. Discrete components allow large capacitors to be used thus storing much more energy, but cannot provide the high multiplication ratios and extremely short rise times of spiral transmission line types.
So after a half period, all the capacitors are in series and the voltages add.
This arrangement has a conceptual equivalence to the spiral VIG, with the alternating capacitors being equivalent to the capacitance between the windings and the common mode chokes being equivalent to the inductance of a winding.
Discrete components allow large lumped capacitors to be used thus storing much more energy, but have difficulty replicating the high voltage multiplication ratios and extremely short rise times of spiral transmission line types.
A spiral VIG consists of four alternating conductor-insulator-conductor-insulator sheets, wound into a cylinder, forming a [[capacitor]] also acting as a single-ended [[transmission line]], connected to a [[spark gap]] switch. The capacitor is charged from a power source, e.g. thean [[Explosive-driven ferroelectric generator|EDFEG]], then the spark gap fires after its [[breakdown voltage]] is reached. The [[electromagnetic wave]] created by the [[electric spark]] discharge travels along the transmission line, converting [[electrostatic field]] to [[electromagnetic field]], then after reflecting from the open end converts back to electrostatic field. A pulse of output amplitude 2nU (where n is the number of turns of the capacitor and U is the initial voltage it was charged to) and a rise time equal to twice the [[electrical length (transmission medium)|electrical length]] of the transmission line.<ref>{{Cite web |url=http://scholarsmine.mst.edu/post_prints/pdf/physics_09007dcc80588630.pdf |title=Completely explosive ultracompact high-voltage nanosecond pulse-generating system |access-date=2010-01-16 |archive-date=2010-06-29 |archive-url=https://web.archive.org/web/20100629162736/http://scholarsmine.mst.edu/post_prints/pdf/physics_09007dcc80588630.pdf |url-status=dead }}</ref><ref>{{cite web| url=http://www.boliven.com/patent/US7151330/drawings | title=Apparatus and method for generating high voltages using a voltage inversion generator and multiple closed-path ferrites | archive-url=https://web.archive.org/web/20120224152607/http://www.boliven.com/patent/US7151330/drawings | archive-date=2012-02-24}}</ref><ref>[http://shadaly.com/vector_inversion_generator_4507567.html Unknown]{{Dead link|date=March 2022 | fix-attempted=yes}}</ref> The device acts as a distributed [[pulse forming network]].
[[Ferrite (magnet)|Ferrite]]s can be attached to the VIG construction to modify its characteristics, typically lowering the resonant frequency and increasing the efficiency.<ref>{{Cite web|url=http://www.findthatpatent.com/Apparatus_and_method_for_generating_high_voltages_using_a_voltage,7151330.html|title=Findthatpatent Resources and Information |website=www.findthatpatent.com}}</ref>
==Applications==
VIGs are advantageous due to their simplicity and the very short pulse [[rise time]]s in range of nanoseconds. Some VIGs can be configured as part of a [[tuned circuit]], acting as [[oscillator]]s with practical upper limit of about 700 MHz, generating energy that can be radiated from a suitable [[Antenna (radio)|antenna]], allowing construction of very simple explosion-generated [[electromagnetic pulse]] generators.<ref>{{cite web| url=http://www.armysbir.com/Technologies/View.aspx?pk=45430111-708f-463e-8fe1-cf1392a6bf99 | title=Unknown}}{{Dead link | date=January 2024| fix-attempted=yes}}</ref><ref> {{cite web | url = http://www.devileye.net/catalog/rope_fastener/spiral_line_oscillator.html | title = Spiral line oscillator | accessdate = 2011-03-06}}</ref>
The use of VIGs includes [[directed-energy weapon]]s, [[x-ray]] pulse power supplies, [[plasma (physics)|plasma]] generators, etc.
VIGs can be constructed by high-voltage hobbyists.<ref>http://4hv.org/e107_plugins/forum/forum_viewtopic.php?43795.last</ref><ref>http://www.sciencemadness.org/talk/viewthread.php?action=printable&fid=6&tid=6032</ref>
==References==
[[Category:Electric power conversion]]
[[Category:Pulsed power]]
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