Trigatron CV100, with loose-knit "sock" to contain any explosion
A trigatron is a type of triggerable spark gap switch designed for high current and high voltage (usually 10–100 kV and 20–100 kA, though devices in the mega-ampere range exist as well). It has very simple construction and in many cases is the lowest cost high energy switching option. It may operate in open air, it may be sealed, or it may be filled with a dielectric gas other than air or a liquid dielectric. The dielectric gas may be pressurized, or a liquid dielectric (e.g. mineral oil) may be substituted to further extend the operating voltage. Trigatrons may be rated for repeated use (over 10,000 switching cycles), or they may be single-shot, destroyed in a single use.
A trigatron has three electrodes. The heavy main electrodes are for the high current switching path, and a smaller third electrode serves as the trigger. During normal operation, the voltage between the main electrodes is somewhat lower than the breakdown voltage corresponding to their distance and the dielectric between them (usually air, argon-oxygen, nitrogen, hydrogen, or sulfur hexafluoride). To switch the device, a high-voltage pulse is delivered to the triggering electrode. This ionizes the medium between it and one of the main electrodes, creating a spark which shortens the thickness of non-ionized medium between the electrodes. The triggering spark also generates ultraviolet light and free electrons in the main gap. These lead to the rapid electrical breakdown of the main gap, culminating in a low resistance electric arc between the main electrodes. The arc will continue to conduct until current flow drops sufficiently to extinguish it.
The triggering electrode is most often mounted through a hole in the center of the positive main electrode. The undrilled main electrode is the negative electrode. When switching high currents, the electrodes undergo considerable heat stress, as they are directly involved in the electric arc. This causes the surfaces to undergo gradual vaporization, so some designs incorporate methods to easily adjust the distance between the electrodes or to actually replace the electrodes. The main electrodes are typically fabricated from brass, copper or its alloys, tungsten, or copper–tungsten composite, to achieve longer electrode life.
The trigger pulse is most often delivered by a trigger transformer. Some trigatron units have trigger modules integrated; others use external ones. The trigger transformer secondary can be galvanically isolated from its primary side. Some manufacturers offer trigger modules controlled by an optical fiber, which isolates the control circuitry from the electromagnetic interference effects of the sharp and intense electrical pulses. The trigger pulse from the transformer output is typically a narrow spike of very high voltage, with relatively small energy compared to the energy controlled by the trigatron.
The energy for the trigger pulse is usually derived from a capacitor, which may be charged from the power source of the trigatron's own circuit. In this regard, the entire circuit is very similar to a flashtube based photoflash, where the trigger transformer provides the ionization in the tube and the tube functions simultaneously as the light source and the power switching element for itself. An air-gap flash type, where the flash gap itself contains a trigger electrode and acts as a switch, is a form of a trigatron with the same dual function.
Trigatrons are often enclosed in resin-impregnated loose-knit fabric "socks", to contain fragments if the device explodes due to internal overpressure.
A Tesla coil is an electrical resonant transformer circuit designed by inventor Nikola Tesla in 1891. It is used to produce high-voltage, low-current, high-frequency alternating-current electricity. Tesla experimented with a number of different configurations consisting of two, or sometimes three, coupled resonant electric circuits.
Electrical discharge machining (EDM), also known as spark machining, spark eroding, die sinking, wire burning or wire erosion, is a metal fabrication process whereby a desired shape is obtained by using electrical discharges (sparks). Material is removed from the work piece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the tool or electrode, while the other is called the workpiece-electrode, or work piece. The process depends upon the tool and work piece not making physical contact.
A spark gap consists of an arrangement of two 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 difference between the conductors exceeds the breakdown voltage of the gas within the gap, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the "holding current". This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound, light, and heat.
A corona discharge is an electrical discharge caused by the ionization of a fluid such as air surrounding a conductor carrying a high voltage. It represents a local region where the air has undergone electrical breakdown and become conductive, allowing charge to continuously leak off the conductor into the air. A corona discharge occurs at locations where the strength of the electric field around a conductor exceeds the dielectric strength of the air. It is often seen as a bluish glow in the air adjacent to pointed metal conductors carrying high voltages, and emits light by the same mechanism as a gas discharge lamp.
A flashtube (flashlamp) is an electric arc lamp designed to produce extremely intense, incoherent, full-spectrum white light for a very short time. A flashtube is a glass tube with an electrode at each end and is filled with a gas that, when triggered, ionizes and conducts a high-voltage pulse to make light. Flashtubes are used most in photography; they also are used in science, medicine, industry, and entertainment.
