HOME

TheInfoList



OR:

A vector inversion generator (VIG) is an electric pulse compression and voltage multiplication device, allowing shaping a slower, lower voltage pulse to a narrower, higher-voltage one. VIGs are used in military technology, e.g. some
directed-energy weapon A directed-energy weapon (DEW) is a ranged weapon that damages its target with highly focused energy without a solid projectile, including lasers, microwaves, particle beams, and sound beams. Potential applications of this technology include ...
s, as a secondary stage of another pulsed power source, commonly an
explosive-driven ferroelectric generator An explosive-driven ferroelectric generator (EDFEG, explosively pumped ferroelectric generator, EPFEG, or FEG) is a compact pulsed power generator, a device used for generation of short high-voltage high-current pulse. The energies available are fai ...
.


Construction

Discrete component VIGs (pictured) consist of a stack of well-coupled common mode chokes interconnected with a stack of capacitors. The inductors present a high inductance to currents that are in-phase in the two windings, and a 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 as a half cycle of oscillation at a frequency set by the capacitance resonating with the differential mode inductance of the chokes. At the same time the other capacitors discharge very slowly due to not having a differential current flowing to cancel the reactance. 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 In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...
also acting as a single-ended
transmission line In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmis ...
, connected to a
spark gap A spark gap consists of an arrangement of two Conductor (material), conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential differenc ...
switch. The capacitor is charged from a power source, e.g. an EDFEG, then the spark gap fires after its
breakdown voltage The breakdown voltage of an insulator (electrical), insulator is the minimum voltage that causes a portion of an insulator to experience electrical breakdown and become electrically Conductor (material), conductive. For diodes, the breakdown vo ...
is reached. The
electromagnetic wave In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ...
created by the
electric spark An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an Ionization, ionized, Electric current, electrically conductive channel through a normally-insulating medium, often air or other ga ...
discharge travels along the transmission line, converting
electrostatic field An electric field (sometimes called E-field) is a physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) describes their capac ...
to
electromagnetic field An electromagnetic field (also EM field) is a physical field, varying in space and time, that represents the electric and magnetic influences generated by and acting upon electric charges. The field at any point in space and time can be regarde ...
, 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 In electrical engineering, electrical length is a dimensionless parameter equal to the physical length of an electrical conductor such as a cable or wire, divided by the wavelength of alternating current at a given frequency traveling through t ...
of the transmission line. The device acts as a distributed pulse forming network. Ferrites can be attached to the VIG construction to modify its characteristics, typically lowering the resonant frequency and increasing the efficiency.


Applications

VIGs are advantageous due to their simplicity and the very short pulse
rise time In electronics, when describing a voltage or current step function, rise time is the time taken by a signal to change from a specified low value to a specified high value. These values may be expressed as ratiosSee for example , and . or, equiva ...
s in range of nanoseconds. Some VIGs can be configured as part of a
tuned circuit An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. The circuit can act ...
, acting as
oscillator Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
s with practical upper limit of about 700 MHz, generating energy that can be radiated from a suitable antenna, allowing construction of very simple explosion-generated
electromagnetic pulse An electromagnetic pulse (EMP), also referred to as a transient electromagnetic disturbance (TED), is a brief burst of electromagnetic energy. The origin of an EMP can be natural or artificial, and can occur as an electromagnetic field, as an ...
generators. The use of VIGs includes
directed-energy weapon A directed-energy weapon (DEW) is a ranged weapon that damages its target with highly focused energy without a solid projectile, including lasers, microwaves, particle beams, and sound beams. Potential applications of this technology include ...
s,
x-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
pulse power supplies, plasma generators, etc.


References

{{reflist Electric power conversion Pulsed power