Trigatron (from the English trigger - a starting device, a starting signal and an electron ) is usually a gas-filled or, less commonly, a three-electrode electronic device filled with a liquid dielectric - a type of controlled spark gap with a cold cathode [1] for switching high currents with high voltages (usually 10 —100 kV , 20–100 kA , switched currents reach millions of amperes ).
They are used to turn on very high currents to a load, usually fed from storage batteries of capacitors , in electrodynamic guns , high-current accelerators of charged particles, Marx generators , etc.
Principle of Operation
It is a three-electrode electronic device, two of which are working electrodes, intended for inclusion in a switched high-power circuit and a third electrode - the initiating (sometimes called igniting), serves to turn on the device. Before switching on, a high voltage is applied between the working electrodes, but no current flows through the device, as they are separated by a liquid or gaseous dielectric. When the device is turned on, a high voltage pulse, an ionizing gas or other dielectric in the space between the working electrodes is applied to the control electrode. The initial ionization of the interelectrode gap causes an avalanche multiplication of charges in the interelectrode plasma, while the electrical resistance between the working electrodes drops by many orders of magnitude, switching the external electrical circuit. The device is restored from a conduction to a non-conductive state after the current decreases below a certain small current, called the quenching current. Thus, this device cannot be turned off after being turned on by applying control to the control electrode, but only by decreasing the current through it.
Design
The designs of trigatrons are quite simple, and in many cases their application is the most cost-effective solution for incorporating powerful electrical circuits.
Sometimes these devices do not have a housing and operate in an air environment; other types have a sealed glass or ceramic case filled with gas, including gas under overpressure.
Some types of trigatrons are filled with a liquid dielectric (for example, transformer mineral oil ) to increase the breakdown voltage. The trigatron can be designed for multiple switching (more than 10,000 switching), can also be a single use, collapsing the first time you turn it on.
The trigatron has 3 electrodes - 2 massive (main) for passing a large current and a small control electrode. In the off state of the trigatron, the voltage between the main electrodes should be less than the breakdown voltage , the interelectrode gap, which depends on the dielectric used ( air , argon - oxygen mixture, nitrogen , hydrogen or SF6 gas ).
To turn on the trigatron, a high-voltage pulse is applied to the control electrode. The resulting electric field ionizes the gas between the control and one of the main electrodes, and a spark discharge arises, which shortens the non-ionized gap between the main electrodes. The ultraviolet radiation of a spark gives rise to many free electrons in the gap due to ionization. This leads to electrical breakdown and an electric arc having a low electrical resistance arises between the main electrodes. An arc exists until the voltage between the main electrodes is less than a certain value.
The control electrode is often located in the hole in the center of the positive main electrode ( anode ); the negative electrode ( cathode ) has no holes.
When working with high currents, the electrodes become very hot, as they are exposed to an electric arc, which leads to the gradual evaporation of the electrode material. In some models of trigatrons, the distance between the electrodes is adjustable, there is also the possibility of a complete replacement of the electrodes. The main electrodes are usually made of bronze or powder pressed copper - tungsten compound.
Trigatrons decorated in a glass flask are often covered with a protective metal mesh that blocks the fragmentation of glass fragments during an emergency bulb explosion.
Application
Trigatrons are used in pulsed technology, for example, they were used in modulators of the first radars to transmit powerful pulses to magnetrons . They are used to control electric detonators and as arresters in Marx generators [2] .
Terminology
According to TSB [3] , the term “trigatron” by the mid-70s of the XX century was almost out of use in the Russian language and it was replaced by the broader term “ controlled arrester ”. However, browsing the Internet shows that the term is still used quite widely (2007).
See also
- Thyratron
- Kraytron
- Marx Generator
Links
Notes
- ↑ The cathode is cold in the sense that it does not require external heating. When a gas-filled device operates with high average currents, the electrodes become heated until they evaporate.
- ↑ In Russian-language literature, it is usually called GIN, "Impulse Voltage Generator"
- ↑ Article "Trigatron" in TSB