In electrical engineering, partial discharge (PD) is a localized dielectric breakdown (DB) of a small portion of a solid or fluid electrical insulation (EI) system under high voltage (HV) stress. While a corona discharge (CD) is usually revealed by a relatively steady glow or brush discharge (BD) in air, partial discharges within solid insulation system are not visible.
A gas-filled tube, also commonly known as a discharge tube or formerly as a Plücker tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Gas-filled tubes exploit phenomena related to electric discharge in gases, and operate by ionizing the gas with an applied voltage sufficient to cause electrical conduction by the underlying phenomena of the Townsend discharge. A gas-discharge lamp is an electric light using a gas-filled tube; these include fluorescent lamps, metal-halide lamps, sodium-vapor lamps, and neon lights. Specialized gas-filled tubes such as krytrons, thyratrons, and ignitrons are used as switching devices in electric devices.
An ignitron is a type of gas-filled tube used as a controlled rectifier and dating from the 1930s. Invented by Joseph Slepian while employed by Westinghouse, Westinghouse was the original manufacturer and owned trademark rights to the name "Ignitron". Ignitrons are closely related to mercury-arc valves but differ in the way the arc is ignited. They function similarly to thyratrons; a triggering pulse to the igniter electrode turns the device "on", allowing a high current to flow between the cathode and anode electrodes. After it is turned on, the current through the anode must be reduced to zero to restore the device to its nonconducting state. They are used to switch high currents in heavy industrial applications.
In electronics, electrical breakdown or dielectric breakdown is a process that occurs when an electrically insulating material, subjected to a high enough voltage, suddenly becomes a conductor and current flows through it. All insulating materials undergo breakdown when the electric field caused by an applied voltage exceeds the material's dielectric strength. The voltage at which a given insulating object becomes conductive is called its breakdown voltage and, in addition to its dielectric strength, depends on its size and shape, and the location on the object at which the voltage is applied. Under sufficient electrical potential, electrical breakdown can occur within solids, liquids, or gases. However, the specific breakdown mechanisms are different for each kind of dielectric medium.
The krytron is a cold-cathode gas-filled tube intended for use as a very high-speed switch, somewhat similar to the thyratron. It consists of a sealed glass tube with four electrodes. A small triggering pulse on the grid electrode switches the tube on, allowing a large current to flow between the cathode and anode electrodes. The vacuum version is called a vacuum krytron, or sprytron. The krytron was one of the earliest developments of the EG&G Corporation.
A Marx generator is an electrical circuit first described by Erwin Otto Marx in 1924. Its purpose is to generate a high-voltage pulse from a low-voltage DC supply. Marx generators are used in high-energy physics experiments, as well as to simulate the effects of lightning on power-line gear and aviation equipment. A bank of 36 Marx generators is used by Sandia National Laboratories to generate X-rays in their Z Machine.
High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, high voltage refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant special safety requirements and procedures.
An electric arc is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma, which may produce visible light. An arc discharge is initiated either by thermionic emission or by field emission. After initiation, the arc relies on thermionic emission of electrons from the electrodes supporting the arc. An arc discharge is characterized by a lower voltage than a glow discharge. An archaic term is voltaic arc, as used in the phrase "voltaic arc lamp".
A nitrogen laser is a gas laser operating in the ultraviolet range using molecular nitrogen as its gain medium, pumped by an electrical discharge.
In electromagnetism, an electric discharge is the release and transmission of electricity in an applied electric field through a medium such as a gas.
An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael Faraday described this phenomenon as "the beautiful flash of light attending the discharge of common electricity".
A brush discharge is an electrical disruptive discharge similar to a corona discharge that takes place at an electrode with a high voltage applied to it, embedded in a nonconducting fluid, usually air. It is characterized by multiple luminous writhing sparks, plasma streamers composed of ionized air molecules, which repeatedly strike out from the electrode into the air, often with a crackling sound. The streamers spread out in a fan shape, giving it the appearance of a "brush".
Dielectric-barrier discharge (DBD) is the electrical discharge between two electrodes separated by an insulating dielectric barrier. Originally called silent (inaudible) discharge and also known as ozone production discharge or partial discharge, it was first reported by Ernst Werner von Siemens in 1857.
A trigger transformer is a small, usually ferrite cored transformer used in applications requiring a high voltage pulse, typically to start ionization of a gas to allow a current to pass.
Piezoelectric direct discharge (PDD) plasma is a type of cold non-equilibrium plasma, generated by a direct gas discharge of a high voltage piezoelectric transformer. It can be ignited in air or other gases in a wide range of pressures, including atmospheric. Due to the compactness and the efficiency of the piezoelectric transformer, this method of plasma generation is particularly compact, efficient and cheap. It enables a wide spectrum of industrial, medical and consumer applications.
